Chronic obstructive pulmonary disease

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https://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_disease 

 

 

Chronic obstructive pulmonary disease
Other names	Chronic obstructive lung disease (COLD), chronic obstructive airway disease (COAD), chronic bronchitis, emphysema, pulmonary emphysema, others
Gross pathology of a lung showing centrilobular emphysema characteristic of smoking. This close-up of the fixed, cut lung surface shows multiple cavities filled with heavy black carbon deposits.
Specialty	Pulmonology
Symptoms	Shortness of breath, cough with sputum production.
Complications	Acute exacerbation of chronic obstructive pulmonary disease
Usual onset	Over 40 years old
Duration	Long term
Causes	Tobacco smoking, air pollution, genetics
Diagnostic method	Lung function tests
Differential diagnosis	Asthma, Asbestosis, Bronchiectasis, Tracheobronchomalacia
Prevention	Improving indoor and outdoor air quality, tobacco control measures
Treatment	Stopping smoking, respiratory rehabilitation, lung transplantation
Medication	Vaccinations, inhaled bronchodilators and steroids, long-term oxygen therapy
Frequency	174.5 million (2015)
Deaths	3.2 million (2015)

Chronic obstructive pulmonary disease (COPD) is a type of obstructive lung disease characterized by long-term breathing problems and poor airflow. The main symptoms include shortness of breath and cough with sputum production. COPD is a progressive disease, meaning it typically worsens over time. Eventually, everyday activities such as walking or getting dressed become difficult. Chronic bronchitis and emphysema are older terms used for different types of COPD. The term "chronic bronchitis" is still used to define a productive cough that is present for at least three months each year for two years. Those with such a cough are at a greater risk of developing COPD. The term "emphysema" is also used for the abnormal presence of air or other gas within tissues.

The most common cause of COPD is tobacco smoking, with a smaller number of cases due to factors such as air pollution and genetics. In the developing world, one of the common sources of air pollution is poorly vented heating and cooking fires. Long-term exposure to these irritants causes an inflammatory response in the lungs, resulting in narrowing of the small airways and breakdown of lung tissue. The diagnosis is based on poor airflow as measured by lung function tests. In contrast to asthma, the airflow reduction does not improve much with the use of a bronchodilator.

Most cases of COPD can be prevented by reducing exposure to risk factors. This includes decreasing rates of smoking and improving indoor and outdoor air quality. While treatment can slow worsening, no cure is known. COPD treatments include smoking cessation, vaccinations, respiratory rehabilitation, and often inhaled bronchodilators and steroids. Some people may benefit from long-term oxygen therapy or lung transplantation. In those who have periods of acute worsening, increased use of medications, antibiotics, steroids, and hospitalization may be needed.

As of 2015, COPD affected about 174.5 million people (2.4% of the global population). It typically occurs in people over the age of 40. Males and females are affected equally commonly. In 2015, it caused 3.2 million deaths, more than 90% in the developing world, up from 2.4 million deaths in 1990. The number of deaths is projected to increase further because of higher smoking rates in the developing world, and an ageing population in many countries. It resulted in an estimated economic cost of US$2.1 trillion in 2010.

Signs and symptoms

The most common symptoms of COPD are shortness of breath, and a cough that produces sputum. These symptoms are present for a prolonged period of time and typically worsen over time. It is unclear whether different types of COPD exist. While previously divided into emphysema and chronic bronchitis, emphysema is only a description of lung changes rather than a disease itself, and chronic bronchitis is simply a descriptor of symptoms that may or may not occur with COPD.

Cough

A chronic cough is often the first symptom to develop. Early on it may just occur occasionally or may not result in sputum. When a cough persists for more than three months each year for at least two years, in combination with sputum production and without another explanation, it is by definition chronic bronchitis. Chronic bronchitis can occur before the restricted airflow and thus COPD fully develops.

The amount of sputum produced can change over hours to days. In some cases, the cough may not be present or may only occur occasionally and may not be productive. Some people with COPD attribute the symptoms to a "smoker's cough". Sputum may be swallowed or spat out, depending often on social and cultural factors. In severe COPD, vigorous coughing may lead to rib fractures or to a brief loss of consciousness. Those with COPD often have a history of "common colds" that last a long time.

Shortness of breath

Shortness of breath is a common symptom and is often the most distressing. It is commonly described as: "my breathing requires effort," "I feel out of breath," or "I can't get enough air in." Different terms, however, may be used in different cultures. Typically, the shortness of breath is worse on exertion of a prolonged duration and worsens over time. In the advanced stages, or end stage pulmonary disease, it occurs during rest and may be always present. Shortness of breath is a source of both anxiety and a poor quality of life in those with COPD. Many people with more advanced COPD breathe through pursed lips and this action can improve shortness of breath in some.

Physical activity limitation

COPD often leads to reduction in physical activity, in part due to shortness of breath. In later stages of COPD muscle wasting (cachexia) may occur. Low levels of physical activity are associated with worse outcomes.

Other symptoms

In COPD, breathing out may take longer than breathing in. Chest tightness may occur, but is not common and may be caused by another problem. Those with obstructed airflow may have wheezing or decreased sounds with air entry on examination of the chest with a stethoscope. A barrel chest is a characteristic sign of COPD, but is relatively uncommon. Tripod positioning may occur as the disease worsens.

Advanced COPD leads to high pressure on the lung arteries, which strains the right ventricle of the heart. This situation is referred to as cor pulmonale, and leads to symptoms of leg swelling and bulging neck veins. COPD is more common than any other lung disease as a cause of cor pulmonale. Cor pulmonale has become less common since the use of supplemental oxygen.

COPD often occurs along with a number of other conditions, due in part to shared risk factors. These conditions include ischemic heart disease, high blood pressure, diabetes mellitus, muscle wasting, osteoporosis, lung cancer, anxiety disorder, sexual dysfunction, and depression. In those with severe disease, a feeling of always being tired is common. Fingernail clubbing is not specific to COPD and should prompt investigations for an underlying lung cancer.

Exacerbation

An acute exacerbation of COPD is defined as increased shortness of breath, increased sputum production, a change in the color of the sputum from clear to green or yellow, or an increase in cough in someone with COPD. They may present with signs of increased work of breathing such as fast breathing, a fast heart rate, sweating, active use of muscles in the neck, a bluish tinge to the skin, and confusion or combative behavior in very severe exacerbations. Crackles may also be heard over the lungs on examination with a stethoscope.

Cause

The primary cause of COPD is tobacco smoke, with occupational exposure and pollution from indoor fires being significant causes in some countries. Typically, these must occur over several decades before symptoms develop. A person's genetic makeup also affects the risk.

Smoking

Percentage of females smoking tobacco as of the late 1990s early 2000s

 

Percentage of males smoking tobacco as of the late 1990s and early 2000s. Note the scales used for females and males differ.

The primary risk factor for COPD globally is tobacco smoking. Of those who smoke, about 20% will get COPD, and of those who are lifelong smokers, about half will get COPD. In the United States and United Kingdom, of those with COPD, 80–95% are either current or previous smokers. The likelihood of developing COPD increases with the total smoke exposure. Additionally, women are more susceptible to the harmful effects of smoke than men. In non-smokers, exposure to second-hand smoke is the cause in up to 20% of cases. Other types of smoke, such as, marijuana, cigar, and water-pipe smoke, also confer a risk. Water-pipe smoke appears to be as harmful as smoking cigarettes. Problems from marijuana smoke may only be with heavy use. Women who smoke during pregnancy may increase the risk of COPD in their child. For the same amount of cigarette smoking, women have a higher risk of COPD than men.

Air pollution

Access to clean fuels and technologies for cooking as of 2016

Poorly ventilated cooking fires, often fueled by coal or biomass fuels such as wood and dung, lead to indoor air pollution and are one of the most common causes of COPD in developing countries. These fires are a method of cooking and heating for nearly 3 billion people, with their health effects being greater among women due to greater exposure. They are used as the main source of energy in 80% of homes in India, China and sub-Saharan Africa.

People who live in large cities have a higher rate of COPD compared to people who live in rural areas. While urban air pollution is a contributing factor in exacerbations, its overall role as a cause of COPD is unclear. Areas with poor outdoor air quality, including that from exhaust gas, generally have higher rates of COPD. The overall effect in relation to smoking, however, is believed to be small.

Occupational exposure

Intense and prolonged exposure to workplace dusts, chemicals, and fumes increases the risk of COPD in both smokers and nonsmokers. Workplace exposure is believed to be the cause in 10–20% of cases. In the United States, it is believed that it is related to more than 30% of cases among those who have never smoked and probably represents a greater risk in countries without sufficient regulations.

A number of industries and sources have been implicated, including high levels of dust in coal mining, gold mining, and the cotton textile industry, occupations involving cadmium and isocyanates, and fumes from welding. Working in agriculture is also a risk. In some professions, the risks have been estimated as equivalent to that of one-half to two packs of cigarettes a day. Silica dust and fiberglass dust exposure can also lead to COPD, with the risk unrelated to that for silicosis. The negative effects of dust exposure and cigarette smoke exposure appear to be additive or possibly more than additive.

Genetics

Genetics play a role in the development of COPD. It is more common among relatives of those with COPD who smoke than unrelated smokers. Currently, the only clearly inherited risk factor is alpha 1-antitrypsin deficiency (AAT). This risk is particularly high if someone deficient in alpha 1-antitrypsin also smokes. It is responsible for about 1–5% of cases and the condition is present in about three to four in 10,000 people. Other genetic factors are being investigated, of which many are likely.

Other

A number of other factors are less closely linked to COPD. The risk is greater in those who are poor, although whether this is due to poverty itself or other risk factors associated with poverty, such as air pollution and malnutrition, is not clear. Tentative evidence indicates that those with asthma and airway hyperreactivity are at increased risk of COPD. Birth factors such as low birth weight may also play a role, as do a number of infectious diseases, including HIV/AIDS and tuberculosis. Respiratory infections such as pneumonia do not appear to increase the risk of COPD, at least in adults.

Exacerbations

An acute exacerbation (a sudden worsening of symptoms) is commonly triggered by infection or environmental pollutants, or sometimes by other factors such as improper use of medications. Infections appear to be the cause of 50 to 75% of cases, with bacteria in 30%, viruses in 23%, and both in 25%.

Environmental pollutants include both poor indoor and outdoor air quality. Exposure to personal smoke and second-hand smoke increases the risk. Cold temperatures may also play a role, with exacerbations occurring more commonly in winter. Those with more severe underlying disease have more frequent exacerbations: in mild disease 1.8 per year, moderate 2 to 3 per year, and severe 3.4 per year. Those with many exacerbations have a faster rate of deterioration of their lung function. A pulmonary embolism (PE) (blood clot in the lung) can worsen symptoms in those with pre-existing COPD. Signs of a PE in COPD include pleuritic chest pain and heart failure without signs of infection.

Pathophysiology

On the left is a diagram of the lungs and airways with an inset showing a detailed cross-section of normal bronchioles and alveoli. On the right are lungs damaged by COPD with an inset showing a cross-section of damaged bronchioles and alveoli.

COPD is a type of obstructive lung disease in which chronic, incompletely reversible poor airflow (airflow limitation) and inability to breathe out fully (air trapping) exist. The poor airflow is the result of breakdown of lung tissue (known as emphysema), and small airways disease known as obstructive bronchiolitis. The relative contributions of these two factors vary between people. Severe destruction of small airways can lead to the formation of large focal lung pneumatoses, known as bullae, that replace lung tissue. This form of disease is called bullous emphysema.

COPD develops as a significant and chronic inflammatory response to inhaled irritants. Chronic bacterial infections may also add to this inflammatory state. The inflammatory cells involved include neutrophil granulocytes and macrophages, two types of white blood cells. Those who smoke additionally have Tc1 lymphocyte involvement and some people with COPD have eosinophil involvement similar to that in asthma. Part of this cell response is brought on by inflammatory mediators such as chemotactic factors. Other processes involved with lung damage include oxidative stress produced by high concentrations of free radicals in tobacco smoke and released by inflammatory cells, and breakdown of the connective tissue of the lungs by proteases that are insufficiently inhibited by protease inhibitors. The destruction of the connective tissue of the lungs leads to emphysema, which then contributes to the poor airflow, and finally, poor absorption and release of respiratory gases. General muscle wasting that often occurs in COPD may be partly due to inflammatory mediators released by the lungs into the blood.

Micrograph showing emphysema (left – large empty spaces) and lung tissue with relative preservation of the alveoli (right)

Narrowing of the airways occurs due to inflammation and scarring within them. This contributes to the inability to breathe out fully. The greatest reduction in air flow occurs when breathing out, as the pressure in the chest is compressing the airways at this time. This can result in more air from the previous breath remaining within the lungs when the next breath is started, resulting in an increase in the total volume of air in the lungs at any given time, a process called hyperinflation or air trapping.

Hyperinflation from exercise is linked to shortness of breath in COPD, as breathing in is less comfortable when the lungs are already partly filled. Hyperinflation may also worsen during an exacerbation.

Some also have a degree of airway hyperresponsiveness to irritants similar to those found in asthma.

Low oxygen levels, and eventually, high carbon dioxide levels in the blood, can occur from poor gas exchange due to decreased ventilation from airway obstruction, hyperinflation, and a reduced desire to breathe. During exacerbations, airway inflammation is also increased, resulting in increased hyperinflation, reduced expiratory airflow, and worsening of gas transfer. This can also lead to insufficient ventilation, and eventually low blood oxygen levels. Low oxygen levels, if present for a prolonged period, can result in narrowing of the arteries in the lungs, while emphysema leads to breakdown of capillaries in the lungs. Both of these changes result in increased blood pressure in the pulmonary arteries, which may cause right-sided heart failure secondary to lung disease, also known as cor pulmonale.

Diagnosis

A person blowing into a spirometer. Smaller handheld devices are available for office use.

The diagnosis of COPD should be considered in anyone over the age of 35 to 40 who has shortness of breath, a chronic cough, sputum production, or frequent winter colds and a history of exposure to risk factors for the disease. Spirometry is then used to confirm the diagnosis. Screening those without symptoms is not recommended.

Spirometry

Spirometry measures the amount of airflow obstruction present and is generally carried out after the use of a bronchodilator, a medication to open up the airways. Two main components are measured to make the diagnosis, the forced expiratory volume in one second (FEV₁), which is the greatest volume of air that can be breathed out in the first second of a breath, and the forced vital capacity (FVC), which is the greatest volume of air that can be breathed out in a single large breath. Normally, 75–80% of the FVC comes out in the first second and a FEV₁/FVC ratio less than 70% in someone with symptoms of COPD defines a person as having the disease. Based on these measurements, spirometry would lead to over-diagnosis of COPD in the elderly. The National Institute for Health and Care Excellence criteria additionally require a FEV₁ less than 80% of predicted. People with COPD also exhibit a decrease in diffusing capacity of the lung for carbon monoxide (D_LCO) due to decreased surface area in the alveoli, as well as damage to the capillary bed.

Evidence for using spirometry among those without symptoms in an effort to diagnose the condition earlier is of uncertain effect, so currently is not recommended. A peak expiratory flow (the maximum speed of expiration), commonly used in asthma, is not sufficient for the diagnosis of COPD.

Severity

MRC shortness of breath scale

Grade	Activity affected
1	Only strenuous activity
2	Vigorous walking
3	With normal walking
4	After a few minutes of walking
5	With changing clothing

GOLD grade

Severity	FEV1 % predicted
Mild (GOLD 1)	≥80
Moderate (GOLD 2)	50–79
Severe (GOLD 3)	30–49
Very severe (GOLD 4)	<30

A number of methods can determine how much COPD is affecting a given individual. The modified  British Medical Research Council questionnaire or the COPD assessment test (CAT) are simple questionnaires that may be used to determine the severity of symptoms. Scores on CAT range from 0–40 with the higher the score, the more severe the disease. Spirometry may help to determine the severity of airflow limitation. This is typically based on the FEV₁ expressed as a percentage of the predicted "normal" for the person's age, gender, height, and weight.

 Both the American and European guidelines recommend partly basing treatment recommendations on the FEV₁. The GOLD guidelines suggest dividing people into four categories based on symptoms assessment and airflow limitation. Weight loss and muscle weakness, as well as the presence of other diseases, should also be taken into account.

Other tests

A chest X-ray and complete blood count may be useful to exclude other conditions at the time of diagnosis. Characteristic signs on X-ray are hyperinflated lungs, a flattened diaphragm, increased retrosternal airspace, and bullae, while it can help exclude other lung diseases, such as pneumonia, pulmonary edema, or a pneumothorax. A high-resolution CT scan of the chest may show the distribution of emphysema throughout the lungs and can also be useful to exclude other lung diseases. Unless surgery is planned, however, this rarely affects management. A saber-sheath trachea deformity may also be present. An analysis of arterial blood is used to determine the need for oxygen; this is recommended in those with an FEV₁ less than 35% predicted, those with a peripheral oxygen saturation less than 92%, and those with symptoms of congestive heart failure. In areas of the world where alpha-1 antitrypsin deficiency is common, people with COPD (particularly those below the age of 45 and with emphysema affecting the lower parts of the lungs) should be considered for testing.

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  Chest X-ray demonstrating severe COPD: Note the small heart size in comparison to the lungs.

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  A lateral chest X-ray of a person with emphysema: Note the barrel chest and flat diaphragm.

• 

  Lung bulla as seen on chest X-ray in a person with severe COPD

• 

  A severe case of bullous emphysema

• 

  Axial CT image of the lung of a person with end-stage bullous emphysema

• 

  Very severe emphysema with lung cancer on the left (CT scan)

Differential diagnosis

COPD may need to be differentiated from other causes of shortness of breath such as congestive heart failure, pulmonary embolism, pneumonia, or pneumothorax. Many people with COPD mistakenly think they have asthma. The distinction between asthma and COPD is made on the basis of the symptoms, smoking history, and whether airflow limitation is reversible with bronchodilators at spirometry.

 Tuberculosis may also present with a chronic cough and should be considered in locations where it is common. Less common conditions that may present similarly include bronchopulmonary dysplasia and obliterative bronchiolitis. Chronic bronchitis may occur with normal airflow and in this situation it is not classified as COPD.

Prevention

Most cases of COPD are potentially preventable through decreasing exposure to smoke and improving air quality. Annual influenza vaccinations in those with COPD reduce exacerbations, hospitalizations and death. Pneumococcal vaccination may also be beneficial. Eating a diet high in beta-carotene may help but taking supplements does not seem to. A review of an oral Haemophilus influenzae vaccine found 1.6 exacerbations per year as opposed to a baseline of 2.1 in those with COPD. This small reduction was not deemed significant.

Smoking cessation

Keeping people from starting smoking is a key aspect of preventing COPD. The policies of governments, public health agencies, and antismoking organizations can reduce smoking rates by discouraging people from starting and encouraging people to stop smoking. Smoking bans in public areas and places of work are important measures to decrease exposure to secondhand smoke, and while many places have instituted bans, more are recommended.

In those who smoke, stopping smoking is the only measure shown to slow down the worsening of COPD. Even at a late stage of the disease, it can reduce the rate of worsening lung function and delay the onset of disability and death. Often, several attempts are required before long-term abstinence is achieved. Attempts over 5 years lead to success in nearly 40% of people.

Some smokers can achieve long-term smoking cessation through willpower alone. Smoking, however, is highly addictive, and many smokers need further support. The chance of quitting is improved with social support, engagement in a smoking cessation program, and the use of medications such as nicotine replacement therapy, bupropion, or varenicline. Combining smoking-cessation medication with behavioral therapy is more than twice as likely to be effective in helping people with COPD stop smoking, compared with behavioral therapy alone.

Occupational health

A number of measures have been taken to reduce the likelihood that workers in at-risk industries—such as coal mining, construction, and stonemasonry—will develop COPD. Examples of these measures include the creation of public policy, education of workers and management about the risks, promoting smoking cessation, checking workers for early signs of COPD, use of respirators, and dust control.

Effective dust control can be achieved by improving ventilation, using water sprays and by using mining techniques that minimize dust generation. If a worker develops COPD, further lung damage can be reduced by avoiding ongoing dust exposure, for example by changing their work role.

Air pollution

Both indoor and outdoor air quality can be improved, which may prevent COPD or slow the worsening of existing disease. This may be achieved by public policy efforts, cultural changes, and personal involvement.

A number of developed countries have successfully improved outdoor air quality through regulations. This has resulted in improvements in the lung function of their populations. Those with COPD may experience fewer symptoms if they stay indoors on days when outdoor air quality is poor.

One key effort is to reduce exposure to smoke from cooking and heating fuels through improved ventilation of homes and better stoves and chimneys. Proper stoves may improve indoor air quality by 85%. Using alternative energy sources such as solar cooking and electrical heating is also effective. Using fuels such as kerosene or coal might be less bad than traditional biomass such as wood or dung.

Management

No cure for COPD is known, but the symptoms are treatable and its progression can be delayed. The major goals of management are to reduce risk factors, manage stable COPD, prevent and treat acute exacerbations, and manage associated illnesses. The only measures that have been shown to reduce mortality are smoking cessation and supplemental oxygen. Stopping smoking decreases the risk of death by 18%. Other recommendations include influenza vaccination once a year, pneumococcal vaccination once every five years, and reduction in exposure to environmental air pollution. In those with advanced disease, palliative care may reduce symptoms, with morphine improving the feelings of shortness of breath. Noninvasive ventilation may be used to support breathing. Providing people with a personalized action plan, an educational session, and support for use of their action plan in the event of an exacerbation, reduces the number of hospital visits and encourages early treatment of exacerbations. When self-management interventions, such as taking corticosteroids and using supplemental oxygen, is combined with action plans, health-related quality of life is improved compared to usual care. Self-management is also associated with improved health-related quality of life, reduced respiratory-related and all-cause hospital admissions and improvement in shortness of breath. The 2019 NICE guidelines also recommends treatment of associated conditions.

Exercise

Pulmonary rehabilitation is a program of exercise, disease management, and counseling, coordinated to benefit the individual. In those who have had a recent exacerbation, pulmonary rehabilitation appears to improve the overall quality of life and the ability to exercise. If pulmonary rehabilitation improves mortality rates or hospital readmission rates is unclear. Pulmonary rehabilitation has been shown to improve the sense of control a person has over their disease, as well as their emotions.

The optimal exercise routine, use of noninvasive ventilation during exercise, and intensity of exercise suggested for people with COPD, is unknown. Performing endurance arm exercises improves arm movement for people with COPD, and may result in a small improvement in breathlessness. Performing arm exercises alone does not appear to improve quality of life. Breathing exercises in and of themselves appear to have a limited role. Pursed lip breathing exercises may be useful. Tai chi exercises appear to be safe to practice for people with COPD, and may be beneficial for pulmonary function and pulmonary capacity when compared to a regular treatment program. Tai Chi was not found to be more effective than other exercise intervention programs. Inspiratory and expiratory muscle training (IMT, EMT) is an effective method for improving activities of daily living (ADL). A combination of IMT and walking exercises at home may help limit breathlessness in cases of severe COPD. Additionally, the use of low amplitude high velocity joint mobilization together with exercise improves lung function and exercise capacity. The goal of spinal manipulation therapy (SMT) is to improve thoracic mobility in an effort to reduce the work on the lungs during respiration, to in turn increase exercise capacity as indicated by the results of a systemic medical review. Airway clearance techniques (ACTs), such as postural drainage, percussion/vibration, autogenic drainage, hand-held positive expiratory pressure (PEP) devices and other mechanical devices, may reduce the need for increased ventilatory assistance, the duration of ventilatory assistance, and the length of hospital stay in people with acute COPD. In people with stable COPD, ACTs may lead to short-term improvements in health-related quality of life and a reduced long-term need for hospitalisations related to respiratory issues.

Being either underweight or overweight can affect the symptoms, degree of disability, and prognosis of COPD. People with COPD who are underweight can improve their breathing muscle strength by increasing their calorie intake. When combined with regular exercise or a pulmonary rehabilitation program, this can lead to improvements in COPD symptoms. Supplemental nutrition may be useful in those who are malnourished.

Bronchodilators

Inhaled bronchodilators are the primary medications used, and result in a small overall benefit. The two major types are β₂ agonists and anticholinergics; both exist in long-acting and short-acting forms. They reduce shortness of breath, wheeze, and exercise limitation, resulting in an improved quality of life. It is unclear if they change the progression of the underlying disease.

In those with mild disease, short-acting agents are recommended on an as needed basis. In those with more severe disease, long-acting agents are recommended. Long-acting agents partly work by reducing hyperinflation. If long-acting bronchodilators are insufficient, then inhaled corticosteroids are typically added. Which type of long-acting agent, long-acting muscarinic antagonist (LAMA) such as tiotropium or a long-acting beta agonist (LABA) is better is unclear, and trying each and continuing with the one that works best may be advisable. Both types of agent appear to reduce the risk of acute exacerbations by 15–25%. A 2018 review found the combination of LABA/LAMA may reduce COPD exacerbations and improve quality-of-life compared to long-acting bronchodilators alone. The 2018 NICE guideline recommends use of dual long-acting bronchodilators with economic modelling suggesting that this approach is preferable to starting one long acting bronchodilator and adding another later.

Several short-acting β₂ agonists are available, including salbutamol (albuterol) and terbutaline. They provide some relief of symptoms for four to six hours. LABAs such as salmeterol, formoterol, and indacaterol are often used as maintenance therapy. Some feel the evidence of benefits is limited, while others view the evidence of benefit as established. Long-term use appears safe in COPD with adverse effects include shakiness and heart palpitations. When used with inhaled steroids they increase the risk of pneumonia. While steroids and LABAs may work better together, it is unclear if this slight benefit outweighs the increased risks. There is some evidence that combined treatment of LABAs with long-acting muscarinic antagonists (LAMA), an anticholinergic, may result in less exacerbations, less pneumonia, an improvement in forced expiratory volume (FEV1%), and potential improvements in quality of life when compared to treatment with LABA and an inhaled corticosteriod (ICS). All three together, LABA, LAMA, and ICS, have some evidence of benefits. Indacaterol requires an inhaled dose once a day, and is as effective as the other long-acting β₂ agonist drugs that require twice-daily dosing for people with stable COPD.

Two main anticholinergics are used in COPD, ipratropium and tiotropium. Ipratropium is a short-acting agent, while tiotropium is long-acting. Tiotropium is associated with a decrease in exacerbations and improved quality of life, and tiotropium provides those benefits better than ipratropium. It does not appear to affect mortality or the overall hospitalization rate. Anticholinergics can cause dry mouth and urinary tract symptoms. They are also associated with increased risk of heart disease and stroke.

Aclidinium, another long-acting agent, reduces hospitalizations associated with COPD and improves quality of life. The LAMA umeclidinium bromide is another anticholinergic alternative. When compared to tiotropium, the LAMAs aclidinium, glycopyrronium, and umeclidinium appear to have a similar level of efficacy; with all four being more effective than placebo. Further research is needed comparing aclidinium to tiotropium.

Corticosteroids

Corticosteroids are usually used in inhaled form, but may also be used as tablets to treat acute exacerbations. While inhaled corticosteroids (ICSs) have not shown benefit for people with mild COPD, they decrease acute exacerbations in those with either moderate or severe disease. By themselves, they have no effect on overall one-year mortality. Whether they affect the progression of the disease is unknown. When used in combination with a LABA, they may decrease mortality compared to either ICSs or LABA alone. Inhaled steroids are associated with increased rates of pneumonia. Long-term treatment with steroid tablets is associated with significant side effects.

The 2018 NICE guidelines recommend use of ICS in people with asthmatic features or features suggesting steroid responsiveness. These include any previous diagnosis of asthma or atopy, a higher blood eosinophil count, substantial variation in FEV₁ over time (at least 400 mL) and at least 20% diurnal variation in peak expiratory flow. “Higher” eosinophil count was chosen, rather than specifying a particular value as it is not clear what the precise threshold should be or on how many occasions or over what time period it should be elevated.

Other medications

Long-term antibiotics, specifically those from the macrolide class such as erythromycin, reduce the frequency of exacerbations in those who have two or more a year. This practice may be cost effective in some areas of the world. Concerns include the potential for antibiotic resistance and side effects including hearing loss, tinnitus, and changes to the heart rhythm (long QT syndrome). Methylxanthines such as theophylline generally cause more harm than benefit and thus are usually not recommended, but may be used as a second-line agent in those not controlled by other measures. Mucolytics may help to reduce exacerbations in some people with chronic bronchitis; noticed by less hospitalization and less days of disability in one month. Cough medicines are not recommended.

For people with COPD, the use of cardioselective (heart-specific) beta-blocker therapy does not appear to impair respiratory function. Cardioselective beta-blocker therapy should not be contraindicated for people with COPD. In those with low levels of vitamin D, supplementation appear to reduce the risk of exacerbations.

Oxygen

Supplemental oxygen is recommended in those with low oxygen levels at rest (a partial pressure of oxygen less than 50–55 mmHg or oxygen saturations of less than 88%). In this group of people, it decreases the risk of heart failure and death if used 15 hours per day and may improve people's ability to exercise. In those with normal or mildly low oxygen levels, oxygen supplementation may improve shortness of breath when given during exercise, but may not improve breathlessness during normal daily activities or affect the quality of life. A risk of fires and little benefit exist when those on oxygen continue to smoke. In this situation, some including NICE recommend against its use. During acute exacerbations, many require oxygen therapy; the use of high concentrations of oxygen without taking into account a person's oxygen saturations may lead to increased levels of carbon dioxide and worsened outcomes. In those at high risk of high carbon dioxide levels, oxygen saturations of 88–92% are recommended, while for those without this risk, recommended levels are 94–98%.

Surgery

For those with very severe disease, surgery is sometimes helpful and may include lung transplantation or lung volume-reduction surgery, which involves removing the parts of the lung most damaged by emphysema, allowing the remaining, relatively good lung to expand and work better. It seems to be particularly effective if emphysema predominantly involves the upper lobe, but the procedure increases the risks of adverse events and early death for people who have diffuse emphysema. The procedure also increases the risk of adverse effects for people with moderate to severe COPD. Lung transplantation is sometimes performed for very severe COPD, particularly in younger individuals.

Exacerbations

Acute exacerbations are typically treated by increasing the use of short-acting bronchodilators. This commonly includes a combination of a short-acting inhaled beta agonist and anticholinergic. These medications can be given either via a metered-dose inhaler with a spacer or via a nebulizer, with both appearing to be equally effective. Nebulization may be easier for those who are more unwell. Oxygen supplementation can be useful. Excessive oxygen; however, can result in increased CO
2 levels and a decreased level of consciousness.

Corticosteroids by mouth improve the chance of recovery and decrease the overall duration of symptoms. They work equally well as intravenous steroids but appear to have fewer side effects. Five days of steroids work as well as ten or fourteen. In those with a severe exacerbation, antibiotics improve outcomes. A number of different antibiotics may be used including amoxicillin, doxycycline and azithromycin; whether one is better than the others is unclear. The FDA recommends against the use of fluoroquinolones when other options are available due to higher risks of serious side effects. There is no clear evidence for those with less severe cases. For people with type 2 respiratory failure (acutely raised CO
2 levels) non-invasive positive pressure ventilation decreases the probability of death or the need of intensive care admission. Additionally, theophylline may have a role in those who do not respond to other measures. Fewer than 20% of exacerbations require hospital admission. In those without acidosis from respiratory failure, home care ("hospital at home") may be able to help avoid some admissions.

Prognosis

Chronic obstructive pulmonary disease deaths per million persons in 2012

  9–63

  64–80

  81–95

  96–116

  117–152

  153–189

  190–235

  236–290

  291–375

  376–1089

Disability-adjusted life years lost to chronic obstructive pulmonary disease per 100,000 inhabitants in 2004.

no data   ≤110   110–220   220–330   330–440   440–550   550–660

660–770   770–880   880–990   990–1100   1100–1350   ≥1350

COPD usually gets gradually worse over time and can ultimately result in death. It is estimated that 3% of all disability is related to COPD. The proportion of disability from COPD globally has decreased from 1990 to 2010 due to improved indoor air quality primarily in Asia. The overall number of years lived with disability from COPD, however, has increased.

The rate at which COPD worsens varies with the presence of factors that predict a poor outcome, including severe airflow obstruction, little ability to exercise, shortness of breath, significant underweight or overweight, congestive heart failure, continued smoking, and frequent exacerbations. Long-term outcomes in COPD can be estimated using the BODE index which gives a score of zero to ten depending on FEV₁, body-mass index, the distance walked in six minutes, and the modified MRC dyspnea scale. Significant weight loss is a bad sign.sults of spirometry are also a good predictor of the future progress of the disease but are not as good as the BODE index.

Epidemiology

Globally, as of 2010, COPD affected approximately 329 million people (4.8% of the population). The disease affects men and women almost equally, as there has been increased tobacco use among women in the developed world. The increase in the developing world between 1970 and the 2000s is believed to be related to increasing rates of smoking in this region, an increasing population and an aging population due to fewer deaths from other causes such as infectious diseases. Some developed countries have seen increased rates, some have remained stable and some have seen a decrease in COPD prevalence. The global numbers are expected to continue increasing as risk factors remain common and the population continues to get older.

Between 1990 and 2010 the number of deaths from COPD decreased slightly from 3.1 million to 2.9 million and became the fourth leading cause of death. In 2012 it became the third leading cause as the number of deaths rose again to 3.1 million. In some countries, mortality has decreased in men but increased in women. This is most likely due to rates of smoking in women and men becoming more similar. COPD is more common in older people; it affects 34–200 out of 1000 people older than 65 years, depending on the population under review.

In England, an estimated 0.84 million people (of 50 million) have a diagnosis of COPD; this translates into approximately one person in 59 receiving a diagnosis of COPD at some point in their lives. In the most socioeconomically deprived parts of the country, one in 32 people were diagnosed with COPD, compared with one in 98 in the most affluent areas. In the United States approximately 6.3% of the adult population, totaling approximately 15 million people, have been diagnosed with COPD.

 25 million people may have COPD if currently undiagnosed cases are included. In 2011, there were approximately 730,000 hospitalizations in the United States for COPD. In the United States, COPD is estimated to be the third leading cause of death in 2011.

History

Giovanni Battista Morgagni, who made one of the earliest recorded descriptions of emphysema in 1769

The word "emphysema" is derived from the Greek ἐμφυσᾶν emphysan meaning "inflate" -itself composed of ἐν en, meaning "in", and φυσᾶν physan, meaning "breath, blast". The term "chronic bronchitis" came into use in 1808 while the term "COPD" is believed to have first been used in 1965.

Previously it has been known by a number of different names, including chronic obstructive bronchopulmonary disease, chronic obstructive respiratory disease, chronic airflow obstruction, chronic airflow limitation, chronic obstructive lung disease, nonspecific chronic pulmonary disease, and diffuse obstructive pulmonary syndrome. The terms chronic bronchitis and emphysema were formally defined in 1959 at the CIBA guest symposium and in 1962 at the American Thoracic Society Committee meeting on Diagnostic Standards.

Early descriptions of probable emphysema include: in 1679 by T. Bonet of a condition of "voluminous lungs" and in 1769 by Giovanni Morgagni of lungs which were "turgid particularly from air". In 1721 the first drawings of emphysema were made by Ruysh. These were followed with pictures by Matthew Baillie in 1789 and descriptions of the destructive nature of the condition. In 1814 Charles Badham used "catarrh" to describe the cough and excess mucus in chronic bronchitis. René Laennec, the physician who invented the stethoscope, used the term "emphysema" in his book A Treatise on the Diseases of the Chest and of Mediate Auscultation (1837) to describe lungs that did not collapse when he opened the chest during an autopsy. He noted that they did not collapse as usual because they were full of air and the airways were filled with mucus. In 1842, John Hutchinson invented the spirometer, which allowed the measurement of vital capacity of the lungs. However, his spirometer could measure only volume, not airflow. Tiffeneau and Pinelli in 1947 described the principles of measuring airflow.

In 1953, Dr. George L. Waldbott, an American allergist, first described a new disease he named "smoker's respiratory syndrome" in the 1953 Journal of the American Medical Association. This was the first association between tobacco smoking and chronic respiratory disease.

Early treatments included garlic, cinnamon and ipecac, among others. Modern treatments were developed during the second half of the 20th century. Evidence supporting the use of steroids in COPD was published in the late 1950s. Bronchodilators came into use in the 1960s following a promising trial of isoprenaline. Further bronchodilators, such as salbutamol, were developed in the 1970s, and the use of LABAs began in the mid-1990s.

Society and culture

COPD is known colloquially as "smoker's lung", but it may also occur in people who have never smoked. People with emphysema have been known as "pink puffers" or "type A" due to their frequent pink complexion, fast respiratory rate and pursed lips, and people with chronic bronchitis have been referred to as "blue bloaters" or "type B" due to the often bluish color of the skin and lips from low oxygen levels and their swollen ankles. This terminology is no longer accepted as useful as most people with COPD have a combination of both emphysema and chronic bronchitis.

Many health systems have difficulty ensuring appropriate identification, diagnosis and care of people with COPD; Britain's Department of Health has identified this as a major issue for the National Health Service and has introduced a specific strategy to tackle these problems.

Economics

Globally, as of 2010, COPD is estimated to result in economic costs of $2.1 trillion, half of which occurring in the developing world. Of this total an estimated $1.9 trillion are direct costs such as medical care, while $0.2 trillion are indirect costs such as missed work. This is expected to more than double by the year 2030. In Europe, COPD represents 3% of healthcare spending. In the United States, costs of the disease are estimated at $50 billion, most of which is due to exacerbation. COPD was among the most expensive conditions seen in U.S. hospitals in 2011, with a total cost of about $5.7 billion.

Research

Mass spectrometry is being studied as a diagnostic tool in COPD.

Infliximab, an immune-suppressing antibody, has been tested in COPD; there was a possibility of harm with no evidence of benefit. Roflumilast, and cilomilast, are phosphodiesterase-4 inhibitors (PDE₄) and act as anti-inflammatories. They show promise in decreasing the rate of exacerbations, but do not appear to change a person's quality of life. Roflumilast and cilomilast may be associated with side effects such as gastrointestinal issues and weight loss. Sleep disturbances and mood disturbances related to roflumilast have also been reported. A PDE₄ is recommended to be used as an add-on therapy in case of failure of the standard COPD treatment during exacerbations.

Several new long-acting agents are under development. Treatment with stem cells is under study. While there is tentative data that it is safe, and the animal data is promising, there is little human data as of 2017. The small amount of human data there is has shown poor results.

A procedure known as targeted lung denervation, which involves decreasing the parasympathetic nervous system supply of the lungs, is being studied but does not have sufficient data to determine its use. The effectiveness of alpha-1 antitrypsin augmentation treatment for people who have alpha-1 antitrypsin deficiency is unclear.

Research continues into the use of telehealthcare to treat people with COPD when they experience episodes of shortness of breath; treating people remotely may reduce the number of emergency-room visits and improve the person's quality of life.

The Elements of Style

From Wikipedia, the free encyclopedia

 

The Elements of Style

First expanded edition (1959)
Author	William Strunk Jr. (1918/1920) and E. B. White (1959)
Illustrator	Maira Kalman (2005 only)
Country	United States
Subject	American English style guide
Publisher	Harcourt, Brace & Howe (1920) Macmillan (1959) Allyn & Bacon (1999)
Media type	Print (Paperback)
Pages	43 (1918), 52 (1920), 71 (1959), 105 (1999)
OCLC	27652766
Dewey Decimal	808/.042 21
LC Class	PE1421 .S7 (Strunk) PE1408 .S772 (Strunk & White)

The Elements of Style is an American English writing style guide in numerous editions. The original was composed by William Strunk Jr. in 1918, and published by Harcourt in 1920, comprising eight "elementary rules of usage", ten "elementary principles of composition", "a few matters of form", a list of 49 "words and expressions commonly misused", and a list of 57 "words often misspelled". E. B. White greatly enlarged and revised the book for publication by Macmillan in 1959. That was the first edition of the so-called Strunk & White, which Time named in 2011 as one of the 100 best and most influential books written in English since 1923.

History

Cornell University English professor William Strunk Jr. wrote The Elements of Style in 1918 and privately published it in 1919, for use at the university. (Harcourt republished it in 52-page format in 1920.) He and editor Edward A. Tenney later revised it for publication as The Elements and Practice of Composition (1935). In 1957 the style guide reached the attention of E.B. White at The New Yorker. White had studied writing under Strunk in 1919 but had since forgotten "the little book" that he described as a "forty-three-page summation of the case for cleanliness, accuracy, and brevity in the use of English". Weeks later, White wrote a feature story about Strunk's devotion to lucid English prose.

Macmillan and Company subsequently commissioned White to revise The Elements for a 1959 edition (Strunk had died in 1946). White's expansion and modernization of Strunk and Tenney's 1935 revised edition yielded the writing style manual informally known as "Strunk & White", the first edition of which sold about two million copies in 1959. More than ten million copies of three editions were later sold. Mark Garvey relates the history of the book in Stylized: A Slightly Obsessive History of Strunk & White's The Elements of Style (2009).

Maira Kalman, who provided the illustrations for The Elements of Style Illustrated (2005, see below), asked Nico Muhly to compose a cantata based on the book. It was performed at the New York Public Library in October 2005.

Audiobook versions of The Elements now feature changed wording, citing "gender issues" with the original.

Content

Strunk concentrated on the cultivation of good writing and composition; the original 1918 edition exhorted writers to "omit needless words", use the active voice, and employ parallelism appropriately.

The 1959 edition features White's expansions of preliminary sections, the "Introduction" essay (derived from his magazine feature story about Prof. Strunk), and the concluding chapter, "An Approach to Style", a broader, prescriptive guide to writing in English. He also produced the second (1972) and third (1979) editions of The Elements of Style, by which time the book's length had extended to 85 pages.

The third edition of The Elements of Style (1979) features 54 points: a list of common word-usage errors; 11 rules of punctuation and grammar; 11 principles of writing; 11 matters of form; and, in Chapter V, 21 reminders for better style. The final reminder, the 21st, "Prefer the standard to the offbeat", is thematically integral to the subject of The Elements of Style, yet does stand as a discrete essay about writing lucid prose. To write well, White advises writers to have the proper mind-set, that they write to please themselves, and that they aim for "one moment of felicity", a phrase by Robert Louis Stevenson. Thus Strunk's 1918 recommendation:

Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that he make every word tell.

— "Elementary Principles of Composition", The Elements of Style

Strunk Jr. no longer has a comma in his name in the 1979 and later editions, due to the modernized style recommendation about punctuating such names.

The fourth edition of The Elements of Style (2000), published 54 years after Strunk's death, omits his stylistic advice about masculine pronouns: "unless the antecedent is or must be feminine". In its place, the following sentence has been added: "many writers find the use of the generic he or his to rename indefinite antecedents limiting or offensive." Further, the re-titled entry "They. He or She", in Chapter IV: Misused Words and Expressions, advises the writer to avoid an "unintentional emphasis on the masculine".

Components new to the fourth edition include a foreword by Roger Angell, stepson of E. B. White, an afterword by the American cultural commentator Charles Osgood, a glossary, and an index. Five years later, the fourth edition text was re-published as The Elements of Style Illustrated (2005), with illustrations by the designer Maira Kalman. This edition excludes the afterword by Osgood and restores the first edition chapter on spelling.

Reception

The Elements of Style was listed as one of the 100 best and most influential books written in English since 1923 by Time in its 2011 list. Upon its release, Charles Poor, writing for The New York Times, called it "a splendid trophy for all who are interested in reading and writing." American poet Dorothy Parker has, regarding the book, said:

If you have any young friends who aspire to become writers, the second-greatest favor you can do them is to present them with copies of The Elements of Style. The first-greatest, of course, is to shoot them now, while they’re happy.

Criticism of Strunk & White has largely focused on claims that it has a prescriptivist nature, or that it has become a general anachronism in the face of modern English usage.

In criticizing The Elements of Style, Geoffrey Pullum, professor of linguistics at the University of Edinburgh, and co-author of The Cambridge Grammar of the English Language (2002), said that:

The book's toxic mix of purism, atavism, and personal eccentricity is not underpinned by a proper grounding in English grammar. It is often so misguided that the authors appear not to notice their own egregious flouting of its own rules ... It's sad. Several generations of college students learned their grammar from the uninformed bossiness of Strunk and White, and the result is a nation of educated people who know they feel vaguely anxious and insecure whenever they write however or than me or was or which, but can't tell you why.

Pullum has argued, for example, that the authors misunderstood what constitutes the passive voice, and he criticized their proscription of established and unproblematic English usages, such as the split infinitive and the use of which in a restrictive relative clause. On Language Log, a blog about language written by linguists, he further criticized The Elements of Style for promoting linguistic prescriptivism and hypercorrection among Anglophones, and called it "the book that ate America's brain".

The Boston Globe's review described The Elements of Style Illustrated (2005), with illustrations by Maira Kalman, as an "aging zombie of a book ... a hodgepodge, its now-antiquated pet peeves jostling for space with 1970s taboos and 1990s computer advice".

In On Writing (2000, p. 11), Stephen King writes: "There is little or no detectable bullshit in that book. (Of course, it's short; at eighty-five pages it's much shorter than this one.) I'll tell you right now that every aspiring writer should read The Elements of Style. Rule 17 in the chapter titled Principles of Composition is 'Omit needless words.' I will try to do that here."

In 2011, Tim Skern remarked (perhaps equivocally) that The Elements of Style "remains the best book available on writing good English".

In 2013, Nevile Gwynne reproduced The Elements of Style in his work Gwynne's Grammar. Britt Peterson of the Boston Globe wrote that it was a "curious addition".

In 2016, the Open Syllabus Project lists The Elements of Style as the most frequently assigned text in US academic syllabuses, based on an analysis of 933,635 texts appearing in over 1 million syllabuses.

Editions

Strunk

• Elements of Style. Composed in 1918 and privately printed in 1919. 43 pages. OCLC 6589433.
• The Elements of Style. New York: Harcourt, Brace and Howe, 1920. 52-page publication of the original.

(Because the text of Strunk's original is now in the public domain and freely available on the Internet, publishers can and do reprint it in book form.)

Strunk & Edward A. Tenney

• The Elements and Practice of Composition. New York: Harcourt, Brace, 1935. Despite the new title, an expansion of (The) Elements of Style; 60 pages plus 47 "practice leaves". OCLC 781988921

Strunk & White

• The Elements of Style. New York: Macmillan, 1959. OCLC 878906498.
• The Elements of Style. 2nd ed. New York: Macmillan; London: Collier-Macmillan, 1972. ISBN 0024182605.
• The Elements of Style. 3rd ed. New York: Macmillan, 1988. ISBN 0024181900 (hardback), ISBN 0024182001 (paperback).
• The Elements of Style. 4th ed. S.l.: Longman, 1999. Hardback. ISBN 0-205-31342-6 (hardback). S.l.: Longman, 2000. ISBN 0-205-30902-X (paperback). With a foreword by Roger Angell.
• The Elements of Style Illustrated. With illustrations by Maira Kalman. Penguin, 2005. ISBN 1-594-20069-6 (hardback). Penguin, 2005. ISBN 9780910301961 (hardback). Penguin. ISBN 9780143112723 (paperback). Penguin, 2008. ISBN 9781439562635 (paperback).
• The Elements of Style. Fiftieth Anniversary Edition. New York: Pearson Longman, 2009. ISBN 0-205-63264-5. Contains the 4th ed. text; with a foreword by Charles Osgood.

Serial comma

From Wikipedia, the free encyclopedia

In English language punctuation, a serial comma, or series comma (also called an Oxford comma or Harvard comma), is a comma placed immediately after the penultimate term (i.e. before the coordinating conjunction [usually and or or]) in a series of three or more terms. For example, a list of three countries might be punctuated either as "France, Italy and Spain" (without the serial comma) or "France, Italy, and Spain" (with the serial comma).

Opinions among writers and editors differ on whether to use the serial comma, and usage also differs somewhat between regional varieties of English. British English allows constructions with or without this comma, while in American English it is common and sometimes even considered mandatory to use the comma. A majority of American style guides mandate use of the serial comma, including APA style, The Chicago Manual of Style, Garner's Modern American Usage, The MLA Style Manual, Strunk and White's Elements of Style and the U.S. Government Printing Office Style Manual. By contrast, the Associated Press Stylebook advises against it. In Canada, the stylebook published by The Canadian Press advises against it. Most British style guides do not mandate its use. The Economist Style Guide notes that most British writers only use it where necessary to avoid ambiguity. However, a few British style guides mandate it, most notably The Oxford Style Manual.

The Oxford Companion to the English Language notes that, "Usage varies as to the inclusion of a comma before and in the last item ... This practice is controversial and is known as the serial comma or Oxford comma, because it is part of the house style of Oxford University Press." There are cases in which the use of the serial comma can avoid ambiguity (see Resolving ambiguity) and also instances in which its use can introduce ambiguity (see Creating ambiguity).

Arguments for and against

Common arguments for consistent use of the serial comma:

1. Use of the comma is consistent with the conventional practice of the region.
2. It matches the spoken cadence of sentences better.
3. It can resolve ambiguity (see examples below).
4. Its use is consistent with other means of separating items in a list (for example, when semicolons are used to separate items, one is always included before the last item).
5. Its omission may suggest a stronger connection between the last two items in a series than actually exists.

Common arguments against consistent use of the serial comma:

1. Use of the comma is inconsistent with the conventional practice of the region.
2. It can introduce ambiguity.
3. Where space is at a premium, the comma adds unnecessary bulk to the text.

Many sources are against both systematic use and systematic avoidance of the serial comma, making recommendations in a more nuanced way.

Ambiguity

Resolving ambiguity

Omitting the serial comma may create ambiguity. Writers who normally avoid the serial comma often use one when it avoids ambiguity. Consider this apocryphal book dedication:

To my parents, Ayn Rand and God.

There is ambiguity about the writer's parentage, because "Ayn Rand and God" can be read as in apposition to my parents, leading the reader to believe that the writer claims Ayn Rand and God are the parents. A comma before and removes the ambiguity:

To my parents, Ayn Rand, and God.

But lists can also be written in other ways that eliminate the ambiguity without introducing the serial comma, such as by changing the word order or by using other punctuation, or none, to introduce or delimit them (though the emphasis may thereby be changed):

To God, Ayn Rand and my parents.

An example collected by Nielsen Hayden was found in a newspaper account of a documentary about Merle Haggard:

Among those interviewed were his two ex-wives, Kris Kristofferson and Robert Duvall.

A serial comma following "Kris Kristofferson" would help prevent this being understood as Kris Kristofferson and Robert Duvall being the ex-wives in question.

Another example is:

My usual breakfast is coffee, bacon and eggs and toast.

It is unclear whether the eggs are being grouped with the bacon or the toast. Adding a serial comma removes this ambiguity:

My usual breakfast is coffee, bacon and eggs, and toast.

Creating ambiguity

In some circumstances using the serial comma can create ambiguity. If the book dedication above is changed to

To my mother, Ayn Rand, and God

the serial comma after Ayn Rand creates ambiguity about the writer's mother because it uses punctuation identical to that used for an appositive phrase, leaving it unclear whether this is a list of three entities (1, my mother; 2, Ayn Rand; and 3, God) or of only two entities (1, my mother, who is Ayn Rand; and 2, God).

Unresolved ambiguity

The Times once published an unintentionally humorous description of a Peter Ustinov documentary, noting that "highlights of his global tour include encounters with Nelson Mandela, an 800-year-old demigod and a dildo collector". This would still be ambiguous if a serial comma were added, as Mandela could still be mistaken for a demigod, although he would be precluded from being a dildo collector.

Or consider

They went to Oregon with Betty, a maid, and a cook.

This is ambiguous because it is unclear whether "a maid" is an appositive describing Betty, or the second in a list of three people. On the other hand, removing the final comma:

They went to Oregon with Betty, a maid and a cook.

leaves the possibility that Betty is both a maid and a cook (with "a maid and a cook" read as a unit, in apposition to Betty). So in this case neither the serial-comma style nor the no-serial-comma style resolves the ambiguity. A writer who intends a list of three distinct people (Betty, maid, cook) may create an ambiguous sentence, regardless of whether the serial comma is adopted. Furthermore, if the reader is unaware of which convention is being used, both versions are always ambiguous.

These forms (among others) would remove the ambiguity:

• One person
  • They went to Oregon with Betty, who was a maid and a cook.
  • They went to Oregon with Betty, both a maid and a cook.
  • They went to Oregon with Betty (a maid and cook).
  • They went to Oregon with Betty, their maid and cook.
• Two people
  • They went to Oregon with Betty (a maid) and a cook.
  • They went to Oregon with Betty – a maid – and a cook.
  • They went to Oregon with Betty, a maid, and with a cook.
  • They went to Oregon with the maid Betty and a cook.
  • They went to Oregon with a cook and Betty, a maid.
• Three people
  • They went to Oregon with Betty, as well as a maid and a cook.
  • They went to Oregon with Betty and a maid and a cook.
  • They went to Oregon with Betty, one maid and a cook.
  • They went to Oregon with a maid, a cook, and Betty.
  • They went to Oregon with a maid, a cook and Betty.
  • They went with Betty to Oregon with a maid and a cook.

In general

• The list x, y and z is unambiguous if y and z cannot be read as in apposition to x.
• Equally, x, y, and z is unambiguous if y cannot be read as in apposition to x.
• If neither y nor y[,] and z can be read as in apposition to x, then both forms of the list are unambiguous; but if both y and y and z can be read as in apposition to x, then both forms of the list are ambiguous.
• x and y and z is unambiguous if x and y and y and z cannot both be grouped.

Ambiguities can often be resolved by the selective use of semicolons instead of commas; this is sometimes called the "super comma" function of semicolons.

Recommendations by style guides

Lynne Truss writes: "There are people who embrace the Oxford comma, and people who don't, and I'll just say this: never get between these people when drink has been taken."

Omitting a serial comma is often characterized as a journalistic style of writing, as contrasted with a more academic or formal style. Journalists typically do not use the serial comma, possibly for economy of space. In Australia, Canada and South Africa, the serial comma tends not to be used in non-academic publications unless its absence produces ambiguity.

It is important that usage within a document be consistent; inconsistent usage can seem unprofessional.

Mainly American style guides supporting mandatory or typical use

The United States Government Printing Office's Style Manual

"After each member within a series of three or more words, phrases, letters, or figures used with and, or, or nor." It notes that an age ("70 years 11 months 6 days") is not a series and should not take commas.

Wilson Follett's Modern American Usage: A Guide (Random House, 1981), pp. 397–401

"What, then, are the arguments for omitting the last comma? Only one is cogent – the saving of space. In the narrow width of a newspaper column this saving counts for more than elsewhere, which is why the omission is so nearly universal in journalism. But here or anywhere one must question whether the advantage outweighs the confusion caused by the omission. … The recommendation here is that [writers] use the comma between all members of a series, including the last two, on the common-sense ground that to do so will preclude ambiguities and annoyances at a negligible cost."

The Chicago Manual of Style, 16th edition (University of Chicago Press, 2010), paragraph 6.18

"When a conjunction joins the last two elements in a series of three or more, a comma … should appear before the conjunction. Chicago strongly recommends this widely practiced usage." In answer to a reader's query, The Chicago Manual of Style Online notes that their style guide has been recommending use of the serial comma ever since the first edition in 1906, but also qualifies this, saying "the serial comma is optional; some mainstream style guides (such as the Associated Press) don't use it. … there are times when using the comma (or omitting it) results in ambiguity, which is why it's best to stay flexible."

The Elements of Style (Strunk and White, 4th edition 1999), Rule 2

"In a series of three or more terms with a single conjunction, use a comma after each term except the last." This has been recommended in The Elements of Style since the first edition by Strunk in 1918.

The American Medical Association Manual of Style, 9th edition (1998) Chapter 6.2.1

"Use a comma before the conjunction that precedes the last term in a series."

The Publication Manual of the American Psychological Association, 6th edition (2010) Chapter 4.03

"Use a comma between elements (including before and and or) in a series of three or more items."

The CSE Manual for Authors, Editors, and Publishers (Council of Science Editors, 7th edition, 2006), Section 5.3.3.1

"To separate the elements (words, phrases, clauses) of a simple series of more than 2 elements, including a comma before the closing 'and' or 'or' (the so-called serial comma). Routine use of the serial comma helps to prevent ambiguity."

Garner's Modern English Usage, 4th edition (Oxford University Press, 2016), "Punctuation," § D, "Comma", p. 748

"Whether to include the serial comma has sparked many arguments. But it's easily answered in favor of inclusion because omitting the final comma may cause ambiguities, whereas including it never will – e.g.: 'A and B, C and D, E and F[,] and G and H'."

MLA Style Manual and Guide to Scholarly Publishing (Modern Language Association 2008), paragraph 3.4.2.b

"Use commas to separate words, phrases, and clauses in a series."

AAMT Book of Style for Medical Transcription

"Medical transcriptionists use the serial comma when two medications or diagnoses must be seen as separate; i.e., for 'The patient was on Aspirin, Coversyl, and Dilaudid', the comma is used before 'and' to avoid the reader erroneously thinking that Coversyl and Dilaudid must be taken together."

AIP Style Manual, American Institute of Physics, fourth edition, 1990

"A comma goes before 'and' or 'or' in a series of three or more: Sn, K, Na, and Li lines are invisible."

Plain English Handbook, Revised Edition (McCormick-Mathers Publishing Co., 1959), § 483, p. 78

"Use commas to separate the items in a series of words, phrases, or short clauses:

    The farmer sold corn, hay, oats, potatoes, and wheat."

Mainly British style guides supporting mandatory or typical use

The Oxford Style Manual, 2002

"For a century it has been part of OUP style to retain or impose this last serial (or series) comma consistently, … but it is commonly used by many other publishers both here and abroad, and forms a routine part of style in US and Canadian English. … Given that the final comma is sometimes necessary to prevent ambiguity, it is logical to impose it uniformly, so as to obviate the need to pause and gauge each enumeration on the likelihood of its being misunderstood – especially since that likelihood is often more obvious to the reader than the writer."

MHRA Style Guide (Modern Humanities Research Association), 3rd edition (2013)

"In an enumeration of three or more items, the practice in MHRA journals is to insert commas after all but the last item, to give equal weight to each enumerated element.  … The conjunctions and and or without a preceding comma are understood as linking the parts of a single enumerated element"

But paragraph 5.1 says "The comma after the penultimate item may be omitted in books published by the MHRA, as long as the sense is clear."

Mainly British style guides opposing typical use

The Times style manual

"Avoid the so-called Oxford comma; say 'he ate bread, butter and jam' rather than 'he ate bread, butter, and jam'."

The Economist Style Guide

"Do not put a comma before and at the end of a sequence of items unless one of the items includes another and. Thus 'The doctor suggested an aspirin, half a grapefruit and a cup of broth. But he ordered scrambled eggs, whisky and soda, and a selection from the trolley.'"

"Sometimes it is essential: compare 'I dedicate this book to my parents, Martin Amis, and JK Rowling' with 'I dedicate this book to my parents, Martin Amis and JK Rowling'."

University of Oxford Public Affairs Directorate Writing and Style Guide

"Note that there is generally no comma between the penultimate item and 'and'/'or' – this is sometimes referred to as the 'Oxford comma'. However, it is essential to use an Oxford comma if required to prevent ambiguity."

Mainly British style guides that consider it generally unnecessary but discretionary

The Guardian Style Guide

"A comma before the final 'and' in lists: straightforward ones (he ate ham, eggs and chips) do not need one, but sometimes it can help the reader (he ate cereal, kippers, bacon, eggs, toast and marmalade, and tea)."

The Cambridge Guide to English Usage

"In British practice there's an Oxford/Cambridge divide … In Canada and Australia the serial comma is recommended only to prevent ambiguity or misreading."

Fowler's Dictionary of Modern English Usage, 4th edition, 2015

"The so-called 'Oxford comma' is an optional comma that follows the penultimate item in a list of three or more items and precedes the word 'and' ... The general rule is that it should be used consistently or not at all ... However, the Oxford comma can help to avoid ambiguity, ... and it is sometimes helpful to the reader to use an isolated serial comma for clarification, even when the convention has not been adopted in the rest of the text."

New Hart's Rules, 2014

"The general rule is that one style or the other should be used consistently. However, the last comma can serve to resolve ambiguity, particularly when any of the items are compound terms joined by a conjunction, and it is sometimes helpful to the reader to use an isolated serial comma for clarification even when the convention has not been adopted in the rest of the text."

Mainly American style guides opposing typical use

The New York Times stylebook

"In general, do not use a comma before and or or in a series."

The AP Stylebook

"Use commas to separate elements in a series, but do not put a comma before the conjunction in a simple series. […] Put a comma before the concluding conjunction in a series, however, if an integral element of the series requires a conjunction: I had orange juice, toast, and ham and eggs for breakfast. Use a comma also before the concluding conjunction in a complex series of phrases: The main points to consider are whether the athletes are skillful enough to compete, whether they have the stamina to endure the training, and whether they have the proper mental attitude. In the United States, the choice is between journalistic style (no serial comma) and "literary" style (with serial comma); consistent use of the serial comma is usually recommended for college writing."

Australian style guides opposing typical use

The Australian Government Publishing Service's Style Manual for Authors, Editors and Printers

"A comma is used before and, or, or etc. in a list when its omission might either give rise to ambiguity or cause the last word or phrase to be construed with a preposition in the preceding phrase. … Generally, however, a comma is not used before and, or or etc. in a list."

Canadian style guides opposing typical use

Public Works and Government Services Canada Translation Bureau's The Canadian Style: A Guide to Writing and Editing

"Items in a series may be separated by commas:

Complacency, urbanity, sentimentality, whimsicality

They may also be linked by co-ordinating conjunctions such as and or or:

economists, sociologists or political scientists

the good, the bad and the ugly

Opinions differ on whether and when a comma should be inserted before the final and or or in a sequence. In keeping with the general trend toward less punctuation, the final comma is best omitted where clarity permits, unless there is a need to emphasize the last element in a series."

Individual disputes

Maine labor dispute

In the U.S. state of Maine, the lack of a serial comma became the deciding factor in a $13 million lawsuit filed in 2014 that was eventually settled for $5 million in 2017. As the U.S. appeals judge David J. Barron wrote, "For want of a comma, we have this case."

In the case known as O'Connor v. Oakhurst Dairy, a federal court of appeals was required to interpret a statute under which the "canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution" of certain goods were activities exempted from the general requirement of overtime pay; the question was whether this list included the distribution of the goods, or only the packing of the goods for distribution. The lack of a comma suggested one meaning, while the omission of the conjunction or before "packing" and the fact that the Maine Legislative Drafting Manual advised against use of the serial comma suggested another. It said "Although authorities on punctuation may differ, when drafting Maine law or rules, don’t use a comma between the penultimate and the last item of a series." In addition to the absence of a comma, the fact that the word chosen was "distribution" rather than "distributing" was also a consideration, as was the question of whether it would be reasonable to consider the list to be an asyndetic list (a list in which the coordinating conjunction is absent). Truck drivers demanded overtime pay, and the defense conceded that the expression was ambiguous, but said it should be interpreted as exempting distribution activity from overtime pay. The district court agreed with the defense and held that "distribution" was an exempt activity. On appeal, however, the First Circuit decided that the sentence was ambiguous and "because, under Maine law, ambiguities in the state's wage and hour laws must be construed liberally in order to accomplish their remedial purpose", adopted the drivers' narrower reading of the exemption and ruled that those who distributed the goods were entitled to overtime pay. Oakhurst Dairy settled the case by paying $5 million to the drivers, and the phrase in the law in question was later changed to use serial semicolons and "distributing" – resulting in "canning; processing; preserving; freezing; drying; marketing; storing; packing for shipment; or distributing".

The opinion in the case said that 43 of the 50 U.S. states had mandated the use of a serial comma and that both chambers of the federal congress had warned against omitting it, in the words of the U.S. House Legislative Counsel's Manual on Drafting Style, "to prevent any misreading that the last item is part of the preceding one"; only seven states "either do not require or expressly prohibited the use of the serial comma".

British 50p Brexit coin

The new United Kingdom 50p coin commemorating Brexit day, 31 January 2020, was minted with the phrase "Peace, prosperity and friendship with all nations". English novelist Sir Philip Pullman and others criticized the omission of the Oxford comma, whilst others claimed it was an Americanism and not required in this instance.

Semantic network

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Semantic_network

A semantic network, or frame network is a knowledge base that represents semantic relations between concepts in a network. This is often used as a form of knowledge representation. It is a directed or undirected graph consisting of vertices, which represent concepts, and edges, which represent semantic relations between concepts, mapping or connecting semantic fields. A semantic network may be instantiated as, for example, a graph database or a concept map.

Typical standardized semantic networks are expressed as semantic triples.

Semantic networks are used in natural language processing applications such as semantic parsing and word-sense disambiguation.

History

Examples of the use of semantic networks in logic, directed acyclic graphs as a mnemonic tool, dates back centuries. The earliest documented use being the Greek philosopher Porphyry's commentary on Aristotle's categories in the third century AD.

In computing history, "Semantic Nets" for the propositional calculus were first implemented for computers by Richard H. Richens of the Cambridge Language Research Unit in 1956 as an "interlingua" for machine translation of natural languages. Although the importance of this work and the CLRU was only belatedly realized.

Semantic networks were also independently implemented by Robert F. Simmons  and Sheldon Klein, using the first order predicate calculus as a base, after being inspired by a demonstration of Victor Yngve. The "line of research was originated by the first President of the Association [Association for Computational Linguistics], Victor Yngve, who in 1960 had published descriptions of algorithms for using a phrase structure grammar to generate syntactically well-formed nonsense sentences. Sheldon Klein and I about 1962-1964 were fascinated by the technique and generalized it to a method for controlling the sense of what was generated by respecting the semantic dependencies of words as they occurred in text." Other researchers, most notably M. Ross Quillian and others at System Development Corporation helped contribute to their work in the early 1960s as part of the SYNTHEX project. It's from these publications at SDC that most modern derivatives of the term "semantic network" cite as their background. Later prominent works were done by Allan M. Collins and Quillian (e.g., Collins and Quillian; Collins and Loftus Quillian). Still later in 2006, Hermann Helbig fully described MultiNet.

In the late 1980s, two Netherlands universities, Groningen and Twente, jointly began a project called Knowledge Graphs, which are semantic networks but with the added constraint that edges are restricted to be from a limited set of possible relations, to facilitate algebras on the graph. In the subsequent decades, the distinction between semantic networks and knowledge graphs was blurred. In 2012, Google gave their knowledge graph the name Knowledge Graph.

The Semantic Link Network was systematically studied as a social semantics networking method. Its basic model consists of semantic nodes, semantic links between nodes, and a semantic space that defines the semantics of nodes and links and reasoning rules on semantic links. The systematic theory and model was published in 2004. This research direction can trace to the definition of inheritance rules for efficient model retrieval in 1998 and the Active Document Framework ADF. Since 2003, research has developed toward social semantic networking. This work is a systematic innovation at the age of the World Wide Web and global social networking rather than an application or simple extension of the Semantic Net (Network). Its purpose and scope are different from that of the Semantic Net (or network). The rules for reasoning and evolution and automatic discovery of implicit links play an important role in the Semantic Link Network. Recently it has been developed to support Cyber-Physical-Social Intelligence. It was used for creating a general summarization method. The self-organised Semantic Link Network was integrated with a multi-dimensional category space to form a semantic space to support advanced applications with multi-dimensional abstractions and self-organised semantic links  It has been verified that Semantic Link Network play an important role in understanding and representation through text summarisation applications.  To investigate special social semantics, competition relation and symbiosis relation as well as their roles in evolving society were studied in the emerging topic: Cyber-Physical-Social Intelligence 

More specialized forms of semantic networks has been created for specific use. For example, in 2008, Fawsy Bendeck's PhD thesis formalized the Semantic Similarity Network (SSN) that contains specialized relationships and propagation algorithms to simplify the semantic similarity representation and calculations.

Basics of semantic networks

A semantic network is used when one has knowledge that is best understood as a set of concepts that are related to one another.

Most semantic networks are cognitively based. They also consist of arcs and nodes which can be organized into a taxonomic hierarchy. Semantic networks contributed ideas of spreading activation, inheritance, and nodes as proto-objects.

Examples

In Lisp

The following code shows an example of a semantic network in the Lisp programming language using an association list.

(setq *database*
'((canary  (is-a bird)
           (color yellow)
           (size small))
  (penguin (is-a bird)
           (movement swim))
  (bird    (is-a vertebrate)
           (has-part wings)
           (reproduction egg-laying))))

To extract all the information about the "canary" type, one would use the assoc function with a key of "canary".

WordNet

An example of a semantic network is WordNet, a lexical database of English. It groups English words into sets of synonyms called synsets, provides short, general definitions, and records the various semantic relations between these synonym sets. Some of the most common semantic relations defined are meronymy (A is a meronym of B if A is part of B), holonymy (B is a holonym of A if B contains A), hyponymy (or troponymy) (A is subordinate of B; A is kind of B), hypernymy (A is superordinate of B), synonymy (A denotes the same as B) and antonymy (A denotes the opposite of B).

WordNet properties have been studied from a network theory perspective and compared to other semantic networks created from Roget's Thesaurus and word association tasks. From this perspective the three of them are a small world structure.

Other examples

It is also possible to represent logical descriptions using semantic networks such as the existential graphs of Charles Sanders Peirce or the related conceptual graphs of John F. Sowa. These have expressive power equal to or exceeding standard first-order predicate logic. Unlike WordNet or other lexical or browsing networks, semantic networks using these representations can be used for reliable automated logical deduction. Some automated reasoners exploit the graph-theoretic features of the networks during processing.

Other examples of semantic networks are Gellish models. Gellish English with its Gellish English dictionary, is a formal language that is defined as a network of relations between concepts and names of concepts. Gellish English is a formal subset of natural English, just as Gellish Dutch is a formal subset of Dutch, whereas multiple languages share the same concepts. Other Gellish networks consist of knowledge models and information models that are expressed in the Gellish language. A Gellish network is a network of (binary) relations between things. Each relation in the network is an expression of a fact that is classified by a relation type. Each relation type itself is a concept that is defined in the Gellish language dictionary. Each related thing is either a concept or an individual thing that is classified by a concept. The definitions of concepts are created in the form of definition models (definition networks) that together form a Gellish Dictionary. A Gellish network can be documented in a Gellish database and is computer interpretable.

SciCrunch is a collaboratively edited knowledge base for scientific resources. It provides unambiguous identifiers (Research Resource IDentifiers or RRIDs) for software, lab tools etc. and it also provides options to create links between RRIDs and from communities.

Another example of semantic networks, based on category theory, is ologs. Here each type is an object, representing a set of things, and each arrow is a morphism, representing a function. Commutative diagrams also are prescribed to constrain the semantics.

In the social sciences people sometimes use the term semantic network to refer to co-occurrence networks. The basic idea is that words that co-occur in a unit of text, e.g. a sentence, are semantically related to one another. Ties based on co-occurrence can then be used to construct semantic networks.

Software tools

There are also elaborate types of semantic networks connected with corresponding sets of software tools used for lexical knowledge engineering, like the Semantic Network Processing System (SNePS) of Stuart C. Shapiro or the MultiNet paradigm of Hermann Helbig, especially suited for the semantic representation of natural language expressions and used in several NLP applications.

Semantic networks are used in specialized information retrieval tasks, such as plagiarism detection. 

They provide information on hierarchical relations in order to employ semantic compression to reduce language diversity and enable the system to match word meanings, independently from sets of words used.

The Knowledge Graph proposed by Google in 2012 is actually an application of semantic network in search engine.

Modeling multi-relational data like semantic networks in low-dimensional spaces through forms of embedding has benefits in expressing entity relationships as well as extracting relations from mediums like text. There are many approaches to learning these embeddings, notably using Bayesian clustering frameworks or energy-based frameworks, and more recently, TransE (NIPS 2013). Applications of embedding knowledge base data include Social network analysis and Relationship extraction.