Fluctuation theorem

From Wikipedia, the free encyclopedia

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

The fluctuation theorem (FT), which originated from statistical mechanics, deals with the relative probability that the entropy of a system which is currently away from thermodynamic equilibrium (i.e., maximum entropy) will increase or decrease over a given amount of time. While the second law of thermodynamics predicts that the entropy of an isolated system should tend to increase until it reaches equilibrium, it became apparent after the discovery of statistical mechanics that the second law is only a statistical one, suggesting that there should always be some nonzero probability that the entropy of an isolated system might spontaneously decrease; the fluctuation theorem precisely quantifies this probability.

Statement

Roughly, the fluctuation theorem relates to the probability distribution of the time-averaged irreversible entropy production, denoted ${\displaystyle {\overline{\mathrm{\Sigma }}}_t}$. The theorem states that, in systems away from equilibrium over a finite time t, the ratio between the probability that ${\displaystyle {\overline{\mathrm{\Sigma }}}_t}$ takes on a value A and the probability that it takes the opposite value, −A, will be exponential in At. In other words, for a finite non-equilibrium system in a finite time, the FT gives a precise mathematical expression for the probability that entropy will flow in a direction opposite to that dictated by the second law of thermodynamics.

Mathematically, the FT is expressed as:

${\displaystyle \frac{Pr({\overline{\mathrm{\Sigma }}}_t=A)}{Pr({\overline{\mathrm{\Sigma }}}_t=-A)}=e^{At}.}$

This means that as the time or system size increases (since ${\displaystyle \mathrm{\Sigma }}$ is extensive), the probability of observing an entropy production opposite to that dictated by the second law of thermodynamics decreases exponentially. The FT is one of the few expressions in non-equilibrium statistical mechanics that is valid far from equilibrium.

Note that the FT does not state that the second law of thermodynamics is wrong or invalid. The second law of thermodynamics is a statement about macroscopic systems. The FT is more general. It can be applied to both microscopic and macroscopic systems. When applied to macroscopic systems, the FT is equivalent to the Second Law of Thermodynamics.

History

The FT was first proposed and tested using computer simulations, by Denis Evans, E.G.D. Cohen and Gary Morriss in 1993. The first derivation was given by Evans and Debra Searles in 1994. Since then, much mathematical and computational work has been done to show that the FT applies to a variety of statistical ensembles. The first laboratory experiment that verified the validity of the FT was carried out in 2002. In this experiment, a plastic bead was pulled through a solution by a laser. Fluctuations in the velocity were recorded that were opposite to what the second law of thermodynamics would dictate for macroscopic systems. In 2020, observations at high spatial and spectral resolution of the solar photosphere have shown that solar turbulent convection satisfies the symmetries predicted by the fluctuation relation at a local level.

Second law inequality

A simple consequence of the fluctuation theorem given above is that if we carry out an arbitrarily large ensemble of experiments from some initial time t=0, and perform an ensemble average of time averages of the entropy production, then an exact consequence of the FT is that the ensemble average cannot be negative for any value of the averaging time t:

${\displaystyle ⟨{\overline{\mathrm{\Sigma }}}_t⟩\ge 0,\mathrm{\forall }t.}$

This inequality is called the second law inequality. This inequality can be proved for systems with time dependent fields of arbitrary magnitude and arbitrary time dependence.

It is important to understand what the second law inequality does not imply. It does not imply that the ensemble averaged entropy production is non-negative at all times. This is untrue, as consideration of the entropy production in a viscoelastic fluid subject to a sinusoidal time dependent shear rate shows (e.g., water waves). In this example the ensemble average of the time integral of the entropy production over one cycle is however nonnegative - as expected from the second law inequality.

Nonequilibrium partition identity

Another remarkably simple and elegant consequence of the fluctuation theorem is the so-called "nonequilibrium partition identity" (NPI):

${\displaystyle ⟨\exp [-{\overline{\mathrm{\Sigma }}}_{t}t]⟩=1,\text{ for all }t.}$

Thus in spite of the Second Law Inequality which might lead you to expect that the average would decay exponentially with time, the exponential probability ratio given by the FT exactly cancels the negative exponential in the average above leading to an average which is unity for all time.

Implications

There are many important implications from the fluctuation theorem. One is that small machines (such as nanomachines or even mitochondria in a cell) will spend part of their time actually running in "reverse". What we mean by "reverse" is that it is possible to observe that these small molecular machines are able to generate work by taking heat from the environment. This is possible because there exists a symmetry relation in the work fluctuations associated with the forward and reverse changes a system undergoes as it is driven away from thermal equilibrium by the action of an external perturbation, which is a result predicted by the Crooks fluctuation theorem. The environment itself continuously drives these molecular machines away from equilibrium and the fluctuations it generates over the system are very relevant because the probability of observing an apparent violation of the second law of thermodynamics becomes significant at this scale.

This is counterintuitive because, from a macroscopic point of view, it would describe complex processes running in reverse. For example, a jet engine running in reverse, taking in ambient heat and exhaust fumes to generate kerosene and oxygen. Nevertheless the size of such a system makes this observation almost impossible to occur. Such a process is possible to be observed microscopically because, as it has been stated above, the probability of observing a "reverse" trajectory depends on system size and is significant for molecular machines if an appropriate measurement instrument is available. This is the case with the development of new biophysical instruments such as the optical tweezers or the atomic force microscope. Crooks fluctuation theorem has been verified through RNA folding experiments.

Dissipation function

Strictly speaking the fluctuation theorem refers to a quantity known as the dissipation function. In thermostatted nonequilibrium states that are close to equilibrium, the long time average of the dissipation function is equal to the average entropy production. However the FT refers to fluctuations rather than averages. The dissipation function is defined as,

${\displaystyle {\mathrm{\Omega }}_t(\mathrm{\Gamma })={\int }_0^{t}ds\mathrm{\Omega }(\mathrm{\Gamma };s)\equiv \ln \left[\frac{f(\mathrm{\Gamma },0)}{f(\mathrm{\Gamma }(t),0)}\right]+\frac{\mathrm{\Delta }Q(\mathrm{\Gamma };t)}{kT}}$

where k is Boltzmann's constant, ${\displaystyle f(\mathrm{\Gamma },0)}$ is the initial (t = 0) distribution of molecular states ${\displaystyle \mathrm{\Gamma }}$, and ${\displaystyle \mathrm{\Gamma }(t)}$ is the molecular state arrived at after time t, under the exact time reversible equations of motion. ${\displaystyle f(\mathrm{\Gamma }(t),0)}$ is the INITIAL distribution of those time evolved states.

Note: in order for the FT to be valid we require that ${\displaystyle f(\mathrm{\Gamma }(t),0)\ne 0,\mathrm{\forall }\mathrm{\Gamma }(0)}$. This condition is known as the condition of ergodic consistency. It is widely satisfied in common statistical ensembles - e.g. the canonical ensemble.

The system may be in contact with a large heat reservoir in order to thermostat the system of interest. If this is the case ${\displaystyle \mathrm{\Delta }Q(t)}$ is the heat lost to the reservoir over the time (0,t) and T is the absolute equilibrium temperature of the reservoir - see Williams et al., Phys Rev E70, 066113(2004). With this definition of the dissipation function the precise statement of the FT simply replaces entropy production with the dissipation function in each of the FT equations above.

Example: If one considers electrical conduction across an electrical resistor in contact with a large heat reservoir at temperature T, then the dissipation function is

${\displaystyle \mathrm{\Omega }=-J{F}_{e}V/kT}$

the total electric current density J multiplied by the voltage drop across the circuit, ${\displaystyle F_e}$, and the system volume V, divided by the absolute temperature T, of the heat reservoir times Boltzmann's constant. Thus the dissipation function is easily recognised as the Ohmic work done on the system divided by the temperature of the reservoir. Close to equilibrium the long time average of this quantity is (to leading order in the voltage drop), equal to the average spontaneous entropy production per unit time. However, the fluctuation theorem applies to systems arbitrarily far from equilibrium where the definition of the spontaneous entropy production is problematic.

Relation to Loschmidt's paradox

The second law of thermodynamics, which predicts that the entropy of an isolated system out of equilibrium should tend to increase rather than decrease or stay constant, stands in apparent contradiction with the time-reversible equations of motion for classical and quantum systems. The time reversal symmetry of the equations of motion show that if one films a given time dependent physical process, then playing the movie of that process backwards does not violate the laws of mechanics. It is often argued that for every forward trajectory in which entropy increases, there exists a time reversed anti trajectory where entropy decreases, thus if one picks an initial state randomly from the system's phase space and evolves it forward according to the laws governing the system, decreasing entropy should be just as likely as increasing entropy. It might seem that this is incompatible with the second law of thermodynamics which predicts that entropy tends to increase. The problem of deriving irreversible thermodynamics from time-symmetric fundamental laws is referred to as Loschmidt's paradox.

The mathematical derivation of the fluctuation theorem and in particular the second law inequality shows that, for a nonequilibrium process, the ensemble averaged value for the dissipation function will be greater than zero. This result requires causality, i.e. that cause (the initial conditions) precede effect (the value taken on by the dissipation function). This is clearly demonstrated in section 6 of that paper, where it is shown how one could use the same laws of mechanics to extrapolate backwards from a later state to an earlier state, and in this case the fluctuation theorem would lead us to predict the ensemble average dissipation function to be negative, an anti-second law. This second prediction, which is inconsistent with the real world, is obtained using an anti-causal assumption. That is to say that effect (the value taken on by the dissipation function) precedes the cause (here the later state has been incorrectly used for the initial conditions). The fluctuation theorem shows how the second law is a consequence of the assumption of causality. When we solve a problem we set the initial conditions and then let the laws of mechanics evolve the system forward in time, we don't solve problems by setting the final conditions and letting the laws of mechanics run backwards in time.

Summary

The fluctuation theorem is of fundamental importance to non-equilibrium statistical mechanics. The FT (together with the universal causation proposition) gives a generalisation of the second law of thermodynamics which includes as a special case, the conventional second law. It is then easy to prove the Second Law Inequality and the NonEquilibrium Partition Identity. When combined with the central limit theorem, the FT also implies the Green-Kubo relations for linear transport coefficients, close to equilibrium. The FT is however, more general than the Green-Kubo Relations because unlike them, the FT applies to fluctuations far from equilibrium. In spite of this fact, scientists have not yet been able to derive the equations for nonlinear response theory from the FT.

The FT does not imply or require that the distribution of time averaged dissipation be Gaussian. There are many examples known where the distribution of time averaged dissipation is non-Gaussian and yet the FT (of course) still correctly describes the probability ratios.

Lastly the theoretical constructs used to prove the FT can be applied to nonequilibrium transitions between two different equilibrium states. When this is done the so-called Jarzynski equality or nonequilibrium work relation, can be derived. This equality shows how equilibrium free energy differences can be computed or measured (in the laboratory), from nonequilibrium path integrals. Previously quasi-static (equilibrium) paths were required.

The reason why the fluctuation theorem is so fundamental is that its proof requires so little. It requires:

• knowledge of the mathematical form of the initial distribution of molecular states,
• that all time evolved final states at time t, must be present with nonzero probability in the distribution of initial states (t = 0) - the so-called condition of ergodic consistency and,
• an assumption of time reversal symmetry.

In regard to the latter "assumption", while the equations of motion of quantum dynamics may be time-reversible, quantum processes are nondeterministic by nature. What state a wave function collapses into cannot be predicted mathematically, and further the unpredictability of a quantum system comes not from the myopia of an observer’s perception, but on the intrinsically nondeterministic nature of the system itself.

In physics, the laws of motion of classical mechanics exhibit time reversibility, as long as the operator π reverses the conjugate momenta of all the particles of the system, i.e. ${\displaystyle \mathbf{p}\to \mathbf{-}\mathbf{p}}$ (T-symmetry).

In quantum mechanical systems, however, the weak nuclear force is not invariant under T-symmetry alone; if weak interactions are present reversible dynamics are still possible, but only if the operator π also reverses the signs of all the charges and the parity of the spatial co-ordinates (C-symmetry and P-symmetry). This reversibility of several linked properties is known as CPT symmetry.

Thermodynamic processes can be reversible or irreversible, depending on the change in entropy during the process.

Elderly care

From Wikipedia, the free encyclopedia

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

An old man at a nursing home in Norway

Elderly care, or simply eldercare (also known in parts of the English-speaking world as aged care), serves the needs of old adults. It encompasses assisted living, adult daycare, long-term care, nursing homes (often called residential care), hospice care, and home care.

Elderly care emphasizes the social and personal requirements of senior citizens who wish to age with dignity while needing assistance with daily activities and with healthcare. Much elderly care is unpaid.

Elderly care includes a broad range of practices and institutions, as there is a wide variety of elderly care needs and cultural perspectives on the elderly throughout the world.

Cultural and geographic differences

A nurse at a nursing home in Norway

The form of care provided for older adults varies greatly by country and even region, and is changing rapidly. Older people worldwide consume the most health spending of any age group. There is also an increasingly large proportion of older people worldwide, especially in developing nations with continued pressure to limit fertility and shrink families.

Traditionally, care for older adults has been the responsibility of family members and was provided within the extended family home. Increasingly in modern societies, care is now provided by state or charitable institutions. The reasons for this change include shrinking families, longer life expectancy and geographical dispersion of families. Although these changes have affected European and North American countries first, they are now increasingly affecting Asian countries.

In most western countries, care facilities for older adults are residential family care homes, freestanding assisted living facilities, nursing homes, and continuing care retirement communities (CCRCs). A family care home is a residential home with support and supervisory personnel by an agency, organization, or individual that provides room and board, personal care and habilitation services in a family environment for at least two and no more than six persons.

Due to the wide variety of elderly care needs and cultural perspectives on the elderly, there is a broad range of practices and institutions across different parts of the world. For example, in many Asian countries whereby younger generations often care for the elderly due to societal norms, government-run elderly care is seldom used in developing countries throughout Asia due to a lack of sufficient taxation necessary to provide an adequate standard of care, whilst privately-run elderly care in developing countries throughout Asia is relatively uncommon due to the stigma of exhibiting insufficient filial piety, having a relatively relaxed work–life interface and insufficient funding from family to pay for privately-run elderly care. However, institutional elderly care is increasingly adopted across various Asian societies, as the work–life interface becomes more constrained and people with increasing incomes being able to afford the cost of elderly care.

Gender discrepancies in caregivers

According to Family Caregiver Alliance, the majority of family caregivers are women:

"Many studies have looked at the role of women as family caregivers. Although not all have addressed gender issues and caregiving specifically, the results are still generalizable [sic] to

• Estimates of the age of family or informal caregivers who are women range from 59% to 75%.
• The average caregiver is age 46, female, married and worked outside the home earning an annual income of $35,000.
• Although men also provide assistance, female caregivers may spend as much as 50% more time providing care than male caregivers."

In developed nations

Australia

Total employment in residential care services in Australia (thousands of people) since 1984

Aged care in Australia is designed to make sure that every Australian can contribute as much as possible towards their cost of care, depending on their individual income and assets. That means that residents pay only what they can afford, and the Commonwealth government pays what the residents cannot pay. An Australian statutory authority, the Productivity Commission, conducted a review of aged care commencing in 2010 and reporting in 2011. The review concluded that approximately 80% of care for older Australians is informal care provided by family, friends and neighbours. Around a million people received government-subsidised aged care services, most of these received low-level community care support, with 160,000 people in permanent residential care. Expenditure on aged care by all governments in 2009-10 was approximately $11 billion.

The need to increase the level of care, and known weaknesses in the care system (such as skilled workforce shortages and rationing of available care places), led several reviews in the 2000s to conclude that Australia's aged care system needs reform. This culminated in the 2011 Productivity Commission report and subsequent reform proposals. In accordance with the Living Longer, Living Better amendments of 2013, assistance is provided in accordance with assessed care needs, with additional supplements available for people experiencing homelessness, dementia and veterans.

Australian Aged Care is often considered complicated due to various state and federal funding. Furthermore, there are many acronyms that customers need to be aware of, including ACAT, ACAR, NRCP, HACC, CACP, EACH, EACH-D and CDC (Consumer Directed Care) to name a few.

Canada

Private for-profit and not-for-profit facilities exist in Canada, but due to cost factors, some provinces operate or subsidize public facilities run by the provincial Ministry of Health. In public care homes, elderly Canadians may pay for their care on a sliding scale, based on annual income. The scale that they are charged on depends on whether they are considered for "Long Term Care" or "Assisted Living." For example, in January 2010, seniors living in British Columbia's government-subsidized "Long Term Care" (also called "Residential Care") started paying 80% of their after-tax income unless their after-tax income is less than $16,500. The "Assisted Living" tariff is calculated more simply as 70% of the after-tax income. As seen in Ontario, there are waiting lists for many long-term care homes, so families may need to resort to hiring home healthcare or paying to stay in a private retirement home.

United Kingdom

Care for the elderly in the UK has traditionally been funded by the state, but it is increasingly rationed, according to a joint report by the King's Fund and Nuffield Trust, as the cost of care to the nation rises. People who have minimal savings or other assets are provided with care either in their own home (from visiting carers) or by moving to a residential care home or nursing home. Larger numbers of old people need help because of an aging population and medical advances increasing life expectancy, but less is being paid out by the government to help them. A million people who need care get neither formal nor informal help.

A growing number of retirement communities, retirement villages or sheltered housing in the UK also offer an alternative to care homes but only for those with simple care needs. Extra Care housing provision can be suitable for older people with more complex needs. These models allow older people to live independently in a residential community or housing complex with other older people, helping to combat problems common amongst older people such as isolation. In these communities, residents may access shared services, amenities, and access care services if required.

In general, retirement communities are privately owned and operated, representing a shift from a ‘care as service’ to ‘care as business’ model. Some commercially operated villages have come under scrutiny for a lack of transparency over exit fees or ‘event fees’. It has been noted, however, that paying less now and more later may suit ‘an equity-rich, yet cash-poor, generation of British pensioners.’

Although most retirement village operators are run for profit, there are some charitable organisations in the space: for example, the ExtraCare Charitable Trust, which operates 14 retirement villages mostly in the Midlands, is a registered charity. Charities may derive additional funding from sources such as statutory agencies, charity appeals, legacies, and income from charity shops. Surplus funds are used to support residents' housing, health and well-being programmes, and for the development of new villages to meet growing national demand.

Extra Care housing usually involves provision of:

• Purpose-built, accessible housing design
• Safety and security e.g. controlled entry to the building
• Fully self-contained properties, where occupants have their own front doors, and legal status as tenants with security of tenure
• Tenants have the right to control who enters their home
• Office space for use by staff serving the scheme (and sometimes the wider community)
• Some communal spaces and facilities
• Access to care and support services 24 hours per day
• Community alarms and other assistive technologies.

United States

"Old Ladies Home" (sic) in Toledo, Ohio, 1895

According to the United States Department of Health and Human Services, the older population—persons 65 years or older—numbered 39.6 million in 2009. They represented 12.9% of the U.S. population, about one in every eight Americans. By 2030, there will be about 72.1 million older persons, more than twice their number in 2000. People aged over 65 years represented 12.4% of the population in the year 2000, but that is expected to grow to be 19% of the population by 2030. This means there will be more demand for elderly care facilities in the coming years. There were more than 36,000 assisted living facilities in the United States in 2009, according to the Assisted Living Federation of America. More than 1 million senior citizens are served by these assisted living facilities.

Last-year-of-life expenses represent 22% of all medical spending in the United States, 26% of all Medicare spending, 18% of all non-Medicare spending, and 25% of all Medicaid spending for the poor. A November 2020 study by the West Health Policy Center stated that more than 1.1 million senior citizens in the U.S. Medicare program are expected to die prematurely over the next decade because they will be unable to afford their prescription medications, requiring an additional $17.7 billion to be spent annually on avoidable medical costs due to health complications.

In the United States, most of the large multi-facility providers are publicly owned and managed as for-profit businesses. However, there are exceptions; the largest operator in the US is the Evangelical Lutheran Good Samaritan Society, a not-for-profit organization that manages 6,531 beds in 22 states, according to a study by the American Health Care Association in 1995.

Given the choice, most older adults would prefer to continue to live in their homes (aging in place). Many elderly people gradually lose functioning ability and require either additional assistance in the home or a move to an eldercare facility. Their adult children often find it challenging to help their elderly parents make the right choices. Assisted living is one option for the elderly who need assistance with everyday tasks. It costs less than nursing home care but is still considered expensive for most people. Home care services may allow seniors to live in their own home for a longer period of time.

One relatively new service in the United States that can help keep older people in their homes longer is respite care. This type of care allows caregivers the opportunity to go on a vacation or a business trip and to know that their family member has good quality temporary care. Also, without this help the elder might have to move permanently to an outside facility. Another unique type of care cropping in U.S. hospitals is called acute care of elder units, or ACE units, which provide "a homelike setting" within a medical center specifically for older adults.

Staff at On Lok Senior Health Services interact with participants in their senior day care program in San Francisco's Chinatown, mid 1970s.

Senior at San Francisco's On Lok Senior Health Services at the Powell Street location takes a rest after social activities, mid 1970s.

Information about long-term care options in the United States can be found by contacting the local Area Agency on Aging, searching through ZIP code, or elder referral agencies such as Silver Living or A Place for Mom. Furthermore, the U.S. government recommends evaluation of health care facilities through websites using data collected from sources such as Medicare records.

In developing nations

China

Population ageing is a challenge across the world, and China is no exception. Due to the one-child policy, rural/urban migration and other social changes, the traditional long-term care (LTC) for the elderly which was through direct family care in the past will no longer suffice. Barely existent now, both institutional and community-based services are expanding to meet the growing need. China is still at an earlier stage in economic development and will be challenged to build these services and train staff.

India

India's cultural view of elderly care is similar to that of Nepal. Parents are typically cared for by their children into old age, most commonly by their sons. In these countries, elderly citizens, especially men, are viewed in very high regard. Traditional values demand honor and respect for older, wiser people. Using data on health and living conditions from India's 60th National Sample Survey, a study found that almost a fourth of the elderly reported poor health. Reports of poor health were clustered among the poor, single, lower-educated, and economically inactive groups.

Under its eleventh Five-Year plan, the Indian government has made many strides similar to that of Nepal. Article 41 of the Indian Constitution states that elderly citizens will be guaranteed Social Security support for health care and welfare. A section of the 1973 Criminal Procedure Code, alluding to its traditional background, mandates that children support their parents if they no longer can themselves.

Nepal

Due to health and economic benefits, the life expectancy in Nepal jumped from 27 years in 1951 to 65 in 2008. Most elderly Nepali citizens, roughly 85%, live in rural areas. Because of this, there is a significant lack of government sponsored programs or homes for the elderly. Traditionally, parents live with their children, and today, it is estimated that 90% of the elderly live in the homes of their families. This number is changing as more children leave home for work or school, leading to loneliness and mental problems in Nepali elderly.

The Ninth Five-Year Plan included policies in an attempt to care for the elderly left without children as caretakers. A Senior Health Facilities Fund has been established in each district. The Senior Citizens Health Facilities Program Implementation Guideline, 2061BS provides medical facilities to the elderly, free medicines as well as health care to people who are poverty stricken in all districts. In its yearly budget, the government has planned to fund free health care for all heart and kidney patients older than 75. Unfortunately, many of these plans are overly ambitious, which has been recognized by the Nepali government. Nepal is a developing nation and may not be able to fund all of these programs after the development of an Old Age Allowance (OAA). OAA provides a monthly stipend to all citizens over 70 years old and widows over 60 years old.

There are a handful of private daycare facilities for the elderly, but they are limited to the capital city. These day care services are very expensive and beyond the reach of the general public.

Thailand

Thailand has observed global patterns of an enlarging elderly class: as fertility control is encouraged and medical advances are being made, the birth rate has diminished and people live longer. The Thai government is noticing and concerned about this trend but tends to let families care for their elderly members rather than create extraneous policies for them. As of 2011, there are only 25 state-sponsored homes for the elderly, with no more than a few thousand members in each home. Such programs are largely run by volunteers and the services tend to be limited, considering there is not always a guarantee that care will be available. Private care is tough to follow, often based on assumptions. Because children are less likely to care for their parents, private caretakers are in demand. Volunteer NGOs are available but in very limited quantities.

While there are certainly programs available for use by the elderly in Thailand, questions of equity have risen since their introduction. The rich elderly in Thailand are much more likely to have access to care resources, while the poor elderly are more likely to use their acquired health care, as observed in a study by Bhumisuk Khananurak. However, over 96% of the nation has health insurance with varying degrees of care available.

Medical (skilled care) versus non-medical (social care)

A distinction is generally made between medical and non-medical care, the latter not being provided by medical professionals and much less likely to be covered by insurance or public funds. In the US, 67% of the one million or so residents in assisted living facilities pay for care out of their own funds. The rest get help from family and friends and from state agencies. Medicare does not pay unless skilled-nursing care is needed and given in certified skilled nursing facilities or by a skilled nursing agency in the home. Assisted living facilities usually do not meet Medicare's requirements. However, Medicare pays for some skilled care if the elderly person meets the requirements for the Medicare home health benefit. 

Thirty-two U.S. states pay for care in assisted living facilities through their Medicaid waiver programs. Similarly, in the United Kingdom the National Health Service provides medical care for the elderly, as for all, free at the point of use, but social care is paid for by the state only in Scotland. England, Wales and Northern Ireland have failed to introduce any legislation on the matter and so social care is not funded by public authorities unless a person has exhausted their private resources, such as by selling the home. Money provided for supporting elderly people in the UK has fallen by 20% per person during the ten years from 2005 to 2015 and in real terms, the fall is even greater. L Experts claim that vulnerable UK people do not get what they need.

However, elderly care is focused on satisfying the expectations of two tiers of customers: the resident customer and the purchasing customer, who are often not identical, since relatives or public authorities, rather than the resident, may be providing the cost of care. If residents are confused or have communication difficulties, it may be very difficult for relatives or other concerned parties to be sure of the standard of care being given, and the possibility of elder abuse is a continuing source of concern. The Adult Protective Services Agency, a component of the human service agency in most states, is typically responsible for investigating reports of domestic elder abuse and providing families with help and guidance. Other professionals who may be able to help include doctors or nurses, police officers, lawyers, and social workers.

Shared-decision making

During primary care

There is currently limited evidence to form a robust conclusion that involving older patients with multiple health conditions in decision-making during primary care consultations has benefits. Examples of patient involvement in decision-making about their health care include patient workshops and coaching, individual patient coaching. Further research in this developing area is needed.

Promoting independence

See also: Dignity of risk

Older adults are scared of losing their independence more than they fear death. Promoting independence in self-care can provide older adults with the capability to maintain independence longer and can leave them with a sense of achievement when they complete a task unaided. Older adults that require assistance with activities of daily living are at a greater risk of losing their independence with self-care tasks as dependent personal behaviours are often met with reinforcement from caregivers. It is important for caregivers to ensure that measures are put into place to preserve and promote function rather than contribute to a decline in status of an older adult that has physical limitations. Caregivers need to be conscious of actions and behaviors that cause older adults to become dependent on them and need to allow older patients to maintain as much independence as possible. Providing information to the older patient on why it is important to perform self-care may allow them to see the benefit in performing self-care independently. If the older adult is able to complete self-care activities on their own, or even if they need supervision, encourage them in their efforts as maintaining independence can provide them with a sense of accomplishment and the ability to maintain independence longer.

A study done by Langer and Rodin in 1976, investigated what the impacts could be if nursing home residents are given more responsibility in different daily activities, and more choices, compared if those responsibilities given to the nursing home staff. Residents in the nursing home were split into two different groups. One group of elderly residents was given more responsibility in their choices, and their day-to-day activities than the other group. This involved differences such as having the hospital administrator talked separately to the two groups. The group that was more responsibility induced was given a talk emphasizing their responsibility for themselves, while the talk given to the second group emphasized the responsibility of the nursing staff in taking care of the elderly residents. Another difference between the two groups is that both groups were given a plant. The group that was more responsibility induced was told they there were responsible for watering the plant each day while, the second group was told that the nursing staff was responsible for watering the plant. Results from this study indicated that the group that was more responsibility induced became more active, reported being happier, and increased alertness and they showed increased behavioral involvement in activities such as socializing, participation, and attendance in the nursing home activities such the nursing home's movie nights. They also showed higher health and mood which also declined more slowly than the previous group over time. It is also noted that these long-term benefits were most likely obtained because the treatment was not directed toward one single behavior or stimulus condition.

Elderly-friendly interior design plays a vital role in promoting independence among the elderly. The integration of Internet of Things (IoT) in smart homes provides a remote monitoring system to keep track of the daily activities of the elderly. Thus adults can live on their own confidently knowing that a feedback alarm will be sent to their caregivers immediately in case of an emergency. This not only allows the aging population to maintain their independence and confidenc, but also brings peace of mind to their friends and family.

Improving physical mobility

See also: Age-related mobility disability

Impaired mobility is a major health concern for older adults, affecting 50% of people over 85 and at least a fourth of those over 75 years old. As adults lose the ability to walk, climb stairs, or rise from a chair, they become completely disabled. The problem cannot be ignored because people over 65 years old constitute the fastest growing segment of the population.

Therapy designed to improve mobility in elderly patients is usually built around diagnosing and treating specific impairments, such as reduced strength or poor balance. It is appropriate to compare older adults seeking to improve their mobility because athletes seeking to improve their split times. People in both groups perform best when they measure their progress and work toward specific goals related to strength, aerobic capacity, and other physical qualities. Someone attempting to improve an older adult's mobility must decide what impairments to focus on, and in many cases, there is little scientific evidence to justify any of the options. Today, many caregivers choose to focus on leg strength and balance. New research suggests that limb velocity and core strength may also be important factors in mobility. Assistive technology and advancements in the health care field are further giving elders greater freedom and mobility. Several platforms now use artificial intelligence to suggest assistive devices to the elder for a better match. Well planned exercise programs can reduce the rate of falls in older people if they involve multiple categories such as balance, functional and resistance exercise.

Family members are one of the most important caregivers to the elderly, often comprising the majority and most commonly being a daughter or a granddaughter. Family and friends can provide a home (i.e. host elderly relatives), help with money and meet social needs by visiting, taking them out on trips, etc.

One of the major causes of elderly falls is hyponatremia, an electrolyte disturbance in which the level of sodium in a person's serum drops below 135 mEq/L. Hyponatremia is the most common electrolyte disorder encountered in the elderly patient population. Studies have shown that older patients are more prone to hyponatremia as a result of multiple factors including physiologic changes associated with aging such as decreases in glomerular filtration rate, a tendency for defective sodium conservation, and increased vasopressin activity. Mild hyponatremia ups the risk of fracture in elderly patients because hyponatremia has been shown to cause subtle neurologic impairment that affects gait and attention, similar to that of moderate alcohol intake.

Improving personal mobility

There are relatively few studies focusing on interventions to improve personal mobility of older adults living at home.

An elderly-friendly interior space can reduce mobility issues as well as other old-age issues. Staircase, lights, flooring etc can help elders combat mobility issues. Interior design can positively influence the physical and psychological wellness of the elderly, and if each area in house is designed for accommodation, it can let older adults live safely, comfortably and happily.

While navigating floors, climbing stairs is one of the greatest challenges due to high risk of collapsing. A poorly designed staircase can negatively impact elders' psychology as they develop loss of confidence and fear of accidents. However, a staircase designed with the ergonomics and usage patterns of the elderly in mind, can make it easier for everyone. A stairlift can be a huge step to combat mobility issues.

Appropriate lighting in the interior space makes it easier for elders to move around in the house. An average 60-year-old person requires three times more illuminance than an average 20-year-old boy. Windows, skylight and door openings can incorporate daylight into interior spaces. However, unplanned opening designs can lead to glare and increase the risk of falls and hinder their ability to perform daily tasks as the elderly are more sensitive to glare than young adults. Dual-layer curtains, drapes, window blinds, light shelves, low visual transmittance glazing or other shading systems can reduce glare. Illuminance can be increased by combining natural light with various kinds of artificial lights.

When a person slips due to mobility issues, the flooring material plays a major role in the level of impact the person experiences after falling. Choosing the right flooring material in homes depending on whether an individual uses a walker, a wheelchair, or a cane, can also resolve many of the mobility issues faced by adults due to decline in physical strength, loss of balance. For elders, tile flooring is the least preferred option. Carpet, cork, sheet vinyl flooring are some of the flooring options which can be used for bedrooms, kitchen and bathrooms used by elders. Tiles can be extremely slippery when they are wet which increases the risk of accidents. Also, they are very hard and cold on feet which makes it difficult to walk barefoot during winters.

Legal issues about incapacity

Legal incapacity is an invasive and sometimes, difficult legal procedure. It requires that a person file a petition with the local courts, stating that the elderly person lacks the capacity to carry out activities that include making medical decisions, voting, making gifts, seeking public benefits, marrying, managing property and financial affairs, choosing where to live and who they socialize with. Most states' laws require two doctors or other health professionals to provide reports as evidence of such incompetence and the person to be represented by an attorney. Only then can the individual's legal rights be removed, and legal supervision by a guardian or conservator be initiated. The legal guardian or conservator is the person to whom the court delegates the responsibility of acting on the incapacitated person's behalf and must report regularly his or her activities to the court.

A less restrictive alternative to legal incapacity is the use of "advance directives," powers of attorney, trusts, living wills and healthcare directives. The person who has such documents in place should have prepared them with their attorney when that person had capacity. Then, if the time comes that the person lacks capacity to carry out the tasks laid out in the documents, the person they named (their agent) can step in to make decisions on their behalf. The agent has a duty to act as that person would have done so and to act in their best interest.

Artificial heart

From Wikipedia, the free encyclopedia

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

 

Artificial heart
An artificial heart displayed at the London Science Museum

An artificial heart is a device that replaces the heart. Artificial hearts are typically used to bridge the time to heart transplantation, or to permanently replace the heart in the case that a heart transplant (from a deceased human or, experimentally, from a deceased genetically engineered pig) is impossible. Although other similar inventions preceded it from the late 1940s, the first artificial heart to be successfully implanted in a human was the Jarvik-7 in 1982, designed by a team including Willem Johan Kolff, William DeVries and Robert Jarvik.

An artificial heart is distinct from a ventricular assist device (VAD; for either one or both of the ventricles, the heart's lower chambers), which can be a permanent solution also, or the intra-aortic balloon pump – both devices are designed to support a failing heart. It is also distinct from a cardiopulmonary bypass machine, which is an external device used to provide the functions of both the heart and lungs, used only for a few hours at a time, most commonly during cardiac surgery. It is also distinct from a ventilator, used to support failing lungs, or the extracorporeal membrane oxygenation (ECMO), which is used to support those with both inadequate heart and lung function for up to days or weeks, unlike the bypass machine.

History

Origins

A synthetic replacement for a heart remains a long-sought "holy grail" of modern medicine. The obvious benefit of a functional artificial heart would be to lower the need for heart transplants because the demand for organs always greatly exceeds supply.

Although the heart is conceptually a pump, it embodies subtleties that defy straightforward emulation with synthetic materials and power supplies. Consequences of these issues include severe foreign-body rejection and external batteries that limit mobility. These complications limited the lifespan of early human recipients from hours to days.

Early development

The first artificial heart was made by the Soviet scientist Vladimir Demikhov in 1938. It was implanted in a dog.

On 2 July 1952, 41-year-old Henry Opitek, suffering from shortness of breath, made medical history at Harper University Hospital at Wayne State University in Michigan. The Dodrill-GMR heart machine, considered to be the first operational mechanical heart, was successfully used while performing heart surgery. Ongoing research was done on calves at Hershey Medical Center, Animal Research Facility, in Hershey, Pennsylvania, during the 1970s.

Forest Dewey Dodrill, working closely with Matthew Dudley, used the machine in 1952 to bypass Henry Opitek's left ventricle for 50 minutes while he opened the patient's left atrium and worked to repair the mitral valve. In Dodrill's post-operative report, he notes, "To our knowledge, this is the first instance of survival of a patient when a mechanical heart mechanism was used to take over the complete body function of maintaining the blood supply of the body while the heart was open and operated on."

A heart–lung machine was first used in 1953 during a successful open heart surgery. John Heysham Gibbon, the inventor of the machine, performed the operation and developed the heart–lung substitute himself.

Following these advances, scientific interest for the development of a solution for heart disease developed in numerous research groups worldwide.

Early designs of total artificial hearts

In 1949, a precursor to the modern artificial heart pump was built by doctors William Sewell and William Glenn of the Yale School of Medicine using an Erector Set, assorted odds and ends, and dime-store toys. The external pump successfully bypassed the heart of a dog for more than an hour.

Paul Winchell invented an artificial heart with the assistance of Henry Heimlich (the inventor of the Heimlich maneuver) and held the first patent for such a device. The University of Utah developed a similar apparatus around the same time, but when they tried to patent it, Winchell's heart was cited as prior art. The university requested that Winchell donate the heart to the University of Utah, which he did. There is some debate as to how much of Winchell's design Robert Jarvik used in creating Jarvik's artificial heart. Heimlich states, "I saw the heart, I saw the patent and I saw the letters. The basic principle used in Winchell's heart and Jarvik's heart is exactly the same. " Jarvik denies that any of Winchell's design elements were incorporated into the device he fabricated for humans which was successfully implanted into Barney Clark in 1982.

On 12 December 1957, Willem Johan Kolff, the world's most prolific inventor of artificial organs, implanted an artificial heart into a dog at Cleveland Clinic. The dog lived for 90 minutes.

In 1958, Domingo Liotta initiated the studies of TAH (Total Artificial Heart) replacement at Lyon, France, and in 1959–60 at the National University of Córdoba, Argentina. He presented his work at the meeting of the American Society for Artificial Internal Organs held in Atlantic City in March 1961. At that meeting, Liotta described the implantation of three types of orthotopic (inside the pericardial sac) TAHs in dogs, each of which used a different source of external energy: an implantable electric motor, an implantable rotating pump with an external electric motor, and a pneumatic pump.

In 1964, the National Institutes of Health started the Artificial Heart Program, with the goal of putting an artificial heart into a human by the end of the decade. The purpose of the program was to develop an implantable artificial heart, including the power source, to replace a failing heart.

In February 1966, Adrian Kantrowitz rose to international prominence when he performed the world's first permanent implantation of a partial mechanical heart (left ventricular assist device) at Maimonides Medical Center.

In 1967, Kolff left Cleveland Clinic to start the Division of Artificial Organs at the University of Utah and pursue his work on the artificial heart.

1. In 1973, a calf named Tony survived for 30 days on an early Kolff heart.
2. In 1975, a bull named Burk survived 90 days on the artificial heart.
3. In 1976, a calf named Abebe lived for 184 days on the Jarvik 5 artificial heart.
4. In 1981, a calf named Alfred Lord Tennyson lived for 268 days on the Jarvik 5.

Over the years, more than 200 physicians, engineers, students and faculty developed, tested and improved Kolff's artificial heart. To help manage his many endeavors, Kolff assigned project managers. Each project was named after its manager. Graduate student Robert Jarvik was the project manager for the artificial heart, which was subsequently renamed the Jarvik 7.

In 1981, William DeVries submitted a request to the FDA for permission to implant the Jarvik 7 into a human being. On 1 December 1982, William DeVries implanted the Jarvik 7 artificial heart into Barney Clark, a dentist from Seattle who had severe congestive heart failure. Clark lived for 112 days tethered to an external pneumatic compressor, a device weighing some 400 pounds (180 kg), but during that time he experienced prolonged periods of confusion and a number of instances of bleeding, and asked several times to be allowed to die.

First clinical implantation of a total artificial heart

On 4 April 1969, Domingo Liotta and Denton A. Cooley replaced a dying man's heart with a mechanical heart inside the chest at The Texas Heart Institute in Houston as a bridge for a transplant. The man woke up and began to recover. After 64 hours, the pneumatic-powered artificial heart was removed and replaced by a donor heart. However thirty-two hours after transplantation, the man died of what was later proved to be an acute pulmonary infection, extended to both lungs, caused by fungi, most likely caused by an immunosuppressive drug complication.

The original prototype of Liotta-Cooley artificial heart used in this historic operation is prominently displayed in the Smithsonian Institution's National Museum of American History "Treasures of American History" exhibit in Washington, D.C.

First clinical applications of a permanent pneumatic total artificial heart

The first clinical use of an artificial heart designed for permanent implantation rather than a bridge to transplant occurred in 1982 at the University of Utah. Artificial kidney pioneer Willem Johan Kolff started the Utah artificial organs program in 1967. There, physician-engineer Clifford Kwan-Gett invented two components of an integrated pneumatic artificial heart system: a ventricle with hemispherical diaphragms that did not crush red blood cells (a problem with previous artificial hearts) and an external heart driver that inherently regulated blood flow without needing complex control systems. Independently, Paul Winchell designed and patented a similarly shaped ventricle and donated the patent to the Utah program. Throughout the 1970s and early 1980s, veterinarian Donald Olsen led a series of calf experiments that refined the artificial heart and its surgical care. During that time, as a student at the University of Utah, Robert Jarvik combined several modifications: an ovoid shape to fit inside the human chest, a more blood-compatible polyurethane developed by biomedical engineer Donald Lyman, and a fabrication method by Kwan-Gett that made the inside of the ventricles smooth and seamless to reduce dangerous stroke-causing blood clots. On 1 December 1982, William DeVries implanted the artificial heart into retired dentist Barney Bailey Clark (born 21 January 1921), who survived 112 days with the device, dying on 23 March 1983. Bill Schroeder became the second recipient and lived for a record 620 days.

Contrary to popular belief and erroneous articles in several periodicals, the Jarvik heart was not banned for permanent use. Today, the modern version of the Jarvik 7 is known as the SynCardia temporary Total Artificial Heart. It has been implanted in more than 1,350 people as a bridge to transplantation.

In the mid-1980s, artificial hearts were powered by dishwasher-sized pneumatic power sources whose lineage went back to Alfa Laval milking machines. Moreover, two sizable catheters had to cross the body wall to carry the pneumatic pulses to the implanted heart, greatly increasing the risk of infection. To speed development of a new generation of technologies, the National Heart, Lung, and Blood Institute opened a competition for implantable electrically powered artificial hearts. Three groups received funding: Cleveland Clinic in Cleveland, Ohio; the College of Medicine of Pennsylvania State University (Penn State Hershey Medical Center) in Hershey, Pennsylvania; and AbioMed, Inc. of Danvers, Massachusetts. Despite considerable progress, the Cleveland program was discontinued after the first five years.

First clinical application of an intrathoracic pump

On 19 July 1963, E. Stanley Crawford and Domingo Liotta implanted the first clinical Left Ventricular Assist Device (LVAD) at The Methodist Hospital in Houston, Texas, in a patient who had a cardiac arrest after surgery. The patient survived for four days under mechanical support but did not recover from the complications of the cardiac arrest; finally, the pump was discontinued, and the patient died.

First clinical application of a paracorporeal pump

1966 DeBakey ventricular assist device.

On 21 April 1966, Michael DeBakey and Liotta implanted the first clinical LVAD in a paracorporeal position (where the external pump rests at the side of the patient) at The Methodist Hospital in Houston, in a patient experiencing cardiogenic shock after heart surgery. The patient developed neurological and pulmonary complications and died after few days of LVAD mechanical support. In October 1966, DeBakey and Liotta implanted the paracorporeal Liotta-DeBakey LVAD in a new patient who recovered well and was discharged from the hospital after 10 days of mechanical support, thus constituting the first successful use of an LVAD for postcardiotomy shock.

First VAD patient with FDA approved hospital discharge

In 1990 Brian Williams was discharged from the University of Pittsburgh Medical Center (UPMC), becoming the first VAD patient to be discharged with Food and Drug Administration (FDA) approval. The patient was supported in part by bioengineers from the University of Pittsburgh's McGowan Institute.

Total artificial hearts

Approved medical devices

SynCardia

SynCardia is a company based in Tucson, Arizona, which currently has two separate models available. It is available in a 70cc and 50cc size. The 70cc model is used for biventricular heart failure in adult men, while the 50cc is for children and women. As good results with the TAH as a bridge to heart transplant accumulated, a trial of the CardioWest TAH (developed from the Jarvik 7 and now marketed as the Syncardia TAH) was initiated in 1993 and completed in 2002. The SynCardia was first approved for use in 2004 by the US Food and Drug Administration.

As of 2014, more than 1,250 patients have received SynCardia artificial hearts. The device requires the use of the Companion 2 in-hospital driver, approved by the FDA in 2012, or the Freedom Driver System, approved in 2014, which allows some patients to return home. These drivers are large, heavy, but portable devices that generate air pulses to power the heart. The drivers also monitor blood flow for each ventricle.

In 2016, Syncardia filed for bankruptcy protection and was later acquired by the private equity firm Versa Capital Management.

Carmat bioprosthetic heart

Carmat's artificial heart.

On 27 October 2008, French professor and leading heart transplant specialist Alain F. Carpentier announced that a fully implantable artificial heart would be ready for clinical trial by 2011 and for alternative transplant in 2013. It was developed and would be manufactured by him, biomedical firm CARMAT SA, and venture capital firm Truffle Capital. The prototype used embedded electronic sensors and was made from chemically treated animal tissues, called "biomaterials", or a "pseudo-skin" of biosynthetic, microporous materials.

According to a press-release by Carmat dated 20 December 2013, the first implantation of its artificial heart in a 75-year-old patient was performed on 18 December 2013 by the Georges Pompidou European Hospital team in Paris (France). The patient died 75 days after the operation.

In Carmat's design, two chambers are each divided by a membrane that holds hydraulic fluid on one side. A motorized pump moves hydraulic fluid in and out of the chambers, and that fluid causes the membrane to move; blood flows through the other side of each membrane. The blood-facing side of the membrane is made of tissue obtained from a sac that surrounds a cow's heart, to make the device more biocompatible. The Carmat device also uses valves made from cow heart tissue and has sensors to detect increased pressure within the device. That information is sent to an internal control system that can adjust the flow rate in response to increased demand, such as when a patient is exercising. This distinguishes it from previous designs that maintain a constant flow rate.

The Carmat device, unlike previous designs, is meant to be used in cases of terminal heart failure, instead of being used as a bridge device while the patient awaits a transplant. At 900 grams it weighs nearly three times the typical heart and is targeted primarily towards obese men. It also requires the patient to carry around an additional Li-Ion battery. The projected lifetime of the artificial heart is around 5 years (230 million beats).

In 2016, trials for the Carmat "fully artificial heart" were banned by the National Agency for Security and Medicine in Europe after short survival rates were confirmed. The ban was lifted in May 2017. At that time, a European report stated that Celyad's C-Cure cell therapy for ischemic heart failure "could only help a subpopulation of Phase III study participants, and Carmat will hope that its artificial heart will be able to treat a higher proportion of heart failure patients".

The Carmat artificial heart was approved for sale in the European Union, receiving a CE marking on December 22, 2020.

Historical prototypes

Total artificial heart pump

The U.S. Army artificial heart pump was a compact, air-powered unit developed by Kenneth Woodward at Harry Diamond Laboratories in the early to mid-1960s. The Army's heart pump was partially made of plexiglass, and consisted of two valves, a chamber, and a suction flapper. The pump operated without any moving parts under the principle of fluid amplification – providing a pulsating air pressure source resembling a heartbeat.

POLVAD

Since 1991, the Foundation for Cardiac Surgery Development (FRK) in Zabrze, Poland, has been working on developing an artificial heart. Nowadays, the Polish system for heart support POLCAS consists of the artificial ventricle POLVAD-MEV and the three controllers POLPDU-401, POLPDU-402 and POLPDU-501. Presented devices are designed to handle only one patient. The control units of the 401 and 402 series may be used only in hospital due to its big size, method of control and type of power supply. The control unit of 501 series is the latest product of FRK. Due to its much smaller size and weight, it is significantly more mobile solution. For this reason, it can be also used during supervised treatment conducted outside the hospital.

Phoenix-7

In June 1996, a 46-year-old man received a total artificial heart implantation done by Jeng Wei at Cheng-Hsin General Hospital in Taiwan. This technologically advanced pneumatic Phoenix-7 Total Artificial Heart was manufactured by Taiwanese dentist Kelvin K. Cheng, Chinese physician T. M. Kao, and colleagues at the Taiwan TAH Research Center in Tainan, Taiwan. With this experimental artificial heart, the patient's BP was maintained at 90–100/40–55 mmHg and cardiac output at 4.2–5.8 L/min. The patient then received the world's first successful combined heart and kidney transplantation after bridging with a total artificial heart.

Abiomed hearts

The first AbioCor to be surgically implanted in a patient was on 3 July 2001. The AbioCor is made of titanium and plastic with a weight of 0.9 kg (two pounds), and its internal battery can be recharged with a transduction device that sends power through the skin. The internal battery lasts for half an hour, and a wearable external battery pack lasts for four hours. The FDA announced on 5 September 2006, that the AbioCor could be implanted for humanitarian uses after the device had been tested on 15 patients. It is intended for critically ill patients who cannot receive a heart transplant. Some limitations of the current AbioCor are that its size makes it suitable for less than 50% of the female population and only about 50% of the male population, and its useful life is only 1–2 years.

By combining its valved ventricles with the control technology and roller screw developed at Penn State, AbioMed designed a smaller, more stable heart, the AbioCor II. This pump, which should be implantable in most men and 50% of women with a life span of up to five years, had animal trials in 2005, and the company hoped to get FDA approval for human use in 2008. After a great deal of experimentation, Abiomed has abandoned development of total official hearts as of 2015. Abiomed as of 2019 only markets heart pumps, "intended to help pump blood in patients who need short-term support (up to 6 days)", which are not total artificial hearts.

Frazier-Cohn

On 12 March 2011, an experimental artificial heart was implanted in 55-year-old Craig Lewis at The Texas Heart Institute in Houston by O. H. Frazier and William Cohn. The device is a combination of two modified HeartMate II pumps that is currently undergoing bovine trials.

Frazier and Cohn are on the board of the BiVACOR company that develops an artificial heart. BiVACOR has been tested as a replacement for a heart in a sheep.

So far, only one person has benefited from Frazier and Cohn's artificial heart. Craig Lewis had amyloidosis in 2011 and sought treatment. After obtaining permission from his family, Frazier and Cohn replaced his heart with their device. Lewis survived for another 5 weeks after the operation; he eventually died from liver and kidney failure due to his amyloidosis, after which his family asked that his artificial heart be unplugged.

Soft Total Artificial Heart, developed in the functional material laboratory at ETH Zürich

Current prototypes

Soft artificial heart

On 10 July 2017, Nicholas Cohrs and colleagues presented a new concept of a soft total artificial heart in the Journal of Artificial Organs. The heart was developed in the Functionals Materials Laboratory at ETH Zurich. (Cohrs was listed as a doctoral student in a group led by Professor Wendelin Stark at ETH Zurich.)

The soft artificial heart (SAH) is a silicone monoblock fabricated with the help of 3D bioprinting technology. It weighs 390g, has a volume of 679 cm^3, and is operated through pressurized air. "Our goal is to develop an artificial heart that is roughly the same size as the patient's own one and which imitates the human heart as closely as possible in form and function", Cohrs said in an interview. The SAH fundamentally moves and works like a natural heart, but the prototype only performed for 3000 beats (about 30 to 50 minutes at an average heart rate) in a hybrid mock circulation machine before the silicone membrane (2.3 mm thick) between the Left Ventricle and the Air Expansion Chamber ruptured.

The working life of a more recent Cohrs prototype (using various polymers instead of silicone) was still limited, according to reports in early 2018, with that model providing a useful life of 1 million heartbeats, roughly ten days in a human body. At the time, Cohrs and his team were experimenting with CAD software and 3D printing, striving to develop a model that would last up to 15 years. "We cannot really predict when we could have a final working heart which fulfills all requirements and is ready for implantation. This usually takes years", said Cohrs.

Others

A centrifugal pump or an axial-flow pump can be used as an artificial heart, resulting in the patient being alive without a pulse. Other pulse-less artificial heart designs include the HeartMate II from Thoratec, which uses an Archimedes screw; and an experimental artificial heart designed by Bud Frazier and Billy Cohn, using turbines spinning at 8,000 to 12,000 RPM.

A centrifugal artificial heart which alternately pumps the pulmonary circulation and the systemic circulation, causing a pulse, has been described.

Researchers have constructed a heart out of foam. The heart is made out of flexible silicone and works with an external pump to push air and fluids through the heart. It currently cannot be implanted into humans, but it is a promising start for artificial hearts.

Hybrid assistive devices

Main article: Ventricular assist device

Patients who have some remaining heart function but who can no longer live normally may be candidates for ventricular assist devices (VAD), which do not replace the human heart but complement it by taking up much of the function.

The first Left Ventricular Assist Device (LVAD) system was created by Domingo Liotta at Baylor College of Medicine in Houston in 1962.

Another VAD, the Kantrowitz CardioVad, designed by Adrian Kantrowitz, boosts the native heart by taking up over 50% of its function. Additionally, the VAD can help patients on the wait list for a heart transplant. In a young person, this device could delay the need for a transplant by 10–15 years, or even allow the heart to recover, in which case the VAD can be removed. The artificial heart is powered by a battery that needs to be changed several times while still working.

The first heart assist device was approved by the FDA in 1994, and two more received approval in 1998. While the original assist devices emulated the pulsating heart, newer versions, such as the Heartmate II, developed by The Texas Heart Institute of Houston, provide continuous flow. These pumps (which may be centrifugal or axial flow) are smaller and potentially more durable and last longer than the current generation of total heart replacement pumps. Another major advantage of a VAD is that the patient keeps the natural heart, which may still function for temporary back-up support if the mechanical pump were to stop. This may provide enough support to keep the patient alive until a solution to the problem is implemented.

In August 2006, an artificial heart was implanted into a 15-year-old girl at the Stollery Children's Hospital in Edmonton, Alberta. It was intended to act as a temporary fixture until a donor heart could be found. Instead, the artificial heart (called a Berlin Heart) allowed for natural processes to occur and her heart healed on its own. After 146 days, the Berlin Heart was removed, and the girl's heart functioned properly on its own. On 16 December 2011 the Berlin Heart gained U.S. FDA approval. The device has since been successfully implanted in several children including a 4-year-old Honduran girl at Children's Hospital Boston.

Several continuous-flow ventricular assist devices have been approved for use in the European Union, and, as of August 2007, were undergoing clinical trials for FDA approval.

In 2012, Craig Lewis, a 55-year-old Texan, presented at the Texas Heart Institute with a severe case of cardiac amyloidosis. He was given an experimental continuous-flow artificial heart transplant which saved his life. Lewis died 5 weeks later of liver failure after slipping into a coma due to the amyloidosis.

In 2012, a study published in the New England Journal of Medicine compared the Berlin Heart to extracorporeal membrane oxygenation (ECMO) and concluded that "a ventricular assist device available in several sizes for use in children as a bridge to heart transplantation [such as the Berlin Heart] was associated with a significantly higher rate of survival as compared with ECMO." The study's primary author, Charles D. Fraser Jr., surgeon in chief at Texas Children's Hospital, explained: "With the Berlin Heart, we have a more effective therapy to offer patients earlier in the management of their heart failure. When we sit with parents, we have real data to offer so they can make an informed decision. This is a giant step forward."

Suffering from end-stage heart failure, former Vice President Dick Cheney underwent a procedure at INOVA Fairfax Hospital, in Fairfax Virginia in July 2010, to have a Heartmate II VAD implanted. In 2012, he received a heart transplant at age 71 after 20 months on a waiting list.