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Lung Transplant Update | Penn Medicine

Tuesday, February 8, 2011

How the Lung Allocation System Works

Nancy P. Blumenthal, CRNP, is director of clinical practice and senior nurse practitioner for the lung transplant program. This post is part one in a two-part series about how donated lungs are distributed to patients in need of lung transplants.

It is important for lung transplant candidates to understand the process by which donated organs are allocated in the United States.

The following questions and answers are excerpts from a patient education booklet produced by the United Network for Organ Sharing (UNOS) titled Questions and Answers for Transplant Candidates about Lung Allocation Policy.


What organizations facilitate organ donation and transplantation?
The Organ Procurement and Transplantation Network (OPTN) is the nation’s organ procurement, donation, and transplantation system.

The United Network for Organ Sharing (UNOS) is the non-profit organization that operates the OPTN within a contract from the federal government.

The OPTN and UNOS continuously evaluate new advances and research, and use that information to improve organ transplantation policies. All transplant programs and organ procurement organizations are OPTN/UNOS members and agree to follow OPTN policies.


How are donor lungs matched to potential recipients?
In the lung allocation system, every lung transplant candidate age 12 and older receives an individualized lung allocation score.
The lung allocation score is an important factor in determining priority for transplant when a donor lung becomes available. The system determines the order of everyone awaiting a lung transplant by their lung allocation scores, blood type, and the geographic distance between the candidates and the hospital where the lung donor is located.
Age also plays a role because lungs from pediatric and adolescent donors are offered first to pediatric and adolescent transplant candidates before they are offered to adults. The lung allocation system uses medical information specific to each lung transplant candidate. This information includes lab values, test results, and disease diagnosis. This medical information is used to calculate a lung allocation score from 0 to 100 for every transplant candidate. The lung allocation score represents an estimate of the severity of each candidate’s illness and his or her chance of success following a lung transplant.
All candidates are placed in order for compatible lung offers according to their score. A candidate with a higher lung allocation score receives higher priority for a lung offer when a compatible lung becomes available.


How was the lung allocation system created?
The supply of donor lungs is limited. The OPTN designed this allocation system to more effectively use the limited number of available donor lungs as well as reduce the number of deaths among people waiting for a transplant. Prior to this system, transplant candidates received donor lungs based on the amount of time they had been on the waitlist for transplantation. The OPTN designed the lung allocation score system by studying scientific data on lung transplantation and by drawing on prior experience with many types of patients with lung diseases.


How is a lung allocation score determined?
In the lung allocation system, every lung transplant candidate age 12 and older receives an individualized lung allocation score. The lung allocation score is an important factor in determining priority for receiving a lung transplant when a donor lung becomes available.
Transplant candidates’ lung allocation scores are calculated from the following medical information:

Forced vital capacity: A lung function test that measures the maximum amount of air a patient can force out after breathing in as deeply as possible.

Pulmonary artery pressure: Measures the pressure the heart must generate to pump blood through the lungs.

Oxygen at rest: The amount of oxygen needed at rest to maintain adequate oxygen levels in the blood.

Age: The candidate’s age at the time donor lungs are offered.

Body mass index: BMI is the ratio of a person’s weight to height that, when interpreted with other medical test results, helps to evaluate health status. Diabetes: Diabetes may be a predictor of health status in some people with lung disease.

Functional status: Functional status measures the effects that lung disease may have on a person’s ability to perform routine daily tasks.

Six-minute walk distance: Transplant candidates are asked to walk as far as they can in six minutes. The distance walked is a measure of functional status.

Assisted ventilation: The use of a ventilator to assist breathing may be a measure of disease severity and can affect success after a transplant.


Pulmonary capillary wedge pressure: The pressure that blood returning to the heart from the lungs must overcome. This pressure can increase when the heart is not pumping effectively.

Serum creatinine: High serum creatinine levels reflect impaired kidney function, which is sometimes associated with severe lung disease.

Diagnosis: Research has shown that urgency among people needing a lung transplant and the success following a lung transplant varies among people with different lung diseases. Therefore, for every lung transplant candidate, diagnosis factors into the calculation of the lung allocation score.

PC02: The candidate’s current PC02 and change in PC02 are both considered in the lung allocation score calculation. A blood gas test is performed to measure the amount of C02 in the blood. When the lung’s ability to exchange oxygen and C02 becomes impaired, the PC02 level may become increased.

Be sure to return to read the second part of this series addressing how lung allocation scores are determined, and what your lung allocation score means for you.

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