Lung transplantation offers a second chance at life for individuals facing end-stage respiratory failure when all other treatments have failed. For people struggling with conditions like severe pulmonary fibrosis or advanced chronic obstructive pulmonary disease, receiving a new set of lungs is the ultimate goal. The process of receiving a donor organ is not a simple queue, but a complex system of organ allocation designed to maximize fairness and the overall benefit of the limited number of available organs. Understanding this system is the first step in navigating the journey toward a transplant.
The Path to Being Placed on the List
Before a patient can officially join the national waiting list, they must complete a rigorous pre-transplant evaluation. This assessment is conducted by a multidisciplinary team, including transplant pulmonologists, surgeons, social workers, and financial coordinators. The goal is to determine if the patient is medically suitable to survive the lengthy surgery and the demanding recovery period that follows.
A patient must be “sick enough to need a transplant, yet well enough to survive one,” meaning they have a high risk of death without the procedure but also the physical reserve to tolerate it. The evaluation involves extensive testing, such as cardiac assessments, imaging studies, and comprehensive blood work. Psychological and social support evaluations are also necessary to confirm the patient can adhere to the lifelong medication schedule and follow-up care required after transplantation.
How Patient Urgency and Benefit are Measured
Priority for receiving a donor lung is determined in the United States by the Lung Composite Allocation Score (CAS), a point-based system implemented in 2023 that replaced the previous Lung Allocation Score (LAS). This score is calculated for every candidate and potential organ offer. The CAS ensures that the lungs go to the person who needs them most and has the best chance of a successful outcome by balancing two main factors: a candidate’s medical urgency and their expected post-transplant survival.
The medical urgency component awards up to 25 points based on the candidate’s predicted chance of dying within the next year without a transplant. Patients with rapidly deteriorating conditions, severe oxygen dependence, or other life-threatening complications receive a higher score, reflecting their immediate need. Similarly, up to 25 points are awarded based on the predicted likelihood of the candidate surviving at least five years following the transplant.
Higher CAS points are also assigned for candidates facing greater biological challenges in finding a match, such as those with rare blood types or high levels of immune sensitization. These factors, along with the distance between the donor and transplant hospitals, are integrated into the single score. The CAS uses a continuous distribution model, ensuring that the candidate with the highest calculated score for a specific donor organ receives the offer first, promoting an equitable distribution system based on objective medical data.
Variables That Determine Actual Waiting Time
The duration of the wait is highly variable and depends less on the time spent on the list and more on a complex interplay of patient-specific and logistical factors. Biological compatibility is a primary constraint, as a successful transplant requires matching the donor and recipient’s ABO blood type. Incompatible blood types will trigger a severe immune reaction, making a transplant impossible.
Beyond blood type, a precise physical match is required, particularly regarding lung size and chest cavity volume. A donor lung that is too large for the recipient’s chest can be compressed and not function properly. Conversely, one that is too small may not provide enough surface area for adequate oxygen exchange. This need for size matching means that a smaller recipient, particularly a shorter adult, may face a longer wait due to a smaller pool of appropriately sized donor lungs.
Geographical location also plays a significant role in wait times, even with the new allocation system. Wait times still fluctuate based on the local supply and demand for donor organs within a region. Centers located in areas with a higher donation rate may have shorter average waits than those in regions with a dense population of waitlisted patients. The CAS partially addresses this by awarding points for “travel efficiency,” giving priority to closer matches to preserve the organ’s viability, which must be transplanted quickly.
What Happens When a Match is Found
The waiting period ends abruptly with the “transplant call,” which can happen at any time of day or night. Once a donor lung is identified and the transplant team accepts the offer based on the candidate’s high CAS, the recipient must travel immediately to the hospital, often within just a few hours. The urgency is paramount because donor lungs have a limited window of viability, typically only four to six hours after removal.
Upon arrival, the transplant team performs final checks on the recipient to ensure they are healthy enough for surgery, including a final medical exam and blood tests. A “crossmatch” test may be performed to confirm there are no pre-existing antibodies in the recipient that would immediately reject the donor lung. Simultaneously, a surgical team is dispatched to the donor hospital to retrieve and inspect the organ, confirming its quality. Only after the donor lung is recovered, deemed suitable, and the recipient is cleared for the operating room does the procedure begin.