Lung transplantation

Lung transplantation is the surgical replacement of one or both diseased lungs with healthy donor lungs.[1] It is a treatment for selected patients with end-stage lung disease who have exhausted other therapies.[1][2] Lung transplantation may be performed as a single-lung or bilateral (double-lung) procedure; combined heart-lung transplantation is performed rarely for specific indications.[1] Long-term survival is limited chiefly by chronic lung allograft dysfunction (CLAD), and the lung's exposure to the external environment and its sensitivity to ischemia make it among the more challenging organs to transplant.[1]

Indications

Common indications include chronic obstructive pulmonary disease (including emphysema), interstitial lung disease such as idiopathic pulmonary fibrosis, cystic fibrosis and other bronchiectatic diseases, and pulmonary arterial hypertension.[1][2] The choice between single- and double-lung transplantation depends on the underlying disease; suppurative diseases such as cystic fibrosis require bilateral transplantation to avoid contamination from a remaining infected native lung.[1]

Contraindications

Contraindications include active malignancy outside accepted limits, uncontrolled infection, severe dysfunction of other vital organs not correctable by multi-organ transplant, significant chest-wall or spinal deformity, and factors precluding adherence; advanced age and frailty are weighed individually.[1][2]

Allocation: the Composite Allocation Score

In the United States, donor lungs are allocated through continuous distribution using the lung Composite Allocation Score (CAS), which took effect on March 9, 2023, replacing the earlier Lung Allocation Score (LAS) used from 2005.[3] The CAS combines several weighted attributes, medical urgency, expected post-transplant survival, blood-type and size compatibility (including pediatric and prior-living-donor priority), candidate access, and proximity efficiency (distance from the donor hospital), into a single score, removing the hard geographic boundaries used previously.[3] Continuous distribution is the framework the OPTN is extending to other organs.

Procedure

Donor lungs are recovered, preserved (increasingly with ex-vivo lung perfusion in some programs to assess and recondition marginal lungs), and transported within a limited cold-ischemia window.[1][4] Implantation involves anastomoses of the bronchus, the pulmonary artery, and the pulmonary veins (via a left-atrial cuff) for each lung; bilateral transplants are commonly performed sequentially.[1] Cardiopulmonary bypass or extracorporeal membrane oxygenation (ECMO) may be used for intraoperative support.[1]

Chronic lung allograft dysfunction (CLAD)

The principal long-term limitation is chronic lung allograft dysfunction (CLAD), a progressive, largely irreversible decline in lung function attributed to chronic rejection and other injury, most often presenting as bronchiolitis obliterans syndrome (an obstructive phenotype) or restrictive allograft syndrome.[1] CLAD is the leading cause of late death after lung transplantation. Early complications include primary graft dysfunction, airway (bronchial anastomotic) complications, infection (the lungs being especially infection-prone), and acute rejection.[1] See Transplant immunology.

Outcomes

Lung transplantation improves quality of life and survival for selected patients, but long-term survival is shorter than for other solid organs, owing chiefly to CLAD and infection.[1] National and program-level survival statistics are published by SRTR and OPTN and should be consulted for current, dated figures.

History

The first human lung transplant was performed in 1963, but durable success awaited improvements in immunosuppression, preservation, and surgical technique in the 1980s and afterward.[1] U.S. lung allocation moved from a waiting-time basis to the urgency-and-benefit-based LAS in 2005, and then to continuous distribution under the CAS in 2023.[3]

See also

• Organ transplantation · Deceased donation
• Transplant immunology

References

• Lung Transplantation. StatPearls. NBK565849. https://www.ncbi.nlm.nih.gov/books/NBK565849/
• MedlinePlus. Lung transplant. https://medlineplus.gov/ency/article/003003.htm (lung transplant overview).
• HRSA/OPTN. Lung continuous distribution policy (Composite Allocation Score, effective March 9, 2023). https://www.hrsa.gov/optn/professionals/resources/heart-lung/lung-continuous-distribution-policy
• Organ preservation and machine perfusion (ex-vivo lung perfusion). PMC12692498. https://pmc.ncbi.nlm.nih.gov/articles/PMC12692498/