Lung transplant airway hypoxia: a diathesis to fibrosis?

Abstract

Rationale: Chronic rejection, manifested pathologically as airway fibrosis, is the major problem limiting long-term survival in lung transplant recipients. Airway hypoxia and ischemia, resulting from a failure to restore the bronchial artery (BA) circulation at the time of transplantation, may predispose patients to chronic rejection. To address this possibility, clinical information is needed describing the status of lung perfusion and airway oxygenation after transplantation.

Objectives: To determine the relative pulmonary arterial blood flow, airway tissue oxygenation and BA anatomy in the transplanted lung was compared with the contralateral native lung in lung allograft recipients.

Methods: Routine perfusion scans were evaluated at 3 and 12 months after transplantation in 15 single transplant recipients. Next, airway tissue oximetry was performed in 12 patients during surveillance bronchoscopies in the first year after transplant and in 4 control subjects. Finally, computed tomography (CT)-angiography studies on 11 recipients were reconstructed to evaluate the post-transplant anatomy of the BAs.

Measurements and main results: By 3 months after transplantation, deoxygenated pulmonary arterial blood is shunted away from the native lung to the transplanted lung. In the first year, healthy lung transplant recipients exhibit significant airway hypoxia distal to the graft anastomosis. CT-angiography studies demonstrate that BAs are abbreviated, generally stopping at or before the anastomosis, in transplant airways.

Conclusions: Despite pulmonary artery blood being shunted to transplanted lungs after transplantation, grafts are hypoxic compared with both native (diseased) and control airways. Airway hypoxia may be due to the lack of radiologically demonstrable BAs after lung transplantation.

Figure 1.

Reconstructed computed tomography–angiogram in a single-lung transplant recipient 3 months after left lung transplantation. Although the high O₂ bronchial artery (BA) circulation is preserved to the native right lung, the BA stops near the anastomosis site of the left lung. This image is further represented in an online supplemental movie, which provides a three dimensional perspective of the anatomy.