Causes of allograft dysfunction after single lung transplantation for emphysema: Extrinsic restriction versus intrinsic obstruction

Background: A subset of patients with emphysema who have undergone single l ung transplantation (SLT) may subsequently present with dyspnea, worsening airways obstruction, hypoxemia, and progressive chronic native lung hyperin flation. The leading cause of late allograft dysfunction is bronchiolitis o bliterans syndrome (BOS). However, extrinsic restriction manifests with a s imilar clinical presentation and is an additional mechanism to consider. We describe the use of the inspiratory lung resistance (R-Li) to distinguish a decline in respiratory status due predominantly to either extrinsic restr iction or BOS. Methods: We studied five patients who underwent SLT for emphysema between 1 992 and 1995, in whom the diagnoses of BOS and extrinsic restriction were s ubsequently entertained. Forced expiratory volume in 1 second (FEV1), R-Li, Static lung compliance, elastic recoil pressure at total lung capacity (TL C), and the slope of the maximum flow static recoil (MFSR) plot were measur ed. Results: All patients had seven ah-how obstruction, with mean FEV1 0.98 +/- 0.24 liter (26 +/- 5% predicted), elevated static lung compliance, reduced elastic recoil pressure at TLC, and reduced slope of the MFSR plot. Three patients had "low" R-Li (9.3-12.8 cm H2O/L/sec). Obstruction was attributed predominantly to extrinsic restriction, These patients underwent lung volu me reduction surgery (LVRS) on the native lung; improvements in pulmonary m echanics were observed at 6 months. In contrast, two patients had markedly elevated R-Li (17.3 and 17.4 cm H2O/L/sec). Obstruction was attributed pred ominantly to intrinsic airway disease from BOS that was subsequently docume nted at autopsy. Conclusions: The R-Li appears to be a useful adjunct to the clinical histor y in distinguishing a decline in respiratory status due predominantly to ei ther BOS or extrinsic restriction in patients who have undergone SLT for em physema. Determination of the mechanism of allograft dysfunction may allow the selection of an appropriate subset of patients who would benefit from L VRS.