Comparison of the functional results of single lung transplantation for pulmonary fibrosis and chronic airway obstruction

Background - Single lung transplantation (SLT) is now a treatment option for patients with both pulmonary fibrosis and advanced chronic airway obstruction. Lung function after transplantation might be expected to be different in these two groups of patients because of the effect of the remaining native lung, but the implications of these differences have not been fully explored. Methods - The functional results of a stable population of 20 patients (13 chronic airway obstruction, seven pulmonary fibrosis) after SLT with no evidence of obliterative bronchiolitis were analysed. The differences between the two populations in the interrelations between and determinants of total lung capacity (TLC), subdivisions of lung volume, airway function (spirometry, maximum expiratory flow volume curves, and moments analysis of the spirogram), respiratory mechanics (PV curves and maximal respiratory pressures), CO transfer factor (TLCO) and the distribution of perfusion, ventilation and volume of the transplanted and native lungs were compared. Results - Total lung capacity after SLT (TLCpost) was normal in the patients with pulmonary fibrosis (mean (SE) 103.9 (6.9)% predicted) but remained significantly elevated in patients with airway obstruction (126.4 (4.4)%). Forced expiratory volume in one second (FEV1) and vital capacity (VC) improved to similar values after SLT in both groups with a final VC of 76.8 (5.9)% and 66.7 (3.9)% in patients with fibrosis and airway obstruction, respectively. Maximum expiratory flows were generally lower and moments analysis of the spirogram showed slower lung emptying with significantly greater second and third moments (alpha(2) and alpha(3)) in patients with airway obstruction. Relative ventilation and perfusion of the transplanted lung were both greater in both populations but relative ventilation of the transplanted lung was significantly greater in patients treated for airway disease than in those with pulmonary fibrosis. TLCO was also significantly higher in patients who had received a transplant for chronic airway obstruction. Conclusions - These results suggest that differences in the functional results of SLT for airway disease and pulmonary fibrosis are relatively minor. In this series the native hyperinflated lung in chronic airway disease was not more disadvantageous to overall function than the native lung in pulmonary fibrosis. However, tests of lung function based on the terminal portion of the forced spirogram are likely to be less sensitive for the detection of obliterative bronchiolitis in patients who have received a transplant for advanced airway obstruction than in those with pulmonary fibrosis.