ALTERED LUNG-MECHANICS AFTER DOUBLE-LUNG TRANSPLANTATION

We studied lung mechanics and small airways function in 15 patients af ter double-lung (DL) transplantation. Patients were classified as stab le (DL-S, n = 11), or having obliterative bronchiolitis syndrome (DL-O BS, n = 4). We performed pulmonary function tests (PFT), measured slop e of phase 3 of the single-breath nitrogen test (N(2)SP3), and obtaine d pressure-volume curves and values: chord compliance (Cst,L), specifi c chord compliance (SCst,L), and elastic recoil pressure at 90% TLC. P FT showed mild restrictive pattern in DL-S and severe obstructive lung disease in DL-OBS. The N2SP3 measurement indicated small airways dysf unction in 82% of DL-S and in all DL-OBS patients. The Cst,L was 0.24 +/- 0.08 L/cm H2O in DL-S and 0.16 +/- 0.05 L/cm H2O in DL-OBS, both l ower than control subjects 0.34 +/- 0.09 L/cm H2O (p < 0.01; p < 0.001 ). Moreover, SCst,L was 0.09 +/- 0.03 cm H2O-1 in DL-S, and 0.05 +/- 0 .02 cm H2O-1 in DL-OBS, significantly lower than control subjects 0.12 +/- 0.02 cm H2O-1 (p < 0.05; p < 0.001). Elastic recoil at 90% TLC wa s normal in 14 of 15 patients. We found a linear correlation between N (2)SP3 and FEV,, and between FEV1 and Cst,L and SCst,L for combined DL -S and DL-OBS. Reduced compliance near FRC with normal elastic recoil at high lung volumes does not suggest changes in lung parenchyma. We s peculate that structural or functional alterations in small airways ma y have contributed to low compliance measurements. Of special concern are our findings that DL-S had significant small airways dysfunction a nd reduced compliance in a pattern similar to the DL-OBS, only smaller in magnitude.