MECHANISM OF SHORT-TERM IMPROVEMENT IN LUNG-FUNCTION AFTER EMPHYSEMA RESECTION

We prospectively investigated the mechanism of airflow limitation befo re and after targeted emphysematous resection in 12 consecutively stud ied adult patients 68 +/- 4 yr of age (mean +/- SD) with very severe C OPD undergoing bilateral thoracoscopic stapling techniques. Lung funct ion, static lung elastic recoil, and airway conductance was measured 2 wk before and 5 to 6 mo after surgery. After surgery, there was a sig nificant (p < 0.01) reduction in TLC (9.3 +/- 0.3 [mean +/- SEM] to 7. 7 +/- 0.4 L), functional residual capacity, and residual volume. Airwa y conductance, FVC, and FEV(1) (0.7 +/- 0.1 to 1.2 +/- 0.2 L) all impr oved significantly (p < 0.01). Lung elastic recoil increased markedly at TLC (from 10.3 +/- 0.5 to 14.6 +/- 1.0 cm H2O; p < 0.001) as did ma ximal expiratory airflow in every patient. Analysis of maximal expirat ory flow-static elastic recoil pressure curve indicated that conductan ce of the 5 segment (Cs) increased from 0.20 +/- 0.03 (mean +/- SEM) t o 0.27 +/- 0.03 L/s/cm H2O (p < 0.01), and the critical transmural pre ssure (Ptm') decreased from 3.1 +/- 0.2 to 2.4 +/- 0.2 cm H2O (p < 0.0 2). Mean airway conductance increased from 0.14 to 0.22 L/s/cm H2O (p < 0.01). The improvement in maximal expiratory airflow can be primaril y attributed to increased lung elastic recoil and its secondary effect on enlarging airway diameter causing increased airway conductance, in creased Gs, and decreased Ptm'.