LUNG REDUCTION SURGERY IN SEVERE COPD DECREASES CENTRAL DRIVE AND VENTILATORY RESPONSE TO CO2

Background and objectives: Lung volume reduction surgery (LVRS) improv es ventilatory function in selected patients with severe COPD. The rea sons for the observed benefits include the following: increased elasti c recoil, improved airflow, and lesser dynamic hyperinflation and decr eased lung volumes. We reasoned that these changes could also alter re spiratory drive. Methods: Respiratory central drive was prospectively assessed using the month occlusion pressure (P-0.1), and the P-0.1 res ponse to increasing CO2 (P-0.1/PETCO2 [end-tidal CO2 pressure]), in ei ght sequential patients before and 3 to 5 months after LVRS. Results w ere compared with those from 13 control subjects.Results: LVRS decreas ed total lung capacity from 7.44+/-1.8 L to 5.92+/-1.3 L (p<0.05) and residual volume from 4.97+/-1.5 L to 3.56+/-1.1 L (p<0.05). It also si gnificantly improved FEV1 from 0.85+/-0.26 L 0.99+/-0.26 L (p<0.05). B aseline P-0.1 (3.4+/-1.8 vs 1.4+/-0.4 cm H2O, p<0.01) and P-0.1/PETCO2 (0.24+/-0.07 vs 0.11+/-0.04 cm H2O/mm Hg, p<0.05) were higher in pati ents than in control subjects. After LVRS, P-0.1 decreased from 3.4+/- 1.8 to 1.3+/-0.75 cm H2O (p<0.01) and P-0.1/PETCO2 from 0.24+/-0.07 to 0.16+/-0.06 cm H2O/mm Hg (p<0.05). These postoperative values were si milar to those of control subjects. There were no correlations between changes in the factors known to influence central drive (PaO2, PaCO2, age, weight, height, FVC, and FEV1) and changes in P-0.1. Conclusions : We conclude that decreased ventilatory drive should be added to the list of benefits of LVRS, and may help explain the symptomatic improve ment reported by many patients after this surgery.