Thoracoscopic Lung Volume Reduction Surgery Reduces Dyspnea and Improves Exercise Capacity in Patients with Emphysema

Abstract

Improved ventilation and exercise capacity follows thoracoscopic lung volume reduction surgery (TLVRS) in patients with severe emphysema. This improvement could be related to changes in inspiratory and expiratory flows following surgery, with consequent improvement in dyspnea indices. Changes in inspiratory/expiratory flows at rest and exercise and their relation to subjective improvement in dyspnea after TLVRS are not well known. We studied 25 patients with severe emphysema who underwent unilateral TLVRS performed in well-defined zones with decreased perfusion in nuclear medicine lung scans. Early follow-up after surgery (4.2 ± 0.8 mo) showed significant improvements in exercise tolerance: The distance covered over a 6 min walk test increased from 934 ± 297 to 1,071 ± 241 ft (p = 0.01). Exercise tolerance using a bicycle ergometer showed increased exercise endurance from 4.43 ± 1.7 to 5.71 ± 1.8 min (p < 0.001). The maximum workload tolerated increased from 37 ± 19 to 52 ± 21 W (p < 0.01) and Vo2 max changed from 9.7 ± 2 to 11.8 ± 3 (ml-kg)/min (p < 0.01). This increment was achieved by generating significantly larger minute ventilation (V̇e), from 24 ± 11 to 29 ± 10 L/min, reached through larger tidal volumes (increasing from 951 ± 330 to 1,145 ± 367 ml), while maintaining the same maximum respiratory rates. Increased V̇e was also accompanied by significant increases in both average inspiratory and expiratory flows measured during exercise: from 0.89 ± 0.41 L/s to 1.06 ± 0.08 L/s, and from 0.77 ± 0.37 to 0.90 ± 0.32 L/s respectively (p < 0.01). The parallel increment in flows resulted in constant Ti/Ttot relationship. These functional changes correlated with increased inspiratory flows at rest measured with pulmonary function tests (forced inspiratory volume in one s [FIV1], expiratory flows [FVC, FEV1], and increased maximum voluntary ventilation [MVV]) following the surgically induced reduction in residual volume (RV). These objective changes occurred parallel to improved dyspnea indices. The Baseline Focal Score was 3.36 ± 1.47 and the Transition Focal Score was 6.12 ± 0.7. The objectively measured variables at rest that best correlated with subjective improvement in dyspnea were the change in MVV, change in resting arterial PaO2, and change in FEV1 following TLVRS. Exercise variables did not have significant correlation with subjective markers indicating improvement in dyspnea, with the exception of the change in Dyspneic Index [(V̇E/MVV)100] at maximum exercise.