Ventilatory mechanics and gas exchange during exercise before and after lung volume reduction surgery

Abstract

Many patients with emphysema are able to meet ventilatory demands during resting conditions, but they show severe limitations during exercise. To examine the effect of lung volume reduction (LVR) surgery on exercise performance and the mechanism of possible improvement, we measured ventilatory mechanics (pulmonary resistance [RL], work of breathing [WOB], dynamic intrinsic positive end-expiratory pressure [PEEPi,dyn], peak expiratory flow rate [PEFR]), breathing pattern, oxygen uptake (V O2), and carbon dioxide removal (V CO2) at rest and during cycle ergometry in eight patients before and 3 mo after LVR surgery. Ventilatory mechanics were evaluated assessing esophageal pressure and air flow. Three months after LVR surgery, the tolerated workload was doubled when compared with the preoperative value (p < 0.0005), associated with a reduction of RL (p < 0.05), PEEPi,dyn (p < 0.005), and WOB (p < 0. 005) at comparable workloads. Maximal ventilatory capacity and maximal tidal volume (VT) increased significantly (p < 0.01). Maximal V O2 increased from 474 +/- 23 to 601 +/- 16 ml/min (p < 0. 005) and maximal V CO2 from 401 +/- 13 to 558 +/- 21 ml/min (p < 0. 005), though no significant difference at comparable workloads could be observed. In conclusion, emphysema surgery leads to an improvement of ventilatory mechanics at rest and during exercise. Higher maximal VT and minute ventilation were observed, resulting in improvement of maximal V O2 and V CO2 and exercise capacity.