Effects of Lung Volume Reduction Surgery for Emphysema on Oxygen Cost of Breathinga

Background Patients with severe pulmonary emphysema have a greatly increased oxygen cost of breathing (O 2 cost), and this is the cause of serious malnutrition, or respiratory cachexia, in such patients. Study objectives To clarify the effect of lung volume reduction surgery (LVRS) on respiratory function and the nutritional state of these patients through a reduction in the O 2 cost of the respiratory muscles. Design Prospective cohort study. Setting, patients, and interventions Twenty-three patients who underwent LVRS in Tohoku University Hospital. Measurements Pulmonary function and O 2 cost were measured perioperatively by utilizing a method of continuous dead space. In addition, we calculated the proportion of oxygen consumption ( V ˙ o 2 ) of respiratory muscles to total V ˙ o 2 (% V ˙ o 2 resp) from the measured energy expenditure and the predicted values. Results FEV 1 and arterial oxygen pressure increased after surgery while lung volume and dyspnea decreased (p 2 cost was also reduced from 0.044 to 0.026 log(mL/min)/(L/min) [p 2 cost had a strong negative correlation with that of FEV 1 ( r = − 0.70, p r = 0.54, p < 0.01). % V ˙ o 2 resp was 23.1% at rest and 55.5% at maximal ventilation. LVRS reduced % V ˙ o 2 resp at maximal ventilation to 49.0% (p < 0.05), but % V ˙ o 2 resp at rest did not decrease after surgery. Conclusions LVRS reduces energy expenditure of respiratory muscles especially during exercise by decreasing small airway obstruction and hyperinflated lung volume. This may reverse the malnourished state in end-stage emphysema.