Mechanisms of Relief of Exertional Breathlessness Following Unilateral Bullectomy and Lung Volume Reduction Surgery in Emphysema

Study objective To explore mechanisms of relief of exertional breathlessness following surgery to reduce thoracic gas volume in patients with emphysema. Materials and methods We studied 8 patients with emphysema (FEV1=39±3% predicted; residual volume [RV]=234 ± 12% predicted; mean±SEM) who were severely breathless despite optimal pharmacotherapy and who underwent unilateral bullectomy for giant bullae (greater than one third hemithorax); 4 of these also had ipsilateral lung reduction (pneumectomy). Pulmonary function and cycle exercise performance (n=6) were evaluated before and 13 ± 3 weeks after surgery. Chronic breathlessness was measured with the Baseline Dyspnea Index and the Medical Research Council dyspnea scale. Exertional breathlessness was measured using Borg ratings at a standardized work rate (BorgSTD). Results FEV1, FVC, and maximal inspiratory pressures increased postsurgery by 29 ± 7% (p<0.05), 24 ± 10% (p=0.06), and 39 ± 12% (p<0.01), respectively. Plethysmographic total lung capacity, RV, and functional residual capacity fell by 14±2%, 30±4%, and 18±3%, respectively (p<0.001). All measures of chronic breathlessness improved significantly (p<0.05). During exercise at a standardized work rate, BorgSTD fell 45% (p<0.05), end-expiratory lung volume (EELV) fell 22% (p<0.01), and breathing frequency (F) fell 25% (p=0.08). By multiple stepwise regression analysis, 99% (p=0.007) of the variance in symptom relief (ABorgSTD) was explained by the combination of decreased ratio of the end-expiratory lung volume to total lung capacity, decreased F, and diminished mechanical constraints on tidal volume (tidal volume to vital capacity ratio). Conclusion Reduced exertional breathlessness at a given workload after volume reduction surgery was attributed to a combination of reduced thoracic hyperinflation, reduced F, and reduced mechanical constraints on lung volume expansion. To explore mechanisms of relief of exertional breathlessness following surgery to reduce thoracic gas volume in patients with emphysema. We studied 8 patients with emphysema (FEV1=39±3% predicted; residual volume [RV]=234 ± 12% predicted; mean±SEM) who were severely breathless despite optimal pharmacotherapy and who underwent unilateral bullectomy for giant bullae (greater than one third hemithorax); 4 of these also had ipsilateral lung reduction (pneumectomy). Pulmonary function and cycle exercise performance (n=6) were evaluated before and 13 ± 3 weeks after surgery. Chronic breathlessness was measured with the Baseline Dyspnea Index and the Medical Research Council dyspnea scale. Exertional breathlessness was measured using Borg ratings at a standardized work rate (BorgSTD). FEV1, FVC, and maximal inspiratory pressures increased postsurgery by 29 ± 7% (p<0.05), 24 ± 10% (p=0.06), and 39 ± 12% (p<0.01), respectively. Plethysmographic total lung capacity, RV, and functional residual capacity fell by 14±2%, 30±4%, and 18±3%, respectively (p<0.001). All measures of chronic breathlessness improved significantly (p<0.05). During exercise at a standardized work rate, BorgSTD fell 45% (p<0.05), end-expiratory lung volume (EELV) fell 22% (p<0.01), and breathing frequency (F) fell 25% (p=0.08). By multiple stepwise regression analysis, 99% (p=0.007) of the variance in symptom relief (ABorgSTD) was explained by the combination of decreased ratio of the end-expiratory lung volume to total lung capacity, decreased F, and diminished mechanical constraints on tidal volume (tidal volume to vital capacity ratio). Reduced exertional breathlessness at a given workload after volume reduction surgery was attributed to a combination of reduced thoracic hyperinflation, reduced F, and reduced mechanical constraints on lung volume expansion.