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 Materials and methods: We studied 8 patients with emphysema (FEV(1)=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) mere 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: FEV(1), 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<0.03), 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 (Delta BorgSTD) 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.