Mechanisms of relief of exertional breathlessness following unilateral bullectomy and lung volume reduction surgery in emphysema.
OBJECTIVE
To explore mechanisms of relief of exertional breathlessness following surgery to reduce thoracic gas volume in patients with emphysema.


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 (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).


CONCLUSIONS
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.
O'Donnell
D E
DE
Department of Medicine, Queen's University, Kingston, Ontario, Canada.
Webb
K A
KA
Bertley
J C
JC
Chau
L K
LK
Conlan
A A
AA
D004417:Dyspnea / Q000209:etiology / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D005652:Functional Residual Capacity; D006801:Humans; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D012115:Residual Volume; D015656:Respiratory Mechanics; D014109:Total Lung Capacity; D014797:Vital Capacity