Abstract
It has been recently reported that some patients with chronic obstructive pulmonary disease (COPD) may actively recruit the expiratory abdominal (AB) muscles in order to avoid exercise-related dynamic hyperinflation. It remains unclear, however, whether this strategy is universally efficacious in counterbalancing the potential increases in rib cage (RC) volumes thereby promoting a net deflating effect on chest wall (CW). Thirty males with COPD (FEV1= 43.8±9.5%) performed a constant work rate cardiopulmonary exercise test (75% max) to the limit of tolerance (Tlim) on a cycle ergometer. Breath-by-breath ventilatory kinematics was continuously monitored by optoelectronic plethysmography (BTS, Italy). End-expiratory volume of the RC (EEVRC) and EEVCW significantly increased from rest to Tlim in 17 patients. EEVAB remained stable in 9 of them (“non-recruiters/hyperinflators”); in contrast, it decreased slightly in 7 “recruiters/hyperinflators” thereby lessening CW hyperinflation. EEVRC remained stable and EEVAB decreased sharply in the remaining 13 “recruiters/non-hyperinflators”. “Recruiters/hyperinflators” showed higher dyspnoea scores and the worst exercise capacity (∼80% lower than the “recruiters/non-hyperinflators”) (p<0.05). In conclusion, CW deflation secondary to extensive AB recruitment was restricted to COPD patients showing no evidences of RC hyperinflation. On the other hand, pronounced increases in RC volumes were associated with milder degrees of AB recruitment. Although this avoided more severe CW hyperinflation, it was related to intense breathlessness and poor exercise tolerance.
Supported by: FAPESP and CNPq, Brazil
- © 2011 ERS