Never-smokers with occupational COPD have better exercise capacities and ventilatory efficiency than matched smokers with COPD.

Soumagne T; Guillien A; Roche N; Dalphin JC; Degano B;

Journal of applied physiology (Bethesda, Md. : 1985) [J Appl Physiol (1985)] 2020 Oct 01. Date of Electronic Publication: 2020 Oct 01.

Background: COPD in never-smokers exposed to organic dusts is still poorly characterized. Therapeutic strategies in COPD are only evaluated in smoking-related COPD. To understand how never-smokers with COPD behave during exercise is an important prerequisite for optimal management.
Objectives: To compare physiological parameters measured at exercise between never-smokers exposed to organic dusts with COPD and patients with smoking-related COPD matched for age, sex and severity of airway obstruction. Healthy controls were also studied.
Methods: Dyspnea (Borg scale), exercise tolerance and ventilatory constraints were assessed during incremental cycle cardiopulmonary exercise testing in COPD patients at mild-to-moderate stages (22 exposed to organic dusts, postbronchodilator FEV 1 /FVC z-score: -2.44±0.72 and FEV 1 z-score: -1.45±0.78; 22 with smoking-related COPD, FEV 1 /FVC z-score: -2.45±0.61; FEV 1 z-score: -1.43±0.69) and 44 healthy controls (including 22 never-smokers).
Results: Despite the occurrence of similar significant dynamic hyperinflation, never-smokers COPD patients exposed to organic dusts had lower dyspnea ratings than those with smoking-related COPD. They also had higher peak oxygen consumption, peak power output and better ventilatory efficiency than smoking-related COPD, all these parameters being similar controls. Differences in exercise capacity between the two groups of COPD were mainly driven by better ventilatory efficiency stemming from preserved diffusing capacity.
Conclusion Never-smokers exposed to organic dusts with mild-to-moderate COPD have better exercise capacities, better ventilatory efficiency and better diffusion capacity than matched patients with smoking-related COPD.