Effect of an acute exercise bout on alveolar–capillary membrane permeability and interstitial fluid accumulation in COPD

Abstract Exertional dyspnoea is a debilitating symptom in chronic obstructive pulmonary disease (COPD) and often persists after the cessation of exercise. The underlying mechanisms are not fully understood, and a potential contributing factor that has not previously been investigated is alveolar–capillary membrane breaching with extravasation of fluid into the lungs. Sixteen individuals with COPD and 16 age‐ and sex‐matched healthy controls were included. Alveolar–capillary membrane permeability was quantified using the pulmonary clearance index (PCI), calculated from scintigraphically determined alveolar clearance of 99m Tc‐labelled diethylenetriaminepentaacetic acid at rest and following an acute exercise bout performed at maximal exertion, as determined by a prior cardiopulmonary exercise test. In addition, lung tissue mass (LTM) was assessed using low‐dose computed tomography, with rest‐to‐post‐exercise changes interpreted as reflecting alterations in interstitial fluid accumulation. The mean change in PCI from rest‐to‐post‐exercise was −0.01 [95% CI: −0.09, 0.06]%/min in the COPD group and −0.05 [95% CI: −0.12, 0.02]%/min in the healthy control group (Group × Time interaction, P = 0.446). The mean change in LTM from rest‐to‐post‐exercise was 16.5 [95% CI: −7.0, 40.0]g/1.73 m 2 in the COPD group and 35.2 [95% CI: 11.7, 58.7]g/1.73 m 2 in the healthy control group (Group × Time interaction, P = 0.258). In conclusion, the present study found no evidence of alveolar–capillary membrane breaching following maximal exercise, neither in individuals with COPD nor in healthy matched controls.