Pulmonary adaptations to 12 weeks of supervised high intensity interval training in COPD: A non-randomized controlled pilot study.

Objective. To investigate the change in diffusing capacity from rest to submaximal exercise in patients with mild to severe COPD compared to a healthy, age- and sex matched control group, and to investigate if the diffusing capacity can be altered by high-intensity interval training (HIIT). Methods. 35 patients with COPD and 15 healthy age- and sex matched controls were included. Pulmonary diffusing capacity was measured using the combined single-breath method using carbon monoxide and nitric oxide (D_L,CO,NO), which were measured at rest and during 60% of peak workload (W_Lpeak) to estimate the alveolar-capillary reserve (change from rest to exercise). A subgroup of 12 patients with COPD and 12 control participants completed a 12-week supervised HIIT intervention with measurements of D_L,CO,NO, computed tomography-based lung tissue mass, and single-photon emission computed tomography to assess the pulmonary perfusion distribution pre and post the HIIT intervention. Results. The alveolar-capillary reserve was reduced in COPD patients in a severity-dependent manner compared to the healthy control group and this was unaltered following the HIIT intervention, despite an increase in exercise capacity. HIIT did not increase lung tissue mass, nor did it improve the pulmonary perfusion distribution during exercise in either group. Conclusion: Alveolar-capillary reserve is reduced in a severity-dependent manner in COPD, and a 12-week supervised HIIT intervention did not induce any changes in either the alveolar-capillary reserve or lung tissue mass, suggesting that the concomitant increase in exercise capacity is likely due to extrapulmonary adaptations.