Ventilatory analysis during 6MWT gives relevant information about exercise limitation in COPD

Abstract

It's well known that exercise performance of COPD is limited by ventilation (VE), in particular the inability of further increasing VE. The 6-minute walk test (6MWT) is the most established field exercise test. The VE analysis during 6MWT can be an useful tool to better understand the causes of exercise limitation in COPD.

Aim: to investigate the respiratory responses during 6MWT in untrained COPD.

Methods: 37M, 12F (age 48-85 yr) performed spirometry and 6MWT equipped with Spiropalm^®, an instrument which allow VE measurement breath by breath and a continuous monitoring of heart rate and SpO₂. Breathing reserve (BR) is calculated by the instrument as the difference between maximal voluntary ventilation (FEV₁x40) and max VE reached during the test.

Results: Subjects were classified according to FEV₁ as % of predicted. 6MWT data are reported in Table 1.

We found a correlation between FEV₁ and BR (r=0.86, p<0.001); BR and oxygen desaturation [basal SpO₂ minus final SpO₂ (r=-0.38, p=0.009)]; BR and dyspnea Borg score (r=-0.36, p=0.01). A correlation between distance and dyspnea was also found (r=-055, p<0.001).

Conclusion: BR is a mark of exercise limitation, therefore the analysis of VE during 6MWT can be a simple tool contributing to explain exercise limitation in COPD even in the absence of more sophisticated tests.