Abstract
Background: Exercise-induced arterial O2 desaturation impacts the management of interstitial lung diseases (ILD). Recent data suggest that arterial O2 desaturation is more severe during the 6-minute walk test (6MWT) than during the 6-minute stepper test (6MST) in ILD patients.
Aims: We hypothesized that a higher ventilation (VE) during the 6MST facilitates the alveolo-arterial oxygen diffusion, minimizing O2 desaturation. Our aim was to investigate differences in ventilator responses and gas exchange during 6MST and 6MWT.
Methods: Twenty-nine patients with ILD performed a 6MWT and a 6MST in a random order. Gas exchange, heart rate (HR), and oxygen pulse saturation (SpO2) were measured continuously and leg discomfort (LD) was quoted on a 10-point Borg Scale, before and at the end of each test.
Results: At rest no difference in HR, VE and VO2 was observed before both tests. As expected, the decrease in SpO2 was significantly lower during the 6MST than during the 6MWT (-5 ± 5% vs -9 ± 7%, p<0.001). Heart rate and VE were not different during both tests. At each time-point, oxygen uptake (VO2) was lower (p=0.01), but VE/VO2 and respiratory exchange ratios were higher during 6MST than during 6MWT (p<0.001). The LD score was also higher at the end of 6MST than after 6MWT (5 ± 3 vs 3 ± 2, p=0.003).
Conclusion: The higher VE/VO2 ratio may have contributed to the lower O2 desaturation during the 6MST. The higher muscle fatigue perceived during 6MST, possibly also indicated differences of active muscle metabolism, which probably contributed to the different ventilatory responses and arterial O2 desaturation between both tests.
- Copyright ©ERS 2015