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Cardiorespiratory Response to Different Exercise Tests in Interstitial Lung Disease.

Med Sci Sports Exerc. 2016 Jul 18;

Authors: Chéhère B, Bougault V, Gicquello A, Wallaert B

Abstract
INTRODUCTION: The 6-minute stepper test (6MST) has been used as an alternative to the 6-minute walk test (6MWT) to assess exercise tolerance in patients with interstitial lung disease (ILD). Recent data suggest that the tests may involve different energy pathways and cardiorespiratory responses. We thus aimed to compare the cardiorespiratory responses of ILD patients during the 6MWT and the 6MST.
METHODS: Thirty-one patients with ILD were randomised to perform both tests in the order 6MST→6MWT (n=16) or 6MWT→6MST (n=15). Gas exchange, heart rate, and pulse O2 saturation (SpO2) were measured continuously, and dyspnoea, leg discomfort, and blood lactate concentration were assessed before and immediately after each test.
RESULTS: Oxygen uptake (VO2) was lower (p=0.002) and respiratory equivalent ratio for O2 (VE/VO2) and respiratory exchange ratios were higher (both p<0.001) during the 6MST compared with the 6MWT. The 6MST was also associated with higher blood lactate concentrations (6MST 4.16±1.95 mmol·L, 6MWT 2.84±1.17 mmol·L; p=0.01), higher leg discomfort scores (6MST 5±3 points, 6MWT 3±2 points; p<0.001), and smaller decreases in SpO2 (6MST -5±5%, 6MWT -9±6%; p<0.001).
CONCLUSIONS: ILD patients exhibited greater ventilatory responses and lower arterial O2 desaturation during the 6MST compared with the 6MWT. The higher lactate concentrations and perceived muscle fatigue observed during the 6MST may indicate the presence of inter-test differences in active muscle metabolism that could contribute to the distinct cardiorespiratory responses.

PMID: 27434081 [PubMed - as supplied by publisher]