Comparison of Exercise Tolerance and Detectability of Silent Hypoxia in Patients with Moderate and Severe COVID-19 Preparing for Discharge Using Different Field Tests

INTRODUCTION: The prevalence of silent hypoxia in patients with COVID-19 has been reported as 20–50%. There is a need for specific field tests to detect silent hypoxia. This comparative study aimed to investigate whether the 2-minute walk test (2MWT), 40-step walk test (40SWT), and 1-minute sit-to-stand test (1MSTST) can be used as alternatives to the 6-minute walk test (6MWT) in the evaluation of silent hypoxia and functional capacity in COVID-19 patients.
METHODS: Of 135 patients in the COVID-19 ward, 30 participants with moderate-to-severe COVID-19 who met the inclusion criteria were included in the study. Participants performed the 6MWT, 2MWT, 40SWT, and 1MSTST in that order. In addition to performance results, the participants’ heart rate, respiratory rate, saturation levels, and perceived dyspnea and fatigue levels were recorded before and immediately after each test.
RESULTS: Saturation values measured during the 6MWT were positively correlated with those in the 2MWT (r=0.793, p<0.001), 40SWT (r=0.554, p=0.001), and 1MSTST (r=0.806, p<0.001). In terms of performance, there was a moderate positive correlation between 6MWT and 2MWT distances (r=0.542, p=0.002) and a moderate negative correlation between 6MWT distance and 40SWT time (r=-0.605, p<0.001).
DISCUSSION AND CONCLUSION: The 2MWT, 40SWT, and 1MSTST could be used in the clinic as alternatives to the 6MWT in the assessment of silent hypoxia, while the 2MWT and 40SWT could also be used as alternatives for determining functional capacity in patients with acute COVID-19.

Keywords: 6-minute walk test, COVID-19, exercise tests, exercise tolerance, hypoxia.