Analysis of vascular reactivity by near-infrared spectroscopy and the 6-minute walk test in patients after hospitalization for covid-19

<bold>Introduction:</bold> Near Infrared Spectroscopy (NIRS) is a technique used to monitor tissue oxygenation (StO2), and when combined with vascular occlusion testing (VOT), it allows the analysis of muscle physiological adaptations. <bold>Objectives:</bold> To assess vascular reactivity before and after VOT , and correlate it with hospitalization data and the six minute walk test variables in patients diagnosed with COVID-19 after being discharged from the hospital. <bold>Methods:</bold> This is a prospective observational study conducted on COVID-19 patients who underwent VOT with NIRS after being discharged from the hospital. The data was collected while the patients were lying on their back with the NIRS sensor and sphygmomanometer attached to their dominant arm. The study involved three minutes of occlusion and the VOT variables at rest were correlated with walking distance (6MWD), SpO2, heart rate (HR), and length of hospital stay. <bold>Results:</bold> During a period of 139.60 ± 57.63 days after hospital discharge, the study included 47 patients, 35 of whom were male, with a mean age of 56±81 years. The mean 6MWD was 476.38 ± 98.34m. The study identified a significant positive correlation between microvascular reactivity (AUC) and 6MWD (p=0.01), as well as between resaturation (RS) and SpO2 (p=0.01). Furthermore, a weak negative correlation was observed between RS and the length of hospital stay (p=0.03). <bold>Conclusions:</bold> In this sample, the length of hospital stay may have affected the resaturation curve, whereas the diagnosis of Covid-19 did not directly impact on post-hospital discharge functionality.