Chronic Fatigue Associated with Post-COVID Syndrome versus Transient Fatigue Caused by High-Intensity Exercise: Are They Comparable in Terms of Vascular Effects?

PURPOSE: The pathophysiology of chronic fatigue associated with post-COVID syndrome is not well recognized. It is assumed that this condition is partly due to vascular dysfunction developed during an acute phase of infection. There is great demand for a diagnostic tool that is able to clinically assess post-COVID syndrome and monitor the rehabilitation process. PATIENTS AND METHODS: The Flow Mediated Skin Fluorescence (FMSF) technique appears uniquely suitable for the analysis of basal microcirculatory oscillations and reactive hyperemia induced by transient ischemia. The FMSF was used to measure vascular circulation in 45 patients with post-COVID syndrome. The results were compared with those for a group of 26 amateur runners before and after high-intensity exercise as well as for a control group of 32 healthy age-matched individuals. RESULTS: Based on the observed changes in the NOI (Normoxia Oscillatory Index) and RHR (Reactive Hyperemia Response) parameters measured with the FMSF technique, it was found that chronic fatigue associated with post-COVID syndrome is comparable with transient fatigue caused by high-intensity exercise in terms of vascular effects, which are associated with vascular stress in the macrocirculation and microcirculation. Acute and chronic fatigue symptomatology shared similarly altered changes in the NOI and RHR parameters and both can be linked to calcium homeostasis modification. CONCLUSION: The NOI and RHR parameters measured with the FMSF technique can be used for non-invasive clinical assessment of post-COVID syndrome as well as for monitoring the rehabilitation process.