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

Abstract

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.

Effect of Psychological Stress on Microcirculation Oscillations: Diagnostic Aspects

“…The results of this study and the results presented in reference 4 for stress due to physical exhaustion and viral infection suggest that the NOI parameter can be used to evaluate stress of any origin. However, some distinctive differences were noticed.…”

“…Very recently, we showed that chronic fatigue associated with post-COVID syndrome and transient fatigue caused by high-intensity exercise are comparable in terms of vascular effects. 4 The analysis of microcirculation oscillations detected at rest using the Flow Mediated Skin Fluorescence (FMSF) technique can be of particular use for monitoring physical stress related to strenuous exercise or post-infection fatigue. It is rational to assume that a similar methodology can be applied to assess the vascular consequences of psychological stress.…”

“…The NOI parameter represents the contribution of endothelial and neurogenic oscillations relative to all oscillations detected at low-frequency intervals (<0.15 Hz). 4 Based on numerous FMSF measurements of patients affected by stress of various origins, it has been established that a low NOI value (<60%) indicates microcirculatory disorders caused by a stress factor, such as emotional stress, physical exhaustion, or post-infection stress, and may be reversible. Chronically low NOI values can lead to the development of serious vascular circulatory disorders.…”

Non-Invasive Assessment of Vascular Circulation Based on Flow Mediated Skin Fluorescence (FMSF)

“…One such exception may be the analysis of the flowmotion at rest, especially the relative ratio of endothelial and neurogenic oscillations to myogenic oscillations. Thus, a new parameter representing the contribution of endothelial and neurogenic oscillations relative to all oscillations detected at low frequency intervals (<0.15 Hz) can be introduced [ 45 ]: NOI = [PSD(endothelial) + PSD (neurogenic)]/[PSD(endothelial) + PSD (neurogenic) + PSD(myogenic)] × 100% …”

Non-invasive Assessment of Vascular Circulation Based on Flow Mediated Skin Fluorescence (FMSF)

“…One such exception may be the analysis of the flowmotion at rest, especially the relative ratio of endothelial and neurogenic oscillations to myogenic oscillations. Thus, a new parameter representing the contribution of endothelial and neurogenic oscillations relative to all oscillations detected at low frequency intervals (< 0.15 Hz) can be introduced [45]: NOI = [PSD(endothelial) + PSD (neurogenic)]/[PSD(endothelial) + PSD (neurogenic) + PSD(myogenic)] × 100% Despite of the decrease of flowmotion (FM) at rest with age, the NOI parameter remains age independent. Moreover, in patients with some diseases affecting the vascular system and thus also basal flowmotion, such as diabetes mellitus (group C -diabetes type-2 patients, n = 70 (40 m, 32 f), mean age 63.1 (45-80 y.…”