Skeletal muscle oxygen tension as a measure of COVID-19 disease severity and predictor of disease progression, 2025, Neil Stacey et al

[Mij]

Highlights​

Diminished muscle oxygen saturation is likely to be closely correlated with COVID-19 disease severity.
•
Diminished muscle oxygen saturation is likely to be predictive of COVID-19 disease progression.
•
Near-Infrared Spectroscopy (NIRS) can augment existing markers tracking disease progression in COVID-19 patients.
•
Diminished muscle oxygen creates a pro-thrombotic, inflammatory environment likely to exacerbate COVID-19 disease severity.

Abstract​

Since the outbreak of the COVID-19 pandemic, over 7 million confirmed deaths from COVID-19 have been reported worldwide, but the true death toll is believed to be much higher. Although the risk contributions of various co-morbidities have been well documented, it remains unclear precisely why some patients become severely ill while the majority have mild symptoms or are asymptomatic, and no accurate means of predicting a patient’s progression to severe illness.

In this paper, it is hypothesized that reduced oxygen tension in skeletal muscle is indicative of COVID-19 disease severity and predictive of subsequent progression in severity of illness. Muscle Oxygen Tension can be measured non-invasively, offering a ready means of determining the extent to which a patient’s overall oxygen inventory in the body has diminished, thereby tracking an important aspect of disease progression.

It is further hypothesized that diminished muscle oxygen tension during acute illness is likely to be a predictor of long-term sequelae.
LINK

 

[SNT Gatchaman]

Summary quotes, reordered —

There are strong arguments that measuring muscle oxygen tension using NIRS would be a valuable clinical tool in managing COVID-19 patients. Treatment protocols that currently depend primarily on pulse oximetry or invasive blood sampling could be modified to utilize muscle oxygen tension not just as a measure of overall severity but also as an indicator of specific mechanisms of disease progression with clinical significance.

While arterial SpO2 is a key parameter in assessing and managing COVID-19 severity, it is important to recognize that using pulse oximetry to measure arterial SpO2 provides an incomplete representation of the body’s total oxygen inventory.

It is possible for tissue hypoxia to occur in the absence of hypoxemia, for instance if oxygen delivery is impaired while blood oxygenation is not

If this hypothesis is correct, skeletal muscle oxygen tension, measured in conjunction with arterial SpO2, will offer a more complete picture of disease progression than arterial SpO2 by itself.

The body has three major stores of accessible oxygen. In an average adult person, 820 mL of oxygen is bound to haemoglobin, 200 mL is bound to myoglobin, and 45 mL is dissolved in tissues. As described in Persichini et al, approximately 70% of available blood volume is venous blood. With an arterial blood oxygen saturation of 95% and a venous oxygen saturation of 75%, it can be calculated that of the 820 ml typically in the blood, roughly 290 mL is contained in arterial blood and the remaining 530 ml are in venous blood. This means that arterial blood comprises just 27% of the body’s total oxygen inventory at any given time. Pulse oximetry, as the main means of monitoring patient oxygen status, is therefore only sampling a small portion of the total oxygen inventory in the body

Oxygen bound to myoglobin constitutes 19% of typical oxygen stores and, assuming that approximately half of the tissue-dissolved oxygen is contained in skeletal muscle, due to its large proportion of total body mass, it can be presumed that, under typical conditions, oxygen contained in muscle constitutes in excess of 20% of the body’s total oxygen inventory.

Unlike pulse oximetry, which only measures the oxygen saturation in arterial blood, NIRS provides insight into the oxygen status of tissues and muscles, capturing another sizable component of total oxygen inventory. This is particularly important in critically ill patients where peripheral tissue oxygenation may be compromised even when arterial SpO2 appears stable

A study tracking past COVID-19 patients found that myopathy and neuropathy can occur even following asymptomatic infection, which implies underlying mechanisms of pathology independent of primary symptoms such as respiratory distress. This would suggest that muscle oxygen tension, even if not a primary indicator of disease severity, may have clinical usefulness as an indicator of these mechanisms and therefore may be clinically useful as a predictor of the various long-term sequelae referred to as Long Covid.