Post-Exertion Rate of Reperfusion vs Point-by-Point analysis of skeletal tissue NIRS during repeated fatigue recovery under normoxia and hypoxemia

Full Title: Post-Exertion Rate of Reperfusion vs Point-by-Point analysis of skeletal tissue near-infrared spectroscopy during repeated fatigue recovery under normoxia and hypoxemia, 2023, Cory M Smith

Highlights

• Point-by-Point analysis identifies the time-point that recovery is initiated.
• Point-by-Point analysis compares groups to one another during composite analysis.
• Post-Exertion Rate of Reperfusion examines changes in recovery during the course of treatment.
• Post-Exertion Rate of Reperfusion is more sensitive to overall recovery of skeletal tissue.

Abstract
Objective
Near-Infrared Spectroscopy (NIRS) analysis techniques can often be complex to perform and interpret resulting in a barrier for wide-spread clinical use. The traditional Point-by-Point analysis methodology and our Post-Exertion Rate of Reperfusion method were examined during the recovery phases following repeated bouts of physical exertion to determine the physiological processes and information captured by each methodology under normal exertion conditions (FiO2: 0.210) and when in hypoxic conditions (FiO2: 0.129).
Methods
To achieve this, a total of n = 15 participants performed 3 sets of leg extensions to failure at 70 % their maximal effort. A 1-min rest was performed following each set where the Point-by-Point analysis means were calculated at every 6-s time to recovery for a total of 10 mean values. The Post-Exertion Rate of Reperfusion examined the linear slopes for the entire 60-s. The near-infrared spectroscopy device was placed over the vastus lateralis and measure for muscle tissue oxygen saturation, oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin were obtained for both the Point-by-Point and Post-Exertion Rate of Reperfusion analysis.
Results
Post-Exertion Rate of Reperfusion slopes were significantly different between normoxia and hypoxia for muscle tissue oxygen saturation (Normoxia: 0.151–0.171; Hypoxia: 0.068–0.116), oxygenated hemoglobin (Normoxia: 0.127 – 0.134; Hypoxia: 0.045 – 0.076), deoxygenated hemoglobin (Normoxia: −0.142 to −0.152; Hypoxia: −0.054 to −0.100), and total hemoglobin (Normoxia: −0.011 to 0.0250; Hypoxia: −0.009 to 0.024). Point-by-Point analysis identified significant differences between muscle tissue oxygen saturation and oxygenated hemoglobin, but not deoxygenated hemoglobin and total hemoglobin.
Conclusion
Point-by-Point analysis and Post-Exertion Rate of Reperfusion can each provide distinctly unique information during exertional recovery. Point-by-Point analysis was ideal for detecting the onset of change in muscle oxygen status. Post-Exertion Rate of Reperfusion identified overall rates of change and was shown to be more sensitive at identifying changes in overall recovery of skeletal tissue reperfusion rates. Point-by-Point analysis and Post-Exertion Rate of Reperfusions may be utilized individually or separately to improve the interpretability of skeletal NIRS metrics within research or clinical settings.

 

Normoxia and hypoxemia? Shouldn't it be hypoxia?

 

@MeSci

Hypoxemia and hypoxia are related conditions that involve low oxygen levels in the body, but they affect different parts of the body.

 

• Hypoxemia Low oxygen levels in the blood. A healthy level of oxygen in the arteries is 75–100 millimeters of mercury (mm Hg), while hypoxemia is defined as a level below 60 mm Hg.
• Hypoxia Low oxygen levels in the tissues. Hypoxia can be caused by hypoxemia, but it can also be caused by other factors, such as inadequate blood flow to the tissue.

Hypoxemia and hypoxia can appear together, but they don't always. For example, a patient can develop hypoxemia without hypoxia if their hemoglobin level and cardiac output increase. Conversely, a patient can have hypoxia without hypoxemia, such as in cyanide poisoning.

Some common symptoms of hypoxemia and hypoxia include: Changes in skin color, Confusion, Cough, Fast heart rate, and Rapid breathing

 

The URL for the study is https://pubmed.ncbi.nlm.nih.gov/36368618/