Monitoring the oxygenation levels of the prefrontal cortex during exercise is crucial in assessing decision-making abilities and cognitive responsibilities. Near-infrared spectroscopy (NIRS) is a non-invasive optical technique that measures and monitors tissue oxygenation levels in real-time. This study aimed to investigate the feasibility of using NIRS to monitor and compare patterns of cerebral and muscle oxygenation during progressive exercise, both before and after the anaerobic threshold (AT) is reached. A cohort of healthy adults with moderate to high fitness levels participated in an incremental exercise protocol using an indoor exercise bike. Two wearable NIRS sensors were used to monitor tissue oxygenation from the forehead and the thigh vastus lateralis (VL) muscle during the exercise. To estimate the anaerobic threshold (AT) time point, we used the Respiratory Exchange Ratio (RER) value greater than 1.0 as measured by a metabolic cart. The concentration difference between oxygenated and deoxygenated hemoglobin (Hb-diff), which indicates the level of tissue oxygenation, exhibited a significant decrease (p<0.05) in the VL muscle of all participants after the AT was reached. Conversely, there was a significant increase in Hb-diff in the cerebral cortex after the AT (p< 0.05). The results of this study demonstrate the efficient hemodynamics autoregulation of the brain even when the body is affected by metabolic fatigue during high-intensity exercise. This study confirms the feasibility of NIRS to monitor prefrontal cortex and muscle oxygenation during exercise as a unique application in exercise science.
Background: Free tissue transfer (FTT) is a surgical procedure that involves taking tissue from one area of the body and transplanting it to a surgical wound. Near-infrared spectroscopy (NIRS) has the potential to provide continuous and non-invasive monitoring of FTT hemodynamics. A novel NIRS system with a miniaturized implantable sensor was developed for FTT monitoring in head and neck surgery. The objectives of this study were to obtain post-operative NIRS measurements on a cohort of patients undergoing FTT surgery for head and neck cancer and to evaluate the patient’s and clinician’s experience with the novel NIRS monitoring method.
Methods: The NIRS sensor was fixed over the FTT for 72 hours post-operatively to provide tissue oxygenation parameters, including oxygenated (O2Hb), deoxygenated (HHb), and tissue saturation index (TSI). After 72 hours, the patient and clinicians completed a questionnaire to evaluate their experience with the NIRS system. All patients undergoing FTT surgery had a successful operation with no complications to the FTT.
Results: The NIRS data showed visible pulsatile O2Hb signals, indicating the proper microvascular function of the FTT. Furthermore, TSI calculations provided an estimated measure of the oxygenation status of the FTT. The questionnaire indicated that the NIRS sensor did not cause additional discomfort or inconvenience to the patients or clinicians.
Conclusions: Our results suggest that the novel NIRS sensor can monitor the FTT continuously and non-invasively for 72 hours with minimal interference to patient care. Incorporating a novel NIRS biosensor into FTT monitoring can improve post-operative care and decrease FTT failure rates.
The anaerobic threshold (AT) is a point during intense exercise that can be used to predict muscular fatigue. Determining the AT non-invasively helps to adjust exercise intensity and prevent overuse injuries. Near-infrared spectroscopy (NIRS) is an optical technology that can provide real-time information about muscle oxidative metabolism. The objective of this pilot study was to investigate the relationship between NIRS parameters of muscle oxygenation and traditional measures of exercise monitoring, such as heart rate and relative body oxygen consumption (VO2). Healthy adults with moderate to high fitness levels participated in an incremental exercise protocol on a stationary bicycle. NIRS parameters were compared to ventilatory VO2 using a metabolic cart. Respiratory Exchange Ratio (RER) < 1.0 was used as a proxy for determining the AT. NIRS data were collected from the primary locomotor muscle (vastus lateralis - VL) and a control muscle (deltoid) using two wearable NIRS sensors. Heart rate data were collected by a wearable ECG sensor. The NIRS data showed a significant decline in VL muscle oxygenated hemoglobin (O2Hb) concentration (p<0.05) at one exercise stage after the AT was identified. Muscle O2Hb did not show a significant decrease in the deltoid at the AT. Furthermore, there were no noticeable changes in heart rate at the AT. Our results indicate that a wearable NIRS sensor can predict the AT in exercising muscles and may provide a localized measure of muscular fatigue during exercise.
The purpose of this study was to investigate the accuracy of infrared thermography for measuring body temperature. We compared a commercially available infrared thermal imaging camera (FLIR One) with a medical-grade oral thermometer (Welch-Allyn) as a gold standard. Measurements using the thermal imaging camera were taken from both a short distance (10cm) and long distance (50cm) from the subject. Thirty young healthy adults participated in a study that manipulated body temperature. After establishing a baseline, participants lowered their body temperature by placing their feet in a cold-water bath for 30 minutes while consuming cold water. Feet were then removed and covered with a blanket for 30 minutes as body temperature returned to baseline. During the course of the 70-minute experiment, body temperature was recorded at a 10-minute interval. The thermal imaging camera demonstrated a significant temperature difference from the gold standard from both close range (mean error: +0.433°C) and long range (mean error: +0.522°C). Despite demonstrating potential as a fast and non-invasive method for temperature screening, our results indicate that infrared thermography does not provide an accurate measurement of body temperature. As a result, infrared thermography is not recommended for use as a fever screening device.
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