Reliability Of Near-infrared Spectroscopy Research Articles

Reliability of near-infrared spectroscopy in measuring muscle oxygenation during squat exercise

Monitoring of changes in skeletal muscle oxygenation during exercise has increased in recent years. Tissue oxygenation, which is related to fatigue and muscle hypertrophy, is often measured using near-infrared spectroscopy (NIRS). ObjectivesThis study aimed to determine the Test–Retest reliability of a non-portable NIRS (NIRO200Nx) during the full-squat exercise and recovery in young healthy men. DesignTwenty-five male participants (21.8 ± 2.6 years) were recruited for this original research. Each participant completed an 8-repetition test with a load that elicited a velocity of 1 m·s−1. The test was conducted twice, with a 48-h washout period between sessions. MethodsThe NIRS measured the changes of oxygenated-Hemoglobin (O2Hb), deoxygenated-Hemoglobin (HHb) and Tissue Oxygenation Index (TOI) in both Vastus Lateralis and Vastus Medialis during rest, exercise, and recovery. Coefficient of Variation (CV), Standard Error Measurement (SEM) and Intraclass Correlation Coefficient (ICC) were used to evaluate the reliability of the data. Significance was set at p < 0.05. ResultsThe results indicated that TOI had good to acceptable absolute reliability (CVTOI = 2.7–10.2 %). A good relative relativity for the overall test was found for Vastus Medialis O2Hb (ICC = 0.851), HHb (ICC = 0.852), and TOI (ICC = 0.864), and Vastus Lateralis O2Hb (ICC = 0.898), HHb (ICC = 0.899), and TOI (ICC = 0.897). ConclusionsWe conclude that NIRO200Nx is a reliable instrument for measuring muscle oxygen saturation through the TOI parameter in not-to-failure dynamic resistance exercises (1 set of 8 reps against ~40 % 1 repetition Maximum). Tissue oxygenation assessment could be a new way of individualizing exercise through dynamic resistance exercises.

Comparative near Infrared (NIR) spectroscopy calibrations performance of dried and undried forage on dry and wet matter bases

The application of Near Infrared (NIR) spectroscopy for analyzing wet feed directly on farms is increasingly recognized for its role in supporting harvest-time decisions and refining the precision of animal feeding practices. This study aims to evaluate the accuracy of NIR spectroscopy calibrations for both undried, unprocessed samples and dried, ground samples. Additionally, it investigates the influence of the bases of reference data (wet vs. dry basis) on the predictive capabilities of the NIR analysis. The study utilized 492 Corn Whole Plant (CWP) and 405 High Moisture Corn (HMC) samples, sourced from various farms across Italy. Spectral data were acquired from both undried, unground and dried, ground samples using laboratory bench NIR instruments, covering a spectral range of 1100 to 2498 nm. The reference chemical composition of these samples was analyzed and presented in two formats: on a wet matter basis and on a dry matter basis.The study revealed that calibrations based on undried samples generally exhibited lower predictive accuracy for most traits, with the exception of Dry Matter (DM). Notably, the decline in predictive performance was more pronounced in highly moist products like CWP, where the average error increased by 60–70%. Conversely, this reduction in accuracy was relatively contained (10–15%) in drier samples such as HMC. The Standard Error of Cross-Validation (SECV) values for DMres, Ash, CP, and EE were notably low, at 0.39, 0.30, 0.29, 0.21% for CWP and 0.49, 0.14, 0.25, 0.14% for HMC, respectively. These results align with previous studies, indicating the reliability of NIR spectroscopy in diverse moisture contexts.The study attributes this variance to the interference caused by water in 'as is' samples, where the spectral features predominantly reflect water content, thereby obscuring the spectral signatures of other nutrients. In terms of calibration development strategies, the study concludes that there is no significant difference in predictive performance between undried calibrations based on either 'dry matter' or 'as is' basis. This finding emphasizes the potential of NIR spectroscopy in diverse moisture contexts, although with varying degrees of accuracy contingent upon the moisture content of the analyzed samples. Overall, this research provides valuable insights into the calibration strategies of NIR spectroscopy and its practical applications in agricultural settings, particularly for on-farm forage analysis.

Reliability of Near-Infrared Spectroscopy with and without Compression Tights during Exercise and Recovery Activities.

Near-infrared spectroscopy (NIRS) is widely used in sports science research, despite the limited reliability of available data. The aim of the present study was to assess the reliability of NIRS with and without compression tights. Thirteen healthy active males, (age 21.5 ± 2.7 years, body mass 82.1 ± 11.2 kg, BMI 24.6 ± 3.2 kg·m-2) completed four trials (two control trials and two trials using compression tights) over a 28-day period. During each trial, participants completed 20 min each of laying supine, sitting, walking (4 km·h-1), jogging, and sitting following the jogging. An NIRS device was attached to the muscle belly of the vastus lateralis and gastrocnemius and recorded tissue saturation index (TSI), muscle oxygenation, and muscle deoxygenation. Systematic bias and 95% limits of agreement (LOA) and coefficient of variation (CV) were used to report reliability measures for each activity type. For TSI, systematic bias (LOA) at the gastrocnemius during the control and tights trial ranged from -0.4 to 1.7% (4.4 to 10.3%) and -1.9 to 3.5% (8.1 to 12.0%), respectively. For the vastus lateralis, the systematic bias (LOA) for the control trial ranged from -2.4 to 1.0% (5.1 to 6.9%) and for the tights trial was -0.8 to 0.6% (7.0 to 9.5%). For TSI, the CV during the control trial ranged from 1.7 to 4.0% for the gastrocnemius and 1.9 to 2.6% for the vastus lateralis. During the tights trials, the CV ranged from 3.0 to 4.5% for the gastrocnemius and 2.6 to 3.5% for the vastus lateralis. The CV for muscle oxygenation during the control and tights trials for the gastrocnemius was 2.7 to 6.2% and 1.0 to 8.8% and for the vastus lateralis was 0.6 to 4.0% and 4.0 to 4.5%, respectively. The relative reliability was poorer in the tights trials, but if the aim was to detect a 5% difference in TSI, NIRS would be sufficiently reliable. However, the reliability of muscle oxygenation and deoxygenation varies considerably with activity type, and this should be considered when determining whether to employ NIRS in research studies.

Measuring tibial hemodynamics and metabolism at rest and after exercise using near-infrared spectroscopy.

The bone vascular system is important, yet evaluation of bone hemodynamics is difficult and expensive. This study evaluated the utility and reliability of near-infrared spectroscopy (NIRS), a portable and relatively inexpensive device, in measuring tibial hemodynamics and metabolic rate. Eleven participants were tested twice using post-occlusive reactive hyperemia technique with the NIRS probes placed on the tibia and the medial gastrocnemius (MG) muscle. Measurements were made at rest and after 2 levels of plantarflexion exercise. The difference between oxygenated and deoxygenated hemoglobin signal could be reliably measured with small coefficients of variation (CV; range 5.7-9.8%) and high intraclass correlation coefficients (ICC; range 0.73-0.91). Deoxygenated hemoglobin rate of change, a potential marker for bone metabolism, also showed good reliability (CV range 7.5-9.8%, ICC range 0.90-0.93). The tibia was characterized with a much slower metabolic rate compared with MG (p< 0.001). While exercise significantly increased MG metabolic rate in a dose-dependent manner (all p< 0.05), no changes were observed for the tibia after exercise compared with rest (all p> 0.05). NIRS is a suitable tool for monitoring hemodynamics and metabolism in the tibia. However, the local muscle exercise protocol utilized in the current study did not influence bone hemodynamics or metabolic rate. Novelty: NIRS can be used to monitor tibial hemodynamics and metabolism with good reliability. Short-duration local muscle exercise increased metabolic rate in muscle but not in bone. High level of loading and exercise volume may be needed to elicit measurable metabolic changes in bone.

Near-infrared spectroscopy using indocyanine green dye for minimally invasive measurement of respiratory and leg muscle blood flow in patients with COPD.

Reliability of near-infrared spectroscopy, measuring indocyanine green (ICG) for minimally invasive assessment of relative muscle blood flow during exercise has been examined in fit young individuals but not in chronic obstructive pulmonary disease (COPD). Here we ask whether it could be used to evaluate respiratory and locomotor muscle perfusion in COPD patients. Vastus lateralis muscle blood flow (MBF, the reference method calculated from arterial and muscle ICG concentration curves) and a blood flow index [BFI, calculated using only the (same) muscle ICG concentration curves] were compared in 10 patients (forced expiratory volume in 1 s: 51 ± 6% predicted) at rest and during cycling at 25, 50, 75, and 100% of peak work rate (WRpeak). Intercostal muscle MBF and BFI were also compared during isocapnic hyperpnea at rest, reproducing ventilation levels up to those at WRpeak. Intercostal and vastus lateralis BFI increased with increasing ventilation during hyperpnea (from 2.5 ± 0.3 to 4.5 ± 0.7 nM/s) and cycling load (from 1.0 ± 0.2 to 12.8 ± 1.9 nM/s), respectively. There were strong correlations between BFI and MBF for both intercostal ( r = 0.993 group mean data, r = 0.872 individual data) and vastus lateralis ( r = 0.994 group mean data, r = 0.895 individual data). Fold changes from rest in BFI and MBF did not differ for either the intercostal muscles or the vastus lateralis. Group mean BFI data showed strong interrelationships with respiratory and cycling workload, and whole body metabolic demand ( r ranged from 0.913 to 0.989) simultaneously recorded during exercise. We conclude that BFI is a reliable and minimally invasive tool for evaluating relative changes in respiratory and locomotor muscle perfusion from rest to peak exercise in COPD patient groups. NEW & NOTEWORTHY We show that noninvasive near-infrared spectroscopic (NIRS) detection of indocyanine green dye (ICG) after peripheral venous injection adequately reflects intercostal and locomotor muscle perfusion during exercise and hyperpnea in patients with chronic obstructive pulmonary disease (COPD). Mean, individual, and fold change responses from rest to exercise or hyperpnea correlated closely with the reference method, which requires arterial sampling. NIRS-ICG is a reliable, robust, and essentially noninvasive tool for assessing relative changes in intercostal and locomotor muscle perfusion in COPD patient groups.

Near-Infrared Spectroscopy versus Transcranial Doppler-Based Monitoring in Carotid Endarterectomy.

BackgroundProper monitoring of cerebral perfusion during carotid artery surgery is crucial for determining if a shunt is needed. We compared the safety and reliability of near-infrared spectroscopy (NIRS) with transcranial Doppler (TCD) for cerebral monitoring.MethodsThis single-center, retrospective review was conducted on patients who underwent carotid endarterectomy (CEA) using selective shunt-based TCD or NIRS at Daegu Catholic University Medical Center from November 2009 to June 2016. Postoperative complications were the primary outcome, and the distribution of risk factors between the 2 groups was compared.ResultsThe medical records of 74 patients (45 TCD, 29 NIRS) were reviewed. The demographic characteristics were similar between the 2 groups. One TCD patient died within the 30-day postoperative period. Postoperative stroke (n=4, p=0.15) and neurologic complications (n=10, p=0.005) were only reported in the TCD group. Shunt usage was 44.4% and 10.3% in the TCD and NIRS groups, respectively (p=0.002).ConclusionNIRS-based selective shunting during CEA seems to be safe and reliable for monitoring cerebral perfusion in terms of postoperative stroke and neurologic symptoms. It also reduces unnecessary shunt usage.

Microcirculatory Assessment of Arterial Below-Knee Stumps: Near-Infrared Spectroscopy Versus Transcutaneous Oxygen Tension—A Preliminary Study in Prosthesis Users

ObjectiveTo examine metrologic properties of near-infrared spectroscopy (NIRS) versus transcutaneous oxygen tension (TcPO2) for microcirculatory assessment of vascular transtibial stumps at the stabilized period of prosthesis fitting, as a preliminary step before exploring its ability to predict stump healing, considering the previously identified limits of TcPO2 (borderline area between 15 and 35mmHg). DesignProspective single-center observational study. SettingUniversity-based rehabilitation center. ParticipantsIndividuals with unilateral transtibial amputation for peripheral artery disease, at the definitive stage of prosthesis fitting, able to perform a 2-minute walk test (N=30). InterventionsNot applicable. Main Outcome MeasuresTest-retest, with the stump being evaluated in supine and inclined positions, first by NIRS (tissue saturation index [TSI], oxyhemoglobin, deoxyhemoglobin, and total hemoglobin) and second by TcPO2. Subjects carried out a 2-minute walk test and visual analog scales (wound healing and pain). ResultsFeasibility and tolerance of NIRS were satisfactory. The reliability of NIRS and TcPO2 values was good (intraclass correlation coefficient >0.7; P<.05). No significant relation was found between NIRS and TcPO2. No responsiveness (inclined vs supine) was reported (P>.05). A significant relation between TSI and the 2-minute walk test (r>.49, P<.05) was found. ConclusionsNIRS is painless, complication-free, and feasible, with good reliability. NIRS evaluates others domain than TcPO2 that are more linked to metabolic adaptation. Its capacity to predict stump healing and tolerance to early prosthesis fitting is therefore interesting to estimate in future studies.

Reliability of laser Doppler, near-infrared spectroscopy and Doppler ultrasound for peripheral blood flow measurements during and after exercise in the heat

ABSTRACTThis study examined the test-retest reliability of near-infrared spectroscopy (NIRS), laser Doppler flowmetry (LDF) and Doppler ultrasound to assess exercise-induced haemodynamics. Nine men completed two identical trials consisting of 25-min submaximal cycling at first ventilatory threshold followed by repeated 30-s bouts of high-intensity (90% of peak power) cycling in 32.8 ± 0.4°C and 32 ± 5% relative humidity (RH). NIRS (tissue oxygenation index [TOI] and total haemoglobin [tHb]) and LDF (perfusion units [PU]) signals were monitored continuously during exercise, and leg blood flow was assessed by Doppler ultrasound at baseline and after exercise. Cutaneous vascular conductance (CVC; PU/mean arterial pressure (MAP)) was expressed as the percentage change from baseline (%CVCBL). Coefficients of variation (CVs) as indicators of absolute reliability were 18.7–28.4%, 20.2–33.1%, 42.5–59.8%, 7.8–12.4% and 22.2–30.3% for PU, CVC, %CVCBL, TOI and tHb, respectively. CVs for these variables improved as exercise continued beyond 10 min. CVs for baseline and post-exercise leg blood flow were 17.8% and 10.5%, respectively. CVs for PU, tHb (r2 = 0.062) and TOI (r2 = 0.002) were not correlated (P > 0.05). Most variables demonstrated CVs lower than the expected changes (35%) induced by training or heat stress; however, minimum of 10 min exercise is recommended for more reliable measurements.

Muscle Oxygenation and Blood Volume Reliability during Continuous and Intermittent Running

The reliability of near infrared spectroscopy derived tissue oxygenation index (TOI) and total haemoglobin concentration (tHb) were examined during continuous (CR) and interval (INT) running. In a repeated measures design, 10 subjects twice performed 30 min of CR at 70% of their peak treadmill velocity, followed by 10 bouts of INT at 100%. Between trial reliability of mean and amplitude changes in TOI and tHb during CR were determined. Muscle de-oxygenation and re-oxygenation rates during INT were calculated using 3 analytical methods; i) linear modelling, ii) minimum and maximum values during work/rest intervals, and iii) mean values during work/rest intervals. Reliability was assessed using coefficient of variation (CV; %). During CR, mean TOI was more reliable (3.5%) compared with TOI amplitude change (34.7%), while mean tHb (12%) was similar to both absolute (9.2%) and relative (10.2%) amplitude changes. During INT, de-oxygenation rates analysed via linear modelling produced the lowest CV (7.2%), while analysis using min-max values produced the lowest CV (9.3%) for re-oxygenation rates. In conclusion, while the variables demonstrated CVs lower than reported changes in training-induced adaptations and/or differences between athletes and controls (23- 450%), practitioners are encouraged to consider the advantages/disadvantages of each method when performing their analysis.

Microleakage and Microtensile Bond Strength Evaluation of the Various Generations of Dentin Bonding Agents

Background: Proper monitoring of cerebral perfusion during carotid artery surgery is crucial for determining if a shunt is needed. We compared the safety and reliability of near-infrared spectroscopy (NIRS) with transcranial Doppler (TCD) for cerebral monitoring. Methods: This single-center, retrospective review was conducted on patients who underwent carotid endarterectomy (CEA) using selective shunt-based TCD or NIRS at Daegu Catholic University Medical Center from November 2009 to June 2016. Postoperative complications were the primary outcome, and the distribution of risk factors between the 2 groups was compared. Results: The medical records of 74 patients (45 TCD, 29 NIRS) were reviewed. The demographic characteristics were similar between the 2 groups. One TCD patient died within the 30-day postoperative period. Postoperative stroke (n=4, p=0.15) and neurologic complications (n=10, p=0.005) were only reported in the TCD group. Shunt usage was 44.4% and 10.3% in the TCD and NIRS groups, respectively (p=0.002). Conclusion: NIRS-based selective shunting during CEA seems to be safe and reliable for monitoring cerebral perfusion in terms of postoperative stroke and neurologic symptoms. It also reduces unnecessary shunt usage.

Abstract P017: Reliability of Near-Infrared Spectroscopy in the Evaluation of Forearm Microvascular Function

Background: The assessment of microvascular reactivity by near-infrared spectroscopy (NIRS) was shown to be associated with cardiovascular status and the number of cardiovascular risk factors and could be of interest in cardiac or high-risk patients. However, the reliability of NIRS parameters measured at the arm has never been studied and should be known before they could be used in research and clinical settings. The aim of this study was to measure the absolute and relative reliability of the most commonly used NIRS parameters during post-occlusive hyperaemia in healthy young men. Methods: 18 healthy men (33.56±7.88 years), without any cardiovascular risk factors (dyslipidemia, hypertension, abdominal obesity, diabetes and smoking) or cardiac symptoms had their fasting microvascular function evaluated twice, on two mornings separated by at least 7 days. Briefly, NIRS optodes were placed on the brachio-radialis muscle and a pressure cuff was installed on the upper-arm of subjects and inflated at 80mm Hg over the systolic blood pressure. NIRS parameters were registered continuously for 2 minutes at rest, 5 minutes during occlusion and 5 minutes post-occlusion. NIRS parameters listed in the table below were then analyzed. Results: CV (%) SEM Pearson r ICC mVO 2 (ml/min/100g) 6.51 0.0043 0.90 0.90 Half time to O 2 Hb max (sec) 20.04 4.15 0.79 0.78 Time to O 2 Hb max (sec) 15.61 8.24 0.79 0.75 O 2 Hb max (%) 6.68 2.39 0.70 0.66 tHb max (%) 13.32 1.66 0.31 0.31 Time to tHb max (sec) 19.61 4.73 0.86 0.85 AUC O2Hb 16.15 184.01 0.83 0.83 AUC tHb 18.59 175.04 0.80 0.80 AUC HHb 20.37 159.38 0.63 0.63 mVO 2 : muscle oxygen consumption, O 2 Hb : oxyhaemoglobin, tHb: total haemoglobin and HHb: deoxyhaemoglobin Conclusion: Reliability of most NIRS parameters was strong (Half time to O 2 Hb max and Time to O 2 Hb max) and very strong (mVO 2 , Time to tHb max and AUC O 2 Hb and tHb). The Coefficient of variations were below 10% for mVO 2 , and O 2 Hb max, and between 10 and 20% for the other parameters, which is in line with previous data at the calf level in healthy subjects and peripheral artery disease patients. We can therefore conclude that NIRS parameters evaluated during brachial post-occlusive hyperaemia were reliable and can be used by physicians and investigators to establish thresholds of relevancy for NIRS parameter changes and to estimate sample sizes in clinical studies.

Towards the next generation of near-infrared spectroscopy

Although near-infrared spectroscopy (NIRS) was originally designed for clinical monitoring of tissue oxygenation, it has also been developing into a useful tool for neuroimaging studies (functional NIRS). Over the past 30 years, technology has developed and NIRS has found a wide range of applications. However, the accuracy and reliability of NIRS have not yet been widely accepted, mainly because of the difficulties in selective and quantitative detection of signals arising in cerebral tissue, which subject the use of NIRS to a number of practical restrictions. This review summarizes the strengths and advantages of NIRS over other neuroimaging modalities and demonstrates specific examples. The issues of selective quantitative measurement of cerebral haemoglobin during brain activation are also discussed, together with the problems of applying the methods of functional magnetic resonance imaging data analysis to NIRS data analysis. Finally, near-infrared optical tomography--the next generation of NIRS--is described as a potential technique to overcome the limitations of NIRS.

Reliability of near infrared spectroscopy (NIRS) for measuring forearm oxygenation during incremental handgrip exercise

The purpose of this study was to test the reliability of a new handgrip exercise protocol measuring forearm oxygenation in 20 healthy subjects on two occasions. The retest took place 48 h later and at the same time of the day. The incremental exercise consisted of 2 min steps of cyclic handgrip contraction (1/2 Hz) separated by 1 min of recovery. The exercise started at 20% MVC, was increased with 10% MVC each step and was performed until exhaustion (69.5 and 73% MVC). Near infrared spectroscopy (NIRS) was used to measure deoxygenation (deoxy[Hb + Mb]) and oxygen saturation (SmO(2)) in the forearm muscles. Prior to the exercise protocol an arterial occlusion of the forearm was performed until deoxy(Hb + Mb) did no longer increase. Maximal increase in deoxy[Hb + Mb] during 10 s of each exercise bout was expressed relative to the occlusion amplitude. ICC was used to examine the test-retest reliability. Significant ICC's were reported at 50% (r = 0.466, p = 0.017) and 60% MVC (r = 0.553, p = 0.005). The group mean of the maximum increase in oxygen extraction was 45.6 ± 16.7% and at the retest 44.9 ± 17.0% with an ICC of r = 0.867 (p < 0.001) which could be classified (Landis and Koch 1979) as almost perfect. The absolute SmO(2) values showed reliable ICC's for every submaximal intensity except at 60% MVC. An ICC of r = 0.774 (p < 0.001) was found at maximal intensity. The results of the present study show that deoxy[Hb + Mb] and SmO(2) responses during this protocol are highly reliable and indicate that this protocol could be used to get insight into deoxygenation and oxygen saturation in a population with low exercise tolerance.

The NIRS Analysis Package: noise reduction and statistical inference.

Near infrared spectroscopy (NIRS) is a non-invasive optical imaging technique that can be used to measure cortical hemodynamic responses to specific stimuli or tasks. While analyses of NIRS data are normally adapted from established fMRI techniques, there are nevertheless substantial differences between the two modalities. Here, we investigate the impact of NIRS-specific noise; e.g., systemic (physiological), motion-related artifacts, and serial autocorrelations, upon the validity of statistical inference within the framework of the general linear model. We present a comprehensive framework for noise reduction and statistical inference, which is custom-tailored to the noise characteristics of NIRS. These methods have been implemented in a public domain Matlab toolbox, the NIRS Analysis Package (NAP). Finally, we validate NAP using both simulated and actual data, showing marked improvement in the detection power and reliability of NIRS.

Optical intrinsic signal imaging from macaque inferotemporal cortex reveals functional structures in different spatial scales

To examine metrologic properties of near-infrared spectroscopy (NIRS) versus transcutaneous oxygen tension (TcPO2) for microcirculatory assessment of vascular transtibial stumps at the stabilized period of prosthesis fitting, as a preliminary step before exploring its ability to predict stump healing, considering the previously identified limits of TcPO2 (borderline area between 15 and 35mmHg).Prospective single-center observational study.University-based rehabilitation center.Individuals with unilateral transtibial amputation for peripheral artery disease, at the definitive stage of prosthesis fitting, able to perform a 2-minute walk test (N=30).Not applicable.Test-retest, with the stump being evaluated in supine and inclined positions, first by NIRS (tissue saturation index [TSI], oxyhemoglobin, deoxyhemoglobin, and total hemoglobin) and second by TcPO2. Subjects carried out a 2-minute walk test and visual analog scales (wound healing and pain).Feasibility and tolerance of NIRS were satisfactory. The reliability of NIRS and TcPO2 values was good (intraclass correlation coefficient >0.7; P<.05). No significant relation was found between NIRS and TcPO2. No responsiveness (inclined vs supine) was reported (P>.05). A significant relation between TSI and the 2-minute walk test (r>.49, P<.05) was found.NIRS is painless, complication-free, and feasible, with good reliability. NIRS evaluates others domain than TcPO2 that are more linked to metabolic adaptation. Its capacity to predict stump healing and tolerance to early prosthesis fitting is therefore interesting to estimate in future studies.

Reliability of Near-Infrared Spectroscopy to Assess Limb Tissue Oxygenation

Reliability of Near-Infrared Spectroscopy to Assess Limb Tissue Oxygenation

Reliability of Near-Infrared Spectroscopy for Determining Muscle Oxygen Saturation During Exercise

Reliability of Near-Infrared Spectroscopy for Determining Muscle Oxygen Saturation During Exercise

Reliability of Near-Infrared Spectroscopy in People With Dark Skin Pigmentation

Near-infrared spectroscopy (NIRS) is a promising non-invasive technique for the continuous monitoring of tissue oxygen delivery. NIRS detects light absorbance of haemoglobin chromophores to determine tissue oxygen saturation (StO2). As skin colour is also determined by the presence of chromophores, it is plausible that NIRS signal quality may be affected by dark skin pigmentation. Tissue saturation in the anterior compartment of the lower leg during isometric contraction was measured using NIRS in 17 volunteers with dark skin pigmentation. Measurements were continued until StO2 was zero percent or until the signal disappeared. The NIRS device failed to register tissue saturation values at some point in nine of seventeen volunteers. This occurred more often in individuals with darker skin. In patients with a dark pigmented skin, NIRS StO2 measurements should be interpreted with caution, as melanin clearly interferes with the quality of the reflected NIRS signal.