Search

In this narrative review, we summarize the current knowledge and applications of somatic near-infrared spectroscopy (NIRS), with a focus on intestinal, renal, limb, and multi-site applications in neonates. Assessing somatic oxygenation at various body locations in neonates may aid in the understanding of underlying pathophysiology of organ injury. Considering cerebral autoregulation may be active to protect the brain during systemic circulatory failure, peripheral somatic oxygenation may potentially provide an early indication of neonatal cardiovascular failure and ultimate hypoxemic injury to vital organs including the brain. Certain intestinal oxygenation patterns appear to be associated with the onset and course of necrotizing enterocolitis, whereas impaired renal oxygenation may indicate the onset of acute kidney injury after various types of hypoxic events. Peripheral muscle oxygenation measured at a limb may be particularly effective in the early prediction of shock in neonates. Using multi-site NIRS may complement current approaches and clinical investigations to alert for neonatal tissue hypoxemia, and potentially even guide management. However, somatic NIRS has its inherent limitations in regard to accuracy. Interpretation of organ-specific values can also be challenging. Last, currently there are limited prospective intervention studies, and clinical benefits need to be examined further, after the clarification of critical threshold-values. IMPACT: The assessment of somatic oxygenation using NIRS may contribute to the prediction of specific diseases in hemodynamically challenged neonates. Furthermore, it may give early warning signs for impending cardiovascular failure, and impaired cerebral circulation and oxygenation. We present a comprehensive overview of the literature on applications of NIRS to various somatic areas, with a focus on its potential clinical applicability, including future research directions. This paper will enable prospective standardized studies, and multicenter collaboration to obtain statistical power, likely to advance the field., (© 2024. The Author(s), under exclusive licence to the International Pediatric Research Foundation, Inc.)

The utilization of continuous wave (CW) near-infrared spectroscopy (NIRS) device to measure non-invasively muscle oxygenation in healthy and disease states is limited by the uncertainties related to the differential path length factor (DPF). DPF value is required to quantify oxygenated and deoxygenated heme groups' concentration changes from measurement of optical densities by NIRS. An integrated approach that combines animal and computational models of oxygen transport and utilization was used to estimate the DPF value in situ. The canine model of muscle oxidative metabolism allowed measurement of both venous oxygen content and tissue oxygenation by CW NIRS under different oxygen delivery conditions. The experimental data obtained from the animal model were integrated in a computational model of O 2 transport and utilization and combined with Beer-Lambert law to estimate DPF value in contracting skeletal muscle. A 2.1 value was found for DPF by fitting the mathematical model to the experimental data obtained in contracting muscle (T3) (Med.Sci.Sports.Exerc.48(10):2013-2020,2016). With the estimated value of DPF, model simulations well predicted the optical density measured by NIRS on the same animal model but with different blood flow, arterial oxygen contents and contraction rate (J.Appl.Physiol.108:1169-1176, 2010 and 112:9-19,2013) and demonstrated the robustness of the approach proposed in estimating DPF value. The approach used can overcome the semi-quantitative nature of the NIRS and estimate non-invasively DPF to obtain an accurate concentration change of oxygenated and deoxygenated hemo groups by CW NIRS measurements in contracting skeletal muscle under different oxygen delivery and contraction rate., Competing Interests: Declaration of Competing Interest No conflicts of interest, financial or otherwise, are declared by the authors., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

This study aimed to investigate the relationship of perioperative cerebral regional oxygen saturation (rSO 2 ) with various preoperative clinical variables and hemodynamic changes during transfemoral transcatheter aortic valve implantation (TAVI) under general anesthesia. We retrospectively analyzed cerebral rSO 2 values from left-hemisphere measurements obtained using near-infrared spectroscopy (O3™ regional oximetry) at five time points: pre-induction, the start of the procedure, the start of valve deployment, time of lowest cerebral rSO 2 value during valve deployment, and the end of the procedure. This study included 91 patients (60 with balloon-expandable valves and 31 with self-expandable valves). The baseline cerebral rSO 2 values were correlated with B-type natriuretic peptide, hemoglobin, fractional shortening, ejection fraction, left ventricular mass index, left ventricular end-systolic diameter, STS risk of mortality, and STS morbidity or mortality. The patients who took longer to recover their systolic blood pressure to 90 mmHg after valve deployment with a balloon-expandable valve (group B) had lower cerebral rSO 2 values during deployment compared to patients with faster recovery with balloon-expandable valve (group A) and with self-expandable valve (group C). Baseline cerebral rSO 2 is associated with preoperative variables related to cardiac failure and function, and a significant decline during valve deployment may indicate a risk of prolonged hypotension during TAVI., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Few reports are available on the monitoring of regional cerebral oxygen saturation (rSO 2 ) in pediatric patients undergoing non-cardiac surgical procedures. In addition, no study has examined the rSO 2 levels in children of a broad age range. In this study, we aimed to assess and compare rSO 2 levels in pediatric patients of different age groups undergoing non-cardiac surgery. We used two oximeters, tNIRS-1, which uses time-resolved spectroscopy, and conventional INVOS 5100C. Seventy-eight children-26 infants, 26 toddlers, and 26 schoolchildren-undergoing non-cardiac surgery were included. We investigated the differences in the rSO 2 levels among the age groups and the correlation between the models and physiological factors influencing the rSO 2 values. rSO 2 measured by INVOS 5100C was significantly lower in infants than those in other patients. rSO 2 measured by tNIRS-1 was higher in the toddler group than those in the other groups. The rSO 2 values of tNIRS-1 and INVOS 5100C were moderately correlated (r = 0.41); however, those of INVOS 5100C were approximately 20% higher, and a ceiling effect was observed. The values in INVOS 5100C and tNIRS-1 were affected by blood pressure and the minimum alveolar concentration of sevoflurane, respectively. In pediatric patients undergoing non-cardiac surgery, rSO 2 values differed across the three age groups, and the pattern of these differences varied between the two oximeters employing different algorithms. Further research must be conducted to clarify cerebral oxygenation in children., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Abstract: Voxelotor is an inhibitor of sickle hemoglobin polymerization that is used to treat sickle cell disease. Although voxelotor has been shown to improve anemia, the clinical benefit on the brain remains to be determined. This study quantified the cerebral hemodynamic effects of voxelotor in children with sickle cell anemia (SCA) using noninvasive diffuse optical spectroscopies. Specifically, frequency-domain near-infrared spectroscopy combined with diffuse correlation spectroscopy were used to noninvasively assess regional oxygen extraction fraction (OEF), cerebral blood volume, and an index of cerebral blood flow (CBFi). Estimates of CBFi were first validated against arterial spin-labeled magnetic resonance imaging (ASL-MRI) in 8 children with SCA aged 8 to 18 years. CBFi was significantly positively correlated with ASL-MRI-measured blood flow (R2 = 0.651; P = .015). Next, a single-center, open-label pilot study was completed in 8 children with SCA aged 4 to 17 years on voxelotor, monitored before treatment initiation and at 4, 8, and 12 weeks (NCT05018728). By 4 weeks, both OEF and CBFi significantly decreased, and these decreases persisted to 12 weeks (both P < .05). Decreases in CBFi were significantly correlated with increases in blood hemoglobin (Hb) concentration (P = .025), whereas the correlation between decreases in OEF and increases in Hb trended toward significance (P = .12). Given that previous work has shown that oxygen extraction and blood flow are elevated in pediatric SCA compared with controls, these results suggest that voxelotor may reduce cerebral hemodynamic impairments. This trial was registered at www.ClinicalTrials.gov as #NCT05018728., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Background: Sufficient oxygen is critical for multiple processes in wound healing. Nonhealing wounds have low tissue oxygen levels due to damaged microvasculature and comorbidities limiting tissue perfusion. Hypoxia may be reversed using continuous topical oxygen therapy (cTOT). Objective measures to identify and track hypoxic wounds and their response to adjunctive oxygen are key., Objective: To understand the effect of cTOT on recalcitrant wounds by tracking wound area and changes in tissue oxygenation using a near-infrared spectroscopy (NIRS) device., Materials and Methods: Five patients with nonhealing wounds received treatment with cTOT over 5 weeks. Routine wound measures and tissue oxygenation were recorded over that period., Results: Reductions in wound area and improvements in tissue oxygenation were seen in all 5 patients, with 3 patients healing within 5 weeks despite the previous long duration of their wounds. Trends in tissue oxygenation and relative wound surface area over the treatment period demonstrated a reduction in wound area as tissue oxygenation improved., Conclusion: This case series reinforces previous studies that cTOT is an effective, noninvasive treatment as a key adjunct to standard care in nonhealing wounds. Moreover, point-of-care tools such as the NIRS imaging device provided objective information concerning tissue oxygenation improvements, thus giving useful insights to the clinician.

Frequency-domain near-infrared spectroscopy (FD-NIRS) has been used for non-invasive assessment of cortical oxygenation since the late 1990s. However, there is limited research demonstrating clinical validity and general reproducibility. To address this limitation, recording duration for adequate validity and within- and between-day reproducibility of prefrontal cortical oxygenation was evaluated. To assess validity, a reverse analysis of 10-min-long measurements ( n = 52) at different recording durations (1-10-min) was quantified via coefficients of variation and Bland-Altman plots. To assess within- and between-day within-subject reproducibility, participants ( n = 15) completed 2-min measurements twice a day (morning/afternoon) for five consecutive days. While 1-min recordings demonstrated sufficient validity for the assessment of oxygen saturation (S t O 2 ) and total hemoglobin concentration (THb), recordings ≥4 min revealed greater clinical utility for oxy- (HbO) and deoxyhemoglobin (HHb) concentration. Females had lower S t O 2, THb, HbO, and HHb values than males, but variability was approximately equal between sexes. Intraclass correlation coefficients ranged from 0.50-0.96. The minimal detectable change for S t O 2 was 1.15% (95% CI: 0.336-1.96%) and 3.12 µM for THb (95% CI: 0.915-5.33 µM) for females and 2.75% (95%CI: 0.807-4.70%) for S t O 2 and 5.51 µM (95%CI: 1.62-9.42 µM) for THb in males. Overall, FD-NIRS demonstrated good levels of between-day reliability. These findings support the application of FD-NIRS in field-based settings and indicate a recording duration of 1 min allows for valid measures; however, data recordings of ≥4 min are recommended when feasible.

Functional near-infrared spectroscopy (fNIRS) can dynamically respond to the relevant state of brain activity based on the hemodynamic information of brain tissue. The cerebral cortex and gray matter are the main regions reflecting brain activity. As they are far from the scalp surface, the accuracy of brain activity detection will be significantly affected by a series of physiological activities. In this paper, an effective algorithm for extracting brain activity information is designed based on the measurement method of dual detectors so as to obtain real brain activity information. The principle of this algorithm is to take the measurement results of short-distance channels as reference signals to eliminate the physiological interference information in the measurement results of long-distance channels. In this paper, the performance of the proposed method is tested using both simulated and measured signals and compared with the extraction results of EEMD-RLS, RLS and fast-ICA, and their extraction effects are quantified by correlation coefficient (R), root-mean-square error (RMSE), and mean absolute error (MAE). The test results show that even under low SNR conditions, the proposed method can still effectively suppress physiological interference and improve the detection accuracy of brain activity signals.

Significance: Mechanical ventilation (MV) is a cornerstone technology in the intensive care unit as it assists with the delivery of oxygen in critically ill patients. The process of weaning patients from MV can be long and arduous and can lead to serious complications for many patients. Despite the known importance of inspiratory muscle function in the success of weaning, current clinical standards do not include direct monitoring of these muscles., Aim: The goal of this project was to develop and validate a combined frequency domain near-infrared spectroscopy (FD-NIRS) and diffuse correlation spectroscopy (DCS) system for the noninvasive characterization of inspiratory muscle response to a load., Approach: The system was fabricated by combining a custom digital FD-NIRS and DCS system. It was validated via liquid phantom titrations and a healthy volunteer study. The sternocleidomastoid (SCM), an accessory muscle of inspiration, was monitored during a short loading period in fourteen young, healthy volunteers. Volunteers performed two different respiratory exercises, a moderate load and a high load, which consisted of a one-minute baseline, a one-minute load, and a six-minute recovery period., Results: The system has low crosstalk between absorption, reduced scattering, and flow when tested in a set of liquid titrations. Faster dynamics were observed for changes in blood flow index ( BF i ), and metabolic rate of oxygen ( MRO 2 ) compared with hemoglobin + myoglobin (Hb+Mb) based parameters after the onset of loads in males. Additionally, larger percent changes in BF i , and MRO 2 were observed compared with Hb+Mb parameters in both males and females. There were also sex differences in baseline values of oxygenated Hb+Mb, total Hb+Mb, and tissue saturation., Conclusions: The dynamic characteristics of Hb+Mb concentration and blood flow were distinct during loading of the SCM, suggesting that the combination of FD-NIRS and DCS may provide a more complete picture of inspiratory muscle dynamics., (© 2024 The Authors.)

Background: The reliability of near-infrared spectroscopy (NIRS) for measuring cerebral oxygenation (ScO 2 ) is controversial due to the possible contamination from extracranial tissues. We compared ScO 2 measured with the NIRS optode on the forehead, the skull and the dura mater in anaesthetised patients undergoing craniotomy. We hypothesised that ScO 2 measured directly on the skull and the dura mater would differ from ScO 2 measured on the skin., Methods: This prospective observational study included 17 adult patients scheduled for elective craniotomy. After induction of general anaesthesia, ScO 2 was measured on the forehead skin, as well as on the skull and on the dura mater in the surgical field. The primary comparison was the difference in ScO 2 measured on the dura mater and on ScO 2 measured on the skin; secondary comparisons were the differences in ScO 2 on the skull and ScO 2 on the skin and the dura mater, respectively. Data were described with median (5%-95% range) and analysed with the Wilcoxon signed-rank test., Results: ScO 2 values on the dura mater were obtained in 11 patients, and median ScO 2 (48%, 29%-95%) did not differ significantly from ScO 2 on the skin (73%, 49%-92%; p = .052), median difference -25% (-35.6% to -1.2%). ScO 2 on the skull (N = 16) was lower than that on the skin (63% [43%-79%] vs. 75% [61%-94%]; p = .0002), median difference -10% (-20.8 to -3.0)., Conclusion: In adults undergoing craniotomy, NIRS-based ScO 2 measured on the dura mater did not reach statistically significantly lower values than ScO 2 measured on the skin, whereas values on the skull were lower than on the skin, indicating a contribution from scalp tissue to the signal., (© 2023 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.)

In the past 20 years, near infrared spectrum technology has been widely used in human body monitoring due to its non-invasive and real-time characteristics. Oxygen, as the main metabolic substance of the human body, is consumed the most in brain tissue. In order to prevent complications caused by a decrease in brain tissue oxygen during treatment, the patient's brain tissue blood oxygen saturation needs to be monitored in real time. Currently, most of the clinically used non-invasive cerebral blood oxygen detection equipments use dual wavelengths. Other substances on the detection path will cause errors in the measurement results. Therefore, this article proposes a three-wavelength method based on the basic principle of non-invasive monitoring of cerebral blood oxygen using near-infrared spectrum. The brain tissue oxygen saturation monitoring method of detecting light sources was initially verified through the built system, laying the foundation for subsequent system engineering.

This study clarifies the effects of head elevation on cerebral oxygenation in patients with acute cerebral infarction. We included 76 patients with anterior circulation cerebral infarction admitted to the stroke care unit within 7 days of symptom onset. Using near-infrared spectroscopy (NIRS), we measured regional saturation oxygen (rSO 2 ), oxygenated haemoglobin (O 2 Hb), deoxygenated haemoglobin (HHb), and total haemoglobin (THb) in both the affected hemisphere (AH) and unaffected hemisphere (UH) after raising the head to 0°, 30°, and 60° for 1 minute each. The mean arterial pressure (MAP) was measured non-invasively at each position. Our result demonstrated a significant decrease in O 2 Hb as the head elevation angle (HEA) increased, with no observable interaction between the AH and UH. A significant decrease in rSO 2 interaction was observed. In contrast, the HHb and THb levels changed significantly as the HEA increased, although no interactions were identified. No significant correlations existed between the observed changes in O 2 Hb, HHb, THb, or rSO 2 and changes in MAP at each HEA., (© 2024. Oxygen Transport to Tissue International.)

Pressure injuries (PI) are debilitating tissue lesions characterised by slow healing and a high risk of severe infection. These injuries result from continued tissue hypoxia, or low tissue oxygen saturation (StO 2 ), which is a consequence of impaired blood circulation caused by continued pressure against tissue. PI result in significant suffering and a substantial financial burden. Therefore, we aim to develop an effective preventive measure. Persons with spinal cord injury (SCI) are at a high risk for PI due to their impaired mobility and lack of sensation to alert them to danger. The aim was to test the feasibility of an alert system based on StO 2 monitoring in persons with SCI using a novel textile-based near-infrared spectroscopy (NIRS) sensor.Sensors consisted of two emission and two detection points, each point comprising eight fibres each with three light-coupling bends. Textile integration of fibres was achieved by stitching on a mass-production stitching machine. Emission fibres were connected to LEDs of 740 nm and 810 nm. Detection fibres were connected to avalanche photodiodes. Sensors were attached to the skin in the high-PI-risk buttocks area covering the bony prominences of the ischial tuberosity. StO 2 was measured in three healthy subjects and two subjects with SCI during repeated sitting and pressure recovery phases.Our experiments showed decreases in StO 2 in both groups during sitting phases: during low-pressure sitting phases, StO 2 decreased on average -0.32%/min in the healthy subjects and at -1.24%/min in the SCI subjects. During high-pressure sitting, these rates increased to -1.16%/min for the healthy subjects and -2.16%/min for the SCI subjects. During recovery phases, StO 2 returned towards normal values, but did not always reach the initial baseline. No discomfort or skin irritation was observed.These first measurements show physiologically reasonable StO 2 values and demonstrate sufficient comfort while sitting on a sensor with no skin irritation or other adverse effects of sitting on the sensor for over 30 min. The nurses involved were satisfied with the easy-of-use, materials used, and patient safety demonstrated during the study. These results show that it is feasible to develop an alert system for PI prevention using a safe, wearable, textile-based NIRS sensor., (© 2024. Oxygen Transport to Tissue International.)

Recent advances in neonatal intensive care have improved the survival rates of extremely low-birth-weight infants (ELBWIs). However, there has been no obvious improvement in the proportion of survivors without sequelae. Therefore, the development of appropriate management methods for ELBWIs in the neonatal intensive care unit is important to improve outcomes. In this study, we utilised time-domain near-infrared spectroscopy (TD-NIRS) for deep brain monitoring in premature infants in the clinical setting and measured the heads of three ELBWIs once weekly using a TD-NIRS system in transmittance mode. We found that optical signals transmitted through the head were detectable in all ELBWIs. We also confirmed that the total haemoglobin concentration and tissue oxygen saturation decreased in the first month after birth, while the reduced scattering coefficient was not correlated with postmenstrual age. We anticipate that this TD-NIRS technique will be useful for clinical assessment of deep brain tissues for appropriate management of cerebral circulation of ELBWIs in the neonatal intensive care unit., (© 2024. Oxygen Transport to Tissue International.)

Near-infrared spectroscopy (NIRS) can be employed for the non-invasive real-time evaluation of cerebral oxygen dynamics. A portable wireless NIRS system has been developed to record measurements using a band worn around the head. In this case report, we describe the clinical findings and cerebral oxygen dynamics of a patient who underwent surgery to remove a left temporal subdural haematoma. The patient was a male in his 70s, who fell while riding a bicycle. Following the gradual onset of gait disturbance, the patient was admitted to our hospital for surgery. After surgical removal of the subdural haematoma, the cerebral oxygen dynamics of the left and right frontal cortical hemispheres were monitored using NIRS in the following sequence: supine, bed-up 70°, sitting, standing, and supine, for 3 min each. Measurements were made on postoperative days (PODs) 2, 3, 7, and 10. Clinically, on POD2, the patient had a decreased level of consciousness, requiring assistance in maintaining each posture. On POD10, his level of consciousness improved and he was able to walk for short distances. The cerebral oxygen dynamics on the injured hemispheres showed the most remarkable changes on POD2 which decreased with the passage of time. NIRS may be useful in non-invasive assessment of the recovery of the cerebral circulation after neurosurgical intervention to inform the medical rehabilitation team on the progress in recovery., (© 2024. Oxygen Transport to Tissue International.)

To investigate the effect of the lithotomy position on lower limb circulation under general anaesthesia, near-infrared spectroscopy (NIRS) was used to measure changes in blood volume and oxygenation in thigh tissue in patients (n = 35) under general anaesthesia in the lithotomy position. The NIRS measurement items, including total haemoglobin concentration (total-Hb), tissue haemoglobin index (nTHI), and tissue oxygenation index (TOI) in the thigh, were recorded for 60 min, while the patients were in the lithotomy position. The correlation between changes in each measurement item and patient characteristics, elevation of the lower extremities, and cardiorespiratory indices were evaluated. Data obtained from 24 patients were analysed. The median values (quartile deviation) of changes in total-Hb, nTHI, and TOI during the 60-min period from baseline were + 3.09 (1.99) μmol/L, +0.08 (0.03) a.u., and + 2.25 (1.75) %, respectively, all of which were significantly increased (p < 0.05). Regression analysis showed that no factor was significantly associated with the increase in any measurement item. The present results suggest that circulation in thigh tissue tends to shift towards hyperaemia during 60 min of general anaesthesia in the lithotomy position, regardless of patient background factors or changes in cardiorespiratory conditions., (© 2024. Oxygen Transport to Tissue International.)

This study aimed to clarify the effect of 1 month of gum chewing (GCh) training on masseter muscle oxygen dynamics and determine its effectiveness in improving muscle endurance and fatigue. A total of 16 healthy adult subjects were included in this study. The subjects were randomly assigned to two groups: control and training groups (eight subjects each). GCh training using prototype gum of moderate hardness was performed for 10 min (5 min for each side) three times a day before each meal for 30 days. Clenching effects were evaluated before and after interventions. Masseter muscle oxygen dynamics were measured using spatially resolved near-infrared spectroscopy. Furthermore, masseter muscle fatigue was assessed using the Visual Analog Scale (VAS). After training, a significant increase was observed in total haemoglobin and oxygenated haemoglobin during clenching, and the 1/2 recovery time was significantly shortened. The changes in the VAS score showed a decreasing trend after training. In conclusion, 1 month of GCh training changed masseter oxygen dynamics during clenching and recovery and improved muscle aerobic capacity., (© 2024. Oxygen Transport to Tissue International.)

Near-infrared spectroscopy (NIRS) has been used to measure skeletal muscle oxidative function for more than 30 years. Several indicators evaluate muscle oxidative function using NIRS during exercise, such as deoxygenation rate at the start of exercise (Deoxy-rate), changes in deoxygenation during exercise (ΔDeoxy), and reoxygenation speed after exercise (T 1/2 reoxy, reoxy rate). Previous studies have reported that these muscle NIRS indicators are significantly correlated with muscle fibre type, phosphocreatine recovery rate, and peak oxygen uptake. In addition, muscle NIRS indicators have been applied to the study of a number of chronic health conditions, including patients with ischaemic heart failure. Recently, wearable NIRS devices monitor muscle function continuously and freely in the field, and we predict that NIRS devices will be widely applied to our lifestyles more than ever before. However, there are some critical problems with measuring muscle oxidative function using NIRS devices. We have previously reported that subcutaneous adipose tissue thickness (SATT) greatly influences the light pathlength and makes it difficult to quantify tissue deoxygenation, especially in the measurements of muscle deoxygenation from the skin surface. The effects of SATT need to, therefore, be corrected when using NIRS devices, especially when comparing differences in sex, age, and trainability, as the subjects' SATT could differ significantly. In addition, we have more recently reported that assuming constant mean pathlength (MPL) in NIRS leads to an inaccurate interpretation of muscle deoxygenation, since there are greater changes in MPL during incremental cycling exercise, especially at shorter wavelengths in the NIRS region. In this mini-review, we will summarise the indicators of muscle oxidative function using NIRS and the challenges of using an NIRS apparatus, especially during exercise., (© 2024. Oxygen Transport to Tissue International.)

Although previous studies have shown correlation between regional cerebral oxygen saturation (rScO 2 ) and mixed venous oxygen saturation (SvO 2 ), there is a lack of pragmatic information on the clinical applicability of these findings, such as tracking ability. We retrospectively analyzed continuous intraoperative recordings of rScO 2 and SvO 2 obtained from a pulmonary artery catheter and either of two near-infrared spectroscopy (NIRS) devices (INVOS 5100C, Medtronic; O3, Masimo) during off-pump cardiopulmonary bypass (OPCAB) surgery in adult patients. The ability of rScO 2 to track SvO 2 was quantitatively evaluated with 5 min interval changes transformed into relative values. The analysis included 176 h of data acquired from 48 subjects (26 and 22 subjects for INVOS and O3 dataset, respectively). The area under ROC of the left-rScO 2 for detecting change of SvO 2  ≥ 10% in INVOS and O3 datasets were 0.919 (95% CI 0.903-0.936) and 0.852 (95% CI 0.818-0.885). The concordance rates between the interval changes of left-rScO 2 and SvO 2 in INVOS and O3 datasets were 90.6% and 91.9% with 10% exclusion zone. rScO 2 can serve as a noninvasive tool for detecting changes in SvO 2 levels, a critical hemodynamic measurement., (© 2023. The Author(s).)

Purpose: It has been reported that cerebral oxygen saturation (rSO 2 ) measured by near infrared spectroscopy is low in dialysis patients. We compared the rSO 2 values of dialysis patients before living donor kidney transplantation and their donors as controls by using three spectroscopes that utilize different principals, the INVOS 5100C (spatially resolved spectroscopy), FORE-SIGHT ELITE (modified Beer-Lambert law) and tNIRS-1 (time-resolved spectroscopy)., Methods: Before induction of anesthesia, the sensors of one of the three spectroscopes were placed on the forehead and rSO 2 values were recorded followed by the same measurement using the other two spectroscopes. The primary objective was to compare the rSO 2 values of the dialysis patients and controls using the three spectroscopes by the unpaired t test. Then we compared the rSO 2 values among the spectroscopes in both dialysis patients and controls by one-way ANOVA. Finally, we examined the relations between the rSO 2 values and the physiological values by using the Pearson correlation coefficient., Results: Fifteen pairs of dialysis patients and controls were studied. With the INVOS 5100 C, the values of the dialysis patients (59.7 ± 9.7% (mean ± standard deviation) were 13% lower than those of the controls (73.3 ± 6.9%) (P < 0.01). With the tNIRS-1, the values were 57.8 ± 4.8% in the dialysis patients and 63.3 ± 3.5% in the controls (P < 0.01). Almost no differences were observed with the FORE-SIGHT ELITE (71.6 ± 4.9% [dialysis patients] vs. 70.8 ± 4.3% [Controls]) (P = 0.62). Among the spectroscopes, the values were significantly different in both dialysis patients and controls. For the INVOS 5100C and tNIRS-1, correlation coefficients between rSO 2 values and blood Hb and serum Alb were more than 0.5., Conclusions: The rSO 2 values for comparisons between the dialysis patients and the controls were different according to differences of the principles of the near infrared spectroscopes. In the INVOS 5100C and tNIRS-1, rSO 2 values may be related to blood Hb and serum Alb., (© 2023. The Author(s) under exclusive licence to Japanese Society of Anesthesiologists.)

Significance: Continuous wave near infrared spectroscopy (CW-NIRS) is widely exploited in clinics to estimate skeletal muscles and brain cortex oxygenation. Spatially resolved spectroscopy (SRS) is generally implemented in commercial devices. However, SRS suffers from two main limitations: the a priori assumption on the spectral dependence of the reduced scattering coefficient [ μ s ' ( λ ) ] and the modeling of tissue as homogeneous., Aim: We studied the accuracy and robustness of SRS NIRS. We investigated the errors in retrieving hemodynamic parameters, in particular tissue oxygen saturation ( S t O 2 ), when μ s ' ( λ ) was varied from expected values, and when layered tissue was considered., Approach: We simulated hemodynamic variations mimicking real-life scenarios for skeletal muscles. Simulations were performed by exploiting the analytical solutions of the photon diffusion equation in different geometries: (1) semi-infinite homogeneous medium and constant μ s ' ( λ ) ; (2) semi-infinite homogeneous medium and linear changes in μ s ' ( λ ) ; (3) two-layered media with a superficial thickness s 1 = 5 , 7.5, 10 mm and constant μ s ' ( λ ) . All simulated data were obtained at source-detector distances ρ = 35 , 40, 45 mm, and analyzed with the SRS approach to derive hemodynamic parameters (concentration of oxygenated and deoxygenated hemoglobin, total hemoglobin concentration, and tissue oxygen saturation, S t O 2 ) and their relative error., Results: Variations in μ s ' ( λ ) affect the estimated S t O 2 (up to ± 10 % ), especially if changes are different at the two wavelengths. However, the main limitation of the SRS method is the presence of a superficial layer: errors strongly larger than 20% were retrieved for the estimated S t O 2 when the superficial thickness exceeds 5 mm., Conclusions: These results highlight the need for more sophisticated strategies (e.g., the use of multiple short and long distances) to reduce the influence of superficial tissues in retrieving hemodynamic parameters and warn the SRS users to be aware of the intrinsic limitation of this approach, particularly when exploited in the clinical environment., (© 2023 The Authors.)

Long periods of bed rest for elderly population, due to a femur fracture event, can cause a deterioration in the muscular capacity. Therefore, monitoring of the muscle oxidative capacity in this fragile population is necessary to define the muscular oxidative metabolism state before and after a rehabilitation period. The time-domain near-infrared spectroscopy (TD-NIRS) technique enables the absolute values to be calculated for hemodynamic parameters such as oxy- (O 2 Hb), deoxy- (HHb), total- (tHb) haemoglobin, and tissue oxygen saturation (SO 2 ) of the muscular tissue. In this work, we have characterized vastus lateralis muscle hemodynamics during a baseline period at two different time points: after the surgery (PRE) and after 15 days of rehabilitation (POST). The mean values for the absolute values of the hemodynamic parameters were: O 2 Hb&#95;PRE = 49.1 ± 14.1 μM; O 2 Hb&#95;POST = 47.1 ± 13.4 μM; HHb&#95;PRE = 28.3 ± 10.3 μM; HHb&#95;POST = 26.7 ± 9.9 μM; tHb&#95;PRE = 77.3 ± 23.6 μM; tHb&#95;POST = 73.8 ± 21.4 μM; SO 2 &#95;PRE = 63.9 ± 4.0% and SO 2 &#95;POST = 64.9 ± 5.6%. The hemodynamic parameters did not show significant differences at both group and single subject level. These results suggest that for this kind of population, the baseline of the hemodynamic parameters is not the best one to consider to assess the rehabilitation progresses in terms of muscular oxidative metabolism., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

Pressure injuries (PI) are dangerous tissue lesions that heal very slowly and pose a high risk of serious infections. They are caused by pressure applied to the tissue, which stops blood circulation and therefore induces hypoxia, i.e., low tissue oxygen saturation (StO 2 ). PI cause severe suffering and are expensive to treat. Hence it is essential to prevent them with a device that detects a dangerous situation, e.g., by measuring StO 2 using near-infrared spectroscopy (NIRS). For such a device to be wearable without causing PI, it must not introduce pressure points itself. This can be achieved by integrating optical fibers into a textile to transport light to and from the tissue.The aim of this paper is to investigate the accuracy of StO 2 measurements using a NIRS device based only on textile-integrated optical fibers.Bundles of fibers were stitched into a textile in such a way that loops of <1 mm diameters were formed at the stitching locations. Detection points (DPs) on the fabric consisted of 8 fibers with 3 loops each. Emission points (EPs) were made from 4 fibers with 3 loops each. All fiber ends of a DP were connected to an avalanche photodiode. One end of each fiber belonging to an EP was connected to an LED (740 nm, 810 nm, or 880 nm; 290, 560, or 610 mW).To verify the accuracy of this textile-based sensor, we placed it on a subject's forearm and compared the derived StO 2 during arterial occlusion to the values of a gold-standard NIRS device (ISS Imagent), which was placed on the forearm too.We found that our textile-based sensor repeatedly measured StO 2 values over a range of 40% with a deviation of <10% from the reference device.By showing the ability to measure StO 2 using textile-integrated optical fibers accurately, we have reached a significant milestone on our way to building a wearable device to monitor tissue health and prevent PI., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

The interchange among the energy-providing phosphagen, glycolytic, and aerobic systems during exercise is often poorly understood by beginning students in exercise physiology. Exercise is oftentimes thought of as being aerobic or anaerobic, with the body progressing sequentially from one system to the next, although the energy systems work synergistically to produce energy from the onset of exercise, and all ultimately use oxygen. Traditional methods of teaching these concepts using only indirect calorimetry and a metabolic cart can be misleading. Relatively inexpensive noninvasive monitors of muscle oxygenation levels ([Formula: see text]) provide a useful tool to help students better understand the contribution and timing of these three systems of ATP generation and convey the concept that ultimately all energy production in the human body is oxygen dependent. In this laboratory, students use near-infrared spectroscopy (NIRS) to visualize oxygen utilization by skeletal muscle during exercise by devising three exercise unique protocols, with each designed to stress a different energy system. Students then perform their protocols while using NIRS to measure and analyze [Formula: see text]. Students generate graphs with collected data, allowing them to visualize and appreciate oxygen consumption during all three protocols as well as elevated oxygen consumption after exercise. The students learn that any exercise is really all about oxygen. NEW & NOTEWORTHY Traditional methods of teaching bioenergetics using indirect calorimetry and a metabolic cart may be misleading. Recent advances in technology have made near-infrared spectroscopy (NIRS) a relatively inexpensive, noninvasive means of monitoring muscle oxygen levels during exercise. In this laboratory activity, NIRS devices are used for hands-on exploration of the synergistic nature of the energy systems, allowing students to appreciate the synergistic nature of the energy systems and how all exercise is really all about oxygen.

Objective. To establish the reference values for peripheral tissue perfusion of the triceps surae muscle assessed by Near-infrared spectroscopy (NIRS) at rest and in progressive effort. Approach. A total of 288 apparently healthy individuals of both sexes were included; between 30 and 79 years of age; nonsmokers; without diagnosis of diabetes mellitus, systemic arterial hypertension, kidney disease, symptoms of angina and intermittent claudication, or any musculoskeletal alteration that would prevent physical exertion; and without diagnosis of Peripheral arterial disease (PAD) or other associated symptoms. All individuals performed anthropometric measurements, physical activity levels, and tissue oxygen saturation (StO 2 ) assessments by NIRS during and after arterial occlusion maneuver and incremental shuttle walking test. The variables obtained by NIRS were presented in percentiles (P) for general comparison between sexes and for comparison between sexes according to age group. The relationship between the NIRS data and other variables was tested. Main results. Considering P50 and p<0.05, men had lower StO2 values, higher deoxygenation and reoxygenation (Tx-reox) rates at rest, and higher Tx-reox during progressive effort. There were correlations (p<0.0001) of body composition with the lowest StO2 and Tx-reox values and of functional capacity with Tx-reox in occlusion and Tx-reox. Significance. The percentiles presented can clinically assist in the diagnosis and monitoring of different health conditions; however, it is important to consider the individual's sex, body composition, and functional capacity., (© 2022 Institute of Physics and Engineering in Medicine.)

There is a clinical need to measure local tissue oxygen saturation (StO 2 ), oxy-, deoxy- and total haemoglobin concentration ([O 2 Hb], [HHb], [tHb]) in human tissue. The aim was to validate an oximeter called OxyVLS applying visible light spectroscopy (VLS) to determine these parameters without needing to assume a reduced scattering coefficient (μ' s ). This problem is solved by appropriate calibrations. Compared to near-infrared spectroscopy (NIRS), OxyVLS determines the oxygenation in a much smaller more superficial volume of tissue, which is useful in many clinical cases. OxyVLS was validated in liquid phantoms with known StO 2 , [tHb], and μ' s and compared to frequency domain NIRS as a reliable reference. OxyVLS showed a high accuracy for all the mentioned parameters and was even able to measure μ' s . Thus, OxyVLS was successfully tested in vitro., (© 2022. Springer Nature Switzerland AG.)

The neonatal transition involves physiological modifications as a consequence of the complexity of the perinatal period. Various strategies can be used to attain the same level of postnatal cerebral oxygenation, depending on the status of the infant at birth. We evaluated such strategies by recording 20 full-term newborns by near-infrared spectroscopy during the first 10 min of life. The acid-base status at birth revealed two clustered profiles of cerebral oxygenation dynamics. Lower pH and base excess and higher lactate levels were associated with more rapid attainment of the 95% maximal tissue oxygenation index value. These results suggest that metabolic mechanisms drive initial cerebral oxygenation dynamics during this critical period. These results confirm the capacity of newborns to develop multiple strategies to protect the brain., (© 2021. The Author(s).)

Cardiothoracic surgeries are life-saving procedures but often it results in various complications. Intraoperative cerebral oximetry monitoring used to detect regional cerebral oxygen saturation (rScO2) is a non-invasive method that provides prognostic importance in cardiac surgery. The main aim of the present study was to evaluate the association of intraoperative cerebral oxygen monitoring during cardiac surgery on postoperative complications. This was a case-controlled retrospective study conducted on adult patients, who underwent open-heart surgery in National Heart Institute, Malaysia. The case group comprised patients on protocolized cerebral oximetry monitoring. They were treated using a standardized algorithm to maintain rScO2 not lower than 20% of baseline rScO2. The control group comprised patients with matched demographic background, preoperative risk factors, and type of surgical procedures. Propensity score stratification was utilized to contend with selection bias. Retrospective analysis was performed on 240 patients (case group) while comparing it to 407 patients (control group). The non-availability of cerebral oximetry monitoring during surgery was the prominent predictor for all outcome of complications; stroke (OR: 7.66), renal failure needing dialysis (OR: 5.12) and mortality (OR: 20.51). Postoperative complications revealed that there were significant differences for risk of mortality (p<0.001, OR = 20.51), renal failure that required dialysis (p<0.001, OR = 5.12) and stroke (p <0.05, OR = 7.66). Protocolized cerebral oximetry monitoring during cardiothoracic surgeries was found to be associated with lower incidence of stroke, renal failure requiring dialysis and mortality rate., Competing Interests: The authors have declared that no competing interests exist.

Background: Previous studies describe a short-term decrease in cerebral oxygen saturation (StO2) after intraventricular hemorrhage (IVH) in premature infants; little is known about long-term implications., Methods: Infants born <30 weeks gestational age (GA) were included. Clinical characteristics, hemoglobin measurements, the highest grade of IVH, and white matter injury (WMI) were noted. NIRS monitoring occurred daily or every other day for 4 weeks; weekly through 36 weeks GA. Recordings were error-corrected before calculation of mean StO2 and fractional tissue oxygen extraction (FTOE). Mean StO2 and FTOE were plotted by postnatal age and injury group (IVH/no IVH; WMI/no WMI). Non-linear regression by locally estimated scatterplot smoothing was used to generate the best-fit line and CI., Results: A total of 1237 recordings from 185 infants were included; mean length = 6.5 h; mean GA = 26.3 w; mean BW = 951 g; overall/severe IVH incidence was 29/8%, WMI incidence was 16%. IVH was independently associated with an acute drop in StO2, which remained lower for 68 d. Severe IVH was associated with lower StO2 values than mild IVH. WMI was associated with early and persistent elevation of FTOE., Conclusion: IVH of any grade is associated with a prolonged cerebral desaturation and WMI is associated with prolonged elevation of FTOE. This finding is exacerbated for infants with severe IVH., Impact: The longitudinal impact of IVH on cerebral oxygenation has not been previously studied. IVH is associated with persistent cerebral desaturation, months in length, and is independent of anemia. More severe IVH is associated with worsened cerebral hypoxia. Infants later diagnosed with white matter injury have an early and persistent elevation of cerebral oxygen extraction (cFTOE). This cerebral desaturation, below previously identified normative ranges, may provide insight into the mechanistic link between IVH and white matter injury.

Recently, tissue oxygenation in pediatric heart surgery is measured by using near-infrared spectroscopy. Monitoring of cerebral oxygen saturation (ScO 2 ) is most common but that of somatic tissue oxygen saturation (SrO 2 ) is also gradually becoming widespread. However, the value of their monitoring is not well established. One of the reasons for this may be that the physiological factors affecting ScO 2 and SrO 2 have not been sufficiently clarified. Accordingly, we prospectively observed the changes in ScO 2 and SrO 2 simultaneously throughout cardiac surgery with cardiopulmonary bypass (CPB) in children weighing under 10 kg and evaluated their relationships with physiological parameters by using the random-effects model. ScO 2 and SrO 2 were measured with an INVOS 5100C (Somanetics, Troy, MI, USA). The random-effects analysis was applied for ScO 2 and SrO 2 , as dependent variables, and seven physiological parameters (mean blood pressure, central venous pressure, rectal temperature, SaO 2 , hematocrit PaCO 2 , and pH) were entered as independent covariates. The analysis was performed during the pre-CPB, CPB, and post-CPB periods. Next, the same analysis was performed by dividing the patients into univentricular and biventricular physiological types. Forty-one children were evaluated. Through the whole surgical period, ScO 2 correlated strongly with mean blood pressure regardless of the physiological type. On the other hand, the contribution of mean blood pressure to SrO 2 was weak and various other parameters were related to SrO 2 changes. Thus, the physiological parameters affecting ScO 2 and SrO 2 were rather different. Accordingly, the significance of monitoring of cerebral and somatic tissue oxygen saturation in pediatric cardiac surgery should be further evaluated.

Smell and taste of food can trigger physiological responses facilitating digestion and metabolism of nutrients. Controlled experimental studies in preterm babies have demonstrated that smell activates the orbitofrontal cortex (OFC) but none have investigated the effect of taste stimulation. Using cotside Near-Infrared Spectroscopy (NIRS), we measured changes in OFC cerebral oxygenation in response to gastric tube feeds five and 10 days after birth in 53 assessments of 35 moderate- to late-preterm babies enrolled in a randomized trial. Babies were randomly assigned to receive smell and taste of milk before gastric tube feeds (intervention group, n = 16) or no exposure (control group, n = 19). The majority of babies were born at 33 weeks of gestation (range 32-34) and 69% were boys. No differences in OFC cerebral oxygenation were observed between control and intervention groups. Gastric tube feeds induced activation of the OFC ( p < 0.05), but sensory stimulation alone with smell and taste did not. Boys, but not girls, showed activation of the OFC following exposure to smell of milk ( p = 0.01). The clinical impact of sensory stimulation prior to tube feeds on nutrition of preterm babies, as well as the impact of environmental inputs on cortical activation, remains to be determined.

The brain tissue partial oxygen pressure (PbtO 2 ) and near-infrared spectroscopy (NIRS) neuromonitoring are frequently compared in the management of acute moderate and severe traumatic brain injury patients; however, the relationship between their respective output parameters flows from the complex pathogenesis of tissue respiration after brain trauma. NIRS neuromonitoring overcomes certain limitations related to the heterogeneity of the pathology across the brain that cannot be adequately addressed by local-sample invasive neuromonitoring (e.g., PbtO 2 neuromonitoring, microdialysis), and it allows clinicians to assess parameters that cannot otherwise be scanned. The anatomical co-registration of an NIRS signal with axial imaging (e.g., computerized tomography scan) enhances the optical signal, which can be changed by the anatomy of the lesions and the significance of the radiological assessment. These arguments led us to conclude that rather than aiming to substitute PbtO 2 with tissue saturation, multiple types of NIRS should be included via multimodal systemic- and neuro-monitoring, whose values then are incorporated into biosignatures linked to patient status and prognosis. Discussion on the abnormalities in tissue respiration due to brain trauma and how they affect the PbtO 2 and NIRS neuromonitoring is given.

Introduction: The prevalence of cognitive impairment in patients undergoing hemodialysis (HD) is higher than that in healthy controls. To date, studies on the association between cognitive function and cerebral oxygenation in these patients are limited. Therefore, in this study, we aimed to cross-sectionally investigate the association between cognitive assessment scores and clinical factors, including cerebral oxygenation, in patients undergoing HD., Methods: In this observational study, 193 HD patients were included. Cerebral regional oxygen saturation (rSO2) was monitored using an INVOS 5,100c oxygen saturation monitor. Poor cognition was defined as a Mini-Mental State Examination (MMSE) score ≤23. We analyzed the association between MMSE score and clinical factors, including cerebral rSO2., Results: MMSE score in HD patients included in this study was 26.8 ± 3.3. There were 164 patients (85%) with MMSE score ≥24 and 29 patients (15%) with an MMSE score ≤23. In the patients with MMSE score ≥24, cerebral rSO2 (53.8% ± 8.3%) was significantly higher than that in patients with MMSE score ≤23 (49.5% ± 9.8%; p = 0.013). Multivariable linear regression analysis was performed using the following confounding factors: age, mean blood pressure, cerebral rSO2, HD duration, ultrafiltration rate, hemoglobin, serum Cr, serum calcium, serum phosphate, total cholesterol, high-density lipoprotein cholesterol levels, serum albumin, presence of diabetes mellitus or chronic glomerulonephritis, history of comorbid cardiovascular or cerebrovascular disease, and use of renin-angiotensin-aldosterone system inhibitors or vitamin D analogs. MMSE score was independently and significantly associated with age (standardized coefficient: -0.244) and cerebral rSO2 (standardized coefficient: 0.180)., Conclusions: MMSE score was independently associated with age (negative effect) and cerebral rSO2 (positive effect) in this cross-sectional study. Further prospective studies are needed to clarify whether maintaining cerebral oxygenation prevents the deterioration of cognitive function in patients undergoing HD., (© 2021 S. Karger AG, Basel.)

Flaps are common in plastic surgery to reconstruct large tissue defects in cases such as trauma or cancer. However, most tissue oximeters used for monitoring ischemia in postoperative flaps are bulky, wired devices, which hinder direct flap observation. Here, we present the results of a clinical trial using a previously untried paintable transparent phosphorescent bandage to assess the tissue's partial pressure of oxygen (pO 2 ). Statistical analysis revealed a strong relationship ( P < 0.0001) between the rates of change of tissue oxygenation measured by the bandage and blood oxygen saturation (%stO 2 ) readings from a standard-of-care ViOptix near-infrared spectroscopy oximeter. In addition, the oxygen-sensing bandage showed no adverse effects, proved easy handling, and yielded bright images across all skin tones with a digital single-lens reflex (DSLR) camera. This demonstrates the feasibility of using phosphorescent materials to monitor flaps postoperatively and lays the groundwork for future exploration in other tissue oxygen sensing applications., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

Background: Extra-corporeal membrane oxygenation (ECMO) is a life-saving intervention for severe respiratory and cardiac diseases. However, 50% of survivors have abnormal neurologic exams. Current ECMO management is guided by systemic metrics, which may poorly predict cerebral perfusion. Continuous optical monitoring of cerebral hemodynamics during ECMO holds potential to detect risk factors of brain injury such as impaired cerebrovascular autoregulation (CA)., Methods: We conducted daily measurements of microvascular cerebral blood flow (CBF), oxygen saturation, and total hemoglobin concentration using diffuse correlation spectroscopy (DCS) and frequency-domain diffuse optical spectroscopy in nine neonates. We characterize CA utilizing the correlation coefficient (DCSx) between CBF and mean arterial blood pressure (MAP) during ECMO pump flow changes., Results: Average MAP and pump flow levels were weakly correlated with CBF and were not correlated with cerebral oxygen saturation. CA integrity varied between individuals and with time. Systemic measurements of MAP, pulse pressure, and left cardiac dysfunction were not predictive of impaired CA., Conclusions: Our pilot results suggest that systemic measures alone cannot distinguish impaired CA from intact CA during ECMO. Furthermore, optical neuromonitoring could help determine patient-specific ECMO pump flows for optimal CA integrity, thereby reducing risk of secondary brain injury., Impact: Cerebral blood flow and oxygenation are not well predicted by systemic proxies such as ECMO pump flow or blood pressure. Continuous, quantitative, bedside monitoring of cerebral blood flow and oxygenation with optical tools enables new insight into the adequacy of cerebral perfusion during ECMO. A demonstration of hybrid diffuse optical and correlation spectroscopies to continuously measure cerebral blood oxygen saturation and flow in patients on ECMO, enabling assessment of cerebral autoregulation. An observation of poor correlation of cerebral blood flow and oxygenation with systemic mean arterial pressure and ECMO pump flow, suggesting that clinical decision making guided by target values for these surrogates may not be neuroprotective. ~50% of ECMO survivors have long-term neurological deficiencies; continuous monitoring of brain health throughout therapy may reduce these tragically common sequelae through brain-focused adjustment of ECMO parameters.

Cardiopulmonary bypass-associated acute kidney injury may appear postoperatively, but predictive factors are unclear. We investigated the potential of regional tissue oxygen saturation as a predictor of cardiopulmonary bypass-associated acute kidney injury. We analyzed the clinical data of 150 adult patients not on dialysis who underwent elective cardiac surgical procedures during January 2015-March 2017. Near-infrared spectroscopy was used to measure regional oxygen saturation. Sensors were placed on the patients' forehead, abdomen, and thigh. The incidence of acute kidney injury was 2% at the end of surgery, 13% at 24 h, and 9% at 48 h, with the highest at 24 h after surgery. The multiple regression analysis revealed that the thigh regional oximetry during cardiopulmonary bypass, oxygen delivery index, and neutrophil count at the end of cardiopulmonary bypass and surgery were independent risk factors for acute kidney injury. The receiver-operating characteristic curve analysis suggested that a cutoff of regional oxygen saturation at the thigh of ≤ 67% was predictive of acute kidney injury within 24 h after surgery. In conclusion, the regional oxygen saturation at the thigh during cardiopulmonary bypass is a crucial marker to predict postoperative acute kidney injury in adults undergoing cardiac surgery.

Purpose: Decline in skeletal muscle mitochondrial oxidative capacity (MOC) is associated with reduced aerobic capacity and increased risk of cardiovascular and metabolic disease. Measuring skeletal muscle MOC may be an alternative method to assess aerobic capacity, especially for individuals unable to perform a whole-body maximum oxygen uptake protocol. In this study, linear regression analysis in two leg muscles was performed to determine whether MOC values could be used to predict whole-body peak oxygen uptake., Methods: MOC was measured with near infrared spectroscopy (NIRS) in the medial gastrocnemius (MG) and vastus lateralis (VL) muscles of 26 participants (age, 27.1 ± 5.8 years old). Whole-body peak oxygen uptake (VO 2 peak) was determined by indirect calorimetry during a continuous ramp protocol on a cycle ergometer., Results: VO 2 peak values were significantly correlated with the muscle recovery rate constant (k) of the MG (kMG, r = 0.59; p < 0.01) and VL (kVL, r = 0.63; p < 0.01) muscles. Summing recovery rate constants of both muscles together (kMG + kVL) improved the strength of the correlation with VO 2 peak (r = 0.78; p < 0.0001) and could explain a majority of the variance (R 2  = 0.61) between the two measurements., Conclusion: Data suggest that NIRS can provide reliable MOC measurements on two leg muscles that correlate well with whole-body peak oxygen uptake.

Purpose: Increased intraabdominal pressure IAP may reduce renal blood flow (RBF). The study aims to evaluate the pneumoperitoneum effect on RBF by comparing renal regional oxygen saturation index (rSrO2) measured by near-infrared spectroscopy (NIRS) in pediatric patients having laparotomy and laparoscopy., Methods: Of 58 patients having laparoscopy and laparotomy, 18 were excluded due to renal pathologies, combined open surgical procedures, and administration of inotropic drugs. Hemodynamic parameters and rSrO2 were recorded in laparoscopy (n = 20) and laparotomy (n = 20) groups before induction and with 5 min intervals up to 60 min and at post-extubation., Results: Decrease in right renal rSrO2 at 45th and 60th min and 30th, 45th and 60th min in left were significant in the laparoscopy group compared to laparotomy group. In the laparoscopy group, reductions at T25, T30, T45, and T60 were significant in both renal rSrO2. Renal rSO2 increased to normal with desufflation., Conclusion: IAP with pneumoperitoneum may lead to renal hypoxia in children. Renal rSO2 returns to normal with desufflation. Renal NIRS monitorization might be needed in patients with renal parenchymal and vascular pathologies, solitary kidney, and multiorgan pathologies that may affect renal oxygenation.

Background and Aim: In patients undergoing congenital cardiac surgery, it is crucial to maintain oxygen demand-consumption balance. Central venous oxygen saturation (ScvO2) is a useful indicator of oxygen demand and consumption balance which is an invasive method. Near-infrared spectroscopy (NIRS) is a noninvasive, continuous monitoring technique that measures regional tissue oxygenation. NIRS that is placed over the internal jugular vein cutaneous area (NIRSijv) has the potential to show ScvO2 indirectly. In this study, we aimed to determine the correlation between ScvO2 with NIRSijv in pediatric patients undergoing congenital cardiac surgery., Materials and Methods: Fifty children participated in the study. Four patients were excluded for the inability of internal jugular vein (IJV) catheterization due to technical difficulties. After anesthesia induction, NIRS probes were placed on the IJV site with ultrasound guidance for the measurement of continuous transcutaneous oxygen saturation. The catheter insertion was also done through the IJV from the other side using ultrasound guidance. Cerebral oxygenation monitoring was done using NIRS with a single pediatric probe placed on the right forehead. Values of NIRSijv, cerebral NIRS (NIRSc) and ScvO2, were recorded at certain times until postoperative 24th hour., Results: Data were collected at 8 different time points. There was a significant correlation between ScvO2 and NIRSijv in all measurement time points (r = 0.91), (P = 0.001). The mean bias between ScvO2 and NIRSijv was 2.92% and the limits of agreement were from 11% to –5.2%. There was a moderate correlation between ScvO2 and NIRSc (r = 0.45), (P = 0.001). The mean bias between ScvO2 and NIRSc was 2.7% and the limits of agreement were from +26% to –20%., Conclusions: In this study, we found a strong correlation between ScvO2 and NIRS measurements taken from the internal jugular vein site. Accordingly, continuous noninvasive monitoring with transcutaneous NIRSijv can be an alternative method as a trend monitor for the central venous oxygen saturation in pediatric cardiac patients undergoing congenital cardiac surgery., Competing Interests: All authors declare that they have no conflict of interest., (This work is licensed under a Creative Commons Attribution 4.0 International License.)

Near-infrared (NIR) spectroscopy occupies a specific spot across the field of bioscience and related disciplines. Its characteristics and application potential differs from infrared (IR) or Raman spectroscopy. This vibrational spectroscopy technique elucidates molecular information from the examined sample by measuring absorption bands resulting from overtones and combination excitations. Recent decades brought significant progress in the instrumentation (e.g., miniaturized spectrometers) and spectral analysis methods (e.g., spectral image processing and analysis, quantum chemical calculation of NIR spectra), which made notable impact on its applicability. This review aims to present NIR spectroscopy as a matured technique, yet with great potential for further advances in several directions throughout broadly understood bio-applications. Its practical value is critically assessed and compared with competing techniques. Attention is given to link the bio-application potential of NIR spectroscopy with its fundamental characteristics and principal features of NIR spectra.

Intraoperative maintenance of optimal tissue oxygenation is critical; however, it is uncertain whether measurements of different tissue beds correlate with each other. Cerebral tissue oxygen saturation (SctO 2 ) measured on the forehead and somatic tissue oxygen saturation (SstO 2 ) measured on limbs, using a tissue near-infrared spectroscopy, were simultaneously recorded every 2 s in patients having spine surgery or robotic hysterectomy. Simple linear regression was used to determine the static correlation between SctO 2 and SstO 2 using the median values of each min for each patient. The dynamic correlation between SctO 2 and SstO 2 was assessed by Pearson's correlation coefficient (CC) for each non-overlapping 2-min epoch. In patients having spine surgery (n = 99), SctO 2 and SstO 2 (mean ± SD) were 69.8 ± 4.9% and 75.5 ± 8.7%, whereas in patients having robotic hysterectomy (n = 106), the corresponding values were 74.9 ± 6.8% and 83.7 ± 6.2%. The static correlation between SctO 2 and SstO 2 was inconsistent (r ranging from - 0.86 to 0.93 in spine surgery and from - 0.74 to 0.85 in robotic hysterectomy). The proportional durations with CC ≤ - 0.3 (negative correlation), - 0.3 < CC < 0.3 (poor correlation) and CC ≥ 0.3 (positive correlation) were 18.3 ± 9.6%, 52.6 ± 12.1% and 29.0 ± 9.6%, respectively, in patients having spine surgery and 19.6 ± 9.0%, 58.6 ± 13.1% and 21.8 ± 8.0%, respectively, in patients having robotic hysterectomy. There are a large discrepancy and inconsistent correlation between intraoperative SctO 2 and SstO 2 measurements, suggesting their non-interchangeability.

Tissue perfusion monitoring is increasingly being employed clinically in a non-invasive fashion. In this end-of-year summary of the Journal of Clinical Monitoring and Computing, we take a closer look at the papers published recently on this subject in the journal. Most of these papers focus on monitoring cerebral perfusion (and associated hemodynamics), using either transcranial doppler measurements or near-infrared spectroscopy. Given the importance of cerebral autoregulation in the analyses performed in most of the studies discussed here, this end-of-year summary also includes a short description of cerebral hemodynamic physiology and its autoregulation. Finally, we review articles on somatic tissue oxygenation and its possible association with outcome.

While the effects of phenylephrine (PE) and ephedrine (E) on cerebral oxygen saturation (rS c O 2 ) already has been studied, the effect on paraspinal oxygen saturation (rS ps O 2 ) is still unexplored. This study aims to assess the effect of PE and E on rS c O 2 and rS ps O 2 , measured with near-infrared spectroscopy. A randomized 4-treatment cross-over trial was designed in 28 patients under BIS-titrated anaesthesia with sevoflurane. If MAP decreased more than 20% from baseline, incremental doses of PE and/or E were given according to the randomization (group I: E-PE-E, group II: PE-E-PE, group III: E-E-E, group IV: PE-PE-PE). rS c O 2 and rS ps O 2 on T 3 -T 4 , T 9 -T 10 and L 1 -L 2 were recorded. Differences in rSO 2 (post-pretreatment) within each group were analyzed with paired Student's t test. Differences in effects of PE and E on rS c O 2 and rS ps O 2 were analyzed with linear mixed-modelling. Following PE administration, rS c O 2 decreased significantly (- 2.7% ± 3.5), while it remained stable following E (- 0.6% ± 3.6). Contrastingly, rS ps O 2 at T 3 -T 4 , T 9 -T 10 and L 1 -L 2 slightly increased following PE (0.4% ± 2.5, 0.7% ± 2.0 and - 0.1% ± 1.4, respectively), while it decreased after E administration (- 1.3% ± 3.4%, - 0.7% ± 2.6% and - 1.3% ± 2.7%, respectively). Compared to E, PE administration was associated with a significant decrease in rS c O 2 (- 2.1%, 95% CI [- 3.1%, - 1.2%], p < 0.001). In contrast, compared to PE, E was associated with a significant decrease in rS ps O 2 at T 3 -T 4 , T 9 -T 10 and L 1 -L 2 (- 2.0%, 95% CI [- 2.8, - 1.1], p < 0.001; - 1.4%, 95% CI [- 2.4%, - 0.4%], p = 0.006; and - 1.5%, 95% CI [- 2.3%, - 0.8%], p < 0.001, respectively). An opposite effect on rS c O 2 and rS ps O 2 was observed after bolus administration of PE and E.

Near infrared spectroscopy (NIRS) has been used to evaluate regional cerebral tissue oxygen saturation (ScO 2 ) during the last decades. Perioperative management algorithms advocate to maintain ScO 2 , by maintaining or increasing cardiac output (CO), e.g. with fluid infusion. We hypothesized that ScO 2 would increase in responders to a standardized fluid challenge (FC) and that the relative changes in CO and ScO 2 would correlate. This study is a retrospective substudy of the FLuid Responsiveness Prediction Using Extra Systoles (FLEX) trial. In the FLEX trial, patients were administered two standardized FCs (5 mL/kg ideal body weight each) during cardiac surgery. NIRS monitoring was used during the intraoperative period and CO was monitored continuously. Patients were considered responders if stroke volume increased more than 10% following FC. Datasets from 29 non-responders and 27 responders to FC were available for analysis. Relative changes of ScO 2 did not change significantly in non-responders (mean difference - 0.3% ± 2.3%, p = 0.534) or in fluid responders (mean difference 1.6% ± 4.6%, p = 0.088). Relative changes in CO and ScO 2 correlated significantly, p = 0.027. Increasing CO by fluid did not change cerebral oxygenation. Despite this, relative changes in CO correlated to relative changes in ScO 2 . However, the clinical impact of the present observations is unclear, and the results must be interpreted with caution.Trial registration:http://ClinicalTrial.gov identifier for main study (FLuid Responsiveness Prediction Using Extra Systoles-FLEX): NCT03002129.

New Findings: What is the central question of this study? Does the presence and extent of heterogeneity in the ratio of O 2 delivery to uptake across human muscles relate specifically to different muscle activation patterns? What is the main finding and its importance? During ramp incremental knee-extension and cycling exercise, the profiles of muscle deoxygenation (deoxy[haemoglobin + myoglobin]) and diffusive O 2 potential (total[haemoglobin + myoglobin]) in the vastus lateralis corresponded to different muscle activation strategies. However, this was not the case for the rectus femoris, where muscle activation and deoxygenation profiles were dissociated and might therefore be determined by other structural and/or functional attributes (e.g. arteriolar vascular regulation and control of red blood cell flux)., Abstract: Near-infrared spectroscopy has revealed considerable heterogeneity in the ratio of O 2 delivery to uptake as identified by disparate deoxygenation {deoxy[haemoglobin + myoglobin] (deoxy[Hb + Mb])} values in the exercising quadriceps. However, whether this represents a recruitment phenomenon or contrasting vascular and metabolic control, as seen among fibre types, has not been established. We used knee-extension (KE) and cycling (CE) incremental exercise protocols to examine whether differential muscle activation profiles could account for the heterogeneity of deoxy[Hb + Mb] and microvascular haemoconcentration (i.e. total[Hb + Mb]). Using time-resolved near-infrared spectroscopy for the quadriceps femoris (vastus lateralis and rectus femoris) during exhaustive ramp exercise in eight participants, we tested the following hypotheses: (i) the deoxy[Hb + Mb] (i.e. fractional O 2 extraction) would relate to muscle activation levels across exercise protocols; and (ii) KE would induce greater total[Hb + Mb] (i.e. diffusive O 2 potential) at task failure (i.e. peak O 2 uptake) than CE irrespective of muscle site. At a given level of muscle activation, as assessed by the relative integrated EMG normalized to maximal voluntary contraction (%iEMG max ), the vastus lateralis deoxy[Hb + Mb] profile was not different between exercise protocols. However, at peak O 2 uptake and until 20% iEMG max for CE, rectus femoris exhibited a lower deoxy[Hb + Mb] (83.2 ± 15.5 versus 98.2 ± 19.4 μm) for KE than for CE (P < 0.05). The total[Hb + Mb] at peak O 2 uptake was not different between exercise protocols for either muscle site. These data support the hypothesis that the contrasting patterns of convective and diffusive O 2 transport correspond to different muscle activation patterns in vastus lateralis but not rectus femoris. Thus, the differential deoxygenation profiles for rectus femoris across exercise protocols might be dependent upon specific facets of muscle architecture and functional haemodynamic events., (© 2020 The Authors. Experimental Physiology © 2020 The Physiological Society.)

Objectives: The effects of hypercapnia on regional cerebral oxygen saturation (rSO 2 ) during surgery are unclear. We conducted a randomised controlled trial to investigate the relationship between mild hypercapnia and rSO 2 . We hypothesised that, compared with targeted normocapnia (TN), targeted mild hypercapnia (TMH) during major surgery would increase rSO 2 ., Design: A prospective, randomised, controlled trial in adult participants undergoing elective major surgery., Setting: A single tertiary centre in Heidelberg, Victoria, Australia., Participants: 40 participants were randomised to either a TMH or TN group (20 to each)., Interventions: TMH (partial pressure of carbon dioxide in arterial blood, PaCO 2 , 45-55 mm Hg) or TN (PaCO 2 35-40 mm Hg) was delivered via controlled ventilation throughout surgery., Primary and Secondary Outcome Measures: The primary endpoint was the absolute difference between the two groups in percentage change in rSO 2 from baseline to completion of surgery. Secondary endpoints included intraoperative pH, bicarbonate concentration, base excess, serum potassium concentration, incidence of postoperative delirium and length of stay (LOS) in hospital., Results: The absolute difference between the two groups in percentage change in rSO 2 from the baseline to the completion of surgery was 19.0% higher in both hemispheres with TMH (p<0.001). On both sides, the percentage change in rSO 2 was greater in the TMH group than the TN group throughout the duration of surgery. The difference between the groups became more noticeable over time. Furthermore, postoperative delirium was higher in the TN group (risk difference 0.3, 95% CI 0.1 to 0.5, p=0.02). LOS was similar between groups (5 days vs 5 days; p=0.99)., Conclusion: TMH was associated with a stable increase in rSO 2 from the baseline, while TN was associated with a decrease in rSO 2 in both hemispheres in patients undergoing major surgery. This resulted in a clear separation of percentage change in rSO 2 from the baseline between TMH and TN over time. Our findings provide the rationale for larger studies on TMH during surgery., Trial Registration Number: The Australian New Zealand Clinical Trials Registry (ACTRN12616000320459)., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Non-invasive quantitative imaging of cerebral oxygen metabolism (CMRO 2 ) in small animal models is crucial to understand the role of oxidative metabolism in healthy and diseased brains. In this study, we developed a multimodal method combining near-infrared spectroscopy (NIRS) and MRI to non-invasively study oxygen delivery and consumption in the cortex of mouse and rat models. The term CASNIRS is proposed to the technique that measures CMRO 2 with ASL and NIRS. To determine the reliability of this method, CMRO 2 values were compared with reported values measured with other techniques. Also, the sensitivity of the CASNIRS technique to detect changes in CMRO 2 in the cortex of the animals was assessed by applying a reduction in core temperature, which is known to reduce CMRO 2 . Cerebral blood flow (CBF) and CMRO 2 were measured in five mice and five rats at a core temperature of 37 °C followed by another measurement at 33 °C. CMRO 2 was 7.8 ± 1.8 and 3.7 ± 0.9 (ml/100 g/min, mean ± SD) in mice and rats respectively. These values are in good agreement with reported values measured by 15 O PET, 17 O NMR, and BOLD fMRI. In hypothermia, we detected a significant decrease of 37% and 32% in CMRO 2 in the cortex of mice and rats, respectively. Q10 was calculated to be 3.2 in mice and 2.7 in rats. In this study we showed that it is possible to assess absolute values of metabolic correlates such as CMRO 2 , CBF and oxygen extraction fraction (OEF) noninvasively in living brain of mice and rats by combining NIRS with MRI. This will open new possibilities for studying brain metabolism in patients as well as the many mouse/rat models of brain disorders., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: To investigate right and left cerebral tissue (ctSO 2 ) and renal tissue oxygenations (rtSO 2 ) in otherwise healthy children., Methods: In this observational cross-sectional study, one hundred children seen as outpatients for well child care or common non-critical complaints, were included. Bilateral ctSO 2 and rtSO 2 were recorded simultaneously with INVOS™ 5100 device., Results: The median age was 6.7 y (IQR 3-10.4) and median weight was 21 kg (IQR 13-33). Right and left sided ctSO 2 and rtSO 2 values were 78.7% ± 6.0% and 79.1% ± 5.7%; 81.5% ± 9.4% and 81.4% ± 9.5% respectively. There were no differences in right and left cerebral and renal near infrared spectroscopy (NIRS) values, and no age centered lateralization effect. Renal measurements were higher than cerebral counterparts in 63% of the children. Interaction between age and regional oxygenation was significant. For both sides, renal oxygenation was higher than that of cerebrum in older children, whereas the opposite held true with younger age., Conclusions: There are no right and left side differences in ctSO 2 and rtSO 2 values in otherwise healthy children. On the other hand, there seem to be differences between cerebral and renal regions with a significant age effect. Acknowledging its limitations, this study sheds light on laterality and cranial and renal NIRS measurements in otherwise healthy children, and may contribute to the interpretation of NIRS data in critically ill patients.

Background: The arterial oxygen saturation of infants requiring resuscitation can be monitored using a pulse oximeter. However, the device cannot provide information about cerebral oxygenation. Thus, we used a new portable near-infrared spectroscopy (NIRS) device that can monitor regional cerebral tissue oxygen saturation (crSO 2 ) with a probe attached to the examiner's finger., Aim: To identify the reference ranges for crSO 2 within the first 10 min after birth in term infants who did not receive any medical intervention in the delivery room., Results: crSO 2 in the left frontoparietal area of the forebrain was measured within the first 10 min of life in 127 healthy term infants. The median gestational age and birth weight were 37.6 weeks and 2742 g, respectively, and 85% of the infants were delivered via a scheduled cesarean section. The 3rd-97th percentile values for crSO 2 ranged from 33.1% to 56.7% at 1 min, from 33.2% to 59.5% at 2 min, and from 38.7% to 66.6% at 5 min after birth. A median of 3.5 min was required to achieve a crSO 2  > 50%., Conclusions: This study showed the reference ranges for crSO 2 measured with the new portable NIRS device within the first 10 min after birth in term infants., Competing Interests: Declaration of competing interest A KN-15 NIRS device was leased from ASTEM Co., Ltd. (Kawasaki, Japan)., (Copyright © 2019 Elsevier B.V. All rights reserved.)