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Significance: The multispectral imaging-based tissue oxygen saturation detecting (TOSD) system offers deeper penetration ( ∼ 2 to 3 mm) and comprehensive tissue oxygen saturation ( StO 2 ) assessment and recognizes the wound healing phase at a low cost and computational requirement. The potential for miniaturization and integration of TOSD into telemedicine platforms could revolutionize wound care in the challenging pandemic era., Aim: We aim to validate TOSD's application in detecting StO 2 by comparing it with wound closure rates and laser speckle contrast imaging (LSCI), demonstrating TOSD's ability to recognize the wound healing process., Approach: Utilizing a murine model, we compared TOSD with digital photography and LSCI for comprehensive wound observation in five mice with 6-mm back wounds. Sequential biochemical analysis of wound discharge was investigated for the translational relevance of TOSD., Results: TOSD demonstrated constant signals on unwounded skin with differential changes on open wounds. Compared with LSCI, TOSD provides indicative recognition of the proliferative phase during wound healing, with a higher correlation coefficient to wound closure rate (TOSD: 0.58; LSCI: 0.44). StO 2 detected by TOSD was further correlated with proliferative phase angiogenesis markers., Conclusions: Our findings suggest TOSD's enhanced utility in wound management protocols, evaluating clinical staging and therapeutic outcomes. By offering a noncontact, convenient monitoring tool, TOSD can be applied to telemedicine, aiming to advance wound care and regeneration, potentially improving patient outcomes and reducing healthcare costs associated with chronic wounds., (© 2024 The Authors.)

Objective: Blood circulation is an important indicator of wound healing. In this study, a tissue oxygen saturation detecting (TOSD) system that is based on multispectral imaging (MSI) is proposed to quantify the degree of tissue oxygen saturation (StO2) in cutaneous tissues., Methods: A wound segmentation algorithm is used to segment automatically wound and skin areas, eliminating the need for manual labeling and applying adaptive tissue optics. Animal experiments were conducted on six mice in which they were observed seven times, once every two days. The TOSD system illuminated cutaneous tissues with two wavelengths of light - red ([Formula: see text] nm) and near-infrared ([Formula: see text] nm), and StO2 levels were calculated using images that were captured using a monochrome camera. The wound segmentation algorithm using ResNet34-based U-Net was integrated with computer vision techniques to improve its performance., Results: Animal experiments revealed that the wound segmentation algorithm achieved a Dice score of 93.49%. The StO2 levels that were determined using the TOSD system varied significantly among the phases of wound healing. Changes in StO2 levels were detected before laser speckle contrast imaging (LSCI) detected changes in blood flux. Moreover, statistical features that were extracted from the TOSD system and LSCI were utilized in principal component analysis (PCA) to visualize different wound healing phases. The average silhouette coefficients of the TOSD system with segmentation (ResNet34-based U-Net) and LSCI were 0.2890 and 0.0194, respectively., Conclusion: By detecting the StO2 levels of cutaneous tissues using the TOSD system with segmentation, the phases of wound healing were accurately distinguished. This method can support medical personnel in conducting precise wound assessments. Clinical and Translational Impact Statement-This study supports efforts in monitoring StO2 levels, wound segmentation, and wound healing phase classification to improve the efficiency and accuracy of preclinical research in the field., (© 2024 The Authors.)

This study aimed to investigate the association between the level of tissue oxygen saturation (StO 2 ) and quadriceps/skeletal muscle dysfunction, measured using the Medical Research Council (MRC) scale and ultrasonography, in critically ill patients. Thirty-four patients hospitalized at the Critical Care Medicine Center of Kindai University Hospital, between January 2022 and March 2023, were enrolled in this study. The StO 2 of the quadriceps muscle was measured via near-infrared spectroscopy. Muscle atrophy was measured by the thickness, cross-sectional area (CSA), and echo intensity of the rectus femoris (RF). These values were evaluated every alternate day until 13 days after admission or until discharge, whichever occurred first. Muscle weakness was assessed using the sum score of the MRC scale (MRC-SS), with the patient sitting at bedside. The mean age of the patients was 67.3 ± 15.3 years, and 20 (59%) were men. Seven patients (21%) were admitted for trauma, and 27 (79%) were admitted for medical emergencies or others. The mean score for the MRC-SS was 51.0 ± 7.9 points. RF thickness and CSA significantly decreased after day 7 (p < 0.05). There were no significant changes in StO 2 levels during hospitalization. However, there were positive correlations between the nadir StO 2 during hospitalization and MRC-SS, and changes in RF thickness and CSA at discharge (r = 0.41, p = 0.03; r = 0.37, p = 0.03; and r = 0.35, p = 0.05, respectively). StO 2 in the quadriceps muscle may be useful for predicting muscle atrophy and dysfunction in patients with critical illnesses., (© 2024. The Author(s).)

Background: The association between tissue oxygenation with postoperative acute kidney injury (AKI) in adult patients undergoing multiple valve surgery has not been specifically studied., Methods: In this prospective exploratory cohort study, 99 patients were enrolled. The left forehead, the left forearm, the left upper thigh, and the left renal region tissue oxygen saturation using near-infrared spectroscopy were monitored. The association between each threshold and AKI was assessed. The relative and absolute thresholds were < 70%, < 75%, < 80%, < 85%, < 90%, < 95%, and < 100% baseline, and baseline-standard deviation (SD), -1.5 SD, -2 SD, -2.5 SD, and -3 SD. Multivariate logistic regression analysis was adopted to explore the association., Results: AKI occurred in 53 (54%) patients. The absolute value-based SrrO2 thresholds associated with AKI were baseline-3 SD (odds ratio [OR], 4.629; 95% confidence interval [CI], 1.238-17.314; P = 0.023) and baseline-2.5 SD (OR, 2.842; 95% CI, 1.025-7.881; P = 0.045) after adjusting for the potential confounders, those are renal region tissue oxygen saturation of 55% and 60%, but not statistically significant after correcting for multiple testing (corrected P = 0.114 and 0.179, respectively)., Conclusion: The SrrO2 desaturation, defined as < baseline - 2.5 SD or < baseline - 3 SD, may be associated with AKI. The thresholds need to be verified in future large-scale studies., Trial Registrations: The study was registered at ClinicalTrials.gov, first trial registration: 26/10/2017, identifier: NCT03323203., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Background: Tourniquets provide better tissue visibility during arthroscopic surgery. However, multiple postoperative adverse events associated with ischemia may be caused by excessive inflation pressure and duration. We aimed to evaluate the degree of tourniquet-induced ischemia using a noninvasive continuous real-time monitoring method and the relationship between changes in tissue oxygen saturation (StO2) and blood biochemical markers of ischemic injuries in patients undergoing arthroscopic knee surgery., Methods: This was a prospective observational study using near-infrared spectroscopy (NIRS). Data were collected from 29 consecutive patients who underwent arthroscopic procedures. Twenty-five patients underwent anterior cruciate ligament reconstruction, and four underwent meniscal repair. We investigated tourniquet-induced changes in StO2, monitored using NIRS, and blood biochemical markers of ischemic injuries., Results: A significant decrease in the mean StO2 from the baseline was observed during tourniquet inflation in the operative legs. The average decrease in the mean StO2 was 58%. A comparison of mean StO2 between the nonoperative and operative legs before tourniquet deflation showed that mean values of StO2 in the operative legs were significantly lower than those in the nonoperative legs. No significant clinical relationships were observed between changes in StO2 and blood biochemical markers of ischemic injuries (creatine kinase) (p = 0.04, r = 0.38) or tourniquet duration (p = 0.05, r = 0.366)., Conclusions: Our results demonstrated that StO2 could be used to evaluate tissue perfusion in real time but did not support the hypothesis that StO2 is a useful method for predicting the degree of tourniquet-induced injury during arthroscopic knee surgery., (© 2022. The Author(s).)

Background: Venous oxygen saturation reflects venous oxygenation status and can be used to assess treatment and prognosis in critically ill patients. A novel method that can measure central venous oxygen saturation (ScvO2) non-invasively may be beneficial and has the potential to change the management routine of critically ill patients., Objective: The study aims to evaluate the potential of sublingual venous oxygen saturation (SsvO2) to be used in the estimation of ScvO2., Methods: We have developed two different approaches to calculate SsvO2. In the first one, near-infrared spectroscopy (NIRS) measurements were performed directly on the sublingual veins. In the second approach, NIRS spectra were acquired from the sublingual tissue apart from the sublingual veins, and arterial oxygen saturation was measured using a pulse oximeter on the fingertip., Results: Twenty-six healthy subjects were included in the study. In the first and second approaches, average SsvO2 values were 75.0% ± 1.8 and 75.8% ± 2.1, respectively. The results of the two different approaches were close to each other and similar to ScvO2 of healthy persons (> 70%)., Conclusion: Oxygen saturation of sublingual veins has the potential to be used in intensive care units, non-invasively and in real-time, to estimate ScvO2.

Managing chronic limb-threatening ischemia (CLTI) is challenging due to difficulties in assessing tissue oxygen saturation in ulcers. Near-infrared spectroscopy (NIRS) is a non-invasive method for measuring tissue oxygen saturation (StO2). This study evaluated the effects of endovascular treatment (EVT) on StO2 and wound healing in CLTI patients, comparing NIRS to standard ankle–brachial index (ABI) measurements. Using the Duesseldorf PTA Registry, 43 CLTI patients were analyzed: 27 underwent EVT, and 16 received conservative treatment. ABI assessed macrocirculation, while NIRS measured wound, wound area, and mean foot StO2 at baseline, post-EVT, and four-month follow-up. Wound severity was classified by wound area and wound, ischemia, and foot infection (WIfI) score. Wound StO2 increased significantly (median (interquartile range (IQR)), 38 (49.3) to 60 (34.5)%, p = 0.004), as did wound area StO2 (median (IQR), 70.9 (21.6) to 72.8 (18.3)%, p < 0.001), with no significant changes in the control group by four-month follow-up. Wound area decreased significantly after EVT (mean ± SD, 343.1 ± 267.8 to 178.1 ± 268.5 mm2, p = 0.01) but not in the control group. Changes in wound StO2, wound area StO2, and WIfI score correlated with wound area reduction, unlike ABI. This small exploratory study shows that NIRS-measured StO2 improvements after EVT correlate with reduced wound area and WIfI scores, highlighting NIRS as a potential enhancement for CLTI wound management in addition to ABI. [ABSTRACT FROM AUTHOR]

Significance: Burn injuries represent a global public health problem that kills an estimated 180,000 people annually. Non-fatal burns result in prolonged hospitalization, disfigurement, and disability. The most common, convenient, and widely used method for assessing burn depth is physical or visual examination, but the accuracy of this method is reportedly poor (60% to 75%). Rapid, correct assessment of burn depth is very important for the optimal management and treatment of burn patients. New methods of burn depth assessment that are inexpensive, simple, rapid, non-contact, and non-invasive are therefore needed. Aim: The aim of this study was to propose an approach to visualize the spatial distribution of burn depth using hemoglobin parameters estimated from spectral diffuse reflectance imaging and to demonstrate the feasibility of the proposed approach for differentiating burn depth in a rat model of scald burn injury. Approach: The new approach to creating a spatial map of burn depth was based on canonical discriminant analysis (CDA) of total hemoglobin concentration, tissue oxygen saturation, and methemoglobin saturation as estimated from spectral diffuse reflectance images. Burns of three different degrees of severity were created in rat dorsal skin by 10-s exposure to water maintained at 70℃, 78℃, and 98℃, respectively. Spectral images for dorsal regions were acquired under anesthesia immediately after burn injury and at 24 h, 48 h, and 72 h after injury. Results: Most areas of images in the group with skin exposed to 70℃ water and 98° C water were classified as 70℃ burn and 98℃ burn, respectively. In contrast, no significant difference between areas classified as 78℃ burn and 98℃ burn from 24 h to 72 h was evident in the group with skin exposed to 78℃ water, suggesting that burn depth was heterogeneous. Conclusions: The proposed approach combining diffuse reflectance spectral imaging and CDA appears promising for differentiating 70℃ burns from 78℃ burns and 98℃ burns, and 98℃ burns from 70℃ burns and 78℃ burns at 24 to 72 h after burn injury in a rat model of scald burn injury. [ABSTRACT FROM AUTHOR]

Background: Tissue oxygen saturation (StO2) decrease could appear earlier than lactate alteration. However, the correlation between StO2 and lactate clearance was unknown. Methods: This was a prospective observational study. All consecutive patients with circulatory shock and lactate over 3 mmol/L were included. Based on the rule of nines, a BSA (body surface area) weighted StO2 was calculated from four sites of StO2 (masseter, deltoid, thenar and knee). The formulation was as follows: masseter StO2 × 9% + (deltoid StO2 + thenar StO2) × (18% + 27%)/ 2 + knee StO2 × 46%. Vital signs, blood lactate, arterial and central venous blood gas were measured simultaneously within 48 h of ICU admission. The predictive value of BSA-weighted StO2 on 6-hour lactate clearance > 10% since StO2 initially monitored was assessed. Results: A total of 34 patients were included, of whom 19 (55.9%) had a lactate clearance higher than 10%. The mean SOFA score was lower in cLac ≥ 10% group compared with cLac < 10% group (11 ± 3 vs. 15 ± 4, p = 0.007). Other baseline characteristics were comparable between groups. Compared to non-clearance group, StO2 in deltoid, thenar and knee were significantly higher in clearance group. The area under the receiver operating curves (AUROC) of BSA-weighted StO2 for prediction of lactate clearance (0.92, 95% CI [Confidence Interval] 0.82-1.00) was significantly higher than StO2 of masseter (0.65, 95% CI 0.45–0.84; p < 0.01), deltoid (0.77, 95% CI 0.60–0.94; p = 0.04), thenar (0.72, 95% CI 0.55–0.90; p = 0.01), and similar to knee (0.87, 0.73-1.00; p = 0.40), mean StO2 (0.85, 0.73–0.98; p = 0.09). Additionally, BSA-weighted StO2 model had continuous net reclassification improvement (NRI) over the knee StO2 and mean StO2 model (continuous NRI 48.1% and 90.2%, respectively). The AUROC of BSA-weighted StO2 was 0.91(95% CI 0.75-1.0) adjusted by mean arterial pressure and norepinephrine dose. Conclusions: Our results suggested that BSA-weighted StO2 was a strong predictor of 6-hour lactate clearance in patients with shock. [ABSTRACT FROM AUTHOR]

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Tourniquet use creates a reduced blood surgical field during total knee arthroplasty (TKA), however, prolonged ischemia may cause postoperative tourniquet complications. To understand the effects of tourniquet‐induced ischemia, we performed a prospective observational study using quantitative broadband diffuse optical spectroscopy (DOS) to measure tissue hemodynamics and water and lipid concentrations before, during, and after tourniquet placement in subjects undergoing TKA. Data was collected for 6 months and, of the total subjects analyzed (n = 24), 22 were primary TKAs and 2 were revision TKA cases. We specifically investigated tourniquet‐induced hemodynamics based upon subject‐specific tissue composition and observed a significant relationship between the linear rate of deoxygenation after tourniquet inflation and water/lipid ratio (W/L, p < 0.0001) and baseline somatic tissue oxygen saturation, StO2 (p = 0.05). Subjects with a low W/L ratio exhibited a lower tissue metabolic rate of oxygen consumption, (tMRO2) (p = 0.008). Changes in deoxyhemoglobin [HbR] (p = 0.009) and lipid fraction (p = 0.001) were significantly different between high and low W/L subject groups during deoxygenation. No significant differences were observed for hemodynamics during reperfusion and total tourniquet time was neither significantly related to the hemodynamic hyperemic response (p = 0.73) nor the time to max StO2 after tourniquet release (p = 0.57). In conclusion, we demonstrate that DOS is capable of real‐time monitoring of tissue hemodynamics distal to the tourniquet during TKA, and that tissue composition should be considered. DOS may help surgeons stratify hemodynamics based upon tissue composition and eventually aid the preoperative risk assessment of vascular occlusions from tourniquet use during TKA. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the acute physiological responses during cycling at various intensities with blood flow restriction (BFR). Subjects (N = 9; ...O2peak = 36.09 ± 5.80 ml⋅kg-1⋅min-1) performed 5 protocols: high-intensity (HIGH), control (CON-90), 90% of ventilatory threshold (VT) work rate with BFR (90-BFR), 70% of VT with BFR (70-BFR), and 30% ...O2peak with BFR (30-BFR). Protocols consisted of five 2-minute work intervals interspersed with 1-minute recovery intervals. Blood flow restriction pressure was 80% of limb occlusion pressure. ...O2, muscle excitation, tissue oxygen saturation (StO2), discomfort, and level of perceived exertion (RPE) were assessed. Muscle excitation was higher during HIGH (302.9 ± 159.9 %BSL [baseline]) compared with 70-BFR (99.7 ± 76.4 %BSL) and 30-BFR (98.2 ± 70.5 %BSL). StO2 was greater during 90-BFR (40.7 ± 12.5 ΔBSL), 70-BFR (34.4 ± 15.2 ΔBSL), and 30-BFR (31.9 ± 18.7 ΔBSL) compared with CON-90 (4.4 ± 11.5 ΔBSL). 90-BFR (39.6 ± 12.0 ΔBSL) resulted in a greater StO2-Avg compared with HIGH (20.5 ± 13.8 ΔBSL). Also, HIGH (23.68 ± 5.31 ml⋅kg-1⋅min-1) resulted in a greater ...O2 compared with 30-BFR (15.43 ± 3.19 ml⋅kg-1⋅min-1), 70-BFR (16.65 ± 3.26 ml⋅kg-1⋅min-1), and 90-BFR (18.28 ± 3.89 ml⋅kg-1⋅min-1); 90-BFR (intervals: 4 = 15.9 ± 2.3; intervals: 5 = 16.4 ± 2.5) resulted in a greater RPE compared with 30-BFR (intervals: 4 = 13.3 ± 1.4; intervals: 5 = 13.7 ± 1.7) during intervals 4 and 5. These results suggest that when adding BFR to various intensities of aerobic exercise, consideration should be given to peak work and VT to provide a balance between high local physiological stress and perceptual responses. [ABSTRACT FROM AUTHOR]

We propose a method to perform simultaneous measurements of percutaneous arterial oxygen saturation (SpO2), tissue oxygen saturation (StO2), pulse rate (PR), and respiratory rate (RR) in real-time, using a digital red–green–blue (RGB) camera. Concentrations of oxygenated hemoglobin (CHbO), deoxygenated hemoglobin (CHbR), total hemoglobin (CHbT), and StO2 were estimated from videos of the human face using a method based on a tissue-like light transport model of the skin. The photoplethysmogram (PPG) signals are extracted from the temporal fluctuations in CHbO, CHbR, and CHbT using a finite impulse response (FIR) filter (low and high cut-off frequencies of 0.7 and 3 Hz, respectively). The PR is calculated from the PPG signal for CHbT. The ratio of pulse wave amplitude for CHbO and that for CHbR are associated with the reference value of SpO2 measured by a commercially available pulse oximeter, which provides an empirical formula to estimate SpO2 from videos. The respiration-dependent oscillation in CHbT was extracted from another FIR filter (low and high cut-off frequencies of 0.05 and 0.5 Hz, respectively) and used to calculate the RR. In vivo experiments with human volunteers while varying the fraction of inspired oxygen were performed to evaluate the comparability of the proposed method with commercially available devices. The Bland–Altman analysis showed that the mean bias for PR, RR, SpO2, and StO2 were -1.4 (bpm), -1.2(rpm), 0.5 (%), and -3.0 (%), respectively. The precisions for PR, RR, Sp O 2, and StO2 were ±3.1 (bpm), ±3.5 (rpm), ±4.3 (%), and ±4.8 (%), respectively. The resulting precision and RMSE for StO2 were pretty close to the clinical accuracy requirement. The accuracy of the RR is considered a little less accurate than clinical requirements. This is the first demonstration of a low-cost RGB camera-based method for contactless simultaneous measurements of the heart rate, percutaneous arterial oxygen saturation, and tissue oxygen saturation in real-time. [ABSTRACT FROM AUTHOR]

Background: The exact influence of tourniquet ischemia on a treated extremity remains unclear. Methods: Twenty patients received an operation on one hand under tourniquet ischemia. Twenty healthy volunteers received 10 min of tourniquet ischemia on one of their arms. Measurements of tissue oxygen saturation using near-infrared reflectance-based imaging and skin temperature of the dorsum of the hand were performed at five different timepoints (t0 was performed just before the application of the tourniquet ischemia, t1 directly after the application of the tourniquet ischemia, t2 before the release of the ischemia, t3 directly after the release of the ischemia, and t4 on the following day). Results: In both groups, tissue oxygen saturation dropped after the application of the tourniquet ischemia compared to t0 and increased after the release of the tourniquet ischemia. In the patient group, tissue oxygen saturation at t4 was higher compared to t0; in contrast, the level of tissue oxygen saturation in the participant group dropped slightly at t4 compared to t0. The measured skin temperature in the patient group showed an increase during the observation period, while it continuously decreased in the group of healthy participants. Conclusions: Short-term ischemia did not appear to permanently restrict perfusion in this study design. The non-invasive imaging modalities used were easy to handle and allowed repetitive measurement. [ABSTRACT FROM AUTHOR]

Pulmonary gas exchange analysis was compared to changes in muscle oxygen saturation as measured by near-infrared spectroscopy. First, ventilatory thresholds determined by common gas exchange analysis and breakpoints in muscle oxygen saturation were assessed for agreement during exercise with increasing intensity. Secondly, the relationship between muscle oxygen saturation as a surrogate for local oxygen extraction and peak oxygen uptake was assessed. In order to lend robustness to future NIRS testing on a broader scale, considering its potential for simple and cost-effective application, the question of a running versus a cycling modality was integrated into the design. Ten participants, of whom five were recreationally trained cyclists and five recreationally trained runners, were tested; each during a cycling test and a running test with increasing intensity to voluntary exhaustion. Muscle oxygen saturation and pulmonary gas exchange measurements were conducted. Bland-Altman analysis showed a moderate degree of agreement between both muscle oxygen saturation breakpoint 1 and muscle oxygen saturation breakpoint 2 and corresponding ventilatory threshold 1 and ventilatory threshold 2, for both cycling and running disciplines; generally speaking, muscle oxygen saturation breakpoints underestimated ventilatory thresholds. Additionally, a strong relationship could be seen between peak oxygen uptake and the minimally attained muscle oxygen saturation during cycling exercise. Muscle oxygen saturation measured using NIRS was determined to be a suitable method to assess ventilatory thresholds by finding breakpoints in muscle oxygen saturation, and muscle oxygen saturation minimum was linked to peak oxygen uptake. [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopy (NIRS) measurements of tissue oxygen saturation (StO2) are frequently used during vascular and cardiac surgeries as a non-invasive means of assessing brain health; however, signal contamination from extracerebral tissues remains a concern. As an alternative, hyperspectral (hs)NIRS can be used to measure changes in the oxidation state of cytochrome c oxidase (ΔoxCCO), which provides greater sensitivity to the brain given its higher mitochondrial concentration versus the scalp. The purpose of this study was to evaluate the depth sensitivity of the oxCCO signal to changes occurring in the brain and extracerebral tissue components. The oxCCO assessment was conducted using multi-distance hsNIRS (source-detector separations = 1 and 3 cm), and metabolic changes were compared to changes in StO2. Ten participants were monitored using an in-house system combining hsNIRS and diffuse correlation spectroscopy (DCS). Data were acquired during carotid compression (CC) to reduce blood flow and hypercapnia to increase flow. Reducing blood flow by CC resulted in a significant decrease in oxCCO measured at rSD = 3 cm but not at 1 cm. In contrast, significant changes in StO2 were found at both distances. Hypercapnia caused significant increases in StO2 and oxCCO at rSD = 3 cm, but not at 1 cm. Extracerebral contamination resulted in elevated StO2 but not oxCCO after hypercapnia, which was significantly reduced by applying regression analysis. This study demonstrated that oxCCO was less sensitive to extracerebral signals than StO2. [ABSTRACT FROM AUTHOR]

Purpose: Infraclavicular block (ICB) and interscalene block (ISB) accompanied by ultrasonography imaging (USI) are the most frequently used brachial plexus block techniques in upper extremity surgeries. It is already known that sympathetic blockage occurs after the application of these blocks, and blood flow increases with vasodilatation caused by the blockage. This study aimed to compare the effect of ICB and ISB, which are applied together with USI, on forearm tissue oxygenation. Materials and Methods: A hundred-four patients were included in this study belonging to ASA I-III risk groups, aged 18–65 years, who were scheduled for elective or emergency arm, elbow, or forearm surgery. The patients were divided into two groups: Group ICB and Group ISB. In addition to the baseline hemodynamic measurements, PI, time average velocity (TAV), brachial artery diameter (BAD), brachial arterial area (BAA), brachial artery beat flow (BF), and tissue oxygen saturation (rSO2) data were recorded before block and at the 10th, 20th, and 30th min after the block was completed. Results: The demographic data of the patients in the Group ICB and Group ISB were compared, no significant differences were detected between the groups. When the distribution of the percentage increase in PI and rSO2 values according to time was examined, significant differences were found between the groups. There were no significant differences in the percentage increases in BF, TAV, BAA, and BAD values between the 0th minute and at 10th, 20th, and 30th min (p>0.05). Horner syndrome was observed in 8 patients (15%) and sudden hoarseness was observed in 3 patients (5%) in Group ISB. No complications developed in the Group ICB. Conclusion: This study shows that the effects of ICB and ISB on forearm tissue oxygenation were compared and it was found that ICB increased rSO2 and PI values. [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopy (NIRS) is widely used to assess flap perfusions by measuring tissue oxygen saturation (StO2). However, the StO2 level for the onset of perfusion failure is still a controversial issue. This study proposes a new threshold of StO2 level for detecting the onset of perfusion failure as early as possible to increase flap salvage rates. Twenty patients undergoing flap surgery were included in this study – 13 flaps were implemented to cover defects that occurred due to trauma and 7 flaps to hide imperfections that occurred after cancer treatment. Thirteen flaps were in the lower extremity, six in the mandible, and one in the breast. NIRS was used to measure StO2 in 240 flap regions of the 20 patients to determine flap viability using descriptive statistics. The mean StO2 values from healthy flap and control regions were obtained as 81.6% ± 0.36 and 82% ± 0.18, respectively. The lowest StO2 value of 77.2% was defined as the onset of a vascular complication at a probability of 99.74% by subtracting three times the standard deviation from the mean StO2 of healthy flaps. Vascular complications were observed from 21 regions in the four flaps with StO2 values lower than 77.2%, but only one was lost. The threshold value for the onset of perfusion failure was a 5% decrease from the expected value, much lower than previously described thresholds that may facilitate the detection of perfusion failure in the early stage and increase salvage rates in flap revisions. [ABSTRACT FROM AUTHOR]

Background: Erector spinae plane block (ESPB) can provide effective analgesia in pediatric abdominal surgery. Additionally, when used as an analgesic method in abdominal surgery, ESPB may increase regional intra-abdominal tissue oxygen saturation (rSO2) throughout the operation. However, the number of related studies conducted on pediatric patients is insufficient. Results: Fifty-two patients undergoing lower abdominal surgery were allocated into two groups, the ESPB (E) and the control (C). Group E received general anesthesia plus unilateral ultrasound-guided ESPB, and group C received general anesthesia alone. Intraoperative fentanyl consumption, Face, Legs, Activity, Cry, Consolability (FLACC) score, time to first rescue analgesia and adverse events were recorded over the first 24 h postoperatively. The rSO2 level was evaluated in both groups throughout the operation. The FLACC score was significantly lower in group E than in group C (p<0.05). Four patients in group E required intraoperative fentanyl compared to 12 patients in group C (p<0.05). The first rescue analgesic administration time was significantly longer in group E than in group C (p<0.05). No significant difference in rSO2 values was detected between the groups (p>0.05). However, in group E, rSO2 values were significantly increased after the block compared to the postinduction values. Conclusions: ESPB provides effective perioperative analgesia in children undergoing low abdominal surgery. Although there was no significant difference in rSO2 values between the groups, ESPB administration consistently increases rSO2 over time. Trial registration: The trial was registered at ClinicalTrials.gov before patient enrolment (NCT03808129-13.12.2018). [ABSTRACT FROM AUTHOR]

One cause of anastomotic leakage after radical esophagectomy is blood flow insufficiency at the cervical anastomosis site.. Eighteen patients, who underwent radical esophagectomy with gastric tube reconstruction, were studied. The regional tissue oxygen saturation (rSO2) was measured at the tip (point pre 0) and 2, 4, and 6 cm on the distal side of the tip (point pre 1, pre 2, and pre 3, respectively) before the gastric tube was raised to the cervical site through the retrosternal route. After that, rSO2 was measured at the tip, 2 and 4 cm on the distal side of the tip (points post 0, post 1, and post 2), the actual anastomotic site (point AN), and the chest skin as an indicator of whole-body oxygenation. The relationship between rSO2 scores and the rate of anastomotic leakage was determined. The mean rSO2 at pre 0, pre 1, pre 2, and pre 3 were 48.9%, 52.3%, 54.8%, and 56.9%, respectively (p < 0.05). The mean rSO2 at post 0, post 1, and post 2 were 47.8%, 50.5%, and 52.3%, respectively, and the rSO2 at point AN was 52.1%. Anastomotic leakage was found in 6 patients. The rSO2 at points pre 0, pre 1, and pre 2, post 0 and point AN were significantly lower in patients with anastomosis leakage than those without (p < 0.05). Tissue oxygen saturation monitoring was a useful indicator of blood flow insufficiency in the gastric tube during radical esophagectomy. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of either normoxic or hypoxic recovery condition on post-exercise hemodynamics after sprint interval leg cycling exercise rather than hemodynamics during exercise. The participants performed five sets of leg cycling with a maximal effort (30 s exercise for each set) with a 4-min recovery of unloaded cycling between the sets in hypoxia [fraction of inspired oxygen (FiO2) = 0.145]. The load during pedaling corresponded to 7.5% of the individual's body weight at the first set, and it gradually reduced from 6.5 to 5.5%, 4.5, and 3.5% for the second to fifth sets. After exercise, the participants rested in a sitting position for 30 min under normoxia (room-air) or hypoxia. Mean arterial pressure decreased over time during recovery (p < 0.001) with no condition and interaction effects (p > 0.05). Compared to pre-exercise values, at 30 min after exercise, mean arterial pressure decreased by 5.6 ± 4.8 mmHg (mean ± standard deviation) during hypoxic recovery, and by 5.3 ± 4.6 mmHg during normoxic recovery. Peripheral arterial oxygen saturation (SpO2) at all time points (5, 10, 20, and 30 min) during hypoxic recovery was lower than during normoxic recovery (all p < 0.05). The area under the hyperemic curve of tissue oxygen saturation (StO2) at vastus lateralis defined as reperfusion curve above the baseline values during hypoxic recovery was lower than during normoxic recovery (p < 0.05). Collectively, post-exercise hypotension after sprint interval leg cycling exercise was not affected by either normoxic or hypoxic recovery despite marked differences in SpO2 and StO2 during recovery between the two conditions. [ABSTRACT FROM AUTHOR]

Background: Adequate tissue oxygenation and perfusion remain fundamental to safe bowel resection surgery. Near infrared (NIR) imaging using indocyanine green has proven itself superior to clinical evaluation alone in assessing bowel perfusion, but requires expensive equipment not readily available in many centers. Methods: We studied the IntraOx device (Vioptix Inc, Newark, CA USA), a handheld, tissue oxygen saturation assessment tool, to assess whether tissue bed oxygen saturation (StO2) is comparable to NIR assessment of bowel viability. Patients undergoing elective colon resection for benign and malignant disease were included. After choosing a clinical margin (CM) and dividing the mesentery, StO2 was measured at 5-cm intervals along the colon. A tissue oxygen saturation margin (TOM) was assigned where StO2 dropped off by at least 10 percentage points. NIR perfusion was then assessed to determine NIR margin (NIRM). Intraoperative and postoperative data were collected. Results: 32 consecutive patients undergoing colectomies were analyzed. IntraOx sensitivity was 90.6%, specificity was 94.3%. The mean StO2 difference across the NIRM was 23.1%. In all but one case, the TOM matched the NIRM. In 3 cases, the TOM and NIRM concurred, but were a mean of 3.3 cm proximal to the CM and altered the surgical plan. At 4-week follow-up, no significant complications were reported. Conclusions: The IntraOx device consistently identified a margin of significant saturation "drop-off" which correlated with the findings on NIR perfusion and clinical assessment. These early data indicate that StO2 measurement may be equivalent to NIR assessment of bowel perfusion. In addition, the IntraOx device may be a more cost-effective solution for surgeons looking for adjunctive evaluation of bowel viability. More study is warranted in a larger group of patients to confirm these preliminary findings and to judge the impact of StO2 assessment on reducing anastomotic leaks. [ABSTRACT FROM AUTHOR]

The influence of topical negative pressure application (TNPA) on tissue perfusion still remains controversial. TNPA was applied for 30 minutes on intact skin of 21 healthy participants. Measurements of tissue oxygen saturation and tissue temperature as signs of tissue perfusion were performed before application of the TNPA, directly after removal of the TNPA and 5, 10, 15, 20, and 30 minutes after removal of the dressing using the near infrared imaging (NIRI) and a thermal imaging camera. Tissue oxygen saturation showed an increase from 67.7% before applying the TNPA to 76.1% directly after removal of TNPA, followed by a decrease of oxygen saturation 30 minutes after removal of TNPA. The measured temperature of the treated skin area increased from 32.1°C to 36.1°C after removal of TNPA with a consecutive decrease of the temperature 30 minutes after removal. TNPA resulted in both a higher tissue oxygen saturation and a higher skin temperature after 30 minutes compared to the beginning. TNPA increases both tissue oxygen saturation and skin temperature as sign of an increase of tissue perfusion. NIRI and thermal imaging proved to be useful for measuring changes in tissue perfusion. [ABSTRACT FROM AUTHOR]

We have reported that pretreatment with the clinically approved superoxide dismutase mimetic, Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl), blunts the cardiorespiratory depressant responses elicited by a subsequent injection of fentanyl, in halothane-anesthetized rats. The objective of the present study was to determine whether Tempol is able to reverse the effects of morphine on arterial blood-gas (ABG) chemistry in freely-moving Sprague Dawley rats. The intravenous injection of morphine (10 mg/kg) elicited substantial decreases in pH, pO2 and sO2 that were accompanied by substantial increases in pCO2 and Alveolar-arterial gradient, which results in diminished gas-exchange within the lungs. Intravenous injection of a 60 mg/kg dose of Tempol 15 min after the injection of morphine caused minor improvements in pO2 and pCO2 but not in other ABG parameters. In contrast, the 100 mg/kg dose of Tempol caused an immediate and sustained reversal of the negative effects of morphine on arterial blood pH, pCO2, pO2, sO2 and Alveolar-arterial gradient. In other rats, we used pulse oximetry to determine that the 100 mg/kg dose of Tempol, but not the 60 mg/kg dose elicited a rapid and sustained reversal of the negative effects of morphine (10 mg/kg, IV) on tissue O2 saturation (SpO2). The injection of morphine caused a relatively minor fall in mean arterial blood pressure that was somewhat exacerbated by Tempol. These findings demonstrate that Tempol can reverse the negative effects of morphine on ABG chemistry in freely-moving rats paving the way of structure-activity and mechanisms of action studies with the host of Tempol analogues that are commercially available. [ABSTRACT FROM AUTHOR]

Cerebral tissue oximetry (CTO) based on near-infrared spectroscopy provides clinically relevant information on tissue perfusion and has been used specifically in infant monitoring and during cardiac surgeries. With different sensor designs in the selection and configuration of light sources and detectors and implemented analysis algorithms in tissue oxygen saturation (StO2) extraction, substantial differences were observed between different commercially available CTO device measurements. Tissue models (phantoms) mimicking a human head both optically and anatomically provide the controllable, safe, universally agreeable, and reproducible environment for the evaluation of CTO device performances. In this article, we implemented our realistic and dynamic multilayer mixed solid and liquid phantom design with controlled and repeatable test procedures in the evaluation of multiple commercially available CTO devices. Performances were evaluated for each CTO device within themselves, across each other and a reference device simultaneously under continuously changing oxygen saturation conditions. Results indicated the feasibility of our phantoms in CTO device performance testing and suggested that in general, CTO device measurements were very precise ($S_{\mathrm {res}} < 1.48$ %) and highly correlated ($R^{2} > 0.89$ and $p < 0.0001$) but had varying levels of accuracy, sensitivity, static, and proportional bias ($15.4{\%}< A_{\mathrm {rms}} < 21.1$ %, 0.31 < sensitivity (regression slope) <0.43, and 35.94< bias (regression intercept) <49.74). In addition, gauge repeatability and reproducibility (Gauge R&R) analysis provided that most of the CTO devices were within acceptable ranges with precision-to-tolerance (P/T) ratio <10%, a number of distinct categories (NDC) >5, and intraclass correlation coefficient (ICC) >80%. [ABSTRACT FROM AUTHOR]

Objective: Hypotension is common in cesarean section due to the sympathetic blockage induced by spinal anesthesia. We aimed to investigate the effect of vasoactive drugs and fluids, and uterotonic drugs on tissue oxygenation. Methodology: Patients scheduled for elective cesarean section were included in this study. Routine monitoring values, thenar oxygen saturation and hemoglobin (Hb) indices were recorded preoperatively at the operating table (T1), at 3rd minute after spinal block (T2) and after the administration of uterotonic drugs (T3). Results: Data of 61 patients were analyzed. In 24 cases (39%), Hb values were < 11 g/dl. The incidence of hypotension following spinal anesthesia was 34.4%. The mean amount of ephedrine administered before the baby removal was similar in all patients (214 mg). Baseline StO2 values of anemic patients were similar to that of non-anemic patients; tissue hemoglobin index values of the former were significantly lower (p = 0.017). T3 systolic arterial blood pressures of patients with intraoperative hypotension were significantly lower (p = 0.001); tissue oxygen saturation and Hb indices were similar (p = 0.301). Conclusion: Tissue oxygenation may be influenced by the presence of anemia, hypovolemia, and hypotension. Its measurement may be influenced by pregnancy-dependent factors like edema and adipose tissue thickness in the monitoring site. We found that maintaining systolic blood pressure above 100 mmHg in this patient cohort was sufficient to preserve tissue oxygenation despite presence of anemia; and tissue oxygen saturation and hemoglobin indices were reliable. [ABSTRACT FROM AUTHOR]

Background: Circulatory shock affects every third patient in intensive care units and is associated with high mortality. Nearinfrared spectroscopy (NIRS) could serve as a means for monitoring tissue perfusion in circulatory shock. Purpose: To assess the evidence of NIRS monitoring in circulatory shock, we conducted a systematic review of the literature. Methods: The study protocol was registered in International Prospective Register of Systematic Reviews (PROSPERO). We searched PubMed, Ovid MEDLINE, Scopus, and EBM Reviews databases. The reference lists of included articles, last volumes of key journals, and NIRS monitor manufacturers' webpages were searched manually. Two reviewers independently selected included studies. The quality of studies was assessed. The qualitative synthesis was guided by 3 questions: First, does NIRS monitoring improve patientcentered outcomes in adult circulatory shock patient? Second, do NIRS-derived parameters predict patient-centered outcomes, such as mortality and organ dysfunction, and third, does NIRS monitoring give additional information to guide treatment decisions? Main Results: Eighteen observational studies with 927 patients were included. Because of considerable clinical heterogeneity of the data, we were not able to perform a meta-analysis. Also, due to lack of randomized controlled trials, the first review question could not be answered. Based on the current review, baseline tissue oxygen saturation (StO2) however seems to predict mortality and identify patients with most severe forms of circulatory shock. Conclusions: Near-infrared spectroscopyderived StO2 can predict mortality in circulatory shock, but high-quality data on the impact of NIRS monitoring are lacking. Furthermore, the marked heterogeneity of the studies makes combining the results of individual studies difficult. Standardization of methodology and clinical randomized trials are needed before wider clinical use. [ABSTRACT FROM AUTHOR]

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 [ μs′(λ) ] and the modeling of tissue as homogeneous. We studied the accuracy and robustness of SRS NIRS. We investigated the errors in retrieving hemodynamic parameters, in particular tissue oxygen saturation (StO2), when μs′(λ) was varied from expected values, and when layered tissue was considered. 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 μs′(λ) ; (2) semi-infinite homogeneous medium and linear changes in μs′(λ) ; (3) two-layered media with a superficial thickness s1 = 5, 7.5, 10 mm and constant μs′(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, StO2) and their relative error. Variations in μs′(λ) affect the estimated StO2 (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 StO2 when the superficial thickness exceeds 5 mm. 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. [ABSTRACT FROM AUTHOR]

• The variations of StO 2 are not necessarily consistent even in some symmetric facial regions when subject's emotion changes. • The signature intensities in anger are usually higher than in happiness in most ROIs with some significant differences. • Substantial experimental results demonstrate that using StO 2 extracted from partial facial ROIs to detect human emotion is technically feasible. • Different ROIs manifest different contributive discrimination performance on emotion recognition. Hyperspectral imaging technology (HSI) can be used to remotely detect emotion levels in humans based on the tissue oxygen saturation (StO 2) from their faces. Our prior research demonstrated some significant differences among the variations of StO 2 in different facial regions of interest (ROIs) when the subjects are truly happy. Experiment is conducted for data collection with HSI where the subjects (a total of fifty participants, who rigidly conform to the research protocol) are required to show spontaneous emotions (calm, happy, and unhappy: angry). Based on the comprehensive analysis of musculoskeletal anatomy and facial action coding system (FACS), 19 ROIs have been determined. Consequently, a 19 dimensional StO 2 vector is constructed as a feature input instead of employing the entire facial region. Lastly, experimental results through basic K -Nearest Neighbor (KNN) report an average accuracy rate of 83.32% when only considering fewer StO 2 features. In addition, some experiments using other advanced machine learning methods also validate its effective recognition performance with facial StO 2 as an affective indicator. Our findings demonstrate the possible practical feasibility of StO 2 in happiness detection. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Acute kidney injury (AKI) is associated with an increased mortality in critically ill patients, especially in patients with multiorgan dysfunction syndrome (MODS). In daily clinical practice, the grading of AKI follows the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. In most cases, a relevant delay occurs frequently between the onset of AKI and detectable changes in creatinine levels as well as clinical symptoms. The aim of the present study was to examine whether a near infrared spectroscopy (NIRS)-based, non-invasive ischemia–reperfusion test (vascular occlusion test (VOT)) together with unprovoked (under resting conditions) tissue oxygen saturation (StO2) measurements, contain prognostic information in the early stage of MODS regarding the developing need for renal replacement therapy (RRT). Methods: Within a period of 18 months, patients at the medical intensive care unit of a tertiary university hospital with newly developed MODS (≤24 h after diagnosis, APACHE II score ≥20) were included in our study. The VOT occlusion slope (OS) and recovery slope (RS) were recorded in addition to unprovoked StO2. StO2 was determined non-invasively in the area of the thenar muscles using a bedside NIRS device. The VOT was carried out by inflating a blood pressure cuff on the upper arm. AKI stages were determined by the changes in creatinine levels, urinary output, and/or the need for RRT according to KDIGO. Results: 56 patients with MODS were included in the study (aged 62.5 ± 14.4 years, 40 men and 16 women, APACHE II score 34.5 ± 6.4). Incidences of the different AKI stages were: no AKI, 16.1% (n = 9); AKI stage I, 19.6% (n = 11); AKI stage II, 25% (n = 14); AKI stage III, 39.3% (n = 22). Thus, 39.3% of the patients (n = 22) developed the need for renal replacement therapy (AKI stage III). These patients had a significantly higher mortality over 28 days (RRT, 72% (n = 16/22) vs. no RRT, 44% (n = 15/34); p = 0.03). The mean unprovoked StO2 of all patients at baseline was 81.7 ± 11.1%, and did not differ between patients with or without the need for RRT. Patients with RRT showed significantly weaker negative values of the OS (−9.1 ± 3.7 vs. −11.7 ± 4.1%/min, p = 0.01) and lower values for the RS (1.7 ± 0.9 vs. 2.3 ± 1.6%/s, p = 0.02) compared to non-dialysis patients. Consistent with these results, weaker negative values of the OS were found in higher AKI stages (no AKI, −12.7 ± 4.1%/min; AKI stage I, −11.5 ± 3.0%/min; AKI stage II, −11.1 ± 3.3%/min; AKI stage III, −9.1 ± 3.7%/min; p = 0.021). Unprovoked StO2 did not contain prognostic information regarding the AKI stages. Conclusions: The weaker negative values of the VOT parameter OS are associated with an increased risk of developing AKI and RRT, and increased mortality in the early phase of MODS, while unprovoked StO2 does not contain prognostic information in that regard. [ABSTRACT FROM AUTHOR]

Conventional renal function markers are unable to measure renal allograft perfusion intraoperatively, leading to delayed recognition of initial allograft function. A handheld near-infrared spectroscopy (NIRS) device that can provide real-time assessment of renal allograft perfusion by quantifying regional tissue oxygen saturation levels (rSO2) was approved by the FDA. This pilot study evaluated the feasibility of intraoperative NIRS monitoring of allograft reperfusion in renal transplant recipients (RTR). Intraoperative renal allograft rSO2 and perfusion rates were measured in living (LDRT, n = 3) and deceased donor RTR (DDRT, n = 4) during the first 50 min post-reperfusion and correlated with renal function markers 30 days post-transplantation. Intraoperative renal allograft rSO2 for the DDRT group remained significantly lower than the LDRT group throughout the 50 min. Reperfusion rates were significantly faster in the LDRT group during the first 5 min post-reperfusion but remained stable thereafter in both groups. Intraoperative rSO2 were similar among the upper pole, renal hilum, and lower pole, and strongly correlated with allograft function and hemodynamic parameters up to 14 days post-transplantation. NIRS successfully detected differences in intraoperative renal allograft rSO2, warranting future studies to evaluate it as an objective method to measure ischemic injury and perfusion for the optimization of preservation/reperfusion protocols and early prediction of allograft function. [ABSTRACT FROM AUTHOR]