Assessment of Anastomotic Viability With Spectroscopic Real-time Oxygen Saturation Measurement in a Porcine Study.

OBJECTIVE: Anastomotic leakage (AL) is a severe complication following intestinal procedures. Intra.Ox™ by ViOptix Inc (Newark, CA, USA) is a novel, FDA-approved spectroscopic device which enables real-time measurement of mixed tissue oxygen saturation (StO2). Using a porcine model, this study explores the correlation between StO2 measurements and AL formation as well as investigates the applicability of Intra.Ox™ in the clinical setting. METHODS: Eleven female swine were divided into 3 groups to explore AL formation in different ischemic conditions. Group 1: 100% mesenteric-vascular ligation, n = 3; Group 2: 50% ligation, n = 5; Group 3: No mesenteric ligation, n = 3. StO2 at the anastomotic line was measured before and after vessel ligation and anastomosis. Measurements were taken at 6 distinct locations along afferent and efferent loops. AL was evaluated on postoperative day 5 by re-laparotomy. RESULTS: AL rate was 100%, 60% and 0% in groups 1, 2 and 3, respectively. Post-anastomotic StO2 in group 1 (22.9 ± 18.5%) and 2 (39.2 ± 20.1%) were significantly lower than in group 3 (53.1 ± 8.3%, p<.0001). Post-anastomotic StO2 readings ≤40% indicated AL potential with 100% sensitivity,+ 80% specificity, positive predictive value of 85.7% and negative predictive value of 100%. CONCLUSION: This study demonstrates the value of Intra.Ox™ in assessing local perfusion and indicate the association between low StO2 and AL by providing accurate, real-time, noninvasive tissue oxygenation measurements at anastomotic sites. Further studies are required to investigate the clinical application of this novel device in intestinal surgery.

Near-Infrared Spectroscopy (NIRS) for Cerebral and Tissue Oximetry: Analysis of Evolving Applications.

THE USE OF NEAR-INFRARED SPECTROSCOPY (NIRS) has increased significantly worldwide in the past decade. This technology, first described more than 40 years ago, is based on the fact that near-infrared light is able to penetrate biologic tissue and can obtain real-time, noninvasive information on tissue oxygenation and metabolism. In the clinical setting, NIRS has been able to provide clinicians potentially valuable information in patients with impaired microcirculations (systemic and cerebral). Near-infrared spectroscopy has progressed beyond assessment of brain oxygenation to monitor local tissue and muscle oxygenation and perfusion. This review analyzes the published data and provides the clinician a comprehensive account of the perioperative utility of NIRS in cardiac, vascular and thoracic surgery, as well as its increasing role in tissue/muscle oxygenation monitoring.

Term Newborns with relatively low Tissue Oxygen Saturation Levels soon after Birth are predisposed to Neonatal Respiratory Disorders in Low-risk, Elective Cesarean Sections.

Background: Neonatal respiratory disorders, such as transient tachypnea of the newborn and respiratory distress syndrome, occur frequently after an elective cesarean delivery. Although conventional pulse oximetry is recommended for neonatal resuscitation, it often requires several minutes after birth to obtain a reliable signal. In a previous study, we used novel tissue oximetry equipment to detect fetal and neonatal early tissue oxygen saturation (StO2) before and immediately after vaginal delivery. Therefore, we hypothesized that low neonatal StO2 levels measured by tissue oximetry may lead to neonatal respiratory disorder after a scheduled cesarean delivery. Hence, this study aimed to evaluate the StO2 levels measured by tissue oximetry in neonates with or without a respiratory disorder subsequently diagnosed after an elective cesarean delivery. Materials and methods: We enrolled 78 pregnant Japanese women who underwent an elective cesarean section at ≥36 weeks' gestation. After combined spinal and epidural anesthesia were administered to the mother, fetal StO2 levels were measured by tissue oximetry using an examiner's finger-mounted sensor during a pelvic examination immediately before the cesarean section. We measured the neonatal StO2 levels at 1, 3, and 5 minutes after birth and retrospectively compared the fetal and neonatal StO2 levels with the incidence of subsequent diagnoses of neonatal respiratory disorders. Results: The data of StO2 levels in 35 neonates were collected. Seven neonates (respiratory disorder (RD) group) were subsequently diagnosed with respiratory disorders by neonatal medicine specialists, whereas the 28 remaining neonates (NR group) were not. The median fetal StO2 (interquartile range) of the RD and NR groups was 52.0% (41.8%-60.8%) and 42.5% (39.0%-52.5%), respectively (P = 0.12). The median neonatal StO2 (interquartile range) of the RD and NR groups at 1 minute after birth was 42.0% (39.0%-44.0%) and 46.0% (42.0%-49.0%), respectively (P = 0.091). At 3 minutes after birth, the median neonatal StO2 (interquartile range) of the RD and NR groups was 41.0% (39.0%-46.0%) and 47.0% (44.3%-53.5%), respectively (P = 0.004). Finally, at 5 minutes after birth, the median neonatal StO2 (interquartile range) of the RD and NR groups was 45.0% (44.0%-52.0%) and 54.0% (49.3%-57.0%), respectively (P = 0.007). Conclusions: The StO2 values in the RD group were lower than those in the NR group at 3 and 5 minutes after birth, suggesting that neonates with low StO2 levels soon after birth may be predisposed to clinically diagnosed neonatal respiratory disorders.

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support.

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO2) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO2. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO2 from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO2 from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO2 increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO2 from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

Near-Infrared Spectroscopy in Pediatric Congenital Heart Disease.

Near-infrared spectroscopy (NIRS) is widely used to monitor tissue oxygenation in the pediatric cardiac surgical population. Clinicians who use NIRS must understand the underlying measurement principles in order to interpret and use this monitoring modality appropriately. The aims of this narrative review are to provide a brief overview of NIRS technology, discuss the normative and critical values of cerebral and somatic tissue oxygen saturation and the interpretation of these values, present the clinical studies (and their limitations) of NIRS as a perioperative monitoring modality in the pediatric congenital heart disease population, and introduce the emerging and future applications of NIRS.

Fabrication and Optical Characterization of Gelatin-Based Phantoms for Tissue Oximetry.

Multispectral/hyperspectral imaging is one of the imaging modalities to visualize and quantify blood supply in surface tissues such as skin or mucosa. The results of visualization can be potentially affected by various factors, for instance by elevated methemoglobin (MetHb) content (e.g., methemoglobinemia). The scope of the current study is to develop a robust approach for fabrication and validation of tissue-mimicking phantoms, which can be used to assess and improve tissue oximetry. METHODS: The realistic tissue mimicking gelatin-based phantoms with intralipid (4% v/v) and/or hemoglobins (oxy-, deoxyhemoglobins, and MetHb) were molded between two coverslips separated by 2-mm wires. The hemoglobin solutions were prepared by dissolving the lyophilized human hemoglobin powder (H7379, Sigma-Aldrich) in the deionized water. Sodium dithionite (85% purity, 157,953, Sigma-Aldrich) was used to reduce MetHb solution. The phantoms were imaged using a multispectral imaging device (Oxilight, Canada).To demonstrate the utility, the developed approach is applied to emulate elevated systemic MetHb content. RESULTS: Initial results show that elevated systemic MetHb (2.0-6.7% of total blood) does not impact the accuracy of tissue oximetry imaging. DISCUSSION: A robust method for fabrication and optical validation of biocompatible tissue-mimicking phantoms has been developed.The proposed phantom design allows combining different phantoms into multilayer (sandwich) structures, which can be used to emulate a wide range of topical and systemic conditions.

Changes in cerebral and renal oxygenation during laparoscopic pyloromyotomy.

Although a laparoscopic approach may be preferred over open procedures for abdominal surgery, there are limited data on the effect of laparoscopic procedures on cerebral and renal oxygenation in neonates and young infants. Here, we evaluated the effect in neonates and infants. In this two-center prospective observational study, we evaluated changes in cerebral and renal regional oxygen saturation (rSO2) in infants during laparoscopic pyloromyotomy. Intraoperative hemodynamic and respiratory parameters and rSO2 were recorded. For the primary outcome, these parameters were compared at incision and at the end of pneumoperitoneum. The study cohort included 25 infants with a mean age of 40 ± 10 days and weight of 4.0 ± 0.6 kg. IAP at the beginning of laparoscopy was 10 ± 2 mmHg (range 7-15 mmHg). Although both cerebral and renal rSO2 decreased from incision compared to the end of laparoscopy, the decrease reached statistical significance only for cerebral rSO2 (81 ± 12 to 76 ± 16, p = 0.033). Similarly, the increase in fractional tissue oxygen extraction (FTOE) was only statistically significant for cerebral FTOE (0.18 ± 0.12 to 0.23 ± 0.16, p = 0.037). No change in hemodynamic or respiratory parameters was found. Although there was a decrease in cerebral rSO2 and increase in cerebral FTOE during pneumoperitoneum, the values did not decrease below those noted before anesthetic induction.

Economic Analysis of Noninvasive Tissue Oximetry for Postoperative Monitoring of Deep Inferior Epigastric Perforator Flap Breast Reconstruction: A Review.

Background. Postoperative monitoring of deep inferior epigastric perforator (DIEP) flaps for breast reconstruction using noninvasive tissue oximetry enables timely recognition of vascular compromise. This may limit ischemic tissue damage, minimizing postoperative morbidity and healthcare costs. The aim of this review was to provide an economic analysis of tissue oximetry for postoperative monitoring of DIEP flap breast reconstruction. Methods. A systematic literature search was conducted utilizing PubMed and Embase. Articles reporting costs related to tissue oximetry following DIEP flap breast reconstruction, costs directly related to DIEP flap surgical procedure, and costs associated with postoperative complications were included. Risk of bias was assessed using different tools depending on study type. Results. Six articles were included. Four studies provided an overview of total costs associated with DIEP flap breast reconstruction; two studies focused on whether tissue oximetry could facilitate a decrease in hospital costs. Average overall costs for DIEP flap procedure were estimated at $28 000, with additional costs up to $37 530 in case of total flap failure. Tissue oximetry to monitor DIEP flaps could potentially save up to $1667 per procedure. Moreover, it might eliminate the need for specialized postoperative care. Conclusion. Tissue oximetry following DIEP flap breast reconstruction can potentially facilitate a decrease in hospital costs since its readings enable physicians to intervene in an early stage of tissue malperfusion, contributing to minimizing complications. Tissue oximetry may eliminate the need for specialized postoperative care. However, based on the current literature, no firm conclusions can yet be drawn regarding cost-effectiveness of standard implementation.

A faster PISTOL for 1 H MR-based quantitative tissue oximetry.

Quantitative mapping of oxygen tension (pO2 ), noninvasively, could potentially be beneficial in cancer and stroke therapy for monitoring therapy and predicting response to certain therapies. Intracellular pO2 measurements may also prove useful in tracking the health of labeled cells and understanding the dynamics of cell therapy in vivo. Proton Imaging of Siloxanes to map Tissue Oxygenation Levels (PISTOL) is a relatively new oximetry technique that measures the T1 of administered siloxanes such as hexamethyldisiloxane (HMDSO), to map the tissue pO2 at various locations with a temporal resolution of 3.5 minutes. We have now developed a siloxane-selective Look-Locker imaging sequence equipped with an echo planar imaging (EPI) readout to accelerate PISTOL acquisitions. The new tissue oximetry sequence, referred to as PISTOL-LL, enables the mapping of HMDSO T1 , and hence tissue pO2 in under one minute. PISTOL-LL was tested and compared with PISTOL in vitro and in vivo. Both sequences were used to record dynamic changes in pO2 of the rat thigh muscle (healthy Fischer rats, n = 6), and showed similar results (P > 0.05) as the other, with each sequence reporting a significant increase in pO2 (P < 0.05) under hyperoxia compared with steady state normoxia. This study demonstrates the ability of the new sequence in rapidly and accurately mapping the pO2 changes and accelerating quantitative 1 H MR tissue oximetry by approximately 4-fold. The faster PISTOL-LL technique could enable dynamic 1 H oximetry with higher temporal resolution for assesing tissue oxygentation and tracking the health of transplanted cells labeled with siloxane-based probes. With minor modifications, this sequence can be useful for 19 F applications as well.

Continuous monitoring of interstitial tissue oxygen using subcutaneous oxygen microsensors: In vivo characterization in healthy volunteers.

Measurements of regional tissue oxygen serve as a proxy to monitor local perfusion and have the potential to guide therapeutic decisions in multiple clinical disciplines. Transcutaneous oximetry (tcpO2) is a commercially available noninvasive technique that uses an electrode to warm underlying skin tissue and measure the resulting oxygen tension at the skin surface. A novel approach is to directly measure interstitial tissue oxygen using subcutaneous oxygen microsensors composed of a biocompatible hydrogel carrier platform with embedded oxygen sensing molecules. After initial injection of the hydrogel into subcutaneous tissue, noninvasive optical measurements of phosphorescence-based emissions at the skin surface are used to sense oxygen in the subcutaneous interstitial space. The object of the present study was to characterize the in vivo performance of subcutaneous microsensors and compare with transcutaneous oximetry (tcpO2). Vascular occlusion tests were performed on the arms of 7 healthy volunteers, with repeated tests occurring 1 to 10 weeks after sensor injection, yielding 95 total tests for analysis. Comparative analysis characterized the response of both devices to decreases in tissue oxygen during occlusion and to increases in tissue oxygen following release of the occlusion. Results indicated: (I) time traces returned by microsensors and tcpO2 were highly correlated, with the median (interquartile range) correlation coefficient of r = 0.93 (0.10); (II) both microsensors and tcpO2 sensed a statistically significant decrease in normalized oxygen during occlusion (p < 0.001 for each device); (III) microsensors detected faster rates change (p < 0.001) and detected overshoot during recovery more frequently (38% vs. 4% of tests); (IV) inter-measurement analysis showed no correlation of baseline values between microsensors and tcpO2 (r = 0.03), but comparison of integrated oxygen dynamics showed similar variation in the normalized response to occlusion between devices (p = 0.06), (V) intra-measurement analysis revealed that microsensors detect greater physiological fluctuations than tcpO2 (p < 0.001) and may provide enhanced sensitivity to processes such as vasomotion. Additionally, the functional response of microsensors was not significantly different across time groupings (per month) post-injection (p = 0.61). Although the compared devices have differences in the mechanisms used to sense oxygen, these findings demonstrate that subcutaneous oxygen microsensors measure changes in interstitial tissue oxygen in human subjects in vivo.

Association Between the Quantity of Subcutaneous Fat and the Inter-Device Agreement of 2 Tissue Oximeters.

OBJECTIVE: This study aimed to evaluate the association between the quantity of subcutaneous fat (assessed by skinfold thickness) and the inter-device agreement of 2 tissue oximeters. DESIGN: This is a prospective cohort study. SETTING: This study was conducted in a tertiary care academic urban hospital. PARTICIPANTS: Healthy volunteers were recruited. INTERVENTIONS: All patients recruited had their tissue saturations and skinfold thickness measured at 4 different sites (shoulder, forearm, knee, and calf) on both sides of the body using 2 tissue oximeters, the INVOS 5100C and the EQUANOX 7600. MEASUREMENTS AND MAIN RESULTS: Higher skinfold measures were associated with an increase in the difference between measures provided by both oximeters (slope = -0.59, Pearson correlation coefficient = -0.51, p < 0.001). This observed association persisted in a linear mixed model (-0.48 [95% confidence interval [CI] -0.61 to -0.36], p < 0.001). The sex of the volunteers also influenced the inter-oximeter agreement (women: -5.77 [95% CI -8.43 to -3.11], p < 0.001), as well as the forearm sites (left forearm: -7.16 [95% CI -9.85 to -4.47], p < 0.001; right forearm:-7.01 [95% CI -9.61 to -4.40], p < 0.001). CONCLUSION: The inter-device agreement of the 2 studied oximeters is correlated to the quantity of subcutaneous fat. Monitoring using tissue oximetry should be interpreted with great care when sensors are placed on sites with a significant quantity of subcutaneous fat. In addition to the monitoring of cerebral oximetry, following the variations of saturations at the same peripheral site seems to remain the most secure way to use that technology for the monitoring of critically ill patients.

Non-Invasive Tissue Oximetry-An Integral Puzzle Piece.

Non-invasive tissue oximetry is a monitoring method for continuous assessment of tissue oxygenation, which may aid in detection of hemodynamic instability and otherwise unnoticed hypoxia. Numerous studies focused on using non-invasive tissue oximetry intraoperatively, proposing its predictive value in relation to clinical outcome. Tissue oximetry may be part of standard monitoring practice for brain monitoring during cardiac surgery in many clinical centers; however, the monitoring method can be deployed in numerous clinical settings. This succinct overview aims to determine the role of non-invasive tissue oximetry in current clinical practice.

Measurement of peripheral muscle oxygen saturation in conscious healthy horses using a near-infrared spectroscopy device.

OBJECTIVE: Maintaining adequate muscle tissue oxygenation is of paramount importance during equine general anesthesia. The objectives of this study were to assess the feasibility, reliability and repeatability of near-infrared spectroscopy (NIRS) muscle oximetry using the Inspectra m650 in conscious healthy adult horses. STUDY DESIGN: Prospective, observational study. ANIMALS: A group of 30 healthy client-owned adult horses admitted to the equine hospital between July 2017 and July 2018. METHODS: The probe of an Inspectra m650 NIRS tissue oximeter was placed on the hairless surface of five muscle sites (omotransversarius, triceps long head, extensor carpi ulnaris, vastus lateralis and lateral digital extensor) on the left side of the body of each standing, unsedated horse. Each site had muscle oxygenation (StO2) recordings measured in triplicate and statistical modeling used to assess the reading reliability and repeatability within and between muscle sites. RESULTS: The readings acquired at the vastus lateralis and extensor carpi ulnaris muscle sites had highly repeatable values [mean (90% confidence interval): StO2, 95% (93.8%, 96.5%) and 93% (91.6%, 93.9%), respectively; intraclass correlation coefficients, 0.92 and 0.80, respectively]. These two sites also had high reliability (represented by the percentage of successful readings; 70% and 86%, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: The use of NIRS muscle oxygenation technology is a clinically feasible means to assess tissue oxygenation in horses. The vastus lateralis and extensor carpi ulnaris muscle sites provided the most reliable and repeatable readings when using the Inspectra m650 machine in horses.

Reevaluation of intrapartum fetal monitoring using fetal oximetry: A review.

AIM: Although several studies reported the measurement of fetal oxygen saturation using fetal pulse oximetry (FPO) for evaluation of the fetal intrapartum condition, a systematic review of the seven randomized controlled trials (RCTs) provided no evidence to support FPO for intrapartum fetal monitoring. In the present review, we re-evaluate an overview for the use of FPO and seven RCTs of FPO. METHODS: We reviewed numerous previous reports on FPO and seven RCTs of intrapartum FPO. RCTs were conducted with the main outcome measure being a reduction in the cesarean section rate. RESULTS: The largest trial with 5341 entries failed to show any reduction. The negative result from this RCT may be explained by the use of a different cutoff value for fetal oxygen saturation compared to the other RCT; in addition, there were differences in the indications for cesarean section due to dystocia and in the definition of non-reassuring fetal status (NRFS). An abnormal FPO value, defined as the fetal oxygen saturation value <30% for at least 10 min, is useful for making a diagnosis of fetal acidosis. A newly developed device, an examiner's finger-mounted tissue oximetry, accurately measures tissue oxygen saturation while overcoming the drawbacks of FPO, such as infection risk and slipping off of the sensor during descent of the fetal head. CONCLUSION: FPO (including the new device) with fetal heart rate monitoring in selected cases of NRFS may reduce the cesarean section rate.

A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements.

We describe the validation methodology for the NIRS based FORE-SIGHT ELITE® (CAS Medical Systems, Inc., Branford, CT, USA) tissue oximeter for cerebral and somatic tissue oxygen saturation (StO2) measurements for adult subjects submitted to the United States Food and Drug Administration (FDA) to obtain clearance for clinical use. This validation methodology evolved from a history of NIRS validations in the literature and FDA recommended use of Deming regression and bootstrapping statistical validation methods. For cerebral validation, forehead cerebral StO2 measurements were compared to a weighted 70:30 reference (REF CXB) of co-oximeter internal jugular venous and arterial blood saturation of healthy adult subjects during a controlled hypoxia sequence, with a sensor placed on the forehead. For somatic validation, somatic StO2 measurements were compared to a weighted 70:30 reference (REF CXS) of co-oximetry central venous and arterial saturation values following a similar protocol, with sensors place on the flank, quadriceps muscle, and calf muscle. With informed consent, 25 subjects successfully completed the cerebral validation study. The bias and precision (1 SD) of cerebral StO2 compared to REF CXB was -0.14 ± 3.07%. With informed consent, 24 subjects successfully completed the somatic validation study. The bias and precision of somatic StO2 compared to REF CXS was 0.04 ± 4.22% from the average of flank, quadriceps, and calf StO2 measurements to best represent the global whole body REF CXS. The NIRS validation methods presented potentially provide a reliable means to test NIRS monitors and qualify them for clinical use.

Soft tissue oxygen saturation to predict admission from the emergency department: A prospective observational study.

OBJECTIVE: We evaluated a soft tissue oxygen saturation (Sto2) measurement at triage for predicting admission to the hospital in adults presenting to the emergency department (ED) in addition to data routinely gathered at triage. METHODS: This was a prospective, observational, single center study of adults presenting to the ED for evaluation. Research assistants obtained thenar eminence Sto2 measurements on subjects in ED triage. ED providers not involved in the study then made all management and disposition decisions. We prospectively collected data on each subject's final ED disposition (admission versus discharge). We identified the optimal Sto2 cutoff value for predicting admission. We then used logistic regression modeling to describe the added predictive value of Sto2 beyond routinely collected triage data including Emergency Severity Index level, age, and vital signs. RESULTS: We analyzed 2588 adult (>17years) subjects with 743 subjects (28.7%) admitted to the hospital. Sto2<76% was the optimal diagnostic cutoff for predicting admission. Of subjects with Sto2<76%, 158 of 384 (41.1%) underwent admission versus 585 of 2204 (26.5%) subjects with Sto2≥76. After controlling for age, vital signs, and ESI level in the logistic regression analysis, Sto2<76% had an odds ratio of 1.54 (95% confidence interval (CI), 1.19 to 1.98) for predicting admission. CONCLUSIONS: Sto2 may provide additional prognostic data to routine triage assessment regarding the disposition for undifferentiated adult patients presenting to the ED.

Tissue oxygen saturation levels from fetus to neonate.

AIM: Oxygen saturation during the term of delivery to the first cry, when fetal circulation dynamically changes, has not yet been examined. The aim of this study was therefore to determine whether the continuous measurement of regional tissue oxygen saturation (rSO2 ) from crowning until 5 min after delivery is possible using fetal tissue oximetry with a sensor attached to the examiner's finger. METHODS: Oxygen saturation levels in fetal cranial tissue between the second stage of delivery to crowning and up to 5 min after delivery were measured using fetal tissue oximetry with a sensor attached to the examiner's finger. Thirty-five deliveries were examined, and oxygen saturation was measured in seven infants from delivery of the head until 5 min after birth. Umbilical cord blood gas was measured in all cases. This clinical test was performed under the permission of the Ethics Committee of Hamamatsu University School of Medicine. RESULTS: Average tissue oxygen saturation in the second stage of delivery and at 5 min after delivery were 50.3 ± 16.3% and 56.8 ± 8.46%, respectively. In cases of continuous measurement, average rSO2 for crowning, immediately after delivery, and the first cry was 32.7 ± 9.5%, 30.0 ± 6.6%, and 31.6 ± 5.5%, respectively. CONCLUSION: We herein successfully measured oxygen saturation levels in fetal cranial tissue during crowning, delivery of the head, the first cry, and 5 min after delivery using fetal tissue oximetry with a sensor attached to the examiner's finger.

Cerebral oxygenation and perfusion kinetics monitoring of military aircrew at high G using novel fNIRS wearable system.

Introduction: Real-time physiological episode (PE) detection and management in aircrew operating high-performance aircraft (HPA) is crucial for the US Military. This paper addresses the unique challenges posed by high acceleration (G-force) in HPA aircrew and explores the potential of a novel wearable functional near-infrared spectroscopy (fNIRS) system, named NIRSense Aerie, to continuously monitor cerebral oxygenation during high G-force exposure. Methods: The NIRSense Aerie system is a flight-optimized, wearable fNIRS device designed to monitor tissue oxygenation 13-20 mm below the skin's surface. The system includes an optical frontend adhered to the forehead, an electronics module behind the earcup of aircrew helmets, and a custom adhesive for secure attachment. The fNIRS optical layout incorporates near-distance, middle-distance, and far-distance infrared emitters, a photodetector, and an accelerometer for motion measurements. Data processing involves the modified Beer-Lambert law for computing relative chromophore concentration changes. A human evaluation of the NIRSense Aerie was conducted on six subjects exposed to G-forces up to +9 Gz in an Aerospace Environmental Protection Laboratory centrifuge. fNIRS data, pulse oximetry, and electrocardiography (HR) were collected to analyze cerebral and superficial tissue oxygenation kinetics during G-loading and recovery. Results: The NIRSense Aerie successfully captured cerebral deoxygenation responses during high G-force exposure, demonstrating its potential for continuous monitoring in challenging operational environments. Pulse oximetry was compromised during G-loading, emphasizing the system's advantage in uninterrupted cerebrovascular monitoring. Significant changes in oxygenation metrics were observed across G-loading levels, with distinct responses in Deoxy-Hb and Oxy-Hb concentrations. HR increased during G-loading, reflecting physiological stress and the anti-G straining maneuver. Discussion: The NIRSense Aerie shows promise for real-time monitoring of aircrew physiological responses during high G-force exposure. Despite challenges, the system provides valuable insights into cerebral oxygenation kinetics. Future developments aim for miniaturization and optimization for enhanced aircrew comfort and wearability. This technology has potential for improving anti-G straining maneuver learning and retention through real-time cerebral oxygenation feedback during centrifuge training.

Tissue Oximetry Changes during Postoperative Dangling in Lower Extremity Free Flap Reconstruction: A Pilot Study.

Background: Lower extremity free flap dangling protocols are still widely practiced, despite a paucity of evidence for their use. This pilot study investigates the use of tissue oximetry to provide further insight into the physiological effect of postoperative dangling in lower limb free flap transfer. Methods: Ten patients undergoing lower extremity free flap reconstruction were included in this study. Free flap tissue oxygen saturation (StO2) was continuously measured using non-invasive near-infrared spectroscopy. Measurements were performed on the free flap and contralateral limb during dangling from postoperative day (POD) 7 until 11, according to the local dangling protocol. Results: StO2 values measured in the free flap diminished to 70 ± 13.7% during dangling. This minimum StO2 was reached significantly later, and correspondingly the area under the curve (AUC) was significantly larger on POD 11 compared to the start of the dangling protocol on POD 7, reflecting an improving free flap microvascular reactivity. The dangling slope was equal between the free flap and contralateral leg. The reperfusion slope was significantly flatter on POD 7 compared to the other PODs (p < 0.001). Thereafter, no significant differences between PODs were observed. Patients with a history of smoking had significantly lower tissue oximetry values compared to non-smokers. Conclusions: The application of tissue oximetry during dangling provides further insight into the physiological effect (i.e., changes in microcirculatory function) of the free flap of the reconstructed lower extremity. This information could potentially be useful to either revise or disrupt the use of such dangling protocols.