Investigation of oxygen saturation in regions of skin by near infrared spectroscopy.

BACKGROUND: Oxygen is essential for life, and investigation of the skin's oxygen environment and identification of its effects on the skin may lead to the discovery of new antiaging targets. To understand individual skin differences and age-related changes, we developed a noninvasive method using near infrared spectroscopy (NIRS) to measure the regional saturation of oxygen (rSO2 ) of human skin. MATERIALS AND METHODS: To construct an NIRS sensor probe specialized for skin measurement, the distance between the sensor transmitter and receiver was optimized based on data for the thickness of the facial skin to the subcutaneous fat layer. To analyze the relationship between skin oxygen saturation and body oxygen saturation, rSO2 was measured by NIRS, oxygen saturation of peripheral artery (SpO2 ) was measured by pulse oximeter, and physical conditions were considered, such as body mass index (BMI) and muscle mass, in Japanese women (age 20s-60s). RESULTS: Both skin rSO2 and SpO2 varied among individuals and decreased with age. Only SpO2 showed a relationship with BMI and muscle mass, whereas rSO2 showed no relationship with these physical conditions. No relationship between rSO2 and SpO2 was observed. CONCLUSION: Individual and age-related differences in skin by rSO2 values were found by NIRS optimized for local skin; however, the factors affecting rSO2 differed from those affecting SpO2 , and further study is needed.

The Patency of Tibial/Peroneal Arteries Affects the Increment of Regional Tissue Saturation of Oxygen in Each Angiosome after Superficial Femoral Artery Revascularization.

Objective: The angiosome model is a controversial concept in the revascularization of patients with chronic limb-threatening ischemia (CLTI). The aim of this study was to demonstrate the importance of patency of the tibial/peroneal arteries for regional tissue oxygenation in each angiosome during endovascular therapy (EVT) of the superficial femoral artery (SFA). Materials and Methods: We devised a novel near-infrared spectroscopy oximeter, "TOE-20," for real-time monitoring of regional tissue oxygen saturation (rSO2). Using TOE-20, we prospectively assessed rSO2 at each angiosome in 23 CLTI patients who underwent successful revascularization of the SFA. During EVT, three sensor probes were placed at the dorsal foot, plantar foot, and outer ankle for rSO2 monitoring. Results: At the end of EVT, rSO2 at all angiosomes was significantly elevated by SFA revascularization. The change in rSO2 in each angiosome was larger in patients with patent relevant arteries than in those with occluded relevant arteries (i.e., anterior tibial artery patency, posterior tibial artery patency, and peroneal artery patency). Conclusion: The patency of the tibial/peroneal arteries is important for regional tissue oxygenation in EVT. Using TOE-20 and rSO2-based revascularization, it may possible to anticipate whether an ischemic ulcer will heal or not.

Real-time assessment of tissue oxygen saturation during endovascular therapy for chronic limb threatening ischemia using a novel oximeter.

In the present study, we have introduced a novel real-time, near-infrared spectroscopy oximeter, the TOE-20 (Astem, Co, Ltd, Kawasaki, Japan), which can simultaneously measure the regional tissue oxygen saturation (rSO2) in the skin and subcutaneous tissue at three angiosomes of the foot. Seven patients with chronic limb threatening ischemia who had undergone successful revascularization of the superficial femoral artery were included. The analysis revealed a significant correlation between the rSO2 and skin perfusion pressure. After revascularization, the rSO2 and skin perfusion pressure had both increased at the three regions, although the increase at the plantar foot was insignificant. These results indicate that the TOE-20 can be successfully used to monitor the rSO2 during endovascular treatment.

Tissue Oximeter with Selectable Measurement Depth Using Spatially Resolved Near-Infrared Spectroscopy.

Tissue oxygenation sensing at a few millimeters deep is useful for surgical and postoperative management. However, the measurement sensitivity at each depth and the proper sensor combination have not been clarified. Here, the measurement characteristics of oximetry by spatially resolved near-infrared spectroscopy were analyzed using Monte Carlo simulation and phantom experiment. From summing the sensitivities of each depth, it was quantitatively found that the measurement sensitivity curve had a peak, and the measurement depth can be adjusted by combining the two distances between the light source and the detector. Furthermore, the gastric tissue was 10-20% smaller in terms of measurement depth than the skin-subcutaneous tissue. A miniaturized oximeter was prototyped so that it could be used in combination with an endoscope or laparoscope. The optical probes consisted of light emitting diodes with wavelengths of 770 nm and 830 nm and photodetectors located 3 to 30 mm from the light source. Phantom experiments using the probes demonstrated the tendency of theoretical analysis. These results suggest the possibility of measuring tissue oxygen saturation with a selectable measurement depth. This selectable method will be useful for obtaining oxygenation information at a depth of 2-5 mm, which is difficult to measure using only laparoscopic surface imaging.

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.

Skeletal Muscle Deoxygenation and Its Relationship to Aerobic Capacity During Early and Late Stages of Aging.

The aim of this study was to compare muscle O2 dynamics during exercise among elderly (n = 10, age: 73 ± 3 years), middle-aged (n = 9, age: 50 ± 6 years), and young (n = 10, age: 25 ± 3 years) adults. The subjects performed ramp bicycle exercise until exhaustion. Muscle O2 saturation (SmO2) and relative changes from rest in oxygenated hemoglobin/myoglobin (∆oxy-Hb/Mb), deoxygenated hemoglobin/myoglobin (∆deoxy-Hb/Mb), and total hemoglobin concentration (∆total-Hb) were monitored continuously at the vastus lateralis muscle by near-infrared spatial resolved spectroscopy. At given absolute workloads, SmO2 and ∆oxy-Hb/Mb were significantly lower in elderly than the other groups, while ∆deoxy-Hb/Mb, ∆total-Hb, and pulmonary O2 uptake (VO2) were similar among the three groups. In contrast, there were no significant differences in muscle O2 dynamics during submaximal exercise between middle-aged and young subjects. Muscle O2 dynamics may be relatively preserved in early stages of aging, although muscle deoxygenation is enhanced in late stages of aging, probably due to reduced convective O2 supply. Moreover, change in SmO2 was significantly positively correlated with peak VO2 in the elderly, while a significant negative relationship was observed in middle-aged and young subjects. In late stages of aging, diminished peak VO2 may be caused by attenuated convective O2 transport, while reduced peak VO2 can be explained by lowered muscle O2 extraction in early stages of aging.

Differences in Muscle O2 Dynamics During Treadmill Exercise Between Aerobic Capacity-Matched Overweight and Normal-Weight Adults.

The aim of this study was to compare muscle O2 dynamics during exercise between aerobic capacity-matched overweight and normal-weight adults. Overweight women (OW, n = 9) and normal-weight women (NW, n = 14) performed graded treadmill exercise until exhaustion. Muscle O2 saturation (SmO2) and relative changes from rest in deoxygenated hemoglobin concentration (∆deoxy-Hb) and total hemoglobin concentration (∆total-Hb) were monitored continuously at gastrocnemius medialis muscle by near infrared spatial resolved spectroscopy. Significantly higher SmO2 and lower ∆deoxy-Hb and ∆total-Hb were observed in OW compared with NW. Pulmonary O2 uptake (VO2) normalized by fat-free mass was matched between groups. In both groups, peak VO2 was significantly correlated with change in SmO2 and ∆deoxy-Hb. Our findings suggest that both muscle blood volume and deoxygenation were lower in overweight adults, compared to aerobic capacity-matched normal-weight adults. Moreover, lowered muscle O2 extraction was related to peak VO2 in overweight adults, as well as in normal-weight adults.

Utility of a Finger-Mounted Tissue Oximeter with Near-Infrared Spectroscopy to Evaluate Limb Ischemia in Patients with Peripheral Arterial Disease.

Objective: To investigate whether a finger-mounted tissue oximeter is useful in evaluating limb blood flow in patients with peripheral arterial disease (PAD). Materials and Methods: Seventy-two patients with PAD were included, and the ankle-brachial index (ABI), transcutaneous oxygen pressure (TcPO2), and skin perfusion pressure (SPP) were measured. The regional tissue oxygenation saturation (rSO2) was measured using a finger-mounted tissue oximeter at the ankle, dorsal foot, and each dorsal and plantar toe. Correlations between rSO2 and ABI and between TcPO2 and SPP were analyzed. The patients were divided into three groups: Fontaine IIa (F-IIa), IIb (F-IIb), and III and IV (F-III/IV) groups. The difference in rSO2 between each group was analyzed. Results: Significant correlations were observed between rSO2 and TcPO2 and between rSO2 and SPP. TcPO2 and SPP in the F-III/IV group were significantly lower than those in the F-IIa group. rSO2 in the F-IIb and F-III/IV groups was significantly lower than that in the F-IIa group. Conclusion: The measurement of rSO2 using finger-mounted tissue oximetry is quick, simple, and painless. It can be used on any skin area and is useful to evaluate limb circulation in patients with PAD.

Implantable Multi-Modality Probe for Subdural Simultaneous Measurement of Electrophysiology, Hemodynamics, and Temperature Distribution.

OBJECTIVE: The purpose of this paper is to demonstrate how the integration of the multi-channel measurement capabilities of near-infrared spectroscopy (NIRS), electrocorticography (ECoG), and negative temperature coefficient thermistor sensors into a single device compact enough for subdural implantation can provide beneficial information on various aspects of brain cortical activity and prove a powerful medical modality for pre-, intra-, and post-operative diagnoses in neurosurgery. METHODS: The development of a flexible multi-modal multi-channel probe for the simultaneous measurement of the NIRS, ECoG, and surficial temperature obtained from the cerebral cortex was carried out. Photoelectric bare chips for NIRS channels, miniature temperature-coefficient thermistors for measuring localized temperature variation, and 3-mm-diameter platinum plates for ECoG recording were assembled on a polyimide-based flexible printed circuit to create six channels for each modality. A conformal coating of Parylene-C was applied on all the channels except the ECoG to make the probe surface biocompatible. RESULTS: As a first-in-human study, the simultaneous measurement capability of the multi-modality probe, with sufficient signal-to-noise ratio and accuracy, to observe pathological neural activities in subjects during surgery and post-operative monitoring, with no complications two weeks since the implantation, was confirmed. CONCLUSION: The feasibility of using a single device to assess the dynamic pathological activity from three different aspects was determined for human patients. SIGNIFICANCE: The simultaneous and accurate multi-channel recording of electrical, hemodynamic, and thermographic cortical activities in a single device small enough for subdural implantation is likely to have major implications in neurosurgery and neuroscience.

Effects of Aerobic Cycling Training on O2 Dynamics in Several Leg Muscles in Early Post-myocardial Infarction.

The aim of this study was to test the effects of aerobic cycling training on O2 dynamics in several leg muscles in early post-myocardial infarction (post-MI). Fifteen post-MI patients were divided into a 12-week training group (TR, n = 9) or a control/non-training group (CON, n = 6). All participants performed ramp bicycle exercise until exhaustion at two times: within 12-35 days of their MI and then again 12 weeks later. Muscle O2 saturation (SmO2) and total hemoglobin concentration (∆total-Hb) were monitored continuously at thigh and lower leg muscles by near infrared spectroscopy. In CON, there were no significant alterations in muscle O2 dynamics between before and after 12 weeks at any measurement sites. In TR, after 12 weeks, lower SmO2 was observed at all measurement sites. In total-Hb, no significant changes were found after training at any measurement sites in TR. Moreover, the muscle deoxygenation after 12 weeks was related to an improvement of peak O2 uptake in all muscles. Our findings suggest that aerobic cycling training may be useful for early post-MI patients to improve peak aerobic capacity via enhancement of muscle deoxygenation and O2 extraction at several leg muscles.

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.

Voxel-based measurement sensitivity of spatially resolved near-infrared spectroscopy in layered tissues.

We quantitatively investigated the measurement sensitivity of spatially resolved spectroscopy (SRS) across six tissue models: cerebral tissue, a small animal brain, the forehead of a fetus, an adult brain, forearm muscle, and thigh muscle. The optical path length in the voxel of the model was analyzed using Monte Carlo simulations. It was found that the measurement sensitivity can be represented as the product of the change in the absorption coefficient and the difference in optical path length in two states with different source-detector distances. The results clarified the sensitivity ratio between the surface layer and the deep layer at each source-detector distance for each model and identified changes in the deep measurement area when one of the detectors was close to the light source. A comparison was made with the results from continuous-wave spectroscopy. The study also identified measurement challenges that arise when the surface layer is inhomogeneous. Findings on the measurement sensitivity of SRS at each voxel and in each layer can support the correct interpretation of measured values when near-infrared oximetry or functional near-infrared spectroscopy is used to investigate different tissue structures.

Multi-site Measurements of Muscle O2 Dynamics During Cycling Exercise in Early Post-myocardial Infarction.

The aim of this study was to compare the muscle oxygen dynamics between early post-myocardial infarction (n = 12; MI) and age-matched elderly subjects without MI (n = 12; CON) in several leg muscles during ramp cycling exercise. Muscle oxygen saturation (SmO2), deoxygenated-hemoglobin concentration (∆deoxy-Hb), and total-hemoglobin concentration (∆total-Hb) were monitored continuously at the distal site of vastus lateralis (VLd), proximal site of the vastus lateralis (VLp), rectus femoris (RF), vastus medialis (VM), gastrocnemius medialis (GM), and tibialis anterior (TA) muscles by near infrared spatial resolved spectroscopy. At given absolute workloads, higher SmO2 was observed at VLd, VLp, RF, and VM in MI, compared to CON. Simultaneously, in MI, deoxy-Hb was lower at VLd, VLp, and VM than CON. In contrast to the thigh muscles, muscle oxygen dynamics were similar between groups in GM and TA. In total-Hb, no significant differences were found at any measurement sites. These results demonstrated that the absence of muscle deoxygenation was observed in MI muscles, especially in the thigh muscles, but not in the lower leg muscles.

Effects of 8 Weeks' Training on Systemic and Muscle Oxygen Dynamics in University Rugby Players.

The aim of this study was to investigate the effects of 8 weeks of training on O2 dynamics in university rugby players. University rugby players (n = 15) participated in 5 strength training sessions and 4 field-based training sessions per week for 8 weeks. Before and after 8-weeks' training, the subjects performed ramp cycling exercise until exhaustion. Muscle O2 saturation (SmO2), relative changes from rest in deoxygenated hemoglobin concentration (∆Deoxy-Hb) and total hemoglobin concentration, cardiac output (CO), and pulmonary O2 uptake (VO2) were monitored continuously during exercise. Peak VO2 and CO were normalized by fat-free mass. Though peak VO2 tended to be increased after training, there were no significant changes in CO, nor any muscle O2 dynamic variables at peak exercise between before and after training. However, an increase in peak VO2 was significantly correlated with diminishment of deoxy-Hb and an increase in SmO2. Changes in CO caused by training were not related to improved peak VO2. The improvement of peak VO2 during 8 weeks of rugby training may have been caused by muscle O2 supply, rather than increased CO or muscle O2 extraction.

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.

Low Volume Aerobic Training Heightens Muscle Deoxygenation in Early Post-Angina Pectoris Patients.

The aim of this study was to investigate the effect of low volume aerobic exercise training on muscle O2 dynamics during exercise in early post-angina pectoris (AP) patients, as a pilot study. Seven AP patients (age: 72 ± 6 years) participated in aerobic exercise training for 12 weeks. Training consisted of continuous cycling exercise for 30 min at the individual's estimated lactate threshold, and the subjects trained for 15 ± 5 exercise sessions over 12 weeks. Before and after training, the subjects performed ramp cycling exercise until exhaustion. Muscle O2 saturation (SmO2) and relative changes from rest in deoxygenated hemoglobin concentration (∆Deoxy-Hb) and total hemoglobin concentration (∆Total-Hb) were monitored at the vastus lateralis by near infrared spatial resolved spectroscopy during exercise. The SmO2 was significantly lower and ∆Deoxy-Hb was significantly higher after training than before training, while there were no significant changes in ∆Total-Hb. These results indicated that muscle deoxygenation and muscle O2 extraction were potentially heightened by aerobic exercise training in AP patients, even though the exercise training volume was low.

Muscle Deoxygenation and Its Heterogeneity Changes After Endurance Training.

The purpose of this study was to elucidate the time course of muscle deoxygenation and its heterogeneity changes through endurance training. Nine healthy untrained male participated in this study. The subjects performed a ramp incremental cycle exercise protocol to estimate VO2peak and muscle tissue oxygen saturation (SmO2) distribution in the VL muscle before and after 3 (3 wk-T) and 6 weeks of endurance training (6 wk-T). The probe of multi-channel near infrared spatially resolved spectroscopy was attached to the left vastus lateralis muscle along the direction of the long axis. The subjects performed cycle exercise at 60 % of VO2peak for 30 min/day, 3 days/week as the endurance training. After the training, VO2peak at 3 wk-T and 6 wk-T were significantly increased compared to pre-training (Pre-T) and VO2peak at 6 wk-T was significantly increased compared to 3 wk-T. Mean SmO2 within measurement sites at VO2peak was significantly decreased after 3 wk-T and 6 wk-T compared to Pre-T, but mean SmO2 was not significantly different between 3 wk-T and 6 wk-T. Conversely, the heterogeneity of the SmO2 during exercise was not significantly changed through endurance training. A significantly negative correlation was found between ΔVO2 and ΔSmO2 after the first 3 weeks of endurance training. In contrast, no correlation was found betweenΔVO2 and ΔSmO2 after the last 3 weeks of endurance training. These results suggest that the enhanced muscle O2 availability may be one of the primary factors in increasing VO2peak after the first 3 weeks of endurance training.

Muscle Oxygen Dynamics During Cycling Exercise in Angina Pectoris Patients.

Muscle O2 dynamics during ramp cycling exercise were compared between angina pectoris patients (AP; n = 7, age: 73 ± 6 years) after coronary artery bypass grafting and age-, height-, and body weight-matched elderly control subjects (CON; n = 7, age: 74 ± 8 years). Muscle O2 saturation (SmO2) and relative change in deoxygenated (∆deoxy-Hb) and total hemoglobin concentration (∆total-Hb) were measured continuously during exercise in the vastus lateralis (VL) by near infrared spatial resolved spectroscopy. Pulmonary O2 uptake (VO2) was also monitored throughout exercise to determine peak VO2. In AP, SmO2 was significantly higher, and ∆deoxy-Hb was significantly lower during exercise, compared to CON. In all subjects, ∆SmO2 (values at peak exercise minus values at resting) was negatively correlated to peak VO2 (r = -0.52, p < 0.05), and ∆deoxy-Hb at peak exercise tended to be negatively associated with peak VO2 (r = 0.48, p = 0.07). Blunted skeletal muscle deoxygenation response was observed in AP patients, which may be related to lower aerobic capacity in AP patients.

Craniofacial tissue oxygen saturation is associated with blood pH using an examiner's finger-mounted tissue oximetry in mice.

Although fetal scalp blood sampling is an examination to assess fetal acidosis during the intrapartum period, it has not been widely used by obstetricians because of its invasiveness. We have developed a small, portable oximetry with a sensor attached to the examiner's finger. Our previous report using this oximetry concluded that fetal head tissue oxygen saturation (StO 2 StO2 ) correlated with umbilical cord artery blood pH. We investigated whether the association between StO 2 StO2 and blood pH in mice could be validated using this oximetry. Eleven the Institute for Cancer Research (ICR) mice were measured using a near-infrared spectroscopy probe at the craniofacial site in a closed polyethylene bag while changing the oxygen concentration. A total of nine blood samples were collected and analyzed for pH. The StO 2 StO2 and tissue blood pH showed a strong positive correlation (r=0.90 r=0.90 and P=0.0009 P=0.0009 ). The StO 2 StO2 and total hemoglobin index also showed a positive correlation (r=0.84 r=0.84 and P=0.0049 P=0.0049 ). Thus, the results of the present study support those of our previous report on clinical cases and allow examiners to easily check the status of fetal acidosis. Fetal management using this oximetry might gain popularity with obstetricians in the near future.

Sex-Related Difference in Muscle Deoxygenation Responses Between Aerobic Capacity-Matched Elderly Men and Women.

Muscle O2 dynamics during ramp cycling exercise were compared between aerobic capacity-matched elderly men (n=8, age 65±2 years) and women (n=8, age 66±3 years). Muscle O2 saturation (SmO2) and relative change in deoxygenated (Δdeoxy-Hb) and total hemoglobin concentration (Δtotal-Hb) were monitored continuously during exercise in the vastus lateralis (VL) and gastrocnemius medialis (GM) by near infrared spatial resolved spectroscopy. SmO2 was significantly higher during exercise in women than in men in VL, but not in GM. In VL, Δdeoxy-Hb and Δtotal-Hb were significantly higher in men than in women, especially during high intensity exercise. However, no significant difference was observed in Δdeoxy-Hb or Δtotal-Hb in GM. Sex-related differences in muscle deoxygenation response may be heterogeneous among leg muscles in elderly subjects.