Publications by authors named "Masatsugu Niwayama"

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 (rSO ) 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.

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: 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). : We devised a novel near-infrared spectroscopy oximeter, "TOE-20," for real-time monitoring of regional tissue oxygen saturation (rSO).

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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 (rSO) 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 rSO and skin perfusion pressure.

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Article Synopsis
  • Tissue oxygenation sensing is crucial for managing surgical procedures and recovery, but optimal sensor design and measurement depth sensitivity are not fully understood.
  • Researchers used Monte Carlo simulations and phantom experiments to analyze oximetry with near-infrared spectroscopy, finding that measurement depth can be adjusted by the distance between light sources and detectors.
  • A prototype miniaturized oximeter was developed to measure tissue oxygen saturation at depths of 2-5 mm, providing valuable data that traditional methods may miss.
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  • The research involved 78 pregnant women undergoing cesarean sections, measuring fetal and neonatal StO levels immediately before and after birth, mainly focusing on the first 5 minutes post-delivery.
  • Results indicated a possible trend where neonates diagnosed with respiratory disorders had lower StO levels compared to those without, although the findings did not reach statistical significance.
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  • The study compared muscle oxygen dynamics during exercise across three age groups: elderly (73 years), middle-aged (50 years), and young adults (25 years), all performing ramp bicycle exercises to exhaustion.
  • Results showed that elderly participants had lower muscle oxygen saturation and oxygenated hemoglobin levels compared to the other groups, while deoxygenated and total hemoglobin levels were similar across all ages.
  • The findings suggest that muscle oxygen dynamics are relatively maintained in early aging stages but decline in later stages, likely due to reduced oxygen delivery, and different mechanisms affect peak oxygen uptake between age groups.
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  • The study compared muscle oxygen dynamics during exercise between overweight (OW) and normal-weight (NW) women who had similar aerobic capacities.
  • Overweight women showed higher muscle oxygen saturation (SmO) and lower levels of deoxygenated hemoglobin and total hemoglobin changes compared to normal-weight women during graded treadmill exercise.
  • The findings indicate that despite matching pulmonary oxygen uptake, overweight adults had reduced muscle blood volume and oxygen extraction during exercise, which correlated with their peak aerobic capacity.
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  • The study aimed to determine the effectiveness of a finger-mounted tissue oximeter in assessing blood flow in patients with peripheral arterial disease (PAD).
  • Researchers measured several indicators, including ankle-brachial index (ABI), transcutaneous oxygen pressure (TcPO), and skin perfusion pressure (SPP) in 72 PAD patients and found significant correlations between tissue oxygenation saturation (rSO) and these measurements.
  • Results indicated that rSO was significantly lower in more severe PAD groups compared to less severe ones, highlighting that the finger-mounted tissue oximeter is a quick, simple, and painless method for evaluating limb circulation in PAD patients.
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  • This study introduces a compact device combining near-infrared spectroscopy (NIRS), electrocorticography (ECoG), and temperature sensors to monitor brain activity, aimed at improving surgical outcomes in neurosurgery.
  • A flexible multi-channel probe was developed to simultaneously measure NIRS, ECoG, and temperature variations from the brain's surface, ensuring biocompatibility for safe implantation.
  • Initial human trials show that this probe can effectively monitor neural activities during and after surgery, suggesting it could revolutionize diagnostics and monitoring in neurosurgery and neuroscience.
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The aim of this study was to test the effects of aerobic cycling training on O 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.

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  • * A significant study with over 5,000 participants did not find a decrease in cesarean sections, potentially due to variations in how fetal oxygen saturation and cesarean indications were defined.
  • * Despite the limitations of FPO, including infection risks, a new finger-mounted device shows promise for measuring tissue oxygen saturation, indicating that combined use with heart rate monitoring might help reduce cesarean rates in certain fetal distress cases.
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  • The study analyzed the measurement sensitivity of spatially resolved spectroscopy across six different tissue models, including brain tissues and muscle tissues, using Monte Carlo simulations to understand the optical path length.
  • It was discovered that measurement sensitivity depends on the change in absorption coefficients and the variance in optical path lengths, particularly highlighting the differences in sensitivity between surface and deep tissues based on the distance between the light source and detectors.
  • The research identified challenges in measuring surface layers that are not uniform and provided insights that could enhance the interpretation of data in near-infrared oximetry and functional near-infrared spectroscopy for various tissue structures.
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The aim of this study was to investigate the effects of 8 weeks of training on O 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.

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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 (SmO), 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 SmO was observed at VLd, VLp, RF, and VM in MI, compared to CON.

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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 (rSO ) 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.

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  • This study compared muscle oxygen dynamics during exercise between elderly patients with angina pectoris (AP) and matched controls.
  • AP patients showed higher muscle oxygen saturation (SmO2) and lower deoxygenated hemoglobin concentrations (∆deoxy-Hb) during exercise compared to the control group.
  • There was a negative correlation between changes in SmO2 and peak oxygen uptake (VO2), indicating that AP patients have a blunted muscle deoxygenation response which may be linked to their reduced aerobic capacity.
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  • The study aimed to understand how muscle deoxygenation changes over time with endurance training in untrained males.
  • Nine male participants underwent a cycling exercise protocol to evaluate their peak oxygen uptake (VO2peak) and muscle oxygen saturation before and after 3 and 6 weeks of endurance training.
  • Results showed that VO2peak significantly improved after both training periods, while muscle oxygen saturation (SmO2) decreased after training but remained consistent between the two training phases, indicating increased muscle oxygen availability contributes to VO2peak improvements mainly in the first 3 weeks.
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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.

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  • Fetal scalp blood sampling is rarely used due to its invasive nature, prompting the development of a portable oximetry device for assessing fetal oxygen levels.
  • A study with mice using this new oximetry showed a strong correlation between fetal head tissue oxygen saturation and blood pH levels (r=0.90), reinforcing prior findings from human cases.
  • The promising results suggest that this non-invasive method may become more popular among obstetricians for monitoring fetal health, particularly regarding acidosis during labor.
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Aging enhances muscle desaturation responses due to reduced O2 supply. Even though aerobic training enhances muscle desaturation responses in young subjects, it is unclear whether the same is true in elderly subjects. Ten elderly women (age: 62±4 years) participated in 12-weeks of cycling exercise training.

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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.

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  • Exercise training early after a myocardial infarction (MI) improves aerobic capacity and muscle deoxygenation in patients.
  • A study divided early post-MI patients into a 12-week aerobic training group and a non-training control group, measuring muscle deoxygenation during exercise.
  • Results showed significant improvements in peak oxygen uptake and muscle oxygen saturation in the training group, indicating that exercise enhances muscle performance following an MI.
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  • - The study introduces LED sensing to improve the miniaturization and balance of Near-Infrared Spectroscopy (NIRS) sensor systems.
  • - Researchers analyzed the spectral responses of LEDs and developed a formula to calculate variations in hemoglobin levels.
  • - A blood phantom experiment demonstrated the ability to track changes in hemoglobin concentration over time using Continuous Wave NIRS with LED sensing.
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  • The study aimed to assess the use of a finger-mounted fetal tissue oximetry probe to measure fetal tissue oxygen saturation (FtO2) during the second stage of labor in 30 healthy pregnant women.
  • Results showed that FtO2 measurements were successfully obtained in all cases, with a mean FtO2 of 65.5% in normal neonates, and a significant correlation was found between FtO2 and umbilical cord arterial pH.
  • The findings suggest that using this oximetry probe is a simple and effective way to monitor fetal oxygen levels during labor.
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The best way to assess fetal condition is to observe the oxygen status of the fetus (as well as to assess the condition of infants, children, and adults). Previously, several fetal oximeters have been developed; however, no instrument has been utilized in clinical practice because of the low-capturing rate of the fetal oxygen saturation. To overcome the problem, we developed a doctor's finger-mounted fetal tissue oximeter, whose sensor volume is one hundredth of the conventional one.

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