Biomedical subjects

Asao Kobayashi

Publications and source records attributed to Asao Kobayashi.

4 recordsLinked to original sources

PubMed2003

Cerebral oxygenation monitor during head-up and -down tilt using near-infrared spatially resolved spectroscopy.

Reflectance near-infrared spectroscopy (NIRS) has become a suitable and easily manageable method to monitor cerebral oxygenation changes in presyncopal and syncopal symptoms caused by postural changing or standing. A new clinical tissue oxygenation monitor has been recently developed which measures absolute tissue haemoglobin saturation (Tissue Oxygenation Index, TOI) utilizing spatially resolved spectroscopy (SRS). The present study examined the effects of postural changes on cerebral oxygenation as reflected in SRS-NIRS findings. Cerebral oxyhaemoglobin (O2Hb), deoxyhaemoglobin (HHb), and the TOI were recorded from both sides of the forehead in five healthy male subjects (age range, 28-40 years) during 90 degrees head-up tilt (HUT) and -6 degrees head-down tilt (HDT). Three series of measurements were carried out on separate days. O2Hb was decreased during HUT. TOI was significantly lower in HUT than in the supine position (SUP). There was no significant change in TOI during HDT. A significant session effect was observed in the left forehead TOI during SUP, but not in the right. SRS-NIRS measurements confirmed sub-clinical alterations of cortical oxygenation during HUT. NIRS data from the left side of the forehead, which may vary with cognitive or emotional activation, were more variable than those from the right side.

Adult↗

PubMed2002

Effect of muscle tensing on cerebral oxygen status during sustained high +Gz.

BACKGROUND: Successful monitoring of oxyhemoglobin during +Gz exposure was recently achieved using near-infrared spectroscopy (NIRS). To assess the effects of muscle tensing on sustained +Gz tolerance, we measured muscle activity and cerebral oxygen status (COS) during anti-G straining maneuvers at sustained high +Gz. METHOD: We exposed 21 male pilots wearing CSU-13/P anti-G suit to two different centrifuge profiles: 1) short-term repeated exposure (5 to 20 s) at 4, 5, 6, 5.5, or 7 Gz; 2) sustained exposure to a + 7Gz plateau for 30 s. During the Gz exposures, surface electromyographic (EMG) measurements were taken from the vastus medialis (VM) and rectus abdominis (RA) muscles. At the same time, the COS was recorded from the left forehead area using a commercial NIRS system. Mean muscular tensing for each muscle was calculated as a percentage of maximal voluntary contraction (% MVC). RESULTS: Oxyhemoglobin (O2Hb) and total hemoglobin (sum of O2Hb and deoxyhemoglobin) were decreased during both short-term and sustained +Gz exposure. RA muscle tensing was positively correlated with changes in the concentration of O2Hb during sustained + 7Gz exposure (r = 0.540, p < 0.05). RA tensing ranged from 6.2 to 36.8%MVC, and O2Hb ranged from -41.3 to -7.28 micromol x L(-1) during the exposures. No significant correlation was observed between VM tensing and O2Hb. CONCLUSION: NIRS measurements confirmed that a muscle straining maneuver increases G tolerance. Higher RA muscle tensing helps preserve brain blood volume during sustained high +Gz.

Adult↗

PubMed2002

Pilot cerebral oxygen status during air-to-air combat maneuvering.

BACKGROUND: Successful monitoring of in-flight cerebral oxygen status (COS; cerebral hemoglobin concentration changes and oxygenation changes under dynamic flight conditions) was recently achieved using near-infrared spectroscopy (NIRS). In this study, we examined the effects of air-to-air combat maneuvering on COS. METHOD: Six F-15 fighter pilots performed 2-vs.-1 air-to-air combat one to three times in each of eight sorties. We took continuous measurements of the pilots' in-flight COS using a commercial NIRS system. We measured the direct effects of G-forces on COS as evidenced by relative concentrations of oxy- and deoxy-hemoglobin. RESULTS: With respect to the G-levels reached during air combat maneuvering (Gz range of -0.4 to + 9.5), oxyhemoglobin concentration (O2Hb) and tissue oxygenation index (TOI, the ratio of oxygenated to total tissue hemoglobin) decreased with increasing G-forces during aerial combat maneuver (ACM). Maximum changes in relative O2Hb ranged from -4.2 to -26 micromol x L(-1). Subjects' experience as measured by total fighter time was an independent determinant of the magnitude of decrease in relative oxygenation. CONCLUSIONS: 1. Pilots' COS declined with dynamic G-forces experienced under aerial combat conditions. 2. Fighter pilots with more flying hours maintained a higher cerebral oxygen level at the same level of G-forces than pilots with less flying time. 3. NIRS technology in the form of the NIRO-300G has matured for continuous monitoring of in-flight cerebral oxygen status under vigorous field conditions.

Adult↗

PubMed2002

Changes in urinary zinc and copper with strenuous physical exercise.

BACKGROUND: Air rescue trainees in the Japan Air Self Defense Force participate in a curriculum that includes 24 wk of strenuous physical training. The trace minerals zinc and copper are directly involved in many physiologic processes that are altered by physical exercise of this sort. It has also been demonstrated that urinary excretion of catecholamines (adrenaline and noradrenaline) increases during both mental work and physical exercise. HYPOTHESIS: Air rescue trainees will exhibit changes in trace mineral excretion and catecholamine levels that vary with the type of training undertaken. METHODS: The levels of urinary zinc (Zn), copper (Cu), noradrenaline (NAd), and adrenaline (Ad) were determined in 11 air rescue trainees before and after daily training sessions for consecutive 3- or 4-d periods during four phases of the curriculum, as follows: control (Cont), classroom instruction without physical exercise; preliminary (Prelim), daily exercise sessions for increased physical strength; basic (Basic), a combination of lectures and demanding physical exercise; and simulated mountain rescue (Sim). RESULTS: The mean urinary concentrations of Zn and Cu increased significantly after sessions with physical exercise (Prelim, Basic, and Sim), but remained unchanged for Cont. The NAd levels also increased significantly after training with physical exercise. In contrast, Ad levels increased significantly after sessions in all phases, both with and without physical exercise. CONCLUSIONS: The urinary levels of Zn, Cu, NAd, and Ad rose with strenuous exertion, whereas only Ad responded to both physical and mental tasking.

Adult↗