Autonomic Nervous System and Oxygen Metabolism of the Brain during Bathing

The dynamic state of circulation during bathing has been studied yet there are very few reports on the dynamic state of blood circulation of blood vessels in the brain. Research on blood flow in the brain has developed through the invention and use of a near-infrared monitoring device (NIRO). We conducted research on heart rate variability (HRV) and oxygen metabolism in brain tissue of the frontal lobe during bathing. We measured the electrocardiogram and blood pressure. The NIRO monitoring device was attached to the subject's frame. The subject then bathed for 20 minutes. Simultaneously with the electrocardiogram, the oxidization hemoglobin concentration of a NIRO monitoring device and TOI were recorded on the data recorder. Quantitative evaluation, statistical handling, and spectrum analysis of data were performed. The data for the 10 minutes before bathing were compared with the data for the 10 minutes after bathing. During measurement, the blood circulation dynamic state was stabilized and the heart rate and blood pressure were maintained within a normal range. The heart rate increased significantly during bathing, while blood pressure decreased significantly. Although HF of heart rate variability increased slightly during bathing, it was not significant. Although LF/HF increased slightly during bathing, it was not significant. Our research found that blood pressure falls during bathing and the heart rate increases. This is considered due to the peripheral blood vessel being opened by bathing. If a peripheral blood vessel opens, blood vessel resistance will fall. To maintain blood pressure, the heart rate goes up. If the heart rate goes up, cardiac output increases. If cardiac output increases, blood pressure returns. Autonomic nerves play an active part in this process. HF and LF/HF increased slightly. This data supports this reaction. O ₂Hb and TOI increased slightly during bathing. This result suggests an increase in brain blood flow. Intellectual activity was not carried out during bathing. It is considered that O ₂Hb increased because supply increased. The result of TOI also supported this consideration. Intracerebral bleeding during bathing may originate in the increase in blood flow. The fall of blood pressure may be desirable. If blood pressure falls, brain blood flow will fall in those who have arteriosclerosis in a brain artery. The fall of a brain blood flow relates to cerebral infarction. Sick people need to be cautious when bathing.