ABSTRACT
Frequently occurred sudden deaths in the bath have become to serious problem in Japan. Sudden death in the bath possibly concerned with neurally mediated syncope. During and after bathing, bather is possibly tended to occur orthostatic intolerance by thermal stress to the circulatory dynamics. The experiment was performed focused on changes in cerebral and cardiovascular hemodynamics by postural change in the bathing to discuss the safe way of bathing.<br>On 9 healthy young subjects, 41±1°C bathing was performed 15 minutes, change in oxidized hemoglobin (ΔOxyHb) on the forehead as an indicator of cerebral blood flow was monitored by near-infrared spectroscopy method at interval of 0.5s through the experiment. In sitting and upright position, blood pressure and heart rate were measured before bathing, at 5 minutes, 10 minutes and 15 minutes (upright with head down) after immersion and after bathing.<br>Some subjects felt dizziness at upright during and/or after bathing. It suggests that orthostatic stress under heat stress is implicative even for healthy young. ΔOxyHb for subjects with dizziness at upright during bathing is significant lower below the baseline than it for subject without dizziness.<br>Degrees of depression of systolic blood pressure, elevation of heart rate and depression of cerebral blood flow by standing at 10 minutes after starting immersion were significant larger than their values before bathing. Degree of elevation of heart rate and depression of cerebral blood flow by standing with head down were significant smaller than their value at standing without head down. It suggests that upright with head down reduce the orthostatic stress to the cerebral and cardiovascular hemodynamics.