Effects of hot bath immersion on autonomic activity and hemodynamics - Comparison of the elderly patient and the healthy young

Hot bathing has been associated with sudden death and so the present study investigated its effects on autonomic activity and hemodynamics in the elde rly patient and the healthy young by analyzing heart rate variability (HRV) , Subjects were 9 elderly men (mean age, 75 years) and 9 young men (mean ag e, 27 years), who were immersed up to shoulder level while in a sitting pos ition for 10 min with the bath temperature at 40 degreesC. Blood pressure ( BP) and heart rate (HR) were monitored. BP in the young decreased during ba thing (p<0.01), whereas in the elderly BP had a maximum value just at the s tart of immersion (p<0.05) with a slight decline at 4 min after the start o f immersion. Although HR in the young increased (p<0.01), in the elderly th ere was an abrupt increase in HR just at the start of immersion (p<0.05), f ollowed by a decrease in HR. With regard to HRV, the high-frequency (HF) co mponent in the young men was suppressed during immersion (p<0.01), but was unaffected in the elderly. The LF (low frequency)/HF ratio in the elderly d ecreased at 4 min (p<0.05). In conclusion, hypotensive syncope may cause su dden death by drowning during hot bathing, and is a consequence of the decr ease in sympathetic tone that develops approximately 4 min after immersion.