Heart rate changes during sleep in response to experimental thermal (nociceptive) stimulations in healthy subjects

Objective: During wakefulness, nociceptive thermal stimulation can trigger a rapid and transient rise in heart rate (HR). During sleep, HR variations are different across sleep stages; HR is more variable in stage 2 and in RE M than in stages 3 and 4. The aim of this study was to assess the HR respon se to experimental thermal stimulation during different sleep stages. Methods: Eight young subjects free of sleep and pain problems, underwent a night of polysomnographic recording during which experimental thermal stimu lations were applied. During all sleep stages (St), a series of cold, warm/ control and heat pain stimulations were applied over the shoulder skin by m eans of a water-driven system. Variation of HR interval was measured for 6 s before and for 6 s during the thermal stimulation. Results: In comparison to control warm stimulation, experimental nociceptiv e thermal stimulation induced a significant rise in HR during sleep; HR inc reased by 7% in St 2, 5.4% in St 3&4, and by 4.3% in REM sleep. Conclusion: The brief increase in cardiac activity with experimental nocice ptive stimulation suggests that during sleep, the autonomic-cardiac nervous system remains reactive to external sensory inputs and is part of the phys iological response to preserve body safety and sleep integrity in the face of potentially harmful stimulation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.