Peripheral cardiovascular responses provide sensitive markers of acoustically induced arousal from nrem sleep

Changes in cardiovascular measures such as heart rate (HR) and pulse transit time (PTT) have been advocated as sensitive markers of autonomie arousal from sleep. In animal studies, alerting stimuli produce particularly marked skin vascular responses. We hypothesised that changes in skin vascular conductance would provide more sensitive markers of autonomie arousal during sleep than more global cardiovascular response measures such as HR and PTT. METHODS: Eleven healthy males (age 20± 1.5 (SEM) years) underwent sleep studies. EEC and beat-by-beat HR, PTT, laser Doppler fingertip skin blood flow (SBF) and finger photoplethysmogram pulse wave amplitudes (PWA) were measured. Throughout the night, auditory tones (5 sec duration, 54-90 db) or shams (recording with no tone) were presented in random order (29-69 tones and shams per subject) during NREM sleep. EEG arousals were scored according to standard criteria (ASDA) into no discernible, 3-10 or 10-15 sec duration arousals. Post-stimulus cardiovascular measurements were expressed as a percentage of the pre-stimulus mean, and response magnitudes quantified from the area under the post-stimulus response curve. The ability of each cardiovascular response measure to discriminate EEG arousals (3sec) was assessed from the area under the receiver operating characteristic (ROC) curve. RESULTS: There were no significant changes in any cardiovascular parameter following sham tones. In contrast to all other parameters, finger PWA and SBF decreased following tones that produced no discernible EEG arousal (P<0.05). A significant HR rise and decreases in all cardiovascular measures occurred with 3sec arousals, with longer duration arousals generally exhibiting larger responses. Conventional EEG arousals (>3 sec) were relatively poorly detected from HR responses (ROC area HR rise 0.737±0.033) compared to changes in SBF (0.856±0.034), PTT (0.912±0.030) and finger PWA (0.938±0.016). CONCLUSIONS: Decreases in skin vascular conductance (finger PWA and SBF) provide sensitive markers of autonomie arousal during sleep. They are at least as sensitive as PTT for detecting conventionally scored EEG arousals, and mav be more sensitive in detecting subcortical'' arousals.