Noninvasive cardiovascular markers of acoustically induced arousal from non-rapid-eye-movement sleep.
OBJECTIVE
Changes in cardiovascular measures such as heart rate (HR) and pulse transit time (PTT) have been advocated as sensitive markers of autonomic arousal from sleep. In animal studies, alerting stimuli produce particularly marked skin vascular responses. We hypothesized that changes in skin vascular conductance would provide more sensitive markers of autonomic arousal during sleep compared to central cardiovascular response measures such as HR and PTT.


METHODS
Cardiovascular responses to auditory-induced arousals were recorded during overnight sleep studies.


METHODS
Sleep disorders unit in a 270-bed teaching hospital.


METHODS
Eleven young healthy male subjects.


METHODS
Throughout ovemight sleep studies, auditory tones (5-second duration, 54-90 decibels, 22-56 per subject) were presented during non-rapid-eye-movement sleep. Beat-by-beat HR, PTT, laser-Doppler fingertip skin blood flow (SBF) and finger and ear photoplethysmogram pulse wave amplitudes (PWA) were measured in the 20 seconds preceding and 30 seconds following each tone and compared to control measurements obtained during 50-second periods of recording with no stimulus (no tone, 6-22 per subject). Electroencephalographic (EEG) arousals were scored according to standard criteria (American Sleep Disorders Association) into no discemible, 3- to 10-second duration, or 10- to 15-second duration arousals. Poststimulus cardiovascular measurements were expressed as a percentage of the prestimulus mean and response magnitudes quantified from peak responses and the area under the poststimulus response curve. The ability of each cardiovascular response measure to discriminate EEG arousals (EEG changes lasting more than 3 seconds) was assessed from the area under the receiver operating characteristic (ROC) curve.


RESULTS
There were no significant changes in any cardiovascular parameter during control recordings. 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 greater than 3-second arousals, with longer duration arousals generally exhibiting larger responses. Conventional EEG arousals (greater than 3 seconds) were relatively poorly detected from HR responses (ROC area HR rise 0.80 +/- 0.04) compared to changes in SBF (0.85 +/- 0.02), PTT (0.85 +/- 0.03) and finger PWA (0.90 +/- 0.01).


CONCLUSIONS
Decreases in skin vascular conductance (finger PWA and SBF) provide sensitive markers of autonomic arousal during sleep. They are at least as sensitive as PTT for detecting conventionally scored EEG arousals and may be more sensitive in detecting "subcortical" arousals.
Catcheside
Peter G
PG
Sleep Disorders Unit, Repatriation General Hospital, Daw Park, South Australia, Australia. peter.catcheside@rgh.sa.gov.au
Chiong
Siau Chien
SC
Mercer
Jeremy
J
Saunders
Nicholas A
NA
McEvoy
R Douglas
RD
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001143:Arousal / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012894:Sleep Stages / Q000502:physiology*; D013997:Time Factors