Pulse transit time and blood pressure changes following auditory-evoked subcortical arousal and waking of infants.
OBJECTIVE
To establish a normal range of data in 3-month-old infants in relation to changes in cardiovascular measurements, with particular reference to pulse transit time (PTT), following subcortical arousals and awakenings from sleep.


METHODS
Prospective study.


METHODS
Sleep laboratory, Dunedin Hospital


METHODS
Twenty healthy infants aged 9-12 weeks.


METHODS
Nap studies were performed using a standard polysomnographic setup with the addition of a Portapres blood pressure (BP) cuff (wrist application) and a piezoelectric sensor on the foot. PTT was measured from the ECG-R waveform to the arrival of the pulse peripherally. Infants were exposed to white noise from 50 to 100 dB at 10 dB intervals within REM and NREM sleep.


RESULTS
Awakening thresholds were higher (P = 0.01) in NREM (>90 dB) than REM sleep (mean +/- SD; 74.3 +/- 9.4dB). Subcortical thresholds were always 10 dB below waking thresholds. Following awakening, there was an immediate increase in HR, SBP, and DBP of 21%, 14%, and 17%, respectively, and a 13% decrease in PTT returning to baseline within 25-30 seconds. PTT at baseline measured 140 +/- 11 and 139 +/- 9 msec in NREM and REM sleep, respectively, and decreased approximately 20 msec with waking. PTT changes were negatively correlated with heart rate (HR) but not BP, although a trend was evident.


CONCLUSIONS
At 3 months of age, infants provoked to arouse from sleep showed PTT changes that inversely mimicked BP trends, suggesting that PTT could be useful in infant studies as a marker for autonomic perturbations that occur during sleep in both clinical and research settings.
Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand. barbara.galland@otago.ac.nz
Barbara C
BC
Galland
Evan
E
Tan
Barry J
BJ
Taylor
D001143:Arousal / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D010100:Oxygen / Q000378:metabolism; D017286:Polysomnography; D011446:Prospective Studies; D012895:Sleep, REM / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*
D010100:Oxygen