Objective. The risk of becoming a victim of sudden infant death syndrome is increased in infants who sleep with their face under bedding items. The present study was designed to evaluate auditory arousal thresholds of infants who sleep with their face covered by bedclothes.

Methods. Twenty healthy infants with a median age of 11.5 weeks (range: 4–22 weeks) were recorded polygraphically for 1 night. Although they slept in their usual supine position, a bed sheet was placed over their face for 60 minutes. Fifteen of the 20 infants were chosen at random and were exposed to white noises of increasing intensities to determine their auditory arousal thresholds. All infants were challenged with the face covered and with the face free during both rapid eye movement (REM) and non-REM (NREM) sleep. Seven infants were first challenged with the face covered, and 8 were challenged with the face free. The following variables were recorded simultaneously: electroencephalogram, breathing and heart rates, and rectal and pericephalic temperatures. In 5 infants who were not exposed to the auditory challenges, end tidal CO2 was recorded for 30 minutes while sleeping with the face covered.

Results. During REM sleep, arousals occurred for significantly more intense auditory stimuli when the infant’s face was covered than when free. No significant difference was seen in NREM sleep. Compared with the face-free periods, the face-covered sleep periods were characterized by greater rectal and pericephalic temperatures, a greater density of body movements, and a decrease in NREM sleep. Respiratory frequency was increased during the face-covered periods in both REM and NREM sleep. No differences were seen in the frequency or duration of apnea. There was a tendency for heart rate to increase during both sleep stages when the face was covered, compared with the face-free periods, but the changes were not statistically significant. A positive correlation was found between pericephalic temperatures and arousal thresholds (r = 0.60) during REM sleep. End tidal CO2 values increased when the face was covered, reaching a maximum value during the first 5 minutes of the experiment. No fall in oxygen saturation was seen.

Conclusions. Covering the infant’s face with a bed sheet was associated with a significant increase in auditory arousal threshold. The finding could be related to an elevation in temperatures within the infant’s microenvironment.

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