RESUMO
OBJECTIVE: To investigate whether the prone sleeping position impaired arousal from sleep in healthy infants and whether this impairment was related to cardiorespiratory variables, temperature, or age. STUDY DESIGN: Healthy term infants (n = 24) were studied with daytime polysomnography on 3 occasions: 2 to 3 weeks after birth, 2 to 3 months after birth, and 5 to 6 months after birth. Multiple measurements of arousal threshold (cm H(2)O) in response to air-jet stimulation applied alternately to the nares were made in both active sleep and quiet sleep when infants slept both prone and supine. RESULTS: Arousal thresholds were significantly higher in both active sleep and quiet sleep when infants slept prone at 2 to 3 weeks and 2 to 3 months, but not at 5 to 6 months. These increases were independent of any sleep position-related change in either rectal or abdominal skin temperature, respiratory rate, oxygen saturation, or heart rate. CONCLUSIONS: The prone position significantly impairs arousal from both active sleep and quiet sleep in healthy term infants. This impairment in arousability occurred with no clinically significant changes in cardiorespiratory variables or body temperature. Decreased arousability from sleep in the prone position provides an important insight into its role as a risk factor for sudden infant death syndrome.