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Ventilatory sensitivity to mild asphyxia: prone versus supine sleep position
B C Galland1, D P Bolton, B J Taylor
1Department of Paediatrics and Child Health, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin, New Zealand. barbara.galland@stonebow.otago.ac.nz
Insights
At 3 months, prone sleep position in infants impairs ventilatory responses to mild asphyxia but increases arousal, a protective factor. Newborns showed no position-dependent effects on these physiological responses.
Area of Science:
- Physiology
- Neonatal Research
- Sleep Medicine
Background:
- Infant sleep position is a critical factor in sudden infant death syndrome (SIDS) research.
- Understanding physiological responses to asphyxia is vital for infant safety.
Purpose of the Study:
- To compare the effects of prone versus supine sleep positions on infant ventilatory and arousal responses to mild asphyxia.
- To assess age-related differences (newborn vs. 3 months) in these responses.
Main Methods:
- 53 healthy infants were studied at newborn and 3 months of age during quiet sleep (QS) and active sleep (AS).
- Mild asphyxia was induced by altering inspired air (CO2 up to 5%, O2 down to 13.5%) to mimic rebreathing.
- Ventilatory asphyxial sensitivity (VAS) and arousal responses were measured and analyzed based on sleep position and state.
Main Results:
- At 3 months, prone positioning during AS significantly lowered VAS compared to supine (0.184 vs. 0.269, p=0.050).
- Infants at 3 months were twice as likely to arouse to the test compared to newborns (p=0.013).
- Prone positioning increased arousal likelihood 1.57-fold compared to supine (p=0.035).
Conclusions:
- Three-month-old infants in the prone sleep position exhibit diminished ventilatory responses to mild asphyxia, especially during AS.
- Despite reduced ventilatory sensitivity, the increased arousal observed in the prone position may act as a protective mechanism.
- Sleep position had no significant effect on ventilatory asphyxial sensitivity in newborns.
Aims:
To compare the effects of prone and supine sleep position on the main physiological responses to mild asphyxia: increase in ventilation and arousal.
Methods:
Ventilatory and arousal responses to mild asphyxia (hypercapnia/hypoxia) were measured in 53 healthy infants at newborn and 3 months of age, during quiet sleep (QS) and active sleep (AS), and in supine and prone sleep positions. The asphyxial test mimicked face down rebreathing by slowly altering the inspired air: CO(2), maximum 5% and O(2), minimum 13.5%. The change in ventilation with inspired CO(2) was measured over 5-6 minutes of the test. The slope of a linear curve fit relating inspired CO(2) to the logarithm of ventilation was taken as a quantitative measure of ventilatory asphyxial sensitivity (VAS). Sleep state and arousal were determined by behavioural criteria.
Results:
At 3 months of age, prone positioning in AS lowered VAS (0.184 prone v 0.269 supine, p = 0.050). At newborn age, sleep position had no effect on VAS. Infants aged 3 months were twice as likely to arouse to the test than newborns (p = 0.013). Placing infants prone as opposed to supine increased the chances of arousal 1.57-fold (p = 0.035).
Conclusion:
Our findings show 3 month old babies sleeping prone compared to supine have poorer ventilatory responses to mild asphyxia, particularly in AS, but the increased prevalence of arousal is a protective factor.