Inspired CO2 and O-2 in sleeping infants rebreathing from bedding: relevance for sudden infant death syndrome

Citation
Al. Patel et al., Inspired CO2 and O-2 in sleeping infants rebreathing from bedding: relevance for sudden infant death syndrome, J APP PHYSL, 91(6), 2001, pp. 2537-2545
Citations number
43
Categorie Soggetti
Physiology
Journal title
JOURNAL OF APPLIED PHYSIOLOGY
ISSN journal
87507587 → ACNP
Volume
91
Issue
6
Year of publication
2001
Pages
2537 - 2545
Database
ISI
SICI code
8750-7587(200112)91:6<2537:ICAOIS>2.0.ZU;2-T
Abstract
Some infants sleep facedown for long periods with no ill effects, whereas o thers become hypoxemic. Rebreathing of expired air has been determined by C O2 measurement; however, O-2 levels under such conditions have not been det ermined. To evaluate this and other factors influencing inspired gas concen trations, we studied 21 healthy infants during natural sleep while facedown on soft bedding. We measured gas exchange with the environment and bedding , ventilatory response to rebreathing, and concentrations of inspired CO2 a nd O-2. Two important factors influencing inspired gas concentrations were 1) a variable seal between bedding and infants' faces and 2) gas gradients in the bedding beneath the infants, with O-2-poor and CO2-rich air nearest to the face, fresher air distal to the face, and larger tidal volumes being associated with fresher inspired air. Minute ventilation increased signifi cantly while rebreathing because of an increase in tidal volume, not freque ncy. The measured drop in inspired O-2 was significantly greater than the a ccompanying rise in inspired CO2. This appears to be due to effects of the respiratory exchange ratio and differential tissue solubilities Of CO2 and O-2 during unsteady conditions.