Rats prenatally exposed to cigarette smoke are more likely to have gasping breathing patterns after hypoxia and take longer to recover normal breathing after hypoxia at higher temperatures, investigators have found. The research suggests that prenatal exposure to cigarette smoke may affect the risk of sudden infant death syndrome (SIDS), according to a report in the June 1 issue of the American Journal of Respiratory and Critical Care Medicine.

Jonathan D. Pendlebury and colleagues from the University of Calgary in Alberta, Canada, examined breathing patterns by whole-body plethysmography in 1-week-old rat pups prenatally exposed to cigarette smoke or room air.

The researchers found that at normal ambient temperatures, hypoxia caused gasping in rats exposed to cigarette smoke but not those exposed to room air. Hypoxia caused gasping in both groups at higher temperatures, but only rats exposed to cigarette smoke had a pronounced and longer-lasting respiratory depression after hypoxia was terminated.

"We show that prenatal cigarette smoke exposure increases the likelihood of gasplike respiration and provide the first experimental evidence that the combined effects of prenatal cigarette smoke exposure and hyperthermia dramatically prolong the time required for neonates to return to eupneic breathing after hypoxia," Pendlebury and colleagues conclude. "These observations provide important evidence of how prenatal cigarette smoke exposure, hypoxic episodes, and hyperthermia might place infants at higher risk for sudden infant death syndrome."

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