Prenatal cigarette smoke exposure attenuates recovery from hypoxemic challenge in preterm infants.
BACKGROUND
The effects of prenatal cigarette smoke (CS) exposure and hypoxemia on cardiorespiratory control have been investigated in full-term infants. However, few data are available in preterm infants, who form a particularly vulnerable population, with developmentally immature cardiorespiratory control.


OBJECTIVE
To investigate the effects of prenatal CS exposure on the duration and recovery of breathing pauses and oxygen saturation levels under baseline and hypoxemic conditions in preterm infants.


METHODS
The study was performed on 22 (12 born to smoking and 10 to nonsmoking mothers) spontaneously breathing preterm infants between 28 and 36 weeks' gestation. Cardiorespiratory variables were recorded under baseline normoxemic and hypoxemic conditions.


RESULTS
Breathing pauses, pause indices, time to recovery, percent pause recovery, oxygen saturation (Sp(O2)), periods of wakefulness, and cardiorespiratory rates were compared between the two groups. Spontaneous recovery of breathing pauses (P = 0.03) and Sp(O(2)) levels (P = 0.017) were attenuated in CS-exposed infants as compared with the control group during the hypoxemic and posthypoxemic periods, respectively. The episodes of wakefulness during the hypoxemic challenge were similar between the two groups. Furthermore, CS-exposed infants showed a greater increase in heart rate (P < 0.001) during the hypoxemic challenge when compared with control infants.


CONCLUSIONS
We provide evidence of how prenatal CS exposure and hypoxemic episodes affect the duration and recovery of breathing pauses in preterm infants. These observations could help explain why these infants are at a particularly high risk for sudden infant death syndrome.
Department of Pediatrics and Institute of Maternal and Child Health, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
Jennifer
J
Schneider
Ian
I
Mitchell
Nalini
N
Singhal
Valerie
V
Kirk
Shabih U
SU
Hasan
D000328:Adult; D000704:Analysis of Variance; D001049:Apnea / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012075:Remission, Spontaneous; D012129:Respiratory Function Tests; D012907:Smoking / Q000009:adverse effects*; D013398:Sudden Infant Death
D010100:Oxygen