Effect of maternal smoking on ventilatory responses to changes in inspiredoxygen levels in infants

Maternal smoking is a major independent risk factor for sudden infant death syndrome (SIDS). Respiratory control deficits have been implicated in SIDS . The aim of this study was to test the hypothesis that infants born to smo king mothers have reduced ventilatory responses to changes in inspired oxyg en. Smoking and nonsmoking women were recruited in midpregnancy and smoking status confirmed by measurement of urinary cotinine. To control for confou nding factors of smoking each mother-infant pair in the smoking group was m atched to a pair in the nonsmoking group for social class, maternal age and parity, feeding, birthweight, gestational age, and infant sex. Infants wer e seen overnight at approximately 10 wk of age for tests of respiratory con trol, using the alternating breath test. Ventilation was measured by respir atory inductance plethysmography and inspired and end-tidal oxygen levels w ere determined by mass spectrometry. Data were obtained from 40 infants (17 in the smoking group). Responses were similar in both groups for 10 respir atory parameters including respiratory drive and timing, and there were no significant differences. The mean end-tidal oxygen level when 40% O-2 was d elivered was an average of 1.13% higher In the smoking group (p = 0.0067), although the inspired oxygen levels were not different. In conclusion, we d id not find an independent effect of maternal smoking on respiratory contro l. The differences in end-tidal oxygen levels during the alternating breath test may represent differences in alveolar ventilation.