Control of breathing in infants born to smoking mothers

Objective: To determine whether infants born to smoking mothers have an abnormal respiratory drive and a blunted ventilatory response to hypoxia. Study design: Sixty-four healthy infants, aged 2 to 24 months, were classified into smoking (n = 19) or non-smoking (n = 45) groups based on maternal smoking habits. Resting ventilation, lung function, and mouth pressure 100 milliseconds after an airway occlusion at the onset of inspiration (P-0.1) were measured. The ventilatory response to hypoxia was assessed in 15 infants (6 in the smoking group and 9 in the non-smoking group) while breathing 14% oxygen. Results: Respiratory drive (P-0.1 = 4.9 +/- 1.3 cm H2O) was lower in infants in the smoking group compared with those in the non-smoking group (P-0.1 = 5.9 +/- 1.2 cm H2O) (P < .05). The time to peak tidal expiratory flow (tPTEF) was also shorter (0.25 +/- 0.04 seconds vs 0.32 +/- 0.09 seconds, P < .05). Infants born to non-smoking mothers showed a significant ventilatory response to hypoxia and a 24.6% increase in P-0.1. Infants in the smoking group showed a blunted ventilatory response to hypoxia and no increase in P-0.1. A dose-response relationship existed between the number of cigarettes smoked by the mother (0, 1 to 10, >10 per day) and the results for P-0.1 and tPTEF. Paternal smoking had no influence on the infant's resting ventilation, respiratory drive, or ventilatory response to hypoxia. Conclusions: Infants born to smoking mothers have a reduced drive to breathe and a blunted ventilatory response to hypoxia. These findings may contribute to the increased risk of sudden infant death syndrome in these infants.