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Published on: October 19, 2013
Ventilatory response to hypercarbia in newborns of smoking and substance-misusing mothers
Kamal Ali1, Kim Wolff, Janet L Peacock
11 Division of Asthma, Allergy, and Lung Biology, Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma.
Rationale:
Infants of mothers who smoked (S) or substance misused (SM) during pregnancy have an increased risk of sudden infant death syndrome (SIDS).
Objectives:
To test the hypothesis that infants of S and SM mothers compared with infants of non-substance-misusing, nonsmoking mothers (control subjects) would have a reduced ventilatory response to hypercarbia and that any reduction would be greater in the SM infants.
Methods:
Infants were assessed before maternity/neonatal unit discharge. Maternal and infant urine samples were obtained and tested for cotinine, cannabinoids, opiates, amphetamines, methadone, cocaine, and benzodiazepines.
Measurements And Main Results:
Respiratory flow and Vt were measured using a pneumotachograph inserted into a face mask placed over the infant's mouth and nose. The ventilatory responses to three levels of inspired carbon dioxide (0 [baseline], 2, and 4% CO2) were assessed. Twenty-three SM, 34 S, and 22 control infants were assessed. The birth weight of the control subjects was higher than the SM and S infants (P = 0.017). At baseline, SM infants had a higher respiratory rate (P = 0.003) and minute volume (P = 0.007) compared with control subjects and S infants. Both the SM and S infants had a lower ventilatory response to 2% (P < 0.001) and 4% (P < 0.001) CO2 than the control subjects. The ventilatory response to CO2 was lower in the SM infants compared with the S infants (P = 0.009).
Conclusions:
These results are consistent with infants of smoking mothers and substance misuse/smoking mothers having a dampened ventilatory response to hypercarbia, which is particularly marked in the latter group.
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