Background: Term newborns can compensate fully for an imposed dead space (tube breathing) by increasing their minute ventilation.
Objective: To test the hypothesis that infants of smoking mothers would have an impaired response to tube breathing.
Design: Prospective study.
Setting: Perinatal service.
Patients: Fourteen infants of smoking and 24 infants of non-smoking mothers (median postnatal age 37 (11–85) hours and 26 (10–120) hours respectively) were studied.
Interventions: Breath by breath minute volume was measured at baseline and when a dead space of 4.4 ml/kg was incorporated into the breathing circuit.
Main outcome measures: The maximum minute ventilation during tube breathing was determined and the time constant of the response calculated.
Results: The time constant of the infants of smoking mothers was longer than that of the infants of non-smoking mothers (median (range) 37.3 (22.2–70.2) v 26.2 (13.8–51.0) seconds, p = 0.016). Regression analysis showed that maternal smoking status was related to the time constant independently of birth weight, gestational or postnatal age, or sex (p = 0.018).
Conclusions: Intrauterine exposure to smoking is associated with a dampened response to tube breathing.
- MMV, maximum minute ventilation
- MV, minute volume
- respiratory control
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Published Online First 5 May 2005
Competing interests: none declared
This study was approved by the King’s College Hospital Ethics Committee.
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