THE VENTILATORY RESPONSE TO CARBON-DIOXIDE IN HIGH-RISK INFANTS

Purpose: To examine the ventilatory response to inspired carbon dioxide in infants considered to be at risk for sudden infant death syndrome or apnea. Design: Clinical data measurement. Setting: Infant apnea evaluation program of a university division of neonatology. Patients: Fifty nine infants were full term characterized by the following diagnoses; siblings of infants who had died from sudden infant death syndrome (SIDS) (n=7), apparent life threatening event (ALTE) (n=24), apnea/cyanosis in the newborn nursery (n=21), and controls [7]. Sixty-nine infants were preterm and consisted of patients suffering from idiopathic apnea (n=61), and bronchopulmonary dysplasia (n=8). Measurements: The ventilatory response to carbon dioxide was measured with a computerized waveform analyzer. Main results: Among full term infants no significant differences in the ventilatory slope in response to CO2 was seen. The range of mean slope was 19.4+/-7.6 in siblings of SIDS and 36+/-17 in control infants. Greater number of sibling of SIDS had slopes less than 20 ml/kg/min/mmHg in comparison to control infants. Sibling of SIDS had less increase in minute ventilation and inspiratory flow in response to CO, administration in comparison to control infants. Preterm infants had similar slopes with a mean of 33 ml/kg/min/mmHg in infants with idiopathic apnea and 28 ml/kg/min/mmHg in infants with bronchopulmonary dysplasia. Conclusions: The large intragroup variability in the ventilatory response to inspired CO2, confirming previously reported data, compromises the benefit of this test. Thus, ventilatory response to CO, administration is not useful in unselected patients at risk of SIDS or apnea.