ABSENCE OF VENTILATORY RESPONSES TO ALTERNATING BREATHS OF MILD HYPOXIA AND AIR IN INFANTS WHO HAVE HAD BRONCHOPULMONARY DYSPLASIA - IMPLICATIONS FOR THE RISK OF SUDDEN INFANT DEATH

Infants who have had bronchopulmonary dysplasia (BPD) are at an increa sed risk of sudden infant death syndrome. Because failure of the cardi orespiratory response to hypoxia is suggested to play a key role in su dden infant death syndrome, we tested the hypothesis that infants who have had BPD have a reduced respiratory chemoreflex response to hypoxi a. We examined the reflex respiratory responses to breath-by-breath al ternations in fractional inspired oxygen concentration in eight infant s who had had BPD (mean gestation = 27 wk, mean postnatal age = 93 d) who were no longer on supplemental oxygen and compared the responses w ith those of 12 preterm infants who had not required supplemental oxyg en or been mechanically ventilated since birth (mean gestation = 30 wk , mean postnatal age = 38 d). For test runs we alternated fractional i nspired oxygen concentration through two gas delivery lines between 0. 21 anti 0.16 on a breath-by-breath basis, and for control runs we alte rnated the inspirate between the two gas lines with a fractional inspi red oxygen concentration of 0.21 in each. Respiration was measured usi ng inductance plethysmography. Infants with BPD showed no significant differences between test and control responses for any respiratory var iable. In contrast, all respiratory variables in the preterm infants s howed test responses significantly greater than control. We speculate that the ''blunted'' chemoreflex respiratory response seen in infants with BPD may predispose them to subsequent respiratory failure, but we do not know which component of the chemoreflex is impaired.