AMINOPHYLLINE AND INCREASED ACTIVITY OF PERIPHERAL CHEMORECEPTORS IN NEWBORN-INFANTS

Peripheral chemoreceptor activity was studied in nine healthy, unsedat ed neonates (with a mean (SD) postconceptional age of 39 (2) weeks and birth weight of 3000 (400) g) by measuring the inhibition of ventilat ion elicited by five breaths of 100% oxygen (Dejours technique). Chang es in tidal volume, frequency, and minute ventilation were measured be fore and after administration of aminophylline (10 mg/kg by mouth). Be fore aminophylline hyperoxia induced a decrease in minute ventilation (from a mean (SE) of 825 (55) to 520 (30) ml/kg/min) as result of redu ction of tidal volume (from 12 (0.3) to 8 (0.3) ml/kg). After aminophy lline administration the hyperoxia induced decrease in tidal volume (f rom 14 (0.7) to 6 (0.3) ml/kg) and minute ventilation (from 847 (57) t o 386 (21) ml/kg/min) was significantly greater than before. It is con cluded that in neonates peripheral chemoreceptors are more active in t he presence of aminophylline. It is speculated that aminophylline incr eases the activity of peripheral chemoreceptors, reducing the breakdow n of cAMP, which is a crucial mediator for peripheral chemoreceptor di scharge.