PERIODIC BREATHING INDUCED ON DEMAND IN AWAKE NEWBORN LAMB

Spontaneous periodic breathing, although a common feature in fullterm and preterm human infants, is scarce in other newborn mammals. The aim of this study was to induce periodic breathing in lambs. Four 10-day- old and two <48-h-old awake lambs were instrumented with jugular cathe ters connected to an extracorporeal membrane lung aimed at controlling arterial PCO2, (Pa-CO2) Arterial PO2 (Pa-O2) was set and maintained a t the desired level by changing inspired O-2 fraction and providing O- 2 through a small catheter into the ''apneic'' lung. At a critical Pa- O2/Pa-CO2, combination, the four 10-day-old lambs exhibited periodic b reathing that could be initiated, terminated, and reinitiated on deman d. In the 2-day-old lambs with low chemoreceptor gain, periodic breath ing was hardly seen, regardless of the trials done to find the critica l PO2/PCO2 combination. We conclude that periodic breathing can be ind uced in lambs and depends on critical Pa-O2/Pa-CO2 combinations and ma turity of the chemoreceptors.