PERIODIC BREATHING OF PREMATURE INFANTS.

Twenty-two premature infants, classified by breathing pattern, were studied on 47occasions with measurements of end-tidal carbon dioxide tensions and arterial P CO 2 , pH, and bicarbonate. The average arterial pH of 7.444±0.015 during periodic breathing was significantly higher than the pH of 7.396±0.012 during regular breathing (p CO 2 of the periodic group, based on end-tidal P CO 2 measurements, was estimated to be 3 or 4 mm. Hg lower than Pa CO 2 during regular breathing. The evidence suggests that there is minimal hyperventilation during periodic breathing. Premature infants breathing regularly are able to maintain a pH close to 7.40. During periodic breathing there is a cyclic change in alveolar P CO 2 of at least 6 or 7 mm. Hg. If the respiratory center responded to a change in P CO 2 as well as to the mean level of P CO 2 this could account for the slight hyperventilation. The babies appeared more wakeful during periodic breathing, could abruptly change from one breathing pattern to another, and regular breathing began at a postconceptual age of about 40 weeks. These observations suggest that the mechanism of periodic breathing may be related to a maturation phenomenon possibly associated with the central nervous system.