CONTINUOUS MONITORING OF PO 2 IN NEONATES WITH APNEA

Recurrent apnea of prematurity was studied in 8 infants (weight 950-1800 gm) with the Huch transcutaneous PO2 electrode during the first month of life (mean age = 10 d). Thirteen uncomplicated apneic episodes (duration 10-50 sec, mean = 22 sec) were analyzed. In all the infants studied apnea occurred following a stable period of at least 60 seconds at a mean PO2 of 75 mmHg (range 48-92 mmHg). After the onset of apnea PO2 fell(log time = 8 sec) and continued to fall after the reestablishment of respiration (delay time = 33 sec). The PO2 recovery to a stable value was much slower (mean time = 164 sec). The mean PO2 decreased from the initial value of 75 mmHg to 62 mmHg at the end of apnea and continued to fall to a mean minimum of 45 mmHg. The mean initial rate of fall was 2.3 mmHg/sec. The recovery was characterized by an initial rate of increase of 1.6 mmHg/sec followed by a period of slower increase at 1 mmHg/sec. The rate of fall of PO2 did not correlate significantly with initial PO2, lag time, birthweight or mode of respiratory support. There was a significant negative correlation of rate of fall with speed of recovery and with recovery time (p < .05). Thus apnea of prematurity does not seem to be preceded by hypoxemia; PO2 continues to fall for a prolonged interval after the onset of respiration; and the initial rate of fall of PO2 is more rapid than the rate of increase after the end of apneo.