Some characteristics of transcutaneously monitored oxygen partial pressure in normal newborns.

The transcutaneous oxygen partial pressure (PtcO2) was monitored in 50 healthy, normally and spontaneously delivered newborns. Measurements were performed during the first to fourth day of life. The electrode temperature was 44.5 degrees C. The mean PtcO2 level recorded during about 45 min was 9.2 kPa (S.D. 1.4) recorded from the minute-to-minute values. The PtcO2 level normally oscillated to a certain extent and the oscillations were closely related to the breathing pattern of the patient. When the patient fell asleep during measurement, the normal oscillating pattern was replaced by a "silent pattern". During crying, the PtcO2 level showed four main reaction aptterns. A decrease in the PtcO2 level could be observed during breast-feeding. One child, recently fed, vomited a small amount of breast milk after a short period of crying and apparently had a laryngospasm, shown by a sudden drop in the PtcO2 level without any other signs of discomfort. The study shows that PtcO2 (and thus also PaO2) very sensitively reacts to changes in activity. This implies that earlier used methods for determination of PaO2 might give values that are not representative for the steady state as the sampling method per se might influence the recorded PO2 value.