Continuous comparison of transcutaneous and arterial oxygen tension in newborn infants with respiratory illnesses.

Transcutaneous oxygen tension (tcPO2) measured by two skin electrodes of different design, and arterial oxygen tension (PaO2) measured by an intravascular oxygen electrode, were continuously compared for periods of 6--27 h in 45 newborn infants with respiratory illnesses. One skin electrode (Dräger) had three microcathodes surrounded by a heated ring-shaped anode and the other (Roche) a large heated cathode. The electrodes were calibrated in vitro; 44 degrees C was found to be a suitable electrode temperature for the estimation of Pao2. tcPo2 recorded by the electrode with the microcathodes estimated Pao2 reasonably accurately for 6 h without the necessity for re-siting. tcPao2 recorded by the electrode with the large cathode gave a similar estimate of Pao2 for 3 h, but then tcPao2 often fell relative to Pao2. This fall was probably caused by skin changes at the electrode site. Poor skin perfusion causing underestimation of Pao2 by tcPo2 could not be identified by a number of methods tried.