Evaluation of a Transcutaneous Oxygen and Carbon Dioxide Monitor in a Neonatal Intensive Care Department

Transcutaneous-Po₂; (tc-Po₂ (tc-Pco₂) at 44^oC and transcutaneous-Pco₂) at 38, 42, 43 and 44^oC were measured with a currently available monitoring system (TCM222, Radiometer, Copenhagen) in 64 newborn infants with severe respiratory insufficiency during the first five days of life. Tc-Pco₂ at all four temperatures correlated better with arterial blood-Pco₂ (aB-Pco₂)> than tc-Po₂ with aB-Po2. However, the sensitivity and specificity of tc-Po₂ and tc-Pco₂ were similar with regard to maintaining aB-Po₂, and aB-Pco₂ within specified limits. Tc-Pco₂ increased relatively with increasing electrode temperature by a factor which was similar to the anaerobic temperature coefficient of Po₂, in blood. The coefficient of variation of duplicate measurements was 10 % for tc-Po₂ and 5 % for tc-Pco₂. Electrode drift after an average of 3 hours patient monitoring was 2%±6% (1SD) for tc-Pco₂, and -3 %±6 % for tc-Pco₂- We conclude that tc-Po₂ and tc-Pco₂ are a valuable supplement to arterial blood gas measurements, but the variable correlation with arterial blood gas values and the electrode drifts which may occur, mean that they cannot fully replace arterial sampling.