TRANSCUTANEOUS MONITORING OF BLOOD-GASES - IS IT COMPARABLE WITH ARTERIALIZED EARLOBE SAMPLING

Researchers are increasingly looking for reliable non-invasive methods of assessing blood gas concentrations, and several new techniques hav e recently become available. Values derived using arterialized earlobe samples have been found to be comparable with conventional arterial s amples and recent studies have compared transcutaneous blood gas analy sis with the traditional arterial samples and found a reasonable level of agreement in particular for the partial pressure of carbon dioxide . There are no data comparing oxygen and carbon dioxide partial pressu res (pO(2), pCO(2)) derived from arterialized samples with one of the newer transcutaneous techniques. We therefore simultaneously studied a rterialized earlobe blood gas samples and values for pO(2) and pCO(2) obtained by a transcutaneous monitor (TINA, Radiometer, Copenhagen) in 26 subjects with varying blood gas values. There was a close agreemen t between the two methods for assessment of pCO(2) [mean difference (9 5% C.I.) between transcutaneous and earlobe values 0.25 kPa (-0.004, 0 .5 kPa)], but not for pO(2) [1.71 kPa (0.35, 3.07 kPa)]. Similarly, th e limits of agreement were narrow for pCO(2) compared to those for pO( 2) (-0.98, 1.47 kPa and -6.44, 3.02 kPa respectively). We conclude tha t transcutaneous measurement of pCO(2) using the TINA is acceptable in the research setting, whereas assessment of pO(2) cannot reliably be made using this technique.