Comparison of Arterial Oxygen Tension with Continuous lranscutaneous and Intravascular P02 Sensors and Intermittent Blood Samples Taken from the Sampling Port of a Bubble Oxygenator

____________ _ Measurements of transcutaneous POz (tc POz), intraarterial P02(P;02) and P02 of blood samples taken from the sampling port of the oxygenator (PoOz) were compared with arterial blood P02 (PaOz) in 16 adult patients undergoing cardiopulmonary bypass. tcP02 and Pi02 were recorded continuously using Roche-Kontron electrodes. Po02 and PaOz were measured intermittently on a Radiometer ABLz blood gas analyser. A total of 86 observations were made on the 16 patients. The correlation coefficient (r) between transcutaneous and arterial P02 was 0.69 (p<0.001 ). The relationship between Po02 and Pa02 was poor (r = 0.45, p<O.Ol). The intra-arterial electrode readings showed no significant difference with the POz measured on arterial blood samples (r=0.99, p<0.001). Introduction ____________ _ The measurement of the arterial blood oxygen tension (Pa02) is a routine part of the assessment of patients' *Present address, Dr. S V S Rithalia, Scientific Officer, Department of Orthopaedic Mechanics, University of Salford, Salford M5 4WT, UK, Tel 061 736 5843 Ex 7386 Volume 20, Number 4, Winter 1988 oxygenation while undergoing open heart surgery. Samples for blood gas analysis are usually withdrawn from the sampling port of the oxygenator provided for this purpose. The Pa02 changes rapidly during cardiopulmonary bypass (CPB) and the variations can only be detected by frequent or continuous monitoring. The current methods, based on intermittent blood sampling, have inherent limitations related to the frequency with which samples can be taken, their storage and their processing before analysis. However, with the development of transcutaneous P02(tcP02) sensors (1 ,2) and intra-arterial P02(Pi02) electrodes (3,4) it has become possible to monitor Pa02 continuously. This study compares tcP02 , Pi02 and P02 of blood samples taken from the sampling port of the oxygenator (Po02) with arterial blood P02 in adult patients. Materials and Methods ________ _ Measurements were made in 16 adult patients (Table 1) whose ages ranged from 37 to 76 years (mean± SD, 53.8 ± 9.9). They were undergoing normothermic cardiopulmonary bypass for valvular or coronary arterial surgery. The extracorporeal circuit consisted of a Bentley BOS-10 bubble oxygenator" and a Gambro (Model H-10) a Bentley Laboratories Inc, Irvine, CA 92714, USA The Journal of Extra-Corporeal Technology 119