A clinical evaluation of a monitor for inline measurement of pO2, pCO2 and pH during cardiopulmonary bypass

Abstract

The Gas STAT is a monitor which continuously measures pO2, pCO2 and pH inline during cardiopulmonary bypass. A clinical evaluation of the inline monitor compared to the standard method of monitoring, that is, intermittent isolated blood sampling and distant measurement on a blood gas analyser (BGA), was undertaken. During stable moderate hypothermia, 115 paired measurements were made in 54 patients undergoing coronary artery or heart valve surgery. The correlations between pO2, pCO2 and pH, as measured by the BGA and the inline monitor, were respectively 0.536 ( P<0.001), 0.811 ( P<0.001) and 0.826 ( P<0-001). pCO2 as measured by the inline monitor was significantly lower than the BGA ( P<0.001 ) whereas pH was significantly higher ( P<0.001). There was no significant difference between pO2 measurements. Possible explanations for the finding of less than complete correlations are discussed and it is suggested that although inline monitoring is of value in the control of PO2, pCO2 and pH during cardiopulmonary bypass, it should not be used without recourse to the standard method of blood gas analysis.