A "virtual" blood gas electrode for use during cardiopulmonary bypass.

We describe the development of a “virtual” blood gas electrode system intended for use during cardiopulmonary bypass (CPB). The electrode functions in real time and predicts the patient’s arterial and mixed venous blood gas results every 500 ms. It takes as its primary inputs the settings of the heart-lung machine (FiO2, sweep gas rate, pump flow) and the patient’s hematocrit and metabolic rate. The electrode system incorporates integrated computer models of the oxygenator in use during the case and the patient’s arterial, venous, and tissue pools. The architecture of the model is a development of that described by Dickinson (1) and is shown schematically in Figure 1.