A computerized system forthe study of oxygen uptake and haemodynamics during cardiopulmonary bypass

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Abstract
A computerized system which incorporated haemodynamic, temperature and arterial pH (pHa) monitoring was developed to record data and to improve temperature and pHa control during hypothermic cardiopulmonary bypass (CPB). The system was evaluated in the course of a study of haemodynamics and metabolism during CPB. It was planned to have three 10 minute periods of study in 24 patients, during which time arterial and nasopharyngeal temperatures would be maintained between 27° and 29°C and pHa between 7.38 and 7.42. Repeated recordings of haemodynamic variables, temperature and pHa were made during each period. Only 59 of a possible 72 periods were obtained due to shortage of time at stable hypothermia. The mean number of total readings was 73.5 (70.1, 77.0) and the mean number of acceptable readings was 71.2 (67.3, 75.1). Good nasopharyngeal temperature control was achieved, with all the 95% confidence intervals of the means falling within the prescribed limits. Control of arterial temperature was less good as there were five periods in which the 95% confidence intervals of the means fell outwith the prescribed range. Poor pHa control was achieved since there were 16 periods in which the 95% confidence intervals of the mean were outside the preset range. The system functioned well in recording data and resulted in good temperature control, but poor pHa control.