During cardiopulmonary bypass, the perfusionist maintains physiological parameters laid down in protocols; this is his or her performance capability. In order to assess his or her performance we need to be able to analyse these physiological parameters objectively. We defined six parameters, pH, BE, PaCO2, PaO2, ACT and oesophageal temperature and gave them ideal values of 7.40+/-0.05, 0.0+/-2.5 mmol/l, 39.0+/-3.0 mmHg, 150+/-50 mmHg, 540+/-60 s and 37.2+/-0.2 degrees C, respectively. We established ranges and a score system: +/- one standard deviation of the mean for a score of zero; between +/- one and two standard deviations for a score of one; and greater than +/- two standard deviations for a score of two. We captured and analysed the most outlying value, with respect to known normal values, for each parameter recorded on the pump sheet. This was performed for 100 consecutive patients. Mean +/- standard deviation (medians) values for pH, BE, PaCO2, PaO2, ACT and oesophageal temperature were 7.41+/-0.07 (7.41), -1.85+/-2.37 mmol/l (-1.85 mmol/l), 34.6+/-5.42 mmHg (34.0 mmHg), 320+/-96.2 mmHg (317 mmHg), 558+/-164 s (503 s) and 37.3+/-0.5 degrees C (37.4 degrees C), respectively. We then analysed what percentage of our 100 patients fell within each score range for each of the six parameters. This is an efficient means in analysing whether the perfusionist abides by the protocols, what quality is supplied to the patient, does he or she react when he or she is faced with parameters that are out of range and finally advocating in-line blood gas monitoring. This is another step towards our goal of total quality management.