Evaluation of a new real continuous cardiac output pulmonary artery catheter
© Current Science Ltd 2000
Published: 12 June 2000
None of the currently available pulmonary artery (PA) catheters allows instantaneous and continuous measurement of pulmonary blood flow. At best, the so-called continuous cardiac output (CO) catheters (and associated software) indicate continuously an averaged value of CO measured over several minutes. A new catheter has been introduced recently, and animal experiments have shown that it allows instantaneous detection of changes in pulmonary blood flow. In this catheter, blood flow is derived from the power required to maintain a temperature gradient between two thermistors that are insulated differently. The technology also allows the clinician to measure CO using the standard thermodilution technique. The aim of the present study was to demonstrate the clinical safety and efficacy of this new PA catheter.
After local research ethics committee approval and informed consent, 20 patients undergoing elective coronary artery bypass grafting were enrolled in this study. The TruCCOMS PA catheter (Aortech International, Bellshill, Scotland) was floated after induction of anaesthesia, through a 9 Fr introducer. CO was measured continuously after arrival in the intensive care unit and for a period of up to 20 h. CO was also determined by using a standardized thermodilution technique at a minimum of 10 time points (as the average of up to six thermodilution curves), each separated by at least 1 h. Haemodynamics were recorded before each measurement of CO by thermodilution. Statistical analysis included Pearson correlation and a Bland-Altman analysis for assessing agreement between the two methods of clinical measurement .
A total of 174 paired results of continuous and thermodilution recordings of CO were obtained in 16 patients. The Pearson correlation was 0.63. Bland-Altman analysis showed a bias of 0.63 l/min and a precision of 0.95 l/min, with 95% limits of agreement from -1.15 to +2.67 l/min. This compares favourably with values obtained for other commercially available CO monitors.
No safety problems were associated with the use of the catheter, but the catheter could not be wedged in one patient. The radiograph taken as a control showed a kinked catheter in the PA, but no stiffness in the catheter was noted after withdrawal. One of the catheters was rejected after use owing to a thermistor defect. Of the remaining 18 patients, two showed a sudden change in the correlation between CO obtained continuously and that obtained by thermodilution. Closer inspection of the obtained data suggested that the heat transfer device of the catheter was located in a branch of the PA, rather than within the PA itself, and may have resulted from patients being moved or extubated.
The present study showed that this catheter is a safe and effective device for continuous real-time monitoring of CO in critically ill patients.
The present study was sponsored by Aortech International, Scotland.