Response time of the Opti-Q continuous cardiac output pulmonary artery catheter in the urgent mode to a step change in cardiac output

Objectives. This study was conducted to determine the response time of the Opti-Q continuous cardiac output (CCO) device to a step change in cardiac. Design. Prospective study. Setting. University hospital animal lab. Model. Female sheep. Interventions. In ten animals, cardiac output was altered suddenly by opening and closing a peripheral arteriovenous shunt to test the response time of the CCO system. Measurements and main results. Cardiac output was measured continuously by thermodilution and ultrasonic techniques while an arteriovenous shunt was opened and closed. A total of 53 dynamic observations were made (5-6 per animal). The mean response time of the continuous cardiac output device was 86 seconds and was unaffected by the magnitude or direction of the change in cardiac output. It was also unaffected by the animal's weight. CCO values were not statistically different from standard thermodilution measurement (p = 0.895). Shunt flow ranged from 430 to 1730 ml/min and averaged 812 ml/min. The mean CCO with the shunt closed was 4.62 L/min. There was 1.5 to 2 minutes under or overshoot in cardiac output in 11% of the measurements. Conclusions. Continuous cardiac output measurement was as accurate as those made by standard bolus thermodilution. The average response time to acute changes in cardiac output was approximately 1.5 minutes or ten times faster than previously reported systems. Response time is independent of animal mass, shunt volume and the direction of cardiac output perturbations.