Cardiac output determination from the arterial pressure wave: clinical testing of a novel algorithm that does not require calibration

OBJECTIVE: The purpose of this study was to evaluate the accuracy and precision of a novel algorithm that evaluates cardiac output by using arterial pressure waveform characteristics. DESIGN: Prospective, observational study comparing the cardiac output values of intermittent thermodilution, continuous thermodilution, and continuous arterial pressure wave assessment. SETTING: The intensive care unit in a tertiary care university hospital. PARTICIPANTS: Fifty postoperative cardiac surgical patients, within the first 12 hours after surgery. Interventions: All patients received a pulmonary artery catheter (PAC) and at least 1 systemic arterial pressure catheter. The data from the arterial catheter were processed by using a new arterial pressure cardiac output (APCO) algorithm. The data from the PAC (continuous and intermittent assessments) were collected for comparison with the APCO. Measurements: Two hundred ninety-five cardiac output measurements using intermittent thermodilution (ICO), continuous thermodilution (CCO), and arterial pressure-based output (APCO) were obtained during various times during the first 12 postoperative hours. The measurements of each method at each time point were compared by using Bland-Altman analysis. RESULTS: The mean cardiac output ranged from 2.77 to 9.60 L/min. APCO, compared with ICO, revealed a bias of 0.55 L/min and precision of 0.98 L/min. APCO, compared with CCO, revealed a bias of 0.06 L/min and precision of 1.06 L/min. The APCO agreement between femoral and radial arterial catheters was close; the bias was -0.15 L/min, and the precision was 0.56 L/min. CONCLUSIONS: This novel arterial pressure cardiac output algorithm provides cardiac output assessments that agree satisfactorily for clinical purposes with intermittent and continuous thermodilution techniques in postoperative cardiac surgical patients. Further study is required for other patient populations and clinical situations.