Evaluation of Partial Carbon Dioxide Rebreathing Cardiac Output Measurement During Thoracic Surgery

Objective: Noninvasive partial CO2 rebreathing (NICO; Novametrix Medical Systems, Inc, Wallingford, CT) is a relatively new alternative to thermodilution (TDCO) for measurement of cardiac output. This study compares the 2 methods during thoracic surgery and one-lung ventilation.Design: A prospective, observational study.Setting: A tertiary hospital.Participants: Twelve adult patients undergoing elective thoracotomy and one-lung ventilation in the lateral decubitus position.Interventions: Paired measurements of cardiac output were performed during (1) 2-lung ventilation in the supine position (postinduction of anesthesia), (2) 10 minutes after initiation of one-lung ventilation in the lateral decubitus position with the nondependent chest open, and (3) after 30 minutes on one-lung ventilation. An average of 3 consecutive (10 mL 20°C saline) TDCO measurements made during end-expiration was compared with corresponding NICO measurements.Measurements and Main Results: The NICO showed a tendency to underestimate cardiac output compared with TDCO at all measurement times. Overall, bias was −0.29 L/min and limits of agreement −1.69 to 1.43 L/min.Conclusions: There was a moderate agreement between cardiac output measurements obtained with the NICO and TDCO. The present data suggest that the NICO technique may be useful during thoracic surgery.