Assessment of the agreement between cardiac output measured by thermal filament continuous thermodilution (CCO) and noninvasive partial CO2 rebreathing (NICO) with particular reference to ETCO2 levels
© BioMed Central Ltd 2002
Published: 1 March 2002
Cardiac output (CO) is an important hemodynamic parameter and its continuous measurement has the potential to enable early recognition of hemodynamic trends and provide earlier therapeutic response. NICO is a new noninvasive cardiopulmonary monitor that provides an alternative to invasive CCO for measurement of CO. NICO uses a differential form of the Fick equation (change in CO2 excretion and end-tidal CO2, in response to a brief period of partial rebreathing) to provide noninvasive estimates of CO . The accuracy and reliability of NICO as a function of the end-tidal CO2 (ETCO2) levels of the patient has not been studied. The purpose of this study was to determine if ETCO2 levels affect the degree of agreement between NICO and CCO.
Matched sets of CO measurements from NICO (Novametrix Medical Systems, Wallingford, CT, USA) and CCO (Vigilance, Baxter-Edwards, Irvine, CA, USA) were collected in 25 patients undergoing elective cardiac surgery. The NICO sensor (consists of on-airway flow sensor, mainstream CO2 sensor, adjustable dead space tubing, and a pneumatic valve) was attached between the endotracheal tube and the breathing circuit of the patient. The two measures, NICO and CCO were assessed for agreement by using methods proposed by Bland and Altman at different levels of ETCO2.
The agreement between the NICO and CCO is clinically acceptable and is unaffected by ETCO2.