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  • Meeting abstract
  • Open Access

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

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Critical Care20026 (Suppl 1) :P195

  • Published:


  • Cardiac Output
  • Breathing Circuit
  • Pneumatic Valve
  • Space Tubing
  • Noninvasive Estimate


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 [1]. 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.


One hundred and fifty-four data points were obtained indicating variations in the difference of cardiac output compared with the variations of ETCO2 of the patient. The range for CCO measures was 2.0-8.4 l/min and for NICO measures 2.5 - 8.3 l/min. The mean bias in CO between the two techniques for the entire protocol was 0.24 l/min and the precision (1 SD) was 0.77 l/min. The difference in CO was independent of the ETCO2 levels of the patient (Fig.).

Difference in Cardiac Output (NICO-CCO) and ETCO2.


The agreement between the NICO and CCO is clinically acceptable and is unaffected by ETCO2.

Authors’ Affiliations

Hospital Pro-Cardíaco, Rua Gal. Polidoro 192, Rio de Janeiro, RJ, Brazil


  1. Haryadi DG, et al.: Partial CO 2 rebreathing indirect Fick technique for non-invasive measurement of cardiac output. J Clin Monit 2000, 16: 361-374. 10.1023/A:1011403717822View ArticleGoogle Scholar


© BioMed Central Ltd 2002