Abstract 19165: Improving Accuracy of Cardiac Output Estimates Using the Fick Principle - Oxygen versus Carbon Dioxide

• Published in: Circulation (New York, N.Y.) N.Y.), 2016-11, Vol.134 (Suppl_1 Suppl 1), p.A19165-A19165
• Main Authors: Perry, Dorothy A, Thomson, Lindsay M, Moore, Abigail R, Kaza, Aditya K, Kheir, John N
• Format: Article
• Language: English
• ISSN: 0009-7322; 1524-4539

IntroductionThe Fick principle is frequently used to estimate cardiac output (CO) in critically ill patients. These data are used to guide patient management and to estimate vascular resistance. Oxygen-based Fick (FickO2) has been shown to systematically overestimate CO. The substitution of all O2 parameters with CO2 parameters may improve the accuracy of Fick.ObjectiveTo compare CO as measured by (1) FickO2, (2) carbon dioxide-based Fick (FickCO2), and (3) aortic flow probe at varying O2 and CO2 tensions.MethodsYorkshire swine (n=8, 29-30kg) were anesthetized, intubated, and paralyzed. Instrumentation included a femoral arterial and pulmonary arterial catheters, myocardial tissue PO2 probe (Oxford Optronix), and a transit time flow probe (Transonic, Inc) placed on the aortic root via sternotomy. Indexed oxygen consumption (VO2) and carbon dioxide production (VCO2) were continuously measured (E-CAiOVX module, GE Healthcare). In separate experiments, PaO2 was varied between 100-650 mmHg, and PaCO2 between 20-80 mmHg in graded fashion. FickCO2 was calculated based on VCO2 and the veno-arterial CO2 content difference (A). Data were compared between each group to flow probe by Bland Altman analysis.ResultsFickO2 consistently overestimated cardiac index (CI) (bias 1.3 L/min/m, SD of bias 0.75), and did so in proportion to FiO2 (B). This overestimation was explained by a correlation with both tissue PO2 and SvO2 with FiO2 (P