Abstract 19722: Cardiac Output Estimation by Inert Gas Rebreathing is Accurate in Mechanically Ventilated Children With Heart Disease
Introduction: Real time estimates of pulmonary (Qp) and systemic blood flow (Qs) could improve pediatric cardiac care. Current generation inert gas rebreathing (IGR) devices are safe, portable, and easy to use; can estimate Qp and Qs rapidly at the bedside; and can now be adapted for use in intubated patients. We compared IGR and two types of Fick Qp estimates, those using measured (FickM) and assumed (FickA) oxygen consumption (VO2) values, in mechanically ventilated pediatric cardiac patients with no shunt lesion or exclusive right-to-left shunt. Secondarily, we compared measured VO2 with assumed values and values back-calculated from the Fick equation (using measured saturations, hemoglobin and IGR Qp).
Methods: In 18 intubated patients in the pediatric catheterization laboratory, the modified ventilator-compatible InnocorTM device was used to measure IGR Qp and breath-by-breath VO2; assumed VO2 was taken from LaFarge tables. Sampled pulmonary arterial and venous saturations were used to calculate FickM and FickA. Bland-Altman agreement and Spearman correlation were assessed for IGR Qp with FickA Qp and FickM Qp. Secondarily, agreement was analyzed between measured VO2, assumed VO2, and VO2 calculated from the Fick equation.
Results: Subjects were aged 4-23 years, with a range of cardiac diagnoses. The figure shows Bland-Altman plots for Qp. Compared with FickA, IGR Qp had mean bias -0.9 L/min, 95% limits of agreement (=±1.96 SD) -2.8 to +1.0 L/min, and r=0.75. Compared with FickM, IGR Qp had mean bias -0.2 L/min, 95% limits of agreement -1.3 to +1.0 L/min, and r=0.90. Agreement of assumed and measured VO2 was poor (bias +23%, ±55%); measured VO2 agreed better with Fick calculated VO2 than assumed VO2.
Conclusions: IGR Qp estimates agree well with Fick Qp estimates. This agreement improves when VO2 is measured, as assumed VO2 agrees poorly with measured VO2. IGR is an attractive option for bedside monitoring of Qp in intubated children.
Author Disclosures: A. Marma: None. A.R. Opotowsky: None. B.K. Walsh: Research Grant; Modest; Modest sum granted by Innovision at conclusion of project to reimburse for time spent in data acquisition; sum to be used for research activities at the Department's discretion. J.J. Esch: None. J.A. Dinardo: None. B.D. Kussman: None. J. Rhodes: Research Grant; Modest; Modest sum granted by Innovision at conclusion of project to reimburse for time spent in data acquisition; sum to be used for research activities at the Department's discretion.
- © 2015 by American Heart Association, Inc.