Abstract 19033: Hyperoxia Reduces Oxygen Consumption in Children With Pulmonary Hypertension
Background: High inspired oxygen concentration (FiO2) and inhaled nitric oxide (iNO), either alone or in combination, are administered to test pulmonary vasoreactivity in children. Oxygen consumption (VO2) cannot be measured accurately with conventional methods if the inspired FiO2 >0.85 and it is usually assumed that (VO2) does not change with hyperoxia or iNO.
Hypothesis: We hypothesised that an inspired FiO2 >0.85 would change VO2 compared with VO2 in room air (RA) and iNO administered with room air and could influence the accuracy of flow calculations using the direct Fick’s equation.
Methods: We reviewed retrospectively the cardiac catheterization data obtained between 2009-14 in children with pulmonary hypertension (PH) without cardiac shunts and cardiac output (CO) measured by thermodilution in 3 conditions of RA, with an FiO2 >0.85 and iNO in RA. VO2 was calculated using the Fick equation CO= VO2 / arterial-venous oxygen content difference. Dissolved O2 was included in the calculation.
Results: Data was available in 20 subjects (median age 8.5 years, range 1 -18, median weight 27 kg range, 8 - 95, BSA median 1m2, range 0.4 - 1.8). The median VO2 in RA was 147 (range 84-231) and decreased in hyperoxia to 134 (range 84-239) (p=0.03). The median percentage change in VO2 from RA to FiO2>0.85 was 10% (range + 24 to - 42%). VO2 was unchanged with iNO 139 (range 78-221) ml/min/m2 (p=0.3). The cardiac index remained unchanged in all 3 conditions (room air: 3.5±1.0, FiO2 >0.85: 3.5±1.0 and iNO: 3.6±1.0 L/min/m2).
Conclusion: VO2 decreased significantly during hyperoxia but not during iNO in children with PH. If VO2 is assumed to remain constant during hyperoxia errors maybe introduced if the direct Fick equation is used to calculate pulmonary and systemic blood flow.
Author Disclosures: G. Long: Research Grant; Modest; Deloitte Clinical Research Fellowship and Stollery Foundation Academic Fellowship. P. Bobhate: None. S. Jain: None. J. Coe: None. J. Rultledge: None. I. Adatia: None.
- © 2014 by American Heart Association, Inc.