Abstract 15166: Measurement of Oxygen Consumption in Mechanically Ventilated Children: A Comparison between Mass Spectrometry and Breath by Breath Method
Background: The measurement of oxygen consumption (VO2) is important to calculate blood flow using the Fick equation. Non-invasive assessment of VO2 may be measured by mass spectroscopy (MS) using mixed expiratory argon dilution or by a breath-by-breath method (BBM) of gas exchange analysis. However, MS is unsuited to routine clinical use. BBM is simple to use but is unvalidated in mechanically ventilated children. We sought to compare VO2 measurements by MS and BBM.
Methods: Once a stable baseline was reached, we measured VO2 continuously and simultaneously for 10minutesby MS (Amis 2000, Innovision, Denmark) and BBM (Innocor, Innovision, Denmark) in consecutive anesthetized children, intubated with a cuffed endotracheal tube, mechanically ventilated and hemodynamically stable with normal body temperature.
Results:We studied 37 patients (20 female, median age 3.0 years range 0.2 -20, median weight 13 kg, 2.8 -73.3). Mean VO2 measured by MS was 5.14 ml/kg/min, (95% confidence interval, CI 4.58 to 5.71) and by BBM was 4.55 ml/kg/min, (95% CI 4.55 to 5.51). The mean difference between MS and BBM (0.11 ml/kg/min, 95% CI -0.77 to 0.31) was not significant (p=0.23). Linear regression of VO2 values measured by MS and BBM showed a strong correlation (R = 0.94, P< 0.0001). In Fig.1, Bland-Altman analysis revealed good agreement between MS and BBM with a mean difference of -0.11 and the 95% limits of agreement of -1.01 to +1.24.
Conclusions:Both MS and BBM may be used to measure VO2 in anesthetized, intubated mechanically ventilated children. We suggest that BBM method may be a useful, accurate, economical and convenient alternative to MS to measure VO2. The accurate measurement of VO2 may be used to calculate cardiac output, vascular resistance and oxygen delivery during cardiac catheterization and in critically ill children. Fig.1 Bland-Altman plot for oxygen consumption (VO2) measured by the mass spectrometry (MS, Amis 2000) and the breath by breath method (BBM, Innocor ).
- © 2012 by American Heart Association, Inc.