Carbon dioxide elimination and oxygen consumption in mechanically ventilated children

Craig D. Smallwood, Brian K. Walsh, Lori J. Bechard, Nilesh M. Mehta

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


BACKGROUND: Accurate measurement of carbon dioxide elimination (VCO2) and oxygen consumption (VO2) at the bedside may help titrate nutritional and respiratory support in mechanically ventilated patients. Continuous VCO2 monitoring is now available with many ventilators. However, because normative data are sparsely available in the literature, we aimed to describe the range of VCO2 and VO2 values observed in mechanically ventilated children. We also aimed to examine the characteristics of VCO2 values that are associated with standard steady state (5-min period when VCO2 and VO2 variability are < 10%). METHODS: Mechanically ventilated patients who underwent indirect calorimetry testing were eligible for inclusion, and subjects who achieved standard steady state were included. Normalized VCO2 and VO2 values (mL/kg/min) were modeled against subject height, and correlation coefficients were computed to quantify the goodness of fit. A steadystate definition using only VCO2 was developed (VCO2 variability of < 5% for a 5-min period) and tested against standard steady state using sensitivity and specificity. RESULTS: Steady-state data from 87 indirect calorimetry tests (in 70 subjects) were included. For age groups < 0.5, 0.5– 8, and > 8 y, the mean VCO2 values were 7.6, 5.8, and 3.5 mL/kg/min. Normalized VCO2 and VO2 values were inversely related to subject height and age. The relationships between normalized gas exchange values and height were demonstrated by the models: VCO2 = 115 × (height in cm)-0.71 (R = 0.61, P < .001) and VO2 = 130 × (height in cm)-0.72 (R = 0.61, P < .001). Steady-state VCO2 predicted standard steady state (sensitivity of 0.84, specificity of 1.0, P < .01). CONCLUSIONS: VCO2 and VO2 measurements correlated with subject height and age. Smaller and younger subjects produced larger amounts of CO2 and consumed more O2 per unit of body weight. The use of a 5-min period when VCO2 varied by < 5% predicted standard steady state. Our observations may facilitate greater utility of VCO2 at the bedside in the pediatric ICU and thereby extend the benefits of metabolic monitoring to a larger group of patients.

Original languageEnglish (US)
Pages (from-to)718-723
Number of pages6
JournalRespiratory care
Issue number5
StatePublished - May 1 2015
Externally publishedYes


  • Carbon dioxide elimination
  • Children
  • Mechanical ventilation
  • Oxygen consumption
  • Pediatric
  • Steady state
  • V
  • Volumetric capnography

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine


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