Changes in end-tidal carbon dioxide and volumetric carbon dioxide as predictors of volume responsiveness in hemodynamically unstable patients

J Cardiothorac Vasc Anesth. 2013 Aug;27(4):681-4. doi: 10.1053/j.jvca.2012.09.025. Epub 2012 Nov 20.


Objective: The purpose of this study was to determine whether changes in PETCO2 and exhaled CO2 (VCO2) can predict fluid responsiveness after a preload challenge.

Design: A retrospective review of prospectively recorded data.

Setting: A medical intensive care unit of a university-affiliated tertiary care hospital.

Participants: Mechanically ventilated patients undergoing a preload challenge.

Interventions: In the authors' intensive care unit, fluid responsiveness is determined by a passive leg raising (PLR) maneuver and/or a 500-mL crystalloid challenge. An increase in the stroke volume index >10% as measured by a NICOM bioreactance cardiac output monitor (Cheetah Medical, Inc, Vancouver, WA) is used to determine fluid responsiveness. PETCO2 and volumetric capnography (VCO2) were monitored via a combined CO2 and flow sensor capnostat (Respironics NM3 Monitor; Philips Healthcare, Eindhoven, Netherlands). Patients were mechanically ventilated with tidal volumes controlled at 8 mL/kg, allowing for consistent minute ventilation.

Measurements and main results: During the study period, 44 challenges (10 PLR and 34 fluid boluses) were performed on 34 patients. There were 24 (54%) positive "fluid" responses. PETCO2 increased by 5.9% ± 7.6% in the responders compared with 1.4% ± 4.4% in the nonresponders (p = 0.02). Similarly, VCO2 increased by 11.0% ± 8.6% in the responders compared with 0.8% ± 5.6% in the nonresponders (p = 0.001). The area under the receiver operating characteristic curve was 0.67 (95% confidence interval, 0.48-0.80) for PETCO2 and 0.79 (95% confidence interval, 0.63-0.89) for VCO2. PETCO2 and VCO2 were predictive of fluid responsiveness only in those patients without underlying lung disease. The stroke volume variation was 15.8 ± 3.7 in the responders compared with 13.6 ± 4.8 in the nonresponders (p = 0.15).

Conclusions: Dynamic changes in PETCO2 and VCO2 may be used as adjunctive indicators of fluid responsiveness in patients without underlying lung disease.

Keywords: NICOM; capnography; cardiac output; end-tidal carbon dioxide; hemodynamic monitoring; volume responsive; volumetric carbon dioxide.

MeSH terms

  • Adult
  • Area Under Curve
  • Blood Volume / drug effects
  • Blood Volume / physiology*
  • Capnography
  • Carbon Dioxide / metabolism*
  • Cardiac Output / physiology
  • Crystalloid Solutions
  • Hemodynamics / physiology*
  • Humans
  • Isotonic Solutions / therapeutic use
  • Leg / blood supply
  • Plasma Substitutes / therapeutic use*
  • Prospective Studies
  • ROC Curve
  • Regional Blood Flow / physiology
  • Respiration, Artificial
  • Retrospective Studies
  • Stroke Volume / physiology
  • Tidal Volume / physiology


  • Crystalloid Solutions
  • Isotonic Solutions
  • Plasma Substitutes
  • Carbon Dioxide