VCO2
Info
Volume of air expired
unit L/min mL/min
Fraction of CO2 in expired air (FECO2)
unit % Fraction
Fraction of CO2 in inspired air (FICO2)
unit % Fraction
Weight
unit Kg lbs
R e s u l t s
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VCO2
 
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VCO2

The amount of carbon dioxide produced as a result of metabolism in designated as VCO2. It may be reported in mL/min or mL/kg/min.

At standard temperature and pressure, the rate at which carbon dioxide enters the alveolar gas from the blood is equal to the metabolic production of carbon dioxide by tissue metabolism in the body.

Calculation of the VCO2 is important for a number of reasons:

  • The value of along with the value of VO2 is utilized for the calculation of the Respiratory Quotient
  • An important application of VCO2 monitoring in the ICU is the determination of physiological dead space ratio. An increase in dead space represents an impaired ability to excrete CO2. Increased dead space fraction is a feature of the early phase of acute respiratory distress syndrome (ARDS)
  • Monitoring of VCO2 has also been found to be useful in the detection of pulmonary embolism
  • In the ICU setting, additional applications include monitoring of ventilation, optimization of PEEP, assessment of pulmonary perfusion, and non-invasive determination of cardiac output

VCO2 is calculated by:

VCO2 (mL/min) = VE (FECO2- FICO2)

mL/kg/min is calculated by:
VCO2 (mL/kg/min) = VCO2 (mL/min) / kg body weight

Variable Definitions:
VCO2 = CO2 exhaled in mL/min
VE = Volume of air expired in mL/min
FECO2 = Fraction of CO2 in expired air
FICO2 = Fraction of CO2 in inspired air

Interpretation:

For a healthy, resting person with a normal Respiratory Quotient (RQ = 0.8), a normal VCO2 is 180- 200 mL/min or 2.5-3.5 mL/kg/min.

Factors affecting VCO2

Factors that increase VCO2:

  • Any increased muscular activity (exercise or pathological causes)
  • Hypermetabolic states (sepsis, hyperthyroidism, etc)
  • Hyperthermia
  • Pain/Stressors

Factors that decrease VCO2:

  • Hypometabolic states (hypothyroidism)
  • Hypothermia
  • Paralysis (anesthesia, mechanical ventilation, Guillain Barré)
  • Sleep or sedation

References.

Arena R, Humphrey R, Peberdy MA. Prognostic ability of VE/VCO2 slope calculations using different exercise test time intervals in subjects with heart failure. Eur J Cardiovasc Prev Rehabil. 2003 Dec;10(6):463-8.

Arena R, et al. Peak VO2 and VE/VCO2 slope in patients with heart failure: a prognostic comparison. Am Heart J. 2004 Feb;147(2):354-60.

Arena. R. et al. Prognostic value of resting end-tidal carbon dioxide in patients with heart failure. Int J Cardiol. 2006 May 24;109(3):351-8. Epub 2005 Jul 19.

Arena. R. et al. Prognostic value of resting end-tidal carbon dioxide in patients with heart failure. Int J Cardiol. 2006 May 24;109(3):351-8. Epub 2005 Jul 19.

Guazzi M. et al. Exercise oscillatory breathing and increased ventilation to carbon dioxide production slope in heart failure: an unfavorable combination with high prognostic value. Am Heart J. 2007 May;153(5):859-67.

Hospital Management.net. Monitoring every breath you take. Last accessed 10 May 2009. Available at URL: http://www.hospitalmanagement.net/features/feature746/

Exercise Physiology Lab-Oxygen Consumption & Aerobic Capacity. Last accessed 10 May 2009. Available at URL: http://www.biosci.ohiou.edu/faculty/schwirian/bios446/eplab07&08vo2&aerobiccapacity.htm