Indirect calorimetry is the calculation of energy expenditure by the measurement of V O2 and V CO2, which are converted to energy expenditure (Kcal/day) by the Weir method:
Indirect calorimetry also allows calculation of the respiratory quotient. Indirect calorimeters can use an open circuit method, a closed circuit method or a breath-by-breath method. Indirect calorimetry may be indicated for patients who are malnourished, who are difficult to wean from mechanical ventilation or who have numerous nutritional stress factors. The open circuit calorimeter measures the concentrations and volumes of inspired and expired gases to determine V O2 and V CO2. The principal components of an open circuit calorimeter (metabolic cart) are the analyzers (oxygen and carbon dioxide), a volume measuring device and a mixing chamber (Figure 4). The analyzers must be capable of measuring small changes in gas concentrations, and the volume monitor must be capable of accurately measuring volumes. It’s time to pay less money – just get buy levitra professional at the best online pharmacy.
Figure 4) Schematic illustration of open circuit calorimeter