Calorimetry indirect

The most accurate clinical tool for estimating energy requirements is indirect calorimetry or metabolic gas monitoring. This noninvasive proce-... 

Data from indirect calorimetry can also be used to determine a respiratory quotient. Values greater than 1 suggest overfeeding, whereas values less than 0.7 suggest a ketogenic diet, fat gluconeogenesis, or ethanol oxidation. Respiratory quotient (RQ) is calculated as follows ... 

Limitations of indirect calorimetry include limited availability, calibration errors, and other errors. 

Indirect calorimetry This approach is so indirect that it does not involve measuring heat at all All the energy expended by a person arises from the oxidation of carbohydrates, fats and/or proteins, which use oxygen and produce carbon dioxide (and urea), all of which can be measured. 

Isotopic methods Indirect calorimetry is limited by the need to measure the gases, which means that it cannot be used for free-living studies. Consequently, methods involving the administration of isotopically labelled compounds have been devised. These are based on the principle of isotopic dilution, a widely employed method for estimating concentrations, particularly of hormones and other proteins in the blood (Appendix 2.6). The requirements for these methods are ... 

The method used for measuring energy expenditure of patients is indirect calorimetry, aldiough it can be calculated from die Harris Benedict or Schofield equations (Ch ter 2). 

Waversveld, J., Addink, A.D.F. and van den Thillart, G. (1989). The anaerobic energy metabolism of goldfish determined by simultaneous direct and indirect calorimetry during anoxia and hypoxia. Journal of Comparative Physiology 159B, 263-268. 

The term indirect calorimetry is often used in biology when the sum of metabolic processes in an animal, e.g., a human being, is investigated by measurement of rates of consumption of oxygen and the production of carbon dioxide and... 

BMR is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (expressed in kcal/day). BMR decreases with age and with the loss of lean body mass. Increasing muscle mass increases BMR. Illness, previously consumed food and beverages, environmental temperature and stress levels can affect overall energy expenditure as well as the BMR. BMR is accurately determined by gas analysis (direct or indirect calorimetry) an estimation can be found using the equation ... 

Indirect calorimetry provides the ability to measure the relative contribution of macronutrients toward energy use. The measurements of expired carbon dioxide and consumed oxygen are used to calculate respiratory quotient (RQ). An RQ of 1.0 indicates use of carbohydrate solely, an RQ of 0.7 indicates use of fat solely, whereas an RQ of 0.85 indicates mixed use of macronutrients. Data in rats demonstrates a significant increase in using fat as an energy substrate following DAG oil infusion (gastric) as observed by a decreased respiratory quotient value between 3-5 hours post-infusion (15). 

The methods of indirect and direct calorimetry may not always result in the same values for energy expenditure. Indirect calorimetry is a measure of the heat produced by oxidative processes. Direct calorimetry measures the rate of dissipation of heat from the body. An increase in the rate of heat production, as with exercise, may not always result in an immediate, measurable increase in heat released by the body (from the skin). Instead, the increase in heat production may result in a rise in body temperature. That part of the energy requirement used to raise... 

The doubly labeled water technique measures CO production, and not O production. Because the heal created per mole of expired CO differs between the three major fuels (carbohydrate, fat, protein), the calculation of energy expenditure requires a knowledge of the Lntemal fuel being oxidized. Thus, the doubly labeled water technique, coupled with infomnatior from RQ measurements, may be used instead of the method of indirect calorimetry (using an insulated chamber to measure heat production) to determine total energy production over the course of several days. 

Roberts, S- 0., Coward, W Schlingenseipen, K., Nohiia, V, and Lucas, A. (1986). Comparison of the doubly labeled water ( H2 0) method with indirect calorimetry and a nutrient balance study for simultaneous determination of energy expenditure, water intake, and metabolisable energy intake in preterm infants. Am.. Clin. Natr. 44,315-322. 

Indirect calorimetry, 299 Indispensable amino adds. 22-23 lndole-3-caTbinol, 914 Infants... 

EUa, M., and Livesay, G. (1988). Theory and validity of indirect calorimetry during net lipid synthesis. Am.. Clin. Nutr. 47,591-607. 

Ferrannini, E. (1988). The theoretical bases of indirect calorimetry A review. Metabolism 37, 287-301. 

Kinney, J. M. (1987). Indirect calorimetry in malnutrition Nutritional assessment or therapeutic reference /. Parenteral Enteral Nutr. 11,90S-94S. 

However, variable relationships between DO2 and V02 have been observed when VO2 was measnred independently by indirect calorimetry. A linear relationship between DO2 and VO2 therefore may be the result of mathematical coupling or flow-dependent V02. Currently available data do not support the concept that patient outcome or survival may be altered by treatment measures directed toward achieving supranormal DO2 and V02 values. In fact, a recent consensus conference concluded that although pulmonary artery catheterization is useful to guide therapy, routinely increasing cardiac index to... 

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