title: Reducing the time period of steady state does not affect the accuracy of energy expenditure measurements by indirect calorimetry.
abstract: Achievement of steady state during indirect calorimetry measurements of resting energy expenditure (REE) is necessary to reduce error and ensure accuracy in the measurement. Steady state is often defined as 5 consecutive min (5-min SS) during which oxygen consumption and carbon dioxide production vary by +/-10%. These criteria, however, are stringent and often difficult to satisfy. This study aimed to assess whether reducing the time period for steady state (4-min SS or 3-min SS) produced measurements of REE that were significantly different from 5-min SS. REE was measured with the use of open-circuit indirect calorimetry in 39 subjects, of whom only 21 (54%) met the 5-min SS criteria. In these 21 subjects, median biases in REE between 5-min SS and 4-min SS and between 5-min SS and 3-min SS were 0.1 and 0.01%, respectively. For individuals, 4-min SS measured REE within a clinically acceptable range of +/-2% of 5-min SS, whereas 3-min SS measured REE within a range of -2-3% of 5-min SS. Harris-Benedict prediction equations estimated REE for individuals within +/-20-30% of 5-min SS. Reducing the time period of steady state to 4 min produced measurements of REE for individuals that were within clinically acceptable, predetermined limits. The limits of agreement for 3-min SS fell outside the predefined limits of +/-2%; however, both 4-min SS and 3-min SS criteria greatly increased the proportion of subjects who satisfied steady state within smaller limits than would be achieved if relying on prediction equations.
authors.affiliation: Centre for Research in Cancer Control, Queensland Cancer Fund, Queensland 4059, Australia. MReeves@qldcancer.com.au
authors.forename: Marina M
authors.initials: MM
authors.lastname: Reeves
authors.forename: Peter S W
authors.initials: PS
authors.lastname: Davies
authors.forename: Judith
authors.initials: J
authors.lastname: Bauer
authors.forename: Diana
authors.initials: D
authors.lastname: Battistutta
mesh_terms: D000368:Aged; D015982:Bias; D001827:Body Height / Q000502:physiology; D002153:Calorimetry, Indirect / Q000379:methods* / Q000592:standards; D002245:Carbon Dioxide / Q000097:blood; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000378:metabolism; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000502:physiology; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen