EE: Duration of Measurement (Steady State) in Healthy and Non-Critically Ill, 2014
Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.
EE: Duration of Measurement (Steady State) in Healthy and Non-Critically Ill Adults
When measuring resting metabolic rate (RMR) in a healthy or non-critically ill adult, the registered dietitian nutritionist (RDN) should discard the data for the first five minutes, and then use a validated steady state definition to determine the duration of the remainder of the measurement. The purpose of the discard period and steady state requirement is to minimize artifact in the measurement. Steady-state definitions vary by measurement length (four to 25 minutes), coefficient of variation (less than 5% to 10%) and combination of gas exchange variables (VO2, VCO2, RQ, minute ventilation).
EE: Duration of Measurement (Steady State) in Healthy Children
When measuring resting metabolic rate (RMR) in a healthy child who is unable to rest, the registered dietitian nutritionist (RDN) should include the rest period in the measurement, discard the first 10 minutes of data and then continue measurement until a steady state is achieved. With this approach, limited evidence in healthy children suggests that data recorded after the 10th minute are not significantly different from data at 30 minutes; data averaged around the 20th minute have the least variability.
Risks/Harms of Implementing This Recommendation
There are no potential risks or harms associated with the application of this recommendation.
Conditions of Application
- For the recommendation, EE: Duration of Measurement (Steady State) in Healthy and Non-Critically Ill Adults, steady state criteria have been tested in healthy adults, adults with cancer and those with stable COPD. Application to other adult populations may be reasonable but is an extrapolation.
- The recommendation, EE: Duration of Measurement (Steady State) in Healthy Children, applies to children who are unable to rest
- When applying the recommendation to children, the child's age should be considered, due to variability in physical and developmental attributes
- Clinical judgment should be used in applying the recommendation, EE: Duration of Measurement (Steady State) in Healthy Children, to non-critically ill children, due to no evidence in this population
- If unable to achieve a steady state, the RDN should recalibrate the instrument and take a second measurement
- If steady state is still not achieved, the RDN should re-measure on a different day or, in an adult, average the two measurements
- Fidgeting further increases RMR. Therefore, the RDN must assure the subject does not fidget during the entire procedure (Levine et al, 2000).
Potential Costs Associated with Application
If the steady state requirements cannot be achieved, time to complete the measurement will be prolonged or the measurement will need to be rescheduled. Additional costs may be incurred.
A total of four studies were included in the evidence analysis for these recommendations:
- One neutral-quality time series study (Horner et al, 2001)
- One neutral-quality diagnostic, validity or reliability study (Reeves et al, 2004)
- One neutral-quality non-randomized crossover trial (McManis and Mellecker, 2009)
- One negative-quality cross-sectional study (Schols et al, 1992).
- Three studies provide evidence that in healthy adults and those with stable COPD, after discarding the first five minutes of data to exclude artifact, achieving at least four minutes of steady state [10% or less coefficient of variation (CV) in VO2 and VCO2] is acceptable
- Research indicates that measurements as short as four minutes in steady state are comparable to longer steady state measurements
- Measurement periods have primarily been tested in healthy adults; one study tested both healthy adults as well as stable COPD patients and found no significant differences between various RMR measurement lengths
- Evidence is based on the following: Horner et al, 2001; Reeves et al, 2004; Schols et al, 1992.
- One study provides evidence that in healthy children, the rest period may be included in the RMR measurement period. When using this approach, RMR measurements recorded after the 10th minute are not significantly different from RMR measured after 30 minutes of rest, but RMR measurements taken around the 20th minute may have the least variability.
- Evidence is based on the following: Mellecker and McManus, 2009.
Recommendation Strength Rationale
- Conclusion statement supporting EE: Duration of Measurement (Steady State) in Healthy and Non-Critically Ill Adults is Grade III
- Conclusion statement supporting EE: Duration of Measurement (Steady State) in Healthy Children is Grade II.
- Risks/Harms of Implementing This Recommendation
The recommendations were created from the evidence analysis on the following questions. To see detail of the evidence analysis, click the blue hyperlinks below (recommendations rated consensus will not have supporting evidence linked).
How long should the duration of the RMR measurement be to achieve a steady state in healthy and non-critically ill adults?
If steady state cannot be achieved, how long should the duration of an indirect calorimetry measurement be in the healthy and non-critically ill?
How long should the duration of the RMR measurement be to achieve a steady state in healthy and non-critically ill children?
Horner NK, Lampe JW, Patterson RE, Neuhouser ML, Beresford SA, Prentice RL. Indirect calorimetry protocol development for measuring resting metabolic rate as a component of total energy expenditure in free-living postmenopausal women. J Nutr. 2001; 131 (8): 2,215-2,218.
Reeves MM, Davies PS, Bauer J, Battistutta D. Reducing the time period of steady state does not affect the accuracy of energy expenditure measurements by indirect calorimetry. J Appl Physiol. 2004 Jul; 97(1): 130-134.
Schols AMWJ, Schoffelen PFM, Ceulemans H, Wouters EFM, Saris WHM. Measurement of resting energy expenditure in patients with chronic obstructive pulmonary disease in a clinical setting. JPEN J Parenter Enteral Nutr. 1992; 16(4): 364-368.
Mellecker RR, McManus AM. Measurement of resting energy expenditure in healthy children. JPEN J Parenter Enteral Nutr. 2009 Nov-Dec; 33(6): 640-645.
References not graded in Academy of Nutrition and Dietetics Evidence Analysis Process
Levine JA, Schleusner SJ, Jensen MD. Energy expenditure of non-exercise activity. Am J Clin Nutr. 2000; 72: 1, 451-1, 454.