EE: Duration of Measurement (Steady State) (2014)


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.

PubMed ID: 15020579
Study Design:
Diagnostic, Validity or Reliability Study
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To compare the agreement between measurements of REE by using five-minute steady-state criteria with steady-state criteria over a shorter period. Energy expenditure measurements using steady-state criteria over a shorter time period may be more likely to be achieved by patients and therefore provide valid, useable results.

Inclusion Criteria:
  • Patients with cancer
  • Healthy subjects participating in another trial.
Exclusion Criteria:
No surgery within the last month before the study.
Description of Study Protocol:


  • Patients were recruited from a radiotherapy treatment center
  • Healthy subjects were recruited from a convenience sample and were grouped and matched by gender, age, weight and height to the cancer patients.


Diagnostic, validity or reliability study.

Blinding Used

Implied with measurements.

Statistical Analysis

  • Analyses were carried out with SPSS for Windows (version 11.0.1)
  • Normally distributed continuous variables are presented as means ±SD
  • Biases between steady-state criteria were not normally distributed
  • Characteristics of subjects who achieved five-minute SS and those who did not were compared for both clinical importance and statistical significance sample T-tests and Fisher's exact test
  • Differences in measured REE between the three steady-state criteria were first assessed by Wilcoxon's signed-rank tests
  • Spearman's rank correlation was used to determine the strength of the relationship of five-minutes SS with four-minutes SS and with three-minute SS criteria
  • Median bias, limits of agreement and plot of bias against average of two measurements by using the Bland-Altman plotting approach were used to describe agreement at the individual level and assess whether the bias was consistent across the entire range of measurements.
Data Collection Summary:

Timing of Measurements

  • Participants fasted overnight for at least 12 hours and attended the clinic on wakening
  • Measurements were conducted between 7 a.m and 9 a.m.

 Dependent Variables

  • Energy expenditure: Measured by a breath-by-breath respiratory gas exchange with the VMax 229 indirect calorimetry device using a mouthpiece and noseclip:
    • Expired gas was analyzed for oxygen concentration by using a paramagnetic oxygen analyzer and for carbon dioxide concentration by using a non-dispersive infrared analyzer
    • The indirect calorimeter was connected to an IBM-compatible personal computer for management and storage of data by using the respiratory quotient (RQ)
    • Three steady state criteria were identified. The criteria were defined by a change in VO2, VCO2 and RQ and minute ventilation of 10% or less but differed by the time period in which these variables were stable:
      • First five minutes (five-minute SS)
      • First four minutes (four-minute SS)
      • First three minutes (three-minutes SS).
  • Height was measured without shoes to the nearest 0.5cm with a stadiometer
  • Weight and fat-free mass were measured without shoes or heavy clothing to the nearest 0.1kg by foot-to-foot bioelectrical impedance analysis
  • REE was estimated from the Harris-Benedict prediction equations using weight, height, age and gender. For subjects with a body mass index of more than 29kg/m2, an adjusted weight was used in the prediction of REE.

Independent Variables

  • Healthy individuals
  • Cancer patients.
Description of Actual Data Sample:
  • Initial N: 39 subjects (22 cancer patients, 17 healthy subjects)
  • Attrition (final N): 21 subjects met the five-minute SS criteria
  • Age: Mean age was 61±12 years
  • Anthropometrics: Mean BMI was 27.4±3.9kg/m2
  • Location: Australia.


Summary of Results:

Key Findings

  • On the basis of the Wilcoxon signed-rank tests, there was no statistically significant difference between REE measured by five-minute SS or four-minute SS (Z=-0.643, P=0.52) or between REE measured by five-minute SS or three-minute SS (Z=-0.521, P=0.60)
  • The correlations between REE by five-minute SS and four-minute SS and REE by five-minute SS and three-minute SS were P=0.99 and P=0.98 (P<0.001 for both).
  • The use of four-minute SS criteria produced limits of agreement of REE measurements that were 1.2% below, up to 2.0% above, REE measured by five-minute SS criteria
  • Correlation analysis indicated a statistically significant correlation between median bias and average of measurements for five-minute SS and three-minute SS data (P=-0.45, P=0.04)
  • The mean difference between REE measured by five-minute SS and REE predicted by the Harris-Benedict equations were -52kcal (3.3%) with limits of agreement of ± 400kcal (-28.3% to 21.8%).
Author Conclusion:

Reducing the time period of steady state to four minutes produced measurements of REE for individuals that were within clinically acceptable, pre-determined limits. Reduction of the time period further to three minutes produced measurements of individuals' REE that were just outside the a priori defined limits, which in certain contexts may be clinically acceptable.

Funding Source:
University/Hospital: Centre for Health Research, Queensland University of Technology, Brisbane, Queensland
Reviewer Comments:

Small sample size. Questionable validity of indirect calorimeter.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? Yes
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  7.5. Was the measurement of effect at an appropriate level of precision? ???
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes