CI: Best Method to Estimate RMR (2010)


Cheng CH, Chen CH, Wong Y, Lee BJ, Kan MN, Huang YC. Measured versus estimated energy expenditure in mechanically ventilated critically ill patients. Clin Nutr. 2002; 21 (2): 165-172.

PubMed ID: 12056791
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
  • To assess and compare the energy expenditure as measured by indirect calorimetry and estimated by five equations in mechanically ventilated critically ill patients receiving enteral nutrition, TPN or both
  • Another purpose was to examine the relationship between energy expenditure and severity of illness (APACHE II score), length of time in the ICU and hospital and length of ventilatory dependency.
Inclusion Criteria:
  • All patients admitted or transferred to ICU were screened for potential study participation
  • Only patients who were hemodynamically stable, not comatose and requiring at least six days of mechanical ventilation were included.
Exclusion Criteria:
Excluded if they received fractions of inspired oxygen over 60%.
Description of Study Protocol:
  • Recruitment: Patients in ICU of Taichung Veteran General Hospital
  • Design: Cross-sectional study
  • Blinding used: Not applicable
  • Intervention: RMR measured using indirect calorimetry and estimated using equations.

Statistical Analysis

  • Differences between measured EE and estimated REE and between measured EE and calculated EE with measured EE as a control group were compared for significant differences using Bonferroni test
  • Pearson correlation coefficients were performed to assess the relationship between measured EE, estimated REE and clinical outcomes
  • Statistical results were considered to be significant at P<0.05
  • Values presented are means ±SD.
Data Collection Summary:

Timing of Measurements

Indirect calorimetry performed on Days One and Six of admission and compared to information for equations.

Dependent Variables

  • RMR measured by indirect calorimetry on two occasions (first and sixth day of admission) with Deltatrac II MBM-200 Metabolic Monitor; all measurements performed by one trained technician, calibrated before each measurement; patients measured for at least 40 minutes
  • RMR estimated using Harris-Benedict equation
  • RMR estimated using Kleiber equation
  • RMR estimated using Liu equation
  • RMR estimated using Ireton-Jones equation
  • RMR estimated using Fusco equation
  • Adjustments were added to all equations of 1.2 for minor surgery and cancer (N=34), 1.3 for fracture and multiple trauma (N=5), and 1.4 for sepsis (N=7).

Independent Variables

  • Anthropometric and biochemical measurements
  • 24-hour urine collection
  • APACHE III score
  • Diagnosis
  • Length of ICU and hospital stay
  • Ventilatory dependency
  • Medication use (i.e., catecholamines).
Description of Actual Data Sample:
  • Initial N: 46 patients, divided into either enteral nutrition (N=12), TPN (N=16) or combined (N=18)
  • Attrition (final N): 46 (37 men, nine women)
  • Age: Enteral nutrition, 63.1±16.1 years; TPN, 69.5±10.4 years; combined, 65.9±14.1 years 
  • Ethnicity: Not mentioned
  • Other relevant demographics: Mean APACHE II score of 18.0±4.2. APACHE II scores for Enteral nutrition, 17.3±4.2; TPN, 17.9±5.1; combined, 18.3±5.5
  • Anthropometrics: The three groups of patients were well matched for demographic characteristics. There were no statistically significant differences among groups for age, height, weight, IBW, severity of illness (APACHE II score), length of ventilator dependency, ICU stay or hospital stay at admission.
  • Location: Taiwan.
Summary of Results:

 All in Kcal per Day

Enteral Nutrition (N=12) TPN (N=16) Combined (N=18) Pooled (N=46)

Indirect Calorimetry

1,597.1±329.6 1,615.2±381.7 1,666.6±343.0 1,631.3±345.3
Harris-Benedict 1,318.5±158.6* 1,290.5±184.5* 1,276.6±171.9* 1,292.3±170.1*
Kleiber 1,348.8±142.9*  1,306.3±184.0* 1,305.3±152.9* 1,316±159.6*
Liu 1,390.9±134.7 1,370.5±194.6 1,354.6±158.2* 1,369±163.5*
Ireton-Jones 1,888.3±234.7* 1,760.2±230.0 1,839.8±233.0 1,824.8±232.9*
Fusco 1,529.7±148.4 1,464.7±214.6 1,469.6±170.8 1,483.6±180.4
Harris-Benedict x Stress Factor 1,614.3±223.6 1,589.3±244.0 1,572.5±262.4 1,589.2±241.6
Kleiber x Stress Factor 1,653.6±204.6 1,613.3±252.2 1,611.7±247.8 1,623.2±234.5
Liu x Stress Factor 1,704.5±183.7 1,693.0±266.6 1,672.6±245.2 1,688.0±237.7

Ireton-Jones x Stress Factor





Fusco x Stress Factor





*P<0.05 significantly different from indirect calorimetry.

 Pearson Correlation Coefficients


Enteral Nutrition (N=12) TPN (N=16) Combined (N=18) Pooled (N=46)
Harris-Benedict NS 0.784 0.559 0.624
Kleiber NS 0.766 0.563 0.613
Liu NS 0.730 0.480 0.555
Ireton-Jones 0.597 0.724 0.718 0.672
Fusco 0.589 0.763 0.593 0.639
Harris-Benedict x Stress Factor 0.623 0.659 0.545 0.577
Kleiber x Stress Factor 0.587 0.634 0.531 0.561
Liu x Stress Factor NS 0.576 NS 0.506

Ireton-Jones x Stress Factor





Fusco x Stress Factor





Other Findings

  • No significant difference was found in MEE among the three groups. The type of nutrition support did not affect MEE.
  • Mean differences in REE estimated by Harris-Benedict, Kleiber, and Liu without the added stress factor significantly under-estimated the measured EE by 20.8%, 19.3% and 16.0% below, respectively. EE estimated by Ireton-Jones without added stress factor overestimated measured EE by 11.9%.
  • EE calculated by the Harris-Benedict, Kleiber, and Liu equations with the estimated stress factor was not significantly different than the values of the MEE in all groups
  • However, EE calculated with Ireton-Jones or Fusco equations with the estimated stress factor significantly over-estimated the measured EE by 37.8% and 12.1%, respectively
  • There were significant correlations (P<0.01) between MEE and patients' sex (R=-0.499), age (-0.402), height (R=0.533), knee height (R=0.431), current body weight (R=0.379), usual body weight (R=0.407), IBW (R=0.466) and urinary urea nitrogen (R=0.383) in the Pooled Group.
Author Conclusion:
Results demonstrated that energy expenditure could be estimated in most critically ill patients by using Harris-Benedict, Kleiber and Liu equations if the estimated stress factor is in the reasonable value, however patient's actual weight and height must be considered when using equations to estimate patient's energy requirement.
Funding Source:
University/Hospital: Chung Shan University, Taichung Veterans General Hospital
Reviewer Comments:
Patients measured twice with valid IC protocol.
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? Yes
  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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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? Yes
  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.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
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? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  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.) N/A
  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? N/A
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? N/A
  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? N/A
  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? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  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? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  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? N/A
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