CI: Best Method to Estimate RMR (2010)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To evaluate the agreement between the indirect calorimetry method and the Harris-Benedict method of estimating energy expenditure in critically ill trauma patients.
Inclusion Criteria:

Critically injured, mechanically ventilated trauma patients admitted to SICU.  Inclusion criteria included:

  • Absence of seizure activity, agitation and shivering
  • FiO2 < 80%
  • Medical or surgical hemodynamic stability
  • Body temperature < 37.8 degrees C
  • Pain controlled
  • More than 6 hours after anesthesia
Exclusion Criteria:
Excluded if not included above.
Description of Study Protocol:


Patients consecutively enrolled over an 8-month period.


Cross-sectional study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

RMR measured using indirect calorimetry and compared to Harris-Benedict equation.

Statistical Analysis

Interclass correlation used to test agreement between BEE unmodified vs MREE, BEE with ICF vs MREE, and BEE with ICF vs MREE plus 20% to account for fasting state (10%) and routine ICU activity (10%).  Agreement also analyzed by dividing subjects into high and low Injury Severity Score groups.  To determine the effect of high vs low Injury Severity Scores on energy expenditure, multiple independent t tests were computed.  Pearson correlation coefficients were derived to determine relationships between select variables and energy expenditure.

Data Collection Summary:

Timing of Measurements

RMR measured twice using indirect calorimetry and predicted using Harris-Benedict equation.

Dependent Variables

  • RMR measured with indirect calorimetry using Sensormedics Deltatrac Metabolic Monitor for 2 consecutive 30-minute readings taken 4 - 6 hours apart within 72 hours of admission to SICU, gas calibration performed before each measurement.  Following measurements, all subjects who had remained on the same ventilator settings in 4 hours and who had not developed exclusion criteria received a second measurement.  All measurements ranged from 16 - 72 hours after hospital admission and 6 - 56 hours postoperatively.  Measures with an SD > 10% were eliminated. 
  • RMR estimated using Harris-Benedict equation with usual body weight and addition of selected injury correction factor (1.3 for nonstressed, nutritionally sound patients, 1.4 for minimally stressed patients, 1.5 for moderately stressed patients, 1.6 for severely stressed patients, 1.7 for extremely stressed patients, and 2.1 for major thermal injury).  Factors ranged from 1.4 to 1.75 and were agreed upon by all members of metabolic team.

Independent Variables

  • SICU environment was kept thermoneutral with room temperature control at 22.2 C
  • Patient in a fasting state
  • Patients were either sleeping undisturbed or sedated with morphine sulfate and midazolam hydrochloride so that minimal voluntary movement occurred 
  • Subjects undisturbed for at least 20 minutes

Control Variables

  •  Height, weight, sex
Description of Actual Data Sample:

Initial N: 24 patients, 75% male, 25% female

Attrition (final N):  24

Age:  39.7 +/- 20.7 years, range 18 - 83 years

Ethnicity:  not mentioned

Other relevant demographics:  None of the subjects were obese


Location:  California 


Summary of Results:


Variables by ISS

Mean +/- SD


t test


Unmodified BEE - low ISS  783.5 +/- 252.8  990 - 2010  -1.27  0.216

Unmodified BEE - high ISS

 1641.4 +/- 305.3

 1464 - 2300



BEE with ICF - low ISS  2750.3 +/- 310.7  1633 - 3179  -1.27  0.216
BEE with ICF - high ISS  2534.2 +/- 484.1  2265 - 3450    
MREE - low ISS  2227.2 +/- 343.2  1420 - 2370  -2.33  0.029
MREE - high ISS  2311.3 +/- 348.3  1810 - 2740    
MREE + 20% - low ISS  2627.7 +/- 411.9  1704 - 2844  -2.33  0.029
MREE + 20% - high ISS  2311.3 +/- 348.3  2172 - 3348    
Age - low ISS  36.7 +/- 17.9  18 - 78  0.64  0.529
Age - high ISS  42.2 +/- 23.2  18 - 79    
Measurement time of MREE after admission - low ISS  49.1 +/- 18.3  16 - 62  -2.18  0.04
Measurement time of MREE after admission - high ISS  35.1 +/- 12.2  21 - 72    
Measurement time of MREE after surgery - low ISS  30 +/- 14.8  20 - 52  -1.05  0.30

Measurement time of MREE after surgery - high ISS

 24 +/- 13.3

 7 - 56



Other Findings

The interclass correlation between unmodified BEE and MREE was 0.24, which was not statistically significant (F = 0.625, p > 0.05). 

The predicted BEE with addition of an ICF was not in agreement with MREE (Icc = 0.05, F = 1.11, p > 0.05), and BEE with and without ICF were not in agreement.

The predicted BEE with an ICF was in significant moderate agreement with MREE when 20% was applied to the measurement (ICC = 0.59, F = 3.92, p < 0.05).

For low injury severity scores (16 - 24), there was significant agreement between MREE and BEE with ICF (ICC = 0.59, p = 0.03), however, there was no significant agreement between MREE and BEE with ICF in the high injury severity scores (25-40), (ICC = 0.49, p > 0.05).


Author Conclusion:
As a result of this study, an agreement between predicted BEE with the addition of an injury correction factor and MREE is recognized.  With the addition of routine ICU physical activity factor (10%) and accounting for the fasting state (10%) to MREE (a total addition of 20%), BEE with the correction factor was found to be in agreement with adjusted MREE.
Funding Source:
Reviewer Comments:
Subjects measured twice.  Valid IC protocol.  Usual body weight used in equation.
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) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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.) N/A
  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? 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? N/A
  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