EE: Duration of Measurement (Steady State) (2013)


van Lanschot JJ, Feenstra BW, Vermeij CG, Bruining HA. Calculation versus measurement of total energy expenditure. Critical Care Medicine. 1986; 14: 981-985.

PubMed ID: 3095026
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To determine the discrepancy between BEE calculated from the basic Harris-Benedict formula and TEE measured by continuous IC in a heterogeneous group of mechanically ventilated surgical patients
  • To compare the accuracy of TEE calculated from the corrected Harris-Benedict formula or estimated by intermittent IC to that of TEE measured by continuous IC.
Inclusion Criteria:
  • All patients were mechanically ventilated with an inspired oxygen concentration of 60% or less
  • At least six hours post-anesthesia, in order to avoid the influence of nitrous oxide on gas-exchange measurements
  • Medications allowed: Seven were heavily sedated and five were treated with muscle relaxants in surgical ICU.
Exclusion Criteria:
  • Patients with air leakage
  • Patients with active bleeding
  • Patients with subcutaneous emphysema
  • Patients on dialysis
  • Not meeting inclusion criteria.
Description of Study Protocol:


Patients in surgical ICU.


Cross-sectional study.

Statistical Analysis

  • Linear correlations between the measured total energy expenditure (TEE) values and the calculated basal energy expenditure (BEE) values and the TEE values obtained by the other methods were determined with an advanced technique in order to be able to compare the statistical significance of two different correlation coefficients by the Student's T-test
  • A best fit was computed by linear regression analysis.
Data Collection Summary:

Timing of Measurements

One measurement over a 24-hour period:

  • VO2 and VCO2 were computed each minute
  • Short sections of the 24-hour recording were used to assess three estimates of TEE; these intervals began at least 30 minutes after a ventilatory intervention:
    • One five-minute interval starting at 8:00 A.M.
    • One 10-minute interval starting at 8:00 A.M.
    • The average of two five-minute intervals starting at 8:00 A.M. and 5:00 P.M., respectively.

Dependent Variables/Outcomes

  • Discrepancy between formula-calculated BEE and continuously measured TEE
  • Accuracy of TEE calculations and intermittent TEE estimations compared with continuous TEE measurements obtained by IC.

Independent Variables

  • Formula calculated BEE vs. measured TEE:
    • Diurnal VO2 and VCO2 were determined by summing all the minute-figures during the 24-hour recording period
    • The 24-hour TEE (kcal per 24 hours) was determined using the abbreviated Weir Equation: TEE = 3.9 VO2 + 1.1 VCO2; where VO2 and VCO2 are expressed in L per 24 hours at STPD
    • IC type: Metabolic cart
    • Rest before measure (state length of time rested if available): Recording intervals began at least 30 minutes after a ventilatory intervention
    • Measurement length: Continuous measurements over 24-hour period. VO2 and VCO2 were recorded continuously every minute for 24 hours; in addition, there were short sections of the 24-hour recording (One five-minute interval starting at 8:00 A.M., one 10-minute interval starting at 10:00 A.M. and the average of two five-minute intervals starting at 8:00 A.M. and 5:00 P.M., respectively)
    • Room temperature: Neutral thermal
    • Were some measures eliminated? Artifacts due to ventilatory disconnections were removed automatically by an algorithm; the algorithm suppressed the next five minutes and the last minute just before the detected artifact from the summing procedure
    • Were a set of measurements averaged? There were two five-minute intervals starting at 8:00 A.M. and 5:00 P.M., respectively, that were averaged. These intervals began at least 30 minutes after a ventilatory intervention.
    • Medications administered? Yes; seven were heavily sedated and five were treated with muscle relaxants
    • Estimated BEE:
      • Used Harris-Benedict (standard formula to calculate BEE (kcal per 24 hours)
      • Used correction factors based on patient clinical condition to calculate TEE from the corrected Harris-Benedict formula
      • Correction factors: Infections, recent extensive operations, respiratory distress syndrome, burn wounds and elevation of body temperature all have an influence, depending on its severity, on TEE. For example, the correction factor for severe infection or sepsis; recent extensive surgery; or fracture or trauma can range from 10% to 30% (percent above 100%); respiratory distress syndrome, 20%; burn wounds, 50% to 150%; and elevated body temperature 12% per °C above 37°C.

      • Corrected Harris-Benedict calculations of TEE were compared to continuous IC measurements of TEE

  • Estimations of TEE from intermittent readings vs. measured TEE:
    • The abbreviated Weir equation was also used to assess three estimates of TEE from short sections of the 24-hour recording (one five-minute interval starting at 8:00 A.M., one 10-minute interval starting at 8:00 A.M. and the average of two five-minute intervals starting at 8:00 A.M. and 5:00 P.M., respectively).


Description of Actual Data Sample:
  • Final N: N=25; 19 male, six female
  • Age: Mean age was 56 years (range 15 to 83 years)
  • Location: The Netherlands.
Summary of Results:


  • There was a low correlation between BEE calculated from the basic Harris-Benedict formula and TEE measured by continuous IC. The coefficient of correlation was 0.5±0.2 (SEM)
  • The mean correction factor was 46%±17% (SD)
  • The corrected Harris-Benedict calculations of TEE as compared to continuous TEE measured by IC resulted in an improved correlation [P<0.05; correlation coefficient is 0.82±0.07 (SEM)]
  • The mean absolute difference between calculated and measured TEE was 8.9%±9.6%. This difference was less than 10% in 19 patients. It was between 10% and 20% in three patients, between 20% and 30% in two patients and above 30% in one patient. 

Comparison of Estimated TEE to Measured TEE (Correlation Coefficient)

  • Five-minute TEE estimate: 0.90±0.04 (SEM)
  • 10-minute TEE estimate: 0.92±0.03 (SEM)
  • Average two five-minute TEE estimate: 0.95±0.03 (SEM)*.

*Of the three above estimates, only the average produced TEE values significantly (P<0.05) more accurate than calculated TEE values.

Author Conclusion:
  • Some authors deny the existence of a relevant hypermetabolic state and the necessity of a clinical correction factor; however, we found a significant discrepancy (i.e., poor correlation) between calculated BEE and measured TEE, which was decreased by supplemental application of the clinical correction factor based on each patient’s clinical condition (calculated TEE)
  • In our group of mechanically ventilated surgical patients, application of the Harris-Benedict formula combined with careful judgment of the clinical condition led to an average difference between calculated and continuously measured TEE of 8.9%±9.6%. Rutten et al proposed multiplying BEE by 1.75 to provide a better calculation of caloric needs compared to the basic Harris-Benedict formula in acutely ill patients; however, this over-estimates caloric needs by 50% to 60%.
  • As an alternative to using BEE with a correction factor IC is generally accepted as reliable for TEE determination. IC has been used with recording periods varying from a few minutes to several hours per day. Continuous 24-hour measurement also has been advocated because VO2 and VCO2 in critically ill patients can fluctuate substantially with changes in body temperature, discomfort and pain, medication and nutrition. This suggests that if continuous measurements are not used, the reliability of intermittent measurements will be related to their duration and frequency, which is confirmed by the results of this study. Calculations were significantly (P<0.05) improved by estimating TEE from two five-minute recording periods, which suggests that continuous IC may not always be necessary to guide caloric replacement.
  • Further investigations are necessary to determine whether the discrepancy between calculated and continuously measured TEE is clinically relevant
  • In spontaneously breathing patients, the obligatory use of a head canopy or a mouthpiece/noseclip probably requires metabolic gas-exchange measurements over a longer period, because these techniques frequently lead to a disturbance of patient’s body gas stores.
Funding Source:
University/Hospital: University Hospital Dijkzigt and Erasmus University
Reviewer Comments:


  • Wide age span
  • Continuous 24-hour measurement period. 


  • Questionable validity of indirect calorimeter
  • Limited generalizability; highly heterogeneous group of surgical ICU patients on ventilators
  • Anthropometrics were not provided.


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? ???
3. Were study groups comparable? N/A
  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? 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")? N/A
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) No
  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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? ???
  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? N/A
  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? 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)? N/A
  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