EE: Number of Measurements (2005)

Citation:

Stokes MA, Hill GL. A single, accurate measurement of resting metabolic expenditure. JPEN J Parenter Enteral Nutr. 1991;15(3):281-287.

PubMed ID: 1820760
 
Study Design:
Prospective Cohort Study
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Negative NEGATIVE: See Quality Criteria Checklist below.
Research Purpose:
  1. Identify what conditions were necessary to achieve a single accurate measurement of resting metabolic expenditure (RME)
  2. Test the hypothesis: A second RME measurements is more accurate than the initial measurement.
Inclusion Criteria:
  1. Understand and give written consent
  2. Diseases in subjects that were allowed:
  3. Either admitted for elective surgery and were normally nourished and had no known serious illness OR patients referred for assessment of their nutritional status
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria
Description of Study Protocol:

Definitions:

Harris Benedict formula – matches study definition

RME calculated [LosAlamos] formula – RME = TBK X 0.314 + 521

RME calculated from Kinney & colleagues [Boston] - 0.899 X 10 -4 X TBK + (0.83 X TBK) + 250

ANTHROPOMETRIC:

  • Ht measured? Not reported
  • Wt measured? Yes

CLINICAL:

  • Monitored heart rate? Not reported
  • Body temperature? No
  • Medications administered? No

Resting energy expenditure:

  • IC type: hood calorimeter
  • Equipment of Calibration: Calibrated daily
  • Coefficient of variation using std gases: Yes or No
  • Rest before measure (state length of time rested if available): Yes, 30 minutes
  • Measurement length: Not reported
  • Steady state: Not reported
  • Fasting length: overnight or for at least 3 hr after a light breakfast
  • Exercise restrictions XX hr prior to test? Not reported but doubt d/t medical illnesses represented
  • Room temp: 21-25 degree C; 50% water vapor saturation
  • No. of measures within the measurement period:
  • Were some measures eliminated?
  • Were a set of measurements averaged?
  • IF avg, identify length of each measure & no. of measurements?
  • Coefficient of variation in subjects measures?
  • Training of measurer? Description indicates measurer knowledge
  • Subject training of measuring process? Not reported
  • TBK measurement:Uses a shadow shield counter. Patient lies on a motorized bed and is moved from head to toe between the two detectors. The time of each scan is preset and depends on the patients height; from this measure of K40, less the measured background count, the TBK can be calculated. The TBK scanner has an overall precision for determining TBk in the range of 1.8-3.0%
  • Weight measuring procedures: Not discussed

 

Data Collection Summary:

Outcome(s) and other measures

  1. Measured REE [(VO2, l/min), VCO2 (l/min; ml/kg/min), RQ, ventilation (l/min)].
  2. Total body potassium (TBK) using the K-scanner
  3. Independent variables of age, sex, height and weight

Blinding used: No
Description of Actual Data Sample:

Preliminary Study Sample:

  • N= 5 healthy volunteers
  • N=1 studies over 2-24-hr periods with hourly measurements; For one 24-hour period, the individual was allowed to eat and drink liquids. For the other 24-hr period, the individual was only allowed water. 25 measurements were made from 0800 to 0800 the next day.
  • The effect of lighting was studied by 10 paired measurements performed sequentially.

Actual Sample:

  • N= 40 patients; aged 17-85 y (mean 46 y)
  • N= 21 males; N= 19 females

The normal and malnourished patients did not differ with regard to age and sex.

Normal patients: N= 20 patients; mean 43 + 4.2 y

Nutritionally depleted patients: N= 20 patients; mean 49 + 5.0 y

Diseases: 20 admitted for elective operations (e.g.,., hernia repair or cholecystectomy) were normally nourished.

20 nutritionally depleted patients: Diseases represented included ulcerative colitis, pancreatitis, fractured hip, mesenteric infarction, small intestinal fistula, Crohn’s disease, apyoderma gangrenosum and cecal volvulus with a stress index from .96-1.45.

Weight: The entire group had a mean wt of 63.5 kg and weights differed significantly between normally-nourished and nutritionally-depleted patient group. (71.6 kg vs. 55.3 kg, p<0.0005).

Statistical tests: Paired t-test, Correlation coefficient, Line of regression using F-test.

Summary of Results:

MEASUREMENT PROCESS:

  • Number of measurements: 2 measurements: Indirect calorimetry was performed following rest, then TBK was measured using the K scanner, and calorimetry was re-measured.
  • The second RME measure is closer to predictive formulas of Harris Benedict equations, making the second measure more accurate.

Length of measurements: Not reported

Steady state: Not reported

There was a fall in RME between the two measurements in 34 of the 40 patients; the mean fall in RME was 125 kcal/d (SE=23; or 7.9%). This was statistically different (p = 0.0001). The fall did not correlate with the size of the RME. The mean fall was greater in the normal patients but RME feel significantly in both groups (normal patients - p=0.0001 and nutritionally depleted patients = 0.02).

RQ: The RQ did not alter significantly, falling from 0.83+ 0.12 (mean +SD) to 0.81+0.1.

INDIVIDUAL CHARACTERISTICS:

  • For normal and nutritionally depleted patients, the results from Harris Benedict equations do not differ significantly from those measured.
Author Conclusion:
  • In the main study, we have shown that the second measurement of RME in these patients is significantly lower than the initial reading. The fall was more marked in the elective patients but was significant in both groups; the initial measurement overestimated RME by a mean of 125 kcal/d
  • Previous findings suggest Harris-Benedict equations estimate RME for normal individuals with a precision of 14% . . our mean RME as estimated by Harris-Benedict equations was within 3% or our measured RME for the normal patients; these equations are not reliable in malnourished patients.”
  • Conditions that vary in studies is that the Boston study was measuring TEE, not RME, this would explain why it is 25% higher than expected.
  • One limitation of our study is [none listed]
  • [Preliminary studies] on the background factors that may affect RME have led to a modification of our protocol. Now, (12) the patient is rested, (2): the patient is post-prandial (at least 3 hr after alight breakfast, longer after a larger meal), (3) there are no loud noises or distractions, and (4) the patient has already been acclimatized to the hood.
  • This study has shown that the lower measurement is more accurate and is significantly lower than when the pat were not acclimatized to the hood. This difference is important in calculating the degree of metabolic stress and energy requirements.

REVIEWER’S NOTE: A Comment was made in the JPEN J Parenter Enteral Nutr. 1992;16(2):193-194. “There is nothing new relative to the measurements of patients at rest or in a postprandial state or conditions concerning how long the single measurement needs to be made. The authors also indicated that I used a 5- to 10-minute measurement of RME to estimate the 24-hour total energy requirements of patients- - all my published data on RME measurements have been with my ventilated hood system over a 20- to 30-minute period in the morning before breakfast or intake. “ Dr. Calvin Long

Funding Source:
Government: FDA, FAA
University/Hospital: University of Illinois Institute of Aviation
Reviewer Comments:

Strengths: 

  • Completed preliminary testing of study protocol on 5 subjects.

Generalizability/Weaknesses: 

  • Small sample size – no differentiation between genders and age
  • Generalizable to patients electing surgery or nutritionally-depleted r/t to critical illness in New Zealand.
  • Nutritionally-depleted sample required a nutrition referral; hence, this subject population contains a nutrition referral bias
  • The researcher did not identify the measurement length of the IC tests nor address steady state. Body temperature was also not addressed.” Also, confounding effect on anxiety of forthcoming body potassium test not accounted for. No rest period following TBK test and second REE measurement.
  • Other important variables on REE measurement accuracy is if any pts receiving enteral or parenteral nutrition.
  • No drop-outs were reported due to decreased tolerance to IC measurement – question if sampling bias r/t to exclusion?
  • Working Group Members had a question regarding anxiety as a confounding factor in the difference between the first and second measure.
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? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
2. Was the selection of study subjects/patients free from bias? No
  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? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
3. Were study groups comparable? No
  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? No
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  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? 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? N/A
  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? N/A
  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? 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? No
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  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? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
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? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  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? N/A
  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? No
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A