EAL

EE: Respiratory Quotient (RQ) (2014)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To explore the disagreement between use of the Harris-Benedict or Owen formula with regard to prediction of resting metabolic rate in young men.

Inclusion Criteria:

Healthy
Non-smoking
Weight-stable men
Between ages 18 and -33 years
Giving consent.

Exclusion Criteria:

Professional or competitive athletes
Individuals with perforated eardrum
Recent weight change
Using drugs or medications
Unusual diets
Not giving consent.

Description of Study Protocol:

Recruitment

Informal advertisements placed around a university and a hospital.

Design

Cross-sectional study with randomized assignment to order of testing.

Blinding Used

Group assignment by test order; however, researcher participated in measurements. No blinding was used.

Statistical Analysis

Subjects were segregated into two groups on the basis of the measurement instrument used first on the first day:
- Modified method of Hills and Armitage used to test possibility that order of measurements affected the results in order to carry out a four-period replicated crossover analysis
- This was accomplished by entering the average of the results with each instrument for the two days into the equation
Two-tailed paired T-test was used for comparisons between measurement days and instruments.

Data Collection Summary:

Timing of Measurements

Study was carried out during hot summer months
First visit: Training visit; data not used
Testing visits: Full test of RMR by use of two measurement methods separated by one to 14 days (4.1±3.9 days); instrument used first on the first day was chosen at random and then used second on the second day.

Dependent Variables

Measured RMR using two methods:
- Indirect Calorimeter (Ventilated Hood): Lusk's equations used to determine RMR from data:
  - IC type: Ventilated hood
  - Air flow: 38.36±0 (19L per minute, N=10 tests)
  - Rest before measure: Supine with head elevated between 20 to 30 degrees for more than 20 minutes
  - Measurement length: 10 minutes with first four minutes under canopy where data were collected, but not included in study analysis
  - Fasting length: 12- to 14-hour fast
  - Exercise condition: Not reported
  - Room temp: 21°C to 25°C
  - Outdoor temp: July or August
  - Number of measures: Two measures separated by one to four days (4.1±3.9)
  - Calibration: Yes; constancy was verified by three RMR measurements on one of the investigators over the period of the study
  - Subject training: Yes, before the measurement
  - Training of measurer: None reported
- Respirometer: Data converted to RMR by use of the equation, Energy generated (kcal per minute) = 4.83 X oxygen uptake (L per minute)
  - Type: Nine-L respirometer corresponding to the Benedict-Roth apparatus
  - Rest before measure: Supine with head elevated between 20 to 30 degrees for 20 minutes or more
  - Measurement length: 10 minutes; First four minutes of data were collected but not included in analysis
  - Fasting length: 12 to 14 hours
  - Exercise condition: Not reported
  - Subject training: Yes, before the measurement
  - Room temp: 21°C to 25°C
  - Outdoor temp: July or August
  - Calibration: “Tested for leaks and operated according to the original operating manual and other appropriate instructional information.”
Predicted RMR using three formulas: Harris-Benedict, Schofield et al, Owen et al.

Independent Variables

Age
Height: Measured barefoot
Weight: Measured with very light clothes (less than 1.0kg)
Body Mass Index (BMI): kg/m².

Control Variables

Heart rate and blood pressure: Measured unobtrusively at the beginning, middle and end of each RMR measurement using an automatic digital sphygmomanometer-heart rate monitor; heart rate calculated as the average of three 15-second sampling periods.

Description of Actual Data Sample:

Attrition (final N): N=29 Caucasian males; no dropouts due to invalid results or inability to adapt to the instrumentation
Age: 24.4±3.3 years; range 18 to 33 years
Ethnicity: All were Caucasian
Other relevant demographics: Unplanned demographic characteristic included one subject taking phenytoin for an inactive seizure disorder; no other subjects were taking medication.

Anthropometrics

Mean ±SD height (cm): 178.2 ±6.5
Mean ±SD weight (kg): 73.4± 9.8.

Location

Montreal, Quebec, Canada.

Summary of Results:

By paired T-test, there was no training effect on RMR (day one vs. day two) with either the respirometer (P=0.98) or the ventilated hood (P=0.58).

Predicted RMR, kcal per Day

	Mean ± SD
HB	1,813±164
Schofield	1,793±149
Owen	1,624±99

Measured Resting Oxygen Consumption

Day One:

Group	Range
Group VR_RV*
VO2 (Respirator)	250±21
VO2 (Ventil Hood)	241±24
RQ (Ventil Hood)	0.82±0.05
Group RV-VR**
VO2 (Respirator)	2,450±23
VO2 (Ventil Hood)	23±19
RQ (Ventil Hood)	0.81±0.05

Day
Two

Group	Range
Group VR_RV*
VO2 (Respirator)	251±224
VO2 (Ventil Hood)	230±25
RQ (Ventil Hood)	0.79±0.00
Group RV-VR**
VO2 (Respirator)	245±20
VO2 (Ventil Hood)	232±19
RQ (Ventil Hood)	0.83±0.00

*VR-RV-Ventil hood first followed by respirator; On day two the reverse order was followed.

**RV-VR-Respirator first followed by ventil hood; on day two, the reverse order was followed.

Combined Results of RMR and Predictive Equations

Combined Results of Resting Metabolic Rate, Heart Rate and Blood Pressure*
	Measured Value	Percentage ± 95% CI of Value Predicted by Harris-Benedict	Percentage ± 95% CI of Value Predicted by Schofield	Percentage ± 95%CI of Value Predicted by Owen
Respirometer
Heart rate (bpm)	56±7
Blood pressure (mm Hg)	116/66±7/5
RMR (kcal per day)	1,721±145^##	95.2±2.9^#	96.2±2.7^#	105.8±2.8^#
Ventilated hood
Heart rate (bpm)	56±7
Blood pressure (mm Hg)	114/65±7/5
RMR (kcal per day)	1,643±148	90.8±2.4¹	91.8±2.3¹	101.0±2.5

^# P<0.05 compared to measured RMR.
^## P<0.001 compared to ventilated hood.

¹P-value not given.

There was a strong correlation between individual values on both instruments (R²=0.80, P<0.001)
The standard error of the regression, which quantifies the random error between methods, was 68kcal per day
True systematic differences between subjects and those of HB, HB original data re-examined; the heart rate was 8% higher in HB subjects’ as compared to the current subjects' resting heart rate [61.2±6.6 bpm vs. 56.3±7.9 bpm (P=0.002)].

Author Conclusion:

“RMR measured by using the ventilated hood is consistently lower than that measured with the classic spirometric oxygen-rebreathing system used to generate . . . Harris-Benedict . . equations”
“The ventilated-hood IC avoids [measurement] difficulties and has the important advantage of output variable calibration by determination of RQ and CO² production”
“Our results of ventilated hood are virtually identical to those predicted from the equation of Owen”
“Although RMR is extremely constant upon repeated measurement, there is an initial training effect that may be important. . . [especially] to obtain maximal relaxation (but without sleep)”
“In our study the RMR by respirometer was 4.8% lower than that predicted by the HB equation when a similar technique was used. . . Mifflin over-predicted RMR by 5% less than HB [using the respirometer].”

Funding Source:

Government:

Medical Research Council

Not-for-profit

Reviewer Comments:

Strengths

“The researchers’ efforts to “re-create” the Respirometer used by Harris-Benedict. While the Nine-L Respirometer was “tested for leaks and operation,” there is higher probability it lacked precision of the ventilated hood, causing instrumentation bias”
Order of testing randomized
Training test conducted prior to collection of data.

Weaknesses/generalizability

“Initially I had concerns regarding Subject Number Three having a BMI of 42.3 as being healthy. However, a recalculation indicates it is a typo.
Convenience sampling and small sample size has risk of selection bias and limits to larger populations
Body temperature (either as a result of the hot weather or metabolism) and prior exercise are variables that were not measured and may influence REE. Also, one subject on a medication “phenytoin” for seizure and time medication was taken was not clarified.
“Study could not qualify for positive because of Relevance Question Number Four, “Is the procedure feasible?” which was answered NO based on the fact that HB respirometry is not feasible in today’s practice”
[NOTE: Comment in Am J Clin Nutr by Azanski MP, et al, 1991 were challenges to the potential of systematic measurement error since comparison of measured results in young men did not agree with HB equations and findings were not supported by similar research by Asanski and Fukagawa (1990). In response, Clark reports that results fall within HB error of prediction. The “mild discomfort” discussed are found in HB respirometer and in ventilated hood.

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)	No

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?		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?	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?		???
	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?	???
	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.)	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?	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?	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?		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?	No
	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?	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?		???
	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?	No
	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