EE: Gas Collection Devices (2013)
McAnena OJ, Harvey LP, Katzeff HL, Daly JM. Indirect calorimetry: Comparison of hood and mask systems for measuring resting energy expenditure in healthy volunteers. J Parenter Enteral Nutri. 1986; 10: 555-557.
To evaluate the accuracy and reproducibility of repeat measurements of resting energy expenditure (REE) in volunteers.
Steady state: Equilibration of respiratory values.
- Understand and give written consent
- Healthy (none had a history of endocrine or respiratory dysfunction)
- Not on medications
- Not trained in pulmonary function or respiratory measurement.
Refusal to consent.
- Height measured? Yes, method not described
- Weight measured? Yes, method not described
- Lean body mass? Calculated from triceps, biceps, subscapular and suprailiac skinfold measurements, and body weight using the equations of Durnin and Womersley.
- Heart rate? Not discussed
- Body temperature? Not discussed
- Medications administered? No.
- Resting energy expenditure:
- IC type: paired measurements performed on 23 occasions using both hood and mask systems
- Equipment of Calibration: Yes; For O2, accuracy = ±0.01% with hood and ±0.02% with mask; for CO2, accuracy = ±0.02% with hood and ±0.1% with mask. With the mask system, measurement of expired volume with the turbine meter (accurate to ±2% of reading) also affects analysis.
- Coefficient of variation using std gases: Yes; containing 16% O2, 4% CO2, 80% N2 and O2 free 100% N2
- Rest before measure: At least 20 minutes prior to initial measurement
- Measurement length: Measurements were performed continuously with averages obtained at four-minutes intervals for at least one hour on at least three occasions for each apparatus (23 occasions total?)
- Steady state: After initial 20 rest, subjects remained supine with equipment in place until equilibration (steady state) was achieved. (Remeasured with second apparatus within five minutes so that subject’s position and environment remained unchanged throughout both measurements)
- Fasting length: Overnight for at least eight hours
- Exercise restrictions: Not mentioned
- Room temp: Not mentioned
- Number of measures within the measurement period: Not clear
- Were some measures eliminated? Yes, non-steady state
- Were sets of measurements averaged? Yes, four-minute intervals
- Coefficient of variation in subjects’ measures? Not discussed
- Training of measurer? Not discussed; Likely
- Subject training of measuring process? Not discussed.
Outcome and Other Measures
- Data were calculated from paired measurements (using both hood and mask systems) as kcal per day and as percent-predicted REE
- Lean body mass was calculated from triceps, biceps, subscapular and suprailiac skinfold measurements, and body weight using the equations of Durnin and Womersley
- Estimation of kcal utilized per day was determined using the modified Wier formula as follows: REE (kcal per day)=[3.9 (VO2)+1.1 (VCO2)] 1,440 minutes per day (VO2 - liters per minute, VCO2 - liters per minute)
- Independent variables of:
- Body weight
- Lean body mass.
- N=28 healthy non-obese men and women (volunteers):
- Mean age: 28.8±0.96 years
- N=10 males mean age 28.9±1.5 years (range not provided)
- N=18 Females mean age 28.7±1.3 years (range not provided)
- N=18 subjects utilized for paired mask and hood testing
- Abstract indicates 23 paired measurements completed in 18 subjects
- Breakdown of 18 by gender, age and anthropometrics not provided.
- Statistical tests: Two-way analysis of variance was used for determination of significance (P<0.05).
|Weight (kg)||74.1±1.6||Not provided|
|Height (cm)||176.4±2.2||Not provided|
|BMI||Not provided||Not provided|
|Fat-free body mass||Not provided||Not provided|
|Fat mass||Not provided||Not provided|
|Weight (kg)||56.6±1.4||Not provided|
|Height (cm)||16.3±1.1||Not provided|
|BMI||Not provided||Not provided|
|Fat-free body mass||Not provided||Not provided|
|Fat mass||Not provided||Not provided|
- Showed a significant difference in hood and mask systems when paired data were compared (hood=0.87±0.02, mask=0.72±0.01). This did not affect the REE correlations between hood and mask systems.
- REE, expressed per kg lean body mass or as percent predicted resting energy expenditure (%PREE=actual REE/predicted REE) showed no significant difference using the hood or mask systems when either individual or paired data were compared
- Linear regression analysis showed a strong positive correlation (R=0.91, P<0.001) between hood and mask measurements of REE.
- This study was designed to evaluate any differences in measuring REE using two, popular methods of IC, particularly in the same subject. We could determine no significant differences in mean REE measurements using the mask and ventilated hood systems.
- The RQ values obtained using the metabolic cart were low. The probably reason for the lower RQ values obtained by the metabolic cart is the decreased sensitivity and accuracy of the O2 and CO2 analyzers of the metabolic cart compared to the hood system. A 10% error in the data received by the metabolic cart’s computer would lower the RQ from 0.88 to 0.70. Errors in the data can include inaccurate readings, inadequate drying of air samples, non-linearity of the analyzers and improper calibration of the conversion of electrical signals from the analyzers to the computer
- Although the measurement of RQ can vary significantly between the two systems, serial measurement of REE does not appear to require any one system or another to be used to obtain reliable and reproducible data
- This study shows that a strong positive correlation exists between hood and mask systems for determination of REE in healthy adult volunteers. There was no significant difference in mean REE for hood and mask systems when tested by analysis of variance. Furthermore, both hood and mask systems displayed similar variability on the same subject tested on multiple occasions. Further studies are necessary to confirm the applicability of these results in post-operative patients.
- Good description of two IC apparatus and calibration (accuracy)
- Multiple skinfold site measurements for determination of lean body mass.
- Small sample size (number of subjects is not clear; abstract states 23 subjects; text indicates 18 subjects and table of subjects provides information on 28 subjects)
- Text of paper discusses paired measurement methodology and results, but does not explain why paired measurements were performed on only a subset or how that was determined
- Gender, age and anthropometrics provided on 28 individuals but not on subset used for paired measurements
- Not clear on how IC measurements on 23 occasions were obtained. In the text, each subject was measured on each apparatus (mask or hood) for at least one hour on at least three occasions and then remeasured, utilizing the second system for at least one hour on at least three occasions. (How does six occasions become 23?)
- Methodology on obtaining heights and body weights was not reported (measured or self-reported?).
- Factors that might affect outcomes: Information on physical activity prior to measurement or subject training, which might reduce anxiety with apparatus known to cause discomfort (mask) were not accounted for
- Did not report a power calculation indicating a sample size necessary to detect a difference of X% with an alpha of X and a beta of X
- Generalizability: Relatively young adult subjects, healthy, convenience sample (self-selection bias)
- Results may not be applicable to hospitalized population.
Quality Criteria Checklist: Primary Research
|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|
|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?||???|
|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?||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?||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?||Yes|
|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?||No|
|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?||Yes|
|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|