EE: Gas Collection Devices (2013)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  1. Determine whether there are significant differences among the values for oxygen consumption, the respiratory exchange ration (RER), and caloric expenditure obtained by open-circuit respirometry using the ventilated hood, the breathing mask, and the mouthpiece and nose clips.

Definitions

  • Steady state: defined as when the appropriate flow rate was attained and CO2 content of the air entering the mixing chamber was stabilized; length of time not specified
Inclusion Criteria:
  1. Understand and give written consent
  2. Adult males and females
Exclusion Criteria:
  1. Refusal to consent

(no inclusion or exclusion criteria provided other than adult males and females)

Description of Study Protocol:

Men and women were randomly assigned to 3 sequences of treatments, where each treatment consisted of one of the 3 measurement methods—ventilated hood, the breathing mask, and the mouthpiece and nose clips (each 20-min treatment periods

ANTHROPOMETRIC

  • Ht measured? Yes, method not described
  • Wt measured? Yes, method not described
  • Fat free mass? Not discussed

CLINICAL

  • Monitored heart rate? Not discussed
  • Body temperature? Not discussed
  • Medications administered? Not discussed

Resting energy expenditure

  • IC type: Open-circuit; Horizon Metabolic Measurement cart
    Each subject underwent 3 measurement methods:
    1. The ventilated canopy
    2. Hans-Randolph face mask
    3. Mouthpiece and nose clips
  • Equipment of Calibration: Yes
  • Coefficient of variation using std gases: Yes
  • Rest before measure: At least 30 min. prior to initial measurement
  • Measurement length: Three 20-min measurement periods:
    • Canopy: 20 min measurement period (continuous)
    • Mask and mouthpiece/nose clip: Two 5-min measurements were made within a 20-min period for each apparatus.
  • Steady state: Defined as when the appropriate flow rate was attained and CO2 content of the air entering the mixing chamber was stabilized; length of time not specified
  • Leakage of face mask: Tested for leakage by passing a mirror around the edges of the mask while the subject breathed in and out. Leakage was eliminated by readjustment or tightening of the mask or by application of a pliable plastic material intended for theatrical use around the edges of the mask.
  • Fasting length: Measured in the postabsorptive state
  • Exercise restrictions: Not discussed
  • Room temp: “Ambient air”
  • No. of measures within the measurement period: Depended on the apparatus used;
    • Canopy: Continuous 20-min measurement after steady state attained
    • Mask and mouthpiece/nose clip: Two-5-min measurement per each apparatus
  • Were some measures eliminated? No
  • Were a set of measurements averaged? The average of the two, 5-min measurements was calculated for the mouthpiece and mask methods.
  • Coefficient of variation in subjects’ measures? 3 subjects reported a feeling of claustrophobia while under the hood
  • Training of measurer? Not discussed
  • Subject training of measuring process? Time allotted before initial measurement for subjects to become familiar with each of the measurement techniques to be used

DIETARY

  • Not assessed

Intervening factor:  No other potential confounders identified

Data Collection Summary:

Outcome(s) and other measures

  1. VO2 (ml/min), VCO2 (ml/min), and the RER (RER=VCO2/VO2
  2. Converted to kcal/min with use of the Wier equation:
    kcal=[(1.1 X RER)+3.9] x VO2(L/min)

Blinding used: No

Description of Actual Data Sample:
  • N=18 men and women
  • N=8 males mean age: 28±5 y
  • N=10 females mean age: 29±3 y

 

Statistical tests

Sample size of 18 determined by calculating the number of observations needed to provide sufficient power (1-ß>0.95) with data from a previous study; Six replications of a Latin square were used in this study to evaluate the differences among the 3 methods while controlling for a possible period effect which would reflect changes in energy expenditure over the 3, 20-min measurement periods. Two-way analysis of variance were applied to the VO2, RER, and kcal data to determine the significance of the main-effects for method and period for each variable. The reliability of the two, 5-min duration measurements for the mask and mouthpiece methods was tested by the intraclass correlation method.

The level of statistical significance was established at p<0.05.

Summary of Results:

ANTHROPOMETRIC

 

Men Mean±SD

Wt, kg

74±9

Ht, cm

177±6

BMI

Not provided

Fat-free
body mass

Not provided

Fat mass

Not provided

Women Mean±SD Range

Wt, kg

60±10 not provided

Ht, cm

163±4

147-175

BMI

not provided

Fat mass

not provided

RQ

In regard to mean RER (±SEM), no significant effects were found for either period (first, second, or third 20-min measurement period) or method of measurement. However, (although not significant, p=0.07) there was a trend for a lower RER with the ventilated hood than the mask and mouthpiece.

The reliability of the two 5-min measures of the RER was r=0.859 for the mask and r=0.818 for the mouthpiece.

In regard to mean (±SEM) O2 consumption, RER, and kcal expenditure, no significant effects were found for either period or method of measurement.

RELIABILITY

The reliability of the two 5-min measures of VO2 was r=0.992 for the mask and r=0.977 for the mouthpiece. The reliability of the two 5-min measures of caloric expenditure was r=0.992 for the mask and r=0.979 for the mouthpiece.

The variation over the two 5-min trials, which represents error of measurement, was not significant for any of the variables for either the mask or mouthpiece.

Author Conclusion:

As stated by the author in body of report:

  • “Discrepancies among the results of studies of energy metabolism have been attributed in part to differences in test protocols and modes of measurement as well as heterogeneity of energy metabolism within groups of subjects.
  • “... the ventilated hood may provide more reliable results than other techniques, owing to discomfort and alteration in the subject’s natural breathing patterns and resistance to inspiration and expiration induced by a tightly fitting breathing apparatus. While the face mask is less restrictive than the mouthpiece and nose clips, leakage of air if a complete seal is not achieved is a potential source of considerable error.”
  • “The high reliability of the brief serial measurements of energy expenditure for both the mouthpiece and mask suggests that such a procedure, which reduces the duration of measurement and thus reduces discomfort to the subject from wearing the mask or mouth piece is an acceptable alternative. However, in many sick individuals or in individuals for whom the tightly fitting mask or mouthpiece and nose clips cause significant apprehension and discomfort, these methods may not be tolerated.”
  • “In summary, significant error in the estimation of energy expenditure is not introduced by use of a mask or mouthpiece compared with the ventilated hood if the former methods are applied carefully with attention to possible leakage in the instrumentation and familiarization of the subjects with the methods.”
Funding Source:
Government: NIH,
University/Hospital: Mount Sinai School of Medicine
Reviewer Comments:

Not used in conclusion Statement Grade due to limitations (especially generalizability).

Strengths

  • Good description of 3 apparatus
  • Power calculation to avoid type 2 error
  • Attention to possible leakage of face mask to reduce error
  • Familiarization of subjects to various apparatus to reduce anxiety prior to testing

Limitations

  • Small sample size; especially when broken down by 2 groups
  • Lack of discussion of inclusion and exclusion criteria other than 18 adult men and women with mean ages and mean heights and weights only (potential confounders)
  • Not clear as to how subjects were chosen (i.e., volunteers?) (selection bias?)
  • Did not discuss medication use (if any) or physical activity restrictions of subjects prior to testing
  • Limited generalizability; methods may not be tolerated in sick or in individuals for whom the tightly fitting mask or mouthpiece and nose clips cause apprehension and discomfort
  • Even with familiarization with apparatus, several subjects experienced claustrophobia; more time may needed to familiarize subjects with this apparatus
  • This method may not be generalizable to the outpatient setting; potential generalizability in a research setting.
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? 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
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? 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. 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
  2.1. 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
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.3. 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
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
  3. Were study groups comparable? 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
  3.1. 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
  3.2. 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
  3.3. 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
  3.4. 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
  3.5. 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
  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. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? N/A
  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
  4.2. 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
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.4. 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
  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. 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
  5.1. 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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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
  6.2. 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
  6.3. 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
  6.4. 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
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? N/A
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? 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. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  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
  10.2. Was the study free from apparent conflict of interest? N/A