EE: Gas Collection Devices (2006)


Askanazi J, Silverberg PA, Foster RJ, Hyman AI, Milic-Emili J, Kinna JM. Effects of respiratory apparatus on breathing pattern. J Appl Physiol. (Respir Environ Exercise Physiol). 1980;48:577-580.

Study Design:
Randomized Crossover Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To study the effect of respiratory apparatus on breathing pattern.
Inclusion Criteria:
  1. Understand and give written consent
  2. Healthy adults.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria.
Description of Study Protocol:
  1. Subjects were studied in the canopy with a) a mask (m), b) mouthpiece plus noseclip (mp+nc), and c) without any attachments to the face or airway.
  2. Each run began when the subject showed a stable level of VO2 and VCO2. (about 10-15 min)
  3. Each run lasted 30 min to 1 h and represents an analysis of 400-900 breaths.

Resting energy expenditure

  • IC type: canopy system
    The validation of the canopy was by having subjects breath through a mouthpiece and pneumotachograph while in the canopy, thus allowing a comparison of the tracing obtained by the canopy with that of the pneumotachograph. (within ±2%)
  • Room temp: Yes
  • Were some measures eliminated? Yes, the program excludes all tidal volumes less than 50 ml as these have been considered too small to represent a breath. Tidal volumes greater than 3 times the mean volume are considered sighs.
  • Coefficient of variation in subjects’ measures? No
  • Training of measurer? Yes
  • Subject training of measuring process? Yes
Data Collection Summary:

Outcome(s) and other measures

  • O2 consumption, CO2 consumption, tidal volume (Vt), frequency (f), minute ventilation, mean inspiratory flow, inspiratory and expiratory time (Ti and Te)

Blinding used: Yes

Description of Actual Data Sample:


  • N=28 (16 males and 12 females)
  • Mean age=27 (range 22-36)
  • No smoking Hx

Subjects in which Ti, Te and Vt/Vi were measured

  • N=12 (6 males and 6 females)
  • Statistical tests
  • Means±SD, linear regression
Summary of Results:

Measurements made with the canopy in the group of 12 subjects (in whom Ti, Te, and Vt/Vi were measured) were not significantly different from the overall group. Changes in Vt, f, and Ve in this group caused by mask and mp+nc were not significantly different from those in the overall group.

Mask (n=28)

  • Vt is increased 32.5% (p<0.001), f is not altered, and Ve is increased 31.3% (p<0.001)

Mouthpiece+noseclip (n=28)

  • Vt is increased 15.5% (p<0.01), f remains unchanged, and Ve increased 14.1% (p<0.01)

Canopy only (n=28)

  • Canopy used as comparison measures for other 2 gas collection devices
  • No significant change in VO2, VCO2, or sign frequency were seen.
Author Conclusion:
  • “The use of mask or mouthpiece plus noseclip is a common practice in the study of respiration. Our data indicate that this type of apparatus induces an increase in both tidal volume and minute ventilation.”
  • “The increase in tidal volume induced by the respiratory was 2ndary to an increase in mean inspiratory flow. Inspiratory duty cycle (Ti/Ttot) was unchanged by either mask or mp+nc.”
Funding Source:
Government: NIH
Reviewer Comments:


  • Comprehensive description of the canopy-computer-spirometry system/program used in the study.
  • Measurements validation was done properly.
  • Study design meets the objective of the study.
  • Have comparison groups to study the different effects of apparatus on breathing pattern in people using canopy system.


  • Statistical analysis (linear regressions) was not described in detail in methodology.
  • Sampling methodology not described.
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? 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? 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? No
  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? 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