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COPD: Determination of Energy Needs (2007)

Citation:

Baarends EM, Schols AMWJ, Nusmeier CM, van der Grinten CPM, Wouters EFM.  Breathing efficiency during inspiratory threshold loading in patients with chronic obstructive pulmonary disease.  Clin Physiol 1998;18(3):235-44.

PubMed ID: 9649911
 
Study Design:
Case-Control Study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To investigate the efficiency of breathing in patients with COPD compared with the breathing efficiency of healthy elderly people, and to investigate a possible relationship between breathing and resting energy expenditure.
Inclusion Criteria:
  • Moderate to severe COPD as defined by American Thoracic Society
Exclusion Criteria:
  • Patients exhibiting an increase in FEV1 > 10% after inhalation of a beta-2 agonist
  • Those requiring supplemental oxygen (arterial oxygen pressure <7.3 kPa)
  • None had respiratory tract infection or clinically visible signs of edema
  • Had no known cardiovascular, neurological or endocrine diseases
  • Controls were not suffering from any of these exclusion criteria and were interviewed to ensure that they had no pulmonary complaints and used no medication
Description of Study Protocol:

Recruitment

Methods not described.  Patients admitted to a pulmonary rehab center in stable clinical condition.  Controls recruited from clubs for elderly people.

Design

Case-Control Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

Mann-Whitney U test was used to test differences between groups.  Wilcoxon rank test was used to test differences within a group.  ANOVA performed when appropriate.

Data Collection Summary:

Timing of Measurements

Breathing efficiency test performed in first week of admission, before rehab program started.

Dependent Variables

  • Resting energy expenditure measured with ventilated hood system
  • Breathing efficiency assessed by measuring oxygen consumption, mean inspiratory mouth pressure, and flow during breathing at rest and subsequently during breathing against an inspiratory threshold (40% of maximal inspiratory pressure)
  • Flow volume measurements included FEV1 and FVC
  • Total lung capacity, intrathoracic gas volume and airways resistance were measured using body plethysmography
  • Body height, weight, BMI
  • Fat free mass measured through bioelectrical impedance

Independent Variables

  • COPD or healthy

Control Variables

 

Description of Actual Data Sample:

Initial N: 16 patients (11 men, 5 women), 16 healthy elderly controls (7 men, 9 women)

Attrition (final N):  16 patients, 16 controls

Age:  mean age patients:  64 years, mean age controls:  66 years 

Ethnicity:  not mentioned

Other relevant demographics:

Anthropometrics:  Groups were age but not gender matched

Location:  The Netherlands

 

Summary of Results:

Other Findings

During loaded breathing there was a significant increase in VO2, mean inspiratory mouth pressure, and external work of breathing compared with unloaded breathing in both groups.

As intended, ventilation did not increase significantly during the breathing efficiency test in the patients with COPD.

The breathing efficiency of the patients with COPD was similar (mean 3.7%, range 1.4 - 8.7%) to that of the healthy elderly subjects (3.2%, 1.7 - 8.3%).

Breathing efficiency was not correlated with REE in either group.   REE was not different between groups.

Author Conclusion:
In summary, in this study in which dynamic hyperinflation was probably prevented, patients with clinically stable COPD have a similar breathing efficiency compared with healthy elderly subjects.  Breathing efficiency was not related to REE.  From the presented calculations, it seems very unlikely that increased work of breathing at rest is responsible for the increased REE observed in many COPD patients.  With respect to the functional performance of patients with COPD, the effect of dynamic hyperinflation on the oxygen cost of breathing is interesting and remains to be studied.
Funding Source:
Reviewer Comments:
Controls not matched for gender.  Small sample sizes.  No power calculations done.
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) N/A
  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) N/A
 
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? ???
  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? ???
  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) N/A
  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? 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.) ???
  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? Yes
  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%.) Yes
  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? 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.) Yes
  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? Yes
  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? N/A
  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? Yes
  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? Yes
  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? Yes
  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? Yes
  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? No
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? No
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