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COPD: Determination of Energy Needs (2007)

Citation:

Creutzberg EC, Schols AM, Bothmer-Quaedvlieg FC, Wouters EF.  Prevalence of an elevated resting energy expenditure in patients with chronic obstructive pulmonary disease in relation to body composition and lung function.  Eur J Clin Nutr 1998;52(6):396-401. 

PubMed ID: 9683390
 
Study Design:
Case-Control Study
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To describe the prevalence and characteristics of hypermetabolism in clinically stable patients with COPD in relation to body composition and lung function.
Inclusion Criteria:

Cases:

  • Stable patients with moderate to severe COPD

Controls:

  • Healthy, age-matched subjects
Exclusion Criteria:

Cases:

  • Patients exhibiting an increase in FEV1 > 10% after inhalation of a beta-2 agonist
  • Patients with confounding disorders such as cancer, unstable cardiac condition, active GI abnormalities, recent surgery, endocrine disorders such as diabetes, hyper/hypothyroidism
  • None of the patients had edema, nor were suffering from a respiratory tract infection as based on a negative bacteriological sputum analysis, had fever or an increase in symptoms

Controls:

  • Volunteers with disorders affecting metabolic rate such as cancer, unstable cardiac condition, GI diseases, recent surgery, endocrine disorders, and diseases of the respiratory tract
Description of Study Protocol:

Recruitment

Patients were consecutively admitted to an inpatient pulmonary rehab centre.

Design

Case-Control Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

ANOVA was performed to investigate if REE differed between groups.  Stepwise regression analysis performed to reveal parameters explaining variation in absolute REE.  Different linear regression equations were generated for men and women.  Hypermetabolism defined as >110% of Harris-Benedict prediction.  For comparing parameters between groups, the Student's t test was used for parametric data and the Mann-Whitney U test for non-parametric data.

Data Collection Summary:

Timing of Measurements

Predicted REE adjusted for FFM of each individual patient was obtained by using the linear regression equation used with males or females in the control group.

Dependent Variables

  • Resting energy expenditure was assessed by indirect calorimetry and adjusted for FFM
  • FFM measured through bioelectrical impedance
  • Lung function measurements:  FEV1 was calculated from flow-volume curve using spirometry, and total lung capacity and residual volume were measured plethysmographically, diffusing capacity for carbon monoxide determined using single breath method, arterial oxygen and carbon dioxide tension analyzed on blood gas analyzer

Independent Variables

  • COPD or healthy

Control Variables

  • Age
  • Sex
  • FFM
  • Fat mass
Description of Actual Data Sample:

Initial N:  172 patients (123 males), 92 healthy controls

Attrition (final N):  172 patients, 92 controls

Age:  mean age patients:  64 +/- 10 years, controls:  67 +/- 8 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics:  Controls were age-matched

Location:  The Netherlands 

 

Summary of Results:

 

Prediction Variables

Cumulative R2

SE

P value

Controls - FFM

0.65 139.4 <0.001

Controls - Sex

0.71

126.7

<0.001

Controls - Fat mass 0.76 117.4 <0.001
Controls - Age 0.77 114.3 <0.05
Patients - FFM 0.51 165.4 <0.001
Patients - Age 0.57 155.7 <0.001

Patients - Fat mass

0.60

150.3

<0.01

Other Findings

On ANOVA, REE was significantly higher in COPD patients than controls (P = 0.013) after correction for sex, age, FFM and fat mass.

26% of the patients were hypermetabolic (REE > 110%REEFFM), characterized by a lower age (60 +/- 10 years vs 65 +/- 9 years) and a lower total lung capacity (122 +/- 27 vs 139 +/- 28% predicted) compared to normometabolic patients (P < 0.001).

The prevalence of FFM depletion was equal among normo- and hypermetabolic patients:  36% vs 33%, respectively.

Depleted patients expressed however a significantly higher residual volume/total lung capacity ratio and a lower maximal inspiratory mouth pressure independently of hypermetabolism (P < 0.05).

In contrast, on base of the Harris-Benedict prediction equations, which do not take body composition into account, 54% of the patients were hypermetabolic (REE > 110% REEHB), characterized by a higher age and lower body mass and FFM (P < 0.05). 

Author Conclusion:
Hypermetabolism commonly occurs in COPD, characterized by less hyperinflation at rest, in contrast to the suggested contribution of an elevated oxygen cost of breathing to hypermetabolism in COPD.  The higher hyperinflation at rest in FFM-depleted patients independently of hypermetabolism suggests a higher oxygen cost of breathing during activities, contributing to the elevated total daily energy expenditure previously reported in COPD.  The Harris-Benedict equations overestimate the prevalence of hypermetabolism and link hypermetabolism incorrectly to aging and depletion.
Funding Source:
Reviewer Comments:
Large sample sizes.
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? 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? 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? Yes
3. Were study groups comparable? Yes
  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? Yes
  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.) Yes
  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? N/A
  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? 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