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COPD: Determination of Energy Needs (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To measure the actual 24-hour energy expenditure of patients with stable COPD in a controlled environment.
Inclusion Criteria:

Cases:

  • Ratio FEV1/FVC <70% predicted value
  • Increase in FEV1 <10% predicted value after inhalation of 400 micrograms albuterol

Controls:

  • Normal lung function
Exclusion Criteria:
  • None of patients or controls had cancer, unstable cardiac condition, or hepatic, renal or endocrine diseases
Description of Study Protocol:

Recruitment

Recruitment methods for patients assumed to be hospital; controls were recruited voluntarily in association of elderly people or among hospital staff.

Design

Case-Control Study.

Blinding used (if applicable)

Not applicable.

Intervention (if applicable)

Not applicable.

Statistical Analysis

EE of COPD subjects was adjusted to weight and fat free mass of control subjects.  Comparisons between groups performed using Student's unpaired t test and within groups using Student's paired t test.  Regression lines compared by ANOVA.

Data Collection Summary:

Timing of Measurements

After overnight fast, subjects came to metabolic unit, entered respiration chamber, and blood was drawn.  Subjects awoke next morning and body composition and metabolic measurements performed.

Dependent Variables

  • Body height, weight, BMI
  • Mid-upper right arm circumference measured with tape measure
  • Total body resistance measured by bioelectrical impedance
  • Energy expenditure measured by indirect calorimetry in respiration chamber
  • Physical activity detected in chamber by radar system
  • Urine tests analyzed for urinary norepinephrine, epinephrine, theophylline
  • Energy intake set at 1.5 x BMR for COPD group, 1.3 x BMR for controls to account for 20% increase in resting metabolism in COPD patients 

Independent Variables

  • COPD or healthy
  • Lung function measurements:  lung volume measured by body plethysmography and forced expiratory flow rates by heated pneumotachograph or by mass flow anemometer

Control Variables

  • Body weight
  • Fat free mass
Description of Actual Data Sample:

Initial N: 16 male ambulatory patients with stable COPD, 12 normal male subjects

Attrition (final N):  16 patients, 12 controls

Age:  mean age patients:  69 +/- 8 years, controls:  62 +/- 10 years 

Ethnicity:  not mentioned

Other relevant demographics:

Anthropometrics:  Subjects matched for age, sex and height.

Location: Switzerland

 

Summary of Results:

 

 

 COPD (n=16)

Control (n=12)

p Value

BMR (kcal/min)

 1.11 +/- 0.14

1.13 +/- 0.11

NS 

BMR (% predicted BMR)

120 +/- 7

108 +/- 12

<0.01

24- hr EE (kcal/24 hr)

1935 +/- 259

2046 +/- 253

NS
24-hr EE (% predicted BMR) 145 +/- 12 137 +/- 19 NS
24-hr EE (% measured BMR) 121 +/- 10 126 +/- 9 NS
Daytime EE (kcal/24 hr) 2233 +/- 338 2355 +/- 293 NS
Daytime EE (% predicted BMR) 166 +/- 16 157 +/- 22 NS
Nighttime EE (kcal/24 hr) 1446 +/- 234 1584 +/- 217 NS
Nighttime EE (% predicted BMR) 109 +/- 15 106 +/- 15 NS
Sleep EE (kcal/24 hr) 1413 +/- 222 1551 +/- 209 NS
Sleep EE (% predicted BMR) 106 +/- 14 105 +/- 15 NS

Other Findings

Body weight was 92 +/- 12% of IBW in COPD group and 105 +/- 11% in control group (p = 0.01).

BMR was 120 +/- 7% of predicted in COPD group and 108 +/- 12% in the control group (p < 0.01).

However, 24-hour EE was similar in the 2 groups, amounting to 1935 +/- 259 kcal in COPD group and 2046 +/- 253 kcal in control group (NS).

There was no difference in 24-hour EE, daytime EE, nighttime EE or sleep EE between groups.

This corresponded to 145% and 137% of predicted BMR, and to 121% and 126% of measured BMR in COPD patients and controls, respectively (NS).

Patients were allowed to pursue usual treatment within the chamber and a positive correlation existed between 24-hour EE and the daily dose of inhaled beta-2 agonists (p < 0.03).

During daytime, physical activity was lower in patients with COPD (79 +/- 36 minutes vs 104 +/- 17 minutes, p = 0.03).

Predicted caloric intake was not significantly different between groups (NS).

Author Conclusion:
In summary, rigorous measurements show that basal metabolic rate is increased in patients with COPD in a stable clinical state.  However, their 24-hour energy expenditure is similar to that of normal subjects.  These patients appear to spare energy by reducing their level of spontaneous physical activity.  24-hour urinary excretion of norepinephrine is increased in stable COPD but fails to correlate with energy expenditure.  Finally, the relationship between daily energy expenditure and daily dose of inhaled beta-2 agonists suggests that the energy cost of this medication may be sizeable in COPD. 
Funding Source:
Reviewer Comments:
Small sample sizes and only men studied.  Energy intake set 20% higher for COPD patients, TEF not addressed.  Power of study was 83% to detect difference of 250 kcal in daily EE.
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? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
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) Yes
  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.) 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? 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? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  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? ???
  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? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? ???
  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? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? ???
  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