COPD: Effectiveness of Therapies (2007-2008)


Cai B, Zhu Y, Ma Y, Xu Z, Zao Y, Wang J, Lin Y, Comer GM.  Effect of supplementing a high-fat, low-carbohydrate enteral formula in COPD patients.  Nutrition 2003;19(3):229-232.

PubMed ID: 12620524
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
To evaluate the efficacy of feeding a high-fat, low-carbohydrate nutritional supplement as opposed to a high-carbohydrate diet in COPD patients on parameters of pulmonary function.
Inclusion Criteria:
  • COPD patients with elevated arterial carbon dioxide tension
  • Low body weight (<90% IBW)
Exclusion Criteria:
  • Liver disease
  • Renal insufficiency
  • Suspicion of other illnesses that could affect nutrition support
  • Demonstrated intolerance to experimental formula
Description of Study Protocol:


Methods not described.

Design:  Randomized, Controlled, Parallel-Group, Open Label Trial

Blinding used (if applicable):  not possible with interventions 

Intervention (if applicable)

  • Control group:  dietary counseling for high-carbohydrate diet (15% protein, 20 - 30% fat, 60 - 70% carbohydrate)
  • Experimental group:  received 2 - 3 cans (237 ml/can) of high-fat, low-carbohydrate oral supplement (16.7% protein, 55.1% fat, 28.2% carbohydrate) in the evening as part of the diet, based on 50% of basal caloric needs by Harris-Benedict

Statistical Analysis

Statistical analysis of all data was based on the t test and presented as mean +/- standard deviation.

Data Collection Summary:

Timing of Measurements

Measurements taken at baseline and after 3 weeks.

Dependent Variables

  • Measurements of lung function (FEV1, minute ventilation, oxygen consumption per unit time, carbon dioxide production in unit time, RQ)
  • Blood gas measurements (pH, arterial carbon dioxide tension, arterial oxugen tension)
  • Blood chemistries:  potassium, sodium, chloride, liver function, cholesterol, triglycerides and albumin

Independent Variables

  • Control group:  dietary counseling for high-carbohydrate diet (15% protein, 20 - 30% fat, 60 - 70% carbohydrate)
  • Experimental group:  received 2 - 3 cans (237 ml/can) of high-fat, low-carbohydrate oral supplement (16.7% protein, 55.1% fat, 28.2% carbohydrate) in the evening as part of the diet
  • Dietary intake determined by food intake diaries

Control Variables


Description of Actual Data Sample:

Initial N: 60 COPD patients, 27 females, 33 males

Attrition (final N):  60, 30 in each group

Age:  mean age control group:  63 +/- 6 years, experimental group:  62 +/- 7 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics:  No significant differences between groups in terms of duration of disease, stage of disease or number of exacerbations per year, or mean age or weight at baseline.

Location: China


Summary of Results:



Experimental Group, Baseline

Experimental Group, 3 weeks

Control Group, Baseline

Control Group, 3 weeks

pH 7.37 +/- 0.26 7.38 +/- 0.21 7.35 +/- 0.24 7.37 +/- 0.21

PaCO2 (mmHg)

55 +/- 5

42 +/- 3, P < 0.05

54 +/- 4

45 +/- 3, P < 0.05

PaO2 (mmHg) 68 +/- 3 79 +/- 4, P < 0.05 69 +/- 5 71 +/- 6
RQ 0.92 +/- 0.07 0.83 +/- 0.06, P < 0.05 0.91 +/- 0.07 0.90 +/- 0.05
VCO2 (ml) 308 +/- 36 269 +/- 24, P < 0.05 295 +/- 37 301 +/- 41

VO2 (ml)

358 +/- 46

324 +/- 37, P < 0.05

347 +/- 59

353 +/- 42

VE (L/min) 12.5 +/- 2.8 10.2 +/- 1.9, P < 0.05 11.6 +/- 2.3 12.1 +/- 2.4
FEV1 (% predicted) 36 +/- 12 48 +/- 9, P < 0.05 39 +/- 11 42 +/- 11
Airway resistance (% predicted) 265 +/- 64 231 +/- 38 274 +/- 76 238 +/- 43

Other Findings

Experimental group consumed 13.6 +/- 3 kcal/kg of fat energy and 16.3 +/- 3.2 kcal/kg of carbohydrate energy, these were significantly different from the control group (8.4 +/- 1.4 kcal/kg from fat, P < 0.0001 and 22.9 +/- 3.8 kcal/kg from carbohydrate, P < 0.001).

Lung function measurements decreased significantly and forced expiratory volume increased significantly in the experimental group. 

Author Conclusion:
The oral supplement evaluated in this study was specifically designed to meet the needs of patients with COPD.  Its low-carbohydrate, high fat composition was clinically effective in improving respiratory function when used as an evening supplement for 3 weeks in patients with chronic COPD.
Funding Source:
Reviewer Comments:
Recruitment methods not well defined.  Measurements of outcome variables not well described, only 3 weeks long.  Both groups improved compared with baseline, but only experimental group was statistically significant.  Author works for Abbott Laboratories.
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? 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.) 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? 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? No
  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? 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
  6.1. 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? Yes
  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? 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? ???
  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? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  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)? N/A
  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? No
  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? No
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? No