EE: Respiratory Quotient (RQ) (2013)


Kan MN, Chang HH, Sheu WF, Cheng CH, Lee BJ, Huang YC. Estimation of energy requirements for mechanically ventilated, critically ill patients using nutritional status. Crit Care. 2003;7(5):R108. 

PubMed ID: 12974978
Study Design:
Retrospective Cohort Study
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
Use nutritional status to determine energy requirement for mechanically ventilated patients.
Inclusion Criteria:
  • patients in mixed ICU that were hemodynamically stable, not comatose, and required at least 7 days of mechanical ventilation
  • gave informed consent
Exclusion Criteria:
  • received a fraction of inspired oxygen > 60% at time of indirect calorimetry measurement
  • oliguric (therefore could not determine urinary nitrogen excretion)
Description of Study Protocol:

Recruitment - informed consent obtained of eligible ICU patients 

Design - retrospective cohort

  • measured energy expenditure (MEE) by indirect calorimetry and determined total energy expenditure as MEE x 1.2
  • recorded daily energy intake
  • compared TEE to energy intake and divided into three cohorts based on energy intake:
    • underfed (UF) energy intake < 90% TEE) n=20
    • appropriately fed (AF) energy intake 100 + 10% TEE n=20
    • overfeeding (OF) energy intake > 110% TEE

Blinding used: not applicable

Intervention: not applicable

Statistical Analysis

  • Used Student's t-test to compare difference between day 1 and day 7 within a group
  • Pearson correlation coefficients
  • Statistical results significant at P< 0.05
Data Collection Summary:

Timing of Measurements

  • MEE per indirect calorimetry on days 1 and 7
  • calculated total energy expenditure (TEE) as MEE x 1.2 (5% activity factor plus 15% for day-to-day variability)
  • calculated energy intake from EN, TPN and nonfood sources

Dependent Variables

  • Length of ICU stay (days)
  • Length of hospital stay (days)
  • time on mechanical ventilation (days)
  • improvement in nutritional status

Independent Variables

  • Energy intake measured as percent goal (TEE)


Description of Actual Data Sample:


Initial N: 118

Attrition: 54 (40 males, 14 females) completed study- no reason given for attrition of the other 64 subjects (54% attrition)

Age: 23-89

Ethnicity: not described, but study took place in Taiwan, so likely Chinese

Other relevant demographics: APACHE II 17.7 - 19.9 (NS differences among groups)

Anthropometrics (e.g., were groups same or different on important measures)

Location:  Taichung VA Hospital, Taiwan


Summary of Results:
  • Underfed (UF) patients (n=15) received only 68% of goal energy intake
  • Adequately fed (AF) patients (n=20) received 100 ± 10% of goal energy intake
  • Overfed (OF) patients (n=19) received 136.5% of goal energy intake or about 40 kcal per kg per day

NS difference by group in:
  • protein intake (NS improvement in Nitrogen balance at mean protein intake of 1.1 per g per kg per day, however N balance in the appropriate feeding group improved
  • ICU stay or hospital stay


Appropriate feeding
P value

Length of hospital stay (days)

79.2 ± 50.5
77.3 ± 69.1 74.1 ± 25 NS at > 0.05

Length of ICU stay (days)

45.2 ±  25

 39.1 ± 19.9

 31.0 ± 6.6

NS at > 0.05

Length of time on ventilator (days)

 65.2 ± 48.3

 53.5 ± 28.1

 58.0 ± 16.8




Author Conclusion:
Underfed patients were more malnourished than appropriately or over fed patients. Provide 120% of MEE to meet energy needs of hemodynamically stable, mechanically ventilated, critically ill patients.
Funding Source:
University/Hospital: Taichang Veterans General Hospital, Chung Shan General Hospital,
Reviewer Comments:
This study received a neutral rather than a positive rating due to questions about the large and unexplained attrition rate. The investigators said there were no significant differences among groups; demographic information was inadequately reported.
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? ???
  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.) 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? Yes
  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? 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%.) No
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? No
  4.4. Were reasons for withdrawals similar across groups? ???
  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? ???
  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? Yes
  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? Yes
  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? No
  6.6. Were extra or unplanned treatments described? No
  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? No
  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? No
  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)? No
  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? ???
  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