EE: Respiratory Quotient (RQ) (2013)

Citation:

Weissman C, Kemper M, Askanazi J, Hyman AI, Kinney JM. Resting metabolic rate of the critically ill patients: Measured versus predicted. J Anesthesiology. 1986;64(6):673-679.

 
Study Design:
Descriptive Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  1. Examine the energy expenditure of a discrete subgroup of critically ill patients: hemodynamically stable, noncomatose, postoperative patients receiving mechanical ventilation.

Definitions

  • Steady state:
  • Resting: lying motionless with eyes open and responsive to surrounding events
Inclusion Criteria:
  1. Understand and give written consent
  2. Hemodynamically stable, not comatose
  3. Medications allowed: yes.
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria.
Description of Study Protocol:

ANTHROPOMETRIC

  • Ht measured? Yes
  • Wt measured? Yes
  • Fat-free mass measured? No
  • IBW: used 1959 Metropolitan Life Tables

CLINICAL

  • Monitored heart rate? Likely
  • Body temperature? Yes
  • Medications administered? Yes
  • Resting energy expenditure:
  • IC type: Beckman MMC I or a Horizon Sensormedics; Pt ventilated at an FIO2that ranged between 0.35-0.45
  • Equipment of Calibration: “machines were validated”
  • Coefficient of variation using std gases: Likely
  • Rest before measure (state length of time rested if available): NA
  • Measurement length: Measured over 6-8 hr period
  • Steady state: Had definition of “resting”
  • Fasting length: Varies; n=6 TPN with add’l isocal; n=1 enteral nutrition; n=3 TPN D10 w/ amino acids & lipids; n=2 D25 with AA & lipid; n=3 peripheral PN; n=22 D5 dextrose; n=1 normal saline
  • Exercise restrictions XX hr prior to test? Mentions monitoring for “rest” times (indicating nursing interventions were noted)
  • Room temp: ICU unit
  • No. of measures within the measurement period: Yes, Horizon continuously measured and provided 3 min avg; Beckman MMCI measured for 4 min every 15 min
  • Were some measures eliminated?
  • Were a set of measurements averaged? Yes, 3 periods when resting was observed, these 3 measured were averaged to provide mean resting VO2and VCO2values
  • Coefficient of variation in subjects measures? Not specified
  • Training of measurer? Likely
  • Subject training of measuring process? No

DIETARY

  • On IV, enteral and parenteral nutrition

Intervening factor:

Data Collection Summary:

Outcome(s) and other measures

  1. Measured REE [(VO2 l/min), VCO2 (l/min; ml/kg/min), RQ, ventilation (l/min)]; kcal/body surface area (m m2 and kcal/kg
  2. Predicted RMR using: HB? Aub-Dubois
  3. Independent variables of weight, height, age.

Blinding used: No

Description of Actual Data Sample:
  • N=40 post-operative receiving mechanical ventilation
  • N=30 receiving one measure
  • N=5 receiving 2 measures
  • Mean age, y: 65.7±18
  • Age range, y: 18-91
  • Gender: 25 M; 20 F

[Analyst note: represent the number of measures; and eliminated 5 measures since n=45 doesn’t match text regarding measures?]

Statistical tests

Simple regression; Relationship of measured REE to sex, age, height, wt, body temp using multiple linear regression analysis, coefficient of determination (r2); Correlation of measured to predicted.

Summary of Results:

INDIRECT CALORIMETRY

There is moderate correlation between measured REE and predicted using Harris-Benedict (r= 0.57). There was little correlation between the ratio of measured to predicted (Harris-Benedict) and age (r=0.17). Or the ratio of actual to ideal body with and body weight (r=0.17).

Multiple regression analysis or the ratio of measured to predicted REEE to body temperature, age, and the ratio of actual to ideal body weight revealed a coefficient of determination (r2) = 0.03.

Multiple regression analysisi revealed an r2 of 0.43 in the relationship of measured REE to heatight,w eight, sex, age, and body temperature.

RQ

The majority of patients (n=22) were receiving D5% dextrose and had an RQ that ranged from 0.71 to 0.83.

[Analyst note: the Figure 4 indicates RQ ranged from 0.71-0.86 for patients receiving 5% dextrose.]

“In the study, the majority of patients were receiving 5% dextrose (100-450 kcals/day) and thus were in a state of semistarvation. Their RQ ranged from 0.70-0.82.

There were 3 instances of RQs of 1.0 or above and in all case, patients were in the process of being switched from enteral to parenteral nutrition and their total intake (enteral plus parenteral) was about twice the measured REE [and] carbohydrate was in excess of REE.

Author Conclusion:

As stated by the author in body of report

In our study, patients had rather wide range of measured to predicted (H-B) ratio from 70-140%. The reason for this wide is not immediately evidence. It was not related to either age, the ratio of actual to IBW, or body temperature.”

“Other conditions (ie., amount of sedation administered, nutrition intake, and clinical condition, and amount of water retention) can affect [accuracy of] metabolic formula.”

“Measurement of metabolic rate in mechanically ventilated patients is difficult and an arduous task for technical and clinical reasons. . .physiologic RQ range is very narrow (0.70-1.2) [and] exacting, reproducible technique and precision are needed . . [In addition], vigilance to monitor potential error from small air leaks. An RQ >1.0 indicates net lipogenesis (the conversion of CHO to fat-a process that has an RQ of 8.0 [and] humans are inefficient at this.”

“RQ can seve as a quality control technique and errors in either or both VO2or VCO2will cause significant alterations in RQ; measures that fall outside the range of 0.67 to 1.254 should lead one to suspect an error in the measurement technique.”
Funding Source:
Government: NIH, US Army contract
University/Hospital: Columbia University
Reviewer Comments:

Strengths

  • “Defined a critically-ill patient population subgroup.”
  • “Reported RQ for D5% separately to control for effect of different nutrition regimens on RQ”

Generalizability/Weaknesses

  • “Since patient population was primarily older adults; is generalizable to this population.”
  • “Adequate representation by age and gender not reported but unlikely to have large enough cell # to identify Beta-error
  • “Researchers do not report sampling methods (every post-op? Every 2nd or 3rd?) and sampling length
  • An intervening variable not measured whether steady state was achieved in patients; a later publication by author states that a “visual” rest may not achieve steady state” A second intervening variable that is discussed it the varying effects of feeding regimens on RQ.”
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? N/A
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? N/A
  1.3. Were the target population and setting specified? N/A
  2. Was the selection of study subjects/patients free from bias? No
2. Was the selection of study subjects/patients free from bias? No
  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? N/A
  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? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
  3. Were study groups comparable? No
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  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? N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? 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? 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
  3.5. 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
  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. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  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%.) N/A
  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%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  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
  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? No
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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? N/A
  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? N/A
  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
  6.4. 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? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  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? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  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. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.1. Were primary and secondary endpoints described and relevant to the question? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.2. Were nutrition measures appropriate to question and outcomes of concern? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.5. Was the measurement of effect at an appropriate level of precision? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
  7.7. Were the measurements conducted consistently across groups? N/A
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? 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? N/A
  8.1. Were statistical analyses adequately described and the results reported appropriately? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.2. Were correct statistical tests used and assumptions of test not violated? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  8.3. Were statistics reported with levels of significance and/or confidence intervals? N/A
  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
  8.4. 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
  8.5. 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? N/A
  8.6. Was clinical significance as well as statistical significance reported? N/A
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
  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. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? N/A
  9.1. Is there a discussion of findings? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
  9.2. Are biases and study limitations identified and discussed? N/A
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A
  10.2. Was the study free from apparent conflict of interest? N/A