EE: Body Positions (2014)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  1. To evaluate the effect of elective thoracic surgery on energy metabolism and gas exchange.
  2. To investigate whether the 30 degree sitting position in which patients were nursed in the early postoperative period would affect these parameters and therefore postoperative management.


  • “Steady state”- Mean values for equilibrated data points (VO2 and VCO2 within a range ±5% of 15 consecutive minutes) were used to calculate energy expenditure (EE)
Inclusion Criteria:
  1. Understand and give written consent
  2. Adult patients scheduled to undergo elective thoracotomy.
  3. Medications allowed:
Exclusion Criteria:
  1. Refusal to consent
  2. Not meeting inclusion criteria
  3. Diseases in subjects that were excluded: emergency thoracotomy, endocrine and metabolic diseases, associated cardiovascular diseases, use of B-agonist, history chronic renal failure, hepatic failure, acute & chronic malnutrition (wt loss =UBW in last 10 weeks preceding surgery), obesity (BMI =30, intraoperative complications, mechanical ventilation in postoperative period.
  4. Medications excluded:
Description of Study Protocol:


  • Ht measured? Yes
  • Wt measured? Yes
  • Fat-free mass measured? No


  • Monitored heart rate? Likely
  • Body temperature? Yes
  • Medications administered? Anesthetic management
  • Arterial blood samples

Resting energy expenditure

  • IC type: Delta trac-ventilated hood
  • Equipment of Calibration: Yes
  • Coefficient of variation using std gases: No
  • Rest before measure (state length of time rested if available): 15 min
  • Measurement length: 60 min in each position
  • Steady state: Evaluate if mention initial acclimatization and then continuous monitoring throughout measurement, if appropriate
  • Fasting length: 12 h
  • Exercise restrictions XX hr prior to test? NA
  • Room temp: 20-24 degrees C
  • No. of measures within the measurement period: 1
  • Were some measures eliminated? Yes, first 15 mins
  • Were a set of measurements averaged? Yes
  • IF avg, identify length of each measure & no. of measurements? 45 minutes
  • Coefficient of variation in subjects measures? No
  • Training of measurer? not specified
  • Subject training of measuring process? No


Intervening factor: Received morphine IM q 6 hr; interval b/t last dose and RMR study was 60 min.

Data Collection Summary:

Outcome(s) and other measures

  1. Measured REE [(VO2, l/min), VCO2 (l/min; ml/kg/min), RQ, ventilation (l/min)].
  2. Predicted RMR using: HB
  3. Independent variables of weight, height, age, BMI

Blinding used: No

Description of Actual Data Sample:

N= 32 enrolled

12 drop outs d/t: post-op complications (n=1); not operated on (n=1), air leaks from chest tubes (3)’ refused to be studied in post-op period (n=7)

Final Sample

  • 22 pt (17 M; 5 F) aged 46-71 yr
  • Mean Age:   61.0±1.6 std error mean (SEM) 
  • Mean BMI:  25.6 kg/m2  (±SEM not provided)
  • Range:  19.0-29.6

Statistical tests

  • Mean ±std error of mean; Lilliefors test for normality of data; ANOVA for repeat measures; Fisher’s protected least significant difference test; Student’s t-test; P<0.05 statistically significant.
Summary of Results:


  • In the preoperative period, no significant changes in mean values of VO2 (mL/min), VCO2 (mL/min), RQ, and RMR (kcal/d) between the two positions. (P>0.05).
  • Mean RMR values postoperatively were significantly higher than the preoperative values for the corresponding postugres (P<0.05 for each position). 
  • Mean VO2 values increased for each postoperative posture (P<0.05).
  • Mean CO2 values increased postoperatively only in the supine positions (P<0.05).

Mean RQ values for each position postoperatively were significantly lower than the preoperative values for corresponding positions (P<0.05)


Postoperative Differences Between Supine and 30 degree sitting

Postoperative (±SEM)

30° Sitting

VO2, mL/min 247±7 237±7*
Range 232-262 222-251
VCO2, mL/min 190±4 184±5*


182-198 174-194


247±7 237±7
Range 232-262 222-251
RMR, kcal/d 1694±44 1627±47*
Range 1,602-1,785 1,529-1,725


  • Mean percent increase in RMR was lower in the 30° sitting position than in supine position (7.9±2.7% vs. 14.4±2.3%, p<0.001).
  • In 30° sitting position, mean percent increase in VO2 and VCO2 were lower than in the supine position, (9.0±3.0% vs. 16.4±2.6%; p<0.001; and 3.2±2.1% vs. 0.5±1.4%; p<0.05, respectively).
  • RQ decreased by 7.8±1.6% in the supine and by 4.7±1.6% in the 30° sitting position.


  • No consistent changes in mean values occurred in PaO2 and all physiological indexes of gas exchanges between the two positions preoperatively and postoperatively. (P>0.05).
Author Conclusion:
  • As stated by the author in body of report:
  • In the early postoperative period of elective thoracic surgery, pt experienced a significant increase in VO2, VCO2, and RMR with a certain degree of impaired oxygen exchange. The 30° sitting position partly mitigates the hypermetabolic response, probably by reducing the work or breathing.”
  • “In the postoperative period, the 30°sitting position induced a lower increase in RMR, VO2 and VCO2 than the supine position without any effect on cardiopulmonary and oxygenation parameters so changes of VO2 from supine to 30° sitting position can be effectively ascribed to changes in the energy metabolism, thus, in the VO2 of respiratory muscles.”
  • “Other studies report a change in posture from supine to sitting position causes an increase in lung volume (35% changes) and a decrease in diaphragmatic length and respiratory resistance.  Therefore, the interpretation of our results could be explained [by] the reduced work of breathing with modification of the inclination angle from supine to 30° sitting position.”
  •  “One can calculate roughly that, in our patients, 35 L of O2 were consumed and 28L of CO2 were produced during the preoperative and postoperative measurements.  Estimating O2 and CO2 stores to be ~1.25L and 16L, respectively, a hypothetical 5% change in blood and body stores of these gases would lead to 3, 0.2, and 1% errors in VCO2, VO2, and RMR , respectively.”
  • “Limitations of our study are  didn’t evaluate other posture positions, pt with important CVD were excluded and unable to generalize to this population, the duration of the positive effect of 30°sitting position cannot be established.   
Funding Source:
University/Hospital: University of Pisa
Reviewer Comments:


  • Explicit indirect calorimetry measurement protocol; including steady state
  • Described drop-outs clearly


  • Generalizable to post-lateral thoracotomy through the fifth intercostals space and in cancer patients with a curative intent.
  • As per researcher, unable to generalize to some post-operative illnesses such as CVD, ventilator-dependent and intra-operative complications.”
  • Study biases include physician referral to a single surgeon.;
  • An intervening variable not measured FFM not reported”

Working Group Member Comments:

There is really little good information on which to base a conclusion about the effect of posture. For the Brandi paper, the post-op data would not apply to most clinic settings health adults, as the differences from supine to semi-recumbent are due to work of breathing and possibly pain.  On the other hand, Brandi's pre-op data are somewhat pertinent and show minimal difference between positions (mean of 29 kcal/day).  The data is a comparison between semi-recumbent vs. supine (the "sitting" position is defined as 30 degree decline with hips and legs horizontal).  Thus, there is a third alternative to lying or sitting, and that is reclining. 

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? 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
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? 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
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
3. Were study groups comparable? 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
  3.3. 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
  3.5. 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? 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
  4.4. 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? No
  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? 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? 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
  6.4. 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
  6.6. 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
  6.8. 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? 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
  7.4. 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
  7.6. Were other factors accounted for (measured) that could affect outcomes? 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
  8.1. 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
  8.3. 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
  8.5. 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
  8.7. 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? 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
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? N/A