CI: Gastric vs. Small Bowel Feeding (2011)


Metheny NA, Davis-Jackson J, Stewart BJ. Effectiveness of an aspiration risk-reduction protocol. Nurs Res. 2010 Jan-Feb; 59 (1): 18-25.

PubMed ID: 20010041
Study Design:
Non-Randomized Controlled Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To evaluate effectiveness of an intervention to reduce aspiration risk in critically ill, mechanically ventilated patients receiving EN.

Inclusion Criteria:
  • Admitted to one of five ICUs at study site
  • Age ≥18 years
  • Informed consent of patient or legal guardian
  • Mechanical ventilation
  • Medical order for blind insertion of feeding tube at bedside.
Exclusion Criteria:
  • Pneumonia present before tube feeding started
  • Medical order for surgically or endoscopically placed feeding tube.
Description of Study Protocol:


All eligible patients admitted to five ICUs were recruited

  • Usual care group admitted December 2002 to September 2004
  • Aspiration Risk Reduction Protocol group admitted January 2007 to April 2008.


Non-randomized control trial

Blinding used 



  • Usual care group served as controls
  • Aspiration Risk Reduction Protocol group:
    • Maintained head-of-bed elevation at 30 degrees or higher, unless contraindicated
    • Feeding tubes inserted into small bowel
    • Used an algorithmic approach for high gastric residuals.

Statistical Analysis

  • T-tests to determine effect of protocol on frequency of aspiration and mean percentage of pepsin-positive tracheal secretions
  • Z-test to determine effect of protocol on incidence of pneumonia
  • Controlled for significant baseline differences between the two groups
  • Z-test using Mann Whitney U procedure to evaluate effect of protocol on hospital resources (because secondary outcomes of hospital LOS, ICU LOS and ventilator days had skewed distributions).


Data Collection Summary:

Timing of Measurements

  • Pepsin assay to detect aspiration of gastric contents (days one, two and three)
  • Clinical Pulmonary Infection Score to assess for pneumonia (days one, two, three and four)
  • Angle of head of bed (hourly backrest elevation recorded on patient flow sheet)
  • Feeding tube tip site (radiographic confirmation immediately after tube insertion; measured length of tubing extending from exit site measured with cm tape and checked pH of fluid every four hours) 
  • Residual from feeding tubes (every four hours)
  • Level of consciousness (every four hours using Glasgow Coma Scale)
  • Level of sedation (Vancouver Interaction and Calmness Scale)
  • Illness severity (APACHE II score at admission)
  • Demographic data by chart review.

Dependent Variables

  • Primary outcome: Aspiration pneumonia
  • Secondary outcomes:
    • ICU length of stay
    • Hospital length of stay
    • Days on mechanical ventilation
    • Cost of hospital resources.

Independent Variables

  • Post-pyloric feeding tube tip site when indicated
  • Head of bed elevation at 30o or higher
  • Algorithmic approach for gastric residual volumes management.

Control Variables

Statistically controlled for significant differences in groups for secondary outcomes.


Description of Actual Data Sample:
  • Initial N: 474 (59% male)
    • NS different by gender
      • Usual care group n=329 (57.1% male)
      • Aspiration risk reduction protocol group n=145 (64.8% male)
  • Attrition: (final N=474): No attrition
  • Age: Significantly different by age (P<0.05)
    • Usual care: 52.5±18.1
    • Protocol 48.8±17.8
  • Ethnicity: Not described
  • Other relevant demographics:
    • Level of sedation (P<0.05)
      • Usual care 35.7±4.1
      • 36.5±4.1
    • Illness severity-APACHE II score (P<0.001)
      • Usual care 22.7±6.4
      • Protocol group 19.5±5.7
  • Anthropometrics: Not described
  • Location: St. Louis University, MO.


Summary of Results:

Key Findings

Results for Primary and Secondary Outcomes



Treatment (SB) Group

(Aspiration Risk Reduction Protocol)

Usual Care (Gastric) Group


Statistical Significance of Group Difference

Aspiration (pepsin positive tracheal secretions)








Hospital length of stay (days) 25.1±14.9 27.3±13.4 2.2 fewer days P=0.17
ICU length of stay (days) 21.3±10.5 19.4±12.1

1.9 fewer days P=0.14

Mechanical ventilation days 16.2±9.7 17.7±9.8 1.5 fewer days P=0.14

Monitoring Criteria for Usual Care and Aspiration Risk Reduction Protocol


Monitoring Criteria


Treatment Group

(Aspiration Risk Reduction Protocol)

Usual Care Group


Statistical Significance of Group Difference

Head of bed elevation >30o 88%  38% P<0.001
Small bowel feeding site achieved 72.4% 48.3% P<0.001
Tube placement past proximal duodenum 18.2% 53.1% P<0.001


Other Findings

  • Three patients met criteria for use of high GRV algorithm, but physicians chose not to implement it due to reluctance to prescribe prokinetic agents
  • No difference in death during hospitalization with 19% in usual care group vs. 14% in protocol group. Mortality was not a secondary outcome, but was listed on the demographic data table.


Author Conclusion:

A combination of elevating head-of-bed position to at least 30 degrees and using small-bowel feeding site beyond first portion of duodenum can dramatically reduce incidence of aspiration and related pneumonia in critically ill, mechanically ventilated patients.

Funding Source:
Government: National Institute of Nursing Research, R01NR05007
University/Hospital: St. Louis University
Reviewer Comments:
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? 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? 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? Yes
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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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? N/A
  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%.) N/A
  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? Yes
  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? 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)? Yes
  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? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
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