CI: Blue Dye Use (2006)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

Compare relative utility of blue dye visualization with a glucose oxidase test strip method for detecting aspiration of enteral feedings.


Inclusion Criteria:

Tracheally intubated persons 18 or older receiving enteral tube feedings and no oral intake, at two community teaching hospitals between October 1990 to April 1991; control group received no enteral nutrition.

Exclusion Criteria:

Under 18, informed consent not obtained.

Description of Study Protocol:

Statistical Analysis

Differences between means analyzed using two-tailed Student’s t test; differences.

Data Collection Summary:
  • Tube placement and all other tube feeding decisions made by patient’s MD
  • Data collection terminated at death or extubation
  • Presumptive aspiration defined as observable blue discoloration in tracheal secretions
  • Blue food coloring (FD&C Blue No. 1, FD&C Red No. 40) added to feeding to achieve visible color according to standard protocols of participating hospitals
  • Nurse investigator suctioned tracheal secretions at eight-hour intervals or whenever acute aspiration event suspected; results of visual inspection immediately recorded
  • Average of 67.5±13µL blue food color added to 100mL undiluted formula (Osmolite, Osmolite HN, Jevity, Ensure); serial twofold dilutions made with normal saline; equal aliquots randomly selected and tested blindly; first for presence or absence of blue discoloration.
Description of Actual Data Sample:

15 patients in experimental group, 14 in control of whom five crossed over to the experimental group.

Summary of Results:

Blue dye visible in all formulas at dilutions from full strength through 1:8 dilutions; color visible in 1:16 dilution in all formulas but Osmolite HN; no color visible in dilutions 1:32, 1:64,l 1:128.

Blue dye not detected in any of the 117 control group samples. Blue dye was present in five of 189 experimental group samples (2.6%) Of 18 experimental group specimens demonstrating a bloodless plus glucose reading or visible blue discoloration, blue dye was detectable in five (28%). Of the 15 samples taken from patients with clinically significant aspiration, blue discoloration was visible in four (27%). Blue dye failed to detect the vast majority of aspiration episodes recognized by glucose testing.

Author Conclusion:

Health care team should remain vigilant for unapparent episodes of aspiration and early signs of clinically significant aspiration. Addition of blue dye to formulas with inspection of tracheal secretions for blue discoloration is inadequate for detection of enteral feeding detection.

Funding Source:
Boehringer Mannheim Corp, Sherwood Medical
Pharmaceutical/Dietary Supplement Company:
University/Hospital: Dept of Medicine, Michigan State University; Ingham Medical Center and E. W. Sparrow Hospital
In-Kind support reported by Industry: Yes
Reviewer Comments:

Relatively small sample, however provides suitable evidence due to clear inability of dye to be detected consistently.

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? N/A
  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? 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? 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? 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")? Yes
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%.) 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? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
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? 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.) No
  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? No
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? 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? 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? 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? 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)? N/A
  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