Evaluation of Above the Cuff Suctioning During General Anesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Above the Cuff Suctioning During General Anesthesia (NCT01386879), a randomized phase 4 study. The primary outcome is Prevention of the Movement of Test Dye (Methylene Blue) From the Pharynx Into Patients' Trachea During Surgery.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group Phase 4 pilot study sponsored by Thomas Jefferson University. The study began in 2011-07, had a primary completion date of 2012-10 and is listed as terminated. The record gives enrollment as 50. In contrast, the brief study description states that 110 adult patients would be randomized among three groups. The reason for this difference is not reported in the registry record.

Participants were assigned to TaperGuard Evac ETT, Teleflex ISIS ETT or Standard ETT. The two suction-port tubes were compared with the standard tube for the primary dye outcome and for measures related to secretion collection, intubation and tissue injury. Randomization and a parallel-group design support comparisons between groups, but the registry record does not describe the randomization procedure, allocation concealment or who was masked.

The primary outcome was assessed over 4 hours. The trial description says methylene blue was instilled into the pharynx every 60 minutes after intubation, with video-recorded bronchoscopy used to assess dye presence every 20 minutes. The endpoint result counts participants with dye in the distal trachea. One bronchoscopy recording was corrupted and could not be evaluated in the GEvac group, as described in the primary outcome record.

The posted primary outcome counts are based on 16 participants in the TaperGuard Evac group, 17 in the Teleflex ISIS group and 16 in the Standard group. These outcome-specific counts need not match the registry's enrollment figure or counts for other outcomes. The registry record does not report a detailed participant flow, reasons for termination or a full protocol.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: We did initial 10 roll-in subjects to be familiar with all of the procedures and recordings.

Overall Study

Analysis population for the primary outcome, as defined in the registry: the number of participants with dye in the distal trachea. One bronchoscopy recording was corrupted and not able to be evaluated in the GEvac group.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Prevention of the Movement of Test Dye (Methylene Blue) From the Pharynx Into Patients' Trachea During Surgery, measured over 4 hours.

The primary endpoint counted participants with methylene blue in the distal trachea during the 4-hour observation period. Dye was introduced into the pharynx after intubation; bronchoscopy recordings were used to assess whether it was present above or below the inflated endotracheal tube cuff. The endpoint therefore represents an observed marker of passage from the pharynx into the trachea, rather than a direct measure of pneumonia or another clinical outcome.

This measure was chosen to address the trial's question about whether the cuff and suction-port tube designs differed in limiting movement of material past the cuff during surgery. As a binary outcome, each participant is counted according to whether dye was detected in the distal trachea. Such a measure is straightforward to interpret as an event count, although it does not describe the amount of dye, the timing of passage or the clinical consequences of detection.

In the posted results, dye was recorded in 0 participants in each suction-port group and 2 participants in the Standard group. The record also notes that one bronchoscopy recording was corrupted and could not be evaluated in the GEvac group. How that recording was handled in the posted analysis is not reported in the registry record. The primary endpoint thus addresses a narrowly defined intraoperative observation; it does not by itself establish whether tube type changes patient-centered outcomes.

7. Results Posted in the Registry

• TaperGuard Evac ETT: 0.0% (0/16) versus 12.5% (2/16) on control; risk difference -12.5 percentage points (95% CI -28.7 to 3.7); unadjusted two-proportion z-test p = 0.144.
• Teleflex ISIS ETT: 0.0% (0/17) versus 12.5% (2/16) on control; risk difference -12.5 percentage points (95% CI -28.7 to 3.7); unadjusted two-proportion z-test p = 0.133.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Evaluation of pH of Secretions Collected Above Endotracheal Tube Cuff During Surgery

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Teleflex ISIS ETT: mean 7.29 versus 7.38 on control; difference -0.09 (95% CI -0.43 to 0.25), standardized effect d = -0.18; z-test p = 0.606.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Teleflex ISIS ETT and the control. The interval gives the range of effects that remain compatible with the data.

the Ease of Tracheal Intubation Following the Induction of General Anesthesia Among the 3 Types of ETT

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • TaperGuard Evac ETT: mean 7.53 versus 7.41 on control; difference 0.12 (95% CI -0.24 to 0.48), standardized effect d = 0.23; z-test p = 0.519.
  • Teleflex ISIS ETT: mean 7.59 versus 7.41 on control; difference 0.18 (95% CI -0.18 to 0.54), standardized effect d = 0.34; z-test p = 0.333.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between TaperGuard Evac ETT and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Teleflex ISIS ETT and the control. The interval gives the range of effects that remain compatible with the data.

Evaluation the Trachea and Vocal Cords at the Time of ETT Extubation to Determine Whether There is a Difference in the Amount of Mucosal Injury Between the 3 Types of ETT.

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • TaperGuard Evac ETT: 76.9% (10/13) versus 50.0% (7/14) on control; risk difference 26.9 percentage points (95% CI -7.9 to 61.7), risk ratio 1.54 (0.84–2.81); unadjusted two-proportion z-test p = 0.148.
  • Teleflex ISIS ETT: 68.8% (11/16) versus 50.0% (7/14) on control; risk difference 18.8 percentage points (95% CI -15.9 to 53.4), risk ratio 1.38 (0.74–2.55); unadjusted two-proportion z-test p = 0.296.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between TaperGuard Evac ETT and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Teleflex ISIS ETT and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover several distinct questions: secretion pH and volume, ease of intubation, mucosal injury and bacterial load. Numerical results are posted for pH, intubation time and mucosal injury; numerical results for secretion volume and bacterial load are not reported in the registry record. The available outcomes do not form a single composite measure, and they should not be treated as interchangeable confirmations of the primary dye endpoint.

Across the available secondary results, estimates vary in direction and scale, and their confidence intervals include values compatible with no difference for the comparisons posted. This general pattern does not resolve the uncertainty in the primary endpoint. The secondary outcomes measure different biological or procedural features, and some have different denominators and comparison groups. The registry record does not report a prespecified hierarchy or an integrated analysis connecting these outcomes to dye passage.

Unadjusted secondary results carry less weight when several outcomes and pairwise comparisons are examined. Considering many tests raises the chance that an apparently notable result could arise by chance, while no multiplicity adjustment or confirmatory testing strategy is reported in the registry record. Conversely, a lack of a small p-value does not establish equivalence or rule out a meaningful difference. The secondary findings are best regarded as exploratory descriptions that may help define questions for further research, not as independent proof of the primary hypothesis.

Because the registry reports no analyses for some listed secondary outcomes and no reported analysis plan, the overall pattern is incomplete. Missing numerical results should not be interpreted as evidence of no effect or as evidence that the outcome was not measured. They are simply not reported in the registry record.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Evaluation of pH of Secretions Collected Above Endotracheal Tube Cuff During Surgery
• the Ease of Tracheal Intubation Following the Induction of General Anesthesia Among the 3 Types of ETT
• Evaluation the Trachea and Vocal Cords at the Time of ETT Extubation to Determine Whether There is a Difference in the Amount of Mucosal Injury Between the 3 Types of ETT.
• Evaluation of Volume of Secretions Collected Above Endotracheal Tube Cuff During Surgery
• Evaluation of Bacterial Load of Secretions Collected Above Endotracheal Tube Cuff During Surgery

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary: each participant is counted as having or not having dye detected in the distal trachea. For a binary outcome, a group proportion is the number of participants with the event relative to the number assessed. The posted counts are 0 of 16, 0 of 17 and 2 of 16 for TaperGuard Evac, Teleflex ISIS and Standard ETT, respectively. These are outcome-specific denominators; they should not be assumed to be the same as enrollment or as denominators for other outcomes.

What does a risk difference represent?

A risk difference subtracts the event proportion in the comparator group from the event proportion in the group being compared. The posted estimate of -0.125 for each suction-port tube indicates a lower observed event proportion than in Standard ETT, expressed on the risk-difference scale. A value of zero represents equal observed proportions. The estimate is a sample-based quantity, not a guarantee that the same difference would occur in another study.

How should a confidence interval be read?

A confidence interval communicates the range of values reasonably compatible with the data under the method used. It reflects sampling uncertainty; it does not describe the range of individual participant outcomes. For both primary comparisons, the interval runs from -0.287 to 0.037 and includes zero. That means the results do not pin down the direction of the underlying difference with precision. A confidence interval is not a statement that there is a specified probability that the true value lies within this particular calculated interval.

What does an unadjusted p-value add?

The unadjusted p-value evaluates how unusual the observed data would be under a specified null hypothesis, using the test's assumptions. The primary comparisons have unadjusted p-values of 0.144 and 0.133. A p-value is not the probability that the null hypothesis is true, nor a measure of the size or clinical importance of an effect. The registry record does not report the test used for the primary comparisons, its assumptions or an adjustment for multiple comparisons. These p-values therefore should be interpreted alongside the event counts and confidence intervals, not as stand-alone conclusions.

Why are small event counts important?

When events are uncommon, a small change in the observed count can materially affect the estimated proportion and comparison. In these results, the primary event occurred in only the Standard group. That pattern yields an estimated difference, but limited event information leaves substantial uncertainty about the underlying rates. General statistical reasoning also cautions that approximations can be less reliable when event counts are sparse; the specific method used for the posted primary confidence intervals is not reported in the registry record.

How should continuous outcomes be read?

For continuous secondary outcomes, the posted summaries use means and standard deviations. A mean describes the center of the recorded values, while a standard deviation describes their spread around that mean. A mean difference compares the group averages. Its confidence interval communicates uncertainty in that comparison. For example, the pH outcome has a mean difference of -0.09 for Teleflex ISIS compared with TaperGuard Evac, with an interval from -0.431 to 0.252. This interval spans zero, so the estimate remains uncertain about the direction of the difference. The registry does not report a distributional assessment or the analysis method for this comparison.

The registry also includes planning illustrations for some continuous and binary comparisons. These are based on the observed effect and stated assumptions: a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation, with the target effect set to a stated fraction of the observed effect. Such figures are hypothetical planning quantities, not observed power and not evidence that the trial was designed around those assumptions. The trial's own sample-size justification is not reported in the registry record.

Finally, the record lists no reported analyses for the secondary outcomes. Posted estimates and unadjusted p-values should therefore not be mistaken for evidence that a full analysis plan was followed. The registry record does not report model adjustments, handling of missing observations or a multiplicity strategy.

11. Confidence Intervals and Precision

The primary risk-difference estimates are -0.125 for both comparisons with Standard ETT, and each confidence interval extends from -0.287 to 0.037. The interval includes zero, the value corresponding to no difference on this scale. It also covers values that would represent a difference in the other direction. This breadth reflects the limited precision of estimates based on the small number of observed primary events.

The interval should be read as uncertainty about the underlying group difference, not as a range containing a fixed proportion of individual outcomes. The registry record does not report the confidence-interval method, so its exact assumptions cannot be assessed from the record. In particular, sparse event data can make interval construction consequential; this is a general statistical consideration, not a claim about which method was used.

The posted unadjusted p-values, 0.144 and 0.133, are consistent with the broad uncertainty reflected in the intervals, but p-values and intervals answer different questions. The p-values summarize compatibility with a null model under a test, while the interval conveys a range of effect values compatible with the data under an interval procedure. Neither alone establishes whether a difference is important in practice.

Precision also depends on the endpoint and the number of observations available for it. The primary outcome has outcome-specific counts of 16, 17 and 16 across the three groups, and the record notes one corrupted bronchoscopy recording in the GEvac group. The handling of that recording is not reported in the registry record. Other outcomes have different denominators, so precision for the primary endpoint should not be inferred from their sample sizes or estimates.

12. Multiplicity, Missing Data and Analysis Populations

The trial includes a primary endpoint and several secondary outcomes, with more than one comparison involving the three tube groups. Repeated testing can increase the chance of at least one apparently unusual result even when there is no underlying difference. A prespecified strategy might control or otherwise address that issue, but a multiplicity plan is not reported in the registry record. The primary p-values are explicitly unadjusted, and the secondary comparison p-values are also posted as unadjusted.

The record does not report whether the primary endpoint was designated before data collection in a protocol, how secondary outcomes were prioritized, or whether any interim analyses were planned. These details are not reported in the registry record. The record lists no reported analyses for the secondary outcomes; it does not explain whether analyses were omitted, not performed or not submitted.

There are also indications that outcome-specific data availability differs. The primary outcome notes one corrupted bronchoscopy recording that could not be evaluated in the GEvac group. How that observation was treated in the primary analysis is not reported in the registry record. The enrollment figure is 50, whereas the study description says 110 participants would be randomized. The reason for the difference and a full accounting of participant flow are not reported in the registry record.

Denominators differ across outcomes, but the record does not give a complete explanation for all missing measurements or exclusions. It does not report whether analyses followed intention-to-treat principles, used a per-protocol population or applied another analysis population. Nor does it describe imputation or sensitivity analyses for missing data. Without those details, the posted comparisons can be described as reported, but their handling of incomplete observations cannot be fully evaluated.

13. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The adverse-event record lists 0 serious adverse events in each of the TaperGuard Evac, Teleflex ISIS and Standard ETT groups. It lists 1 other adverse event in each group. The numbers at risk are 17, 17 and 16, respectively, for these safety summaries. These are safety-record denominators and should not be assumed to match the denominators for the primary endpoint or other outcomes.

These figures are counts in a small study, not precise estimates of the frequency of uncommon harms. The record gives no serious adverse event terms, and deaths are not reported in the registry record. The description and severity of the other adverse events are not included in the posted figures. The absence of a recorded serious event in these groups cannot establish that serious events cannot occur, and the counts alone do not support a broad safety comparison. They describe only what is recorded for this trial.

14. What the Result Does, and Does Not, Mean

The primary result describes a difference in observed methylene-blue detection between the suction-port groups and the Standard group during the 4-hour intraoperative assessment. No dye events were recorded in the two suction-port groups, while 2 were recorded in the Standard group. The estimated risk differences are negative, but their confidence intervals include zero and extend across a range of possible underlying differences. The data therefore provide an uncertain estimate rather than a definitive comparison.

The endpoint is a surrogate observation of dye passage past the cuff. It is not a diagnosis of infection and does not measure pneumonia, recovery, length of stay or other later outcomes. The results cannot establish whether any tube reduces clinical complications. The study description discusses a rationale based on intensive care unit research, but the trial itself evaluates use during general anesthesia and surgery; those settings and outcomes should not be conflated.

The results also do not establish that the groups are equivalent. Evidence of no difference would require an appropriate design and analysis for equivalence or non-inferiority, and such a design is not reported in the registry record. A confidence interval spanning zero indicates uncertainty, not proof that the true difference is zero.

Finally, the listed results should be interpreted in light of the pilot nature of the study, limited event counts, varying outcome-specific denominators and unreported analysis details. They can inform the description of observed outcomes and the uncertainty around them. They do not determine how the tubes should be used, and no treatment recommendation follows from these data alone.

15. Why This Trial Matters Statistically

This trial illustrates why the event count and the uncertainty around an estimate both matter. A simple comparison of observed proportions might suggest fewer dye events in the suction-port groups, but only 2 primary events were recorded in the Standard group and none in the other groups. With sparse events, estimated differences can be unstable, and the confidence intervals are essential for showing how much uncertainty remains.

It also highlights the distinction between a mechanistic or procedural endpoint and a clinical outcome. Detection of dye provides an observable measure related to movement past the cuff. It does not directly answer whether patients experience infection or other clinical consequences. Statistical interpretation must stay aligned with what was actually measured.

The record further demonstrates that enrollment, planned enrollment and endpoint-specific denominators are not interchangeable. It lists 50 enrolled participants, while its study description planned randomization of 110. Outcome denominators vary, and one bronchoscopy recording was not evaluable. Transparent participant flow and analysis-population details are important for judging how estimates relate to the original randomized groups.

Finally, several secondary outcomes and pairwise comparisons make multiplicity and prespecification relevant. Without a reported analysis plan or adjustment strategy, secondary findings are more appropriately considered exploratory. Together, these features make the study a useful example of careful interpretation: report the observed estimates, attend to their precision, distinguish measurement from clinical benefit, and avoid treating an uncertain pilot comparison as conclusive.

16. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several limitations specific to this trial affect interpretation. The registry lists enrollment of 50, but the study description says 110 participants would be randomized. The reason the study ended with the recorded enrollment, and the reason it is listed as terminated, are not reported in the registry record. A full account of screening, allocation, follow-up and reasons for missing outcome data is also not reported.

The primary endpoint is based on a dye observation during surgery, not a clinical event such as pneumonia. One bronchoscopy recording was corrupted and could not be evaluated in the GEvac group; its treatment in the posted results is not reported in the registry record. The primary groups have few observed events, and the confidence intervals are broad. These features limit the precision and scope of the comparison.

Outcome-specific denominators differ. The record does not explain all differences in available observations or identify the analysis population used for each outcome. It does not report the randomization method, concealment, details of masking, an analysis plan, multiplicity handling, or the method used to calculate the primary confidence intervals. These details are not reported in the registry record.

Numerical results are not posted for all listed secondary outcomes, and adverse-event descriptions are limited. The small pilot study and incomplete analysis information restrict conclusions about uncommon events, consistency across outcomes and clinical relevance. These limitations do not negate the recorded observations, but they constrain how broadly those observations can be interpreted.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Evaluation of Above the Cuff Suctioning During General Anesthesia — NCT01386879.
• Registry record last updated 2022-06-08; status last verified 2022-05.
• Results first posted 2022-06-08.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

20. Record Summary

NCT01386879 is a randomized, single-masked, parallel-group Phase 4 pilot study of two endotracheal tubes with above-cuff suction ports and a standard tube. It is listed as terminated, with enrollment of 50 and primary completion in 2012-10. The study description states an intended enrollment of 110.

The primary endpoint counted participants with methylene blue in the distal trachea during a 4-hour assessment. The posted counts were 0 of 16 for TaperGuard Evac, 0 of 17 for Teleflex ISIS and 2 of 16 for Standard ETT. The estimated risk difference for each suction-port group versus Standard was -0.125, with a confidence interval from -0.287 to 0.037.

Some secondary results are posted, but numerical results for secretion volume and bacterial load are not reported in the registry record. The record does not report a detailed analysis plan, multiplicity strategy or full handling of missing observations. The primary findings are preliminary and imprecise.