GlideScope Video Laryngoscope Versus Fiberoptic Intubation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for GlideScope Video Laryngoscope Versus Fiberoptic Intubation (NCT01091948), a randomized na study. The primary outcome is Time to Intubation (TTI) as Measured in Seconds.

2. Clinical Question

The trial addresses a comparison of procedure duration under the study conditions, rather than a broad comparison of all possible benefits or harms of the two approaches. The primary measure begins when the device or airway used for the assigned technique is inserted into the mouth and ends when the specified end-tidal carbon dioxide threshold is reached. The protocol description also caps the measurement at 100 seconds.

Random assignment was intended to make the groups comparable on average, while the registry summary states that intubators were required to have experience with both techniques. The posted results describe 37 participants in the fiberoptic group and 38 in the GlideScope group. They report medians and interquartile ranges for the primary outcome, as well as an overall analysis result. They do not report enough detail to assess all aspects of the patient mix, the distribution of procedure times, or whether the results apply to settings beyond those studied.

3. Trial Design

This was a completed, randomized, parallel-group trial sponsored by The Cleveland Clinic. The registry reports an enrollment of 75 and lists a start date of 2008-02 and a primary completion date of 2009-06. Participants were assigned to oral fiberoptic intubation or oral intubation with the GlideScope® Video Laryngoscope. The registry describes single masking, but does not report who was masked or how masking was maintained.

The study summary describes opening a sealed envelope after induction of general anesthesia to reveal the assigned technique. A stopwatch was to begin at the start of the procedure and stop at completion of intubation, with the elapsed time recorded alongside other data. The primary outcome definition further specifies the start and end points used to determine time to intubation. The registry summary says intubators were required to have at least 10 uses of each technique, intended to support comparability in operator experience.

The summary describes a plan to study fifty patients, while the posted enrollment is 75 and the primary outcome results include 37 participants in one group and 38 in the other. The reason for the difference between the stated planned number and posted enrollment is not reported in the registry record. The summary says that average time would be compared with a two-sided T-test at a significance level of 0.05. The posted primary outcome is instead presented as a median with an interquartile range, and the reported analysis is identified as Cox regression. The registry record does not explain this difference in the planned and posted descriptions, or provide a detailed statistical analysis plan. No phase is applicable as reported.

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.

Overall Study

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 Time to Intubation (TTI) as Measured in Seconds, measured over from start of intubation to successfully intubated up to 100 seconds.

The primary endpoint is time to intubation, recorded in seconds. The registry defines the interval as starting when the GlideScope or, for fiberoptic intubation, a Williams airway is inserted into the mouth. It ends when end-tidal PCO2 exceeds 2.7 kPa (20 mmHg), which the record uses as the indicator of successful intubation. The protocol description states that time was measured up to 100 seconds.

This endpoint captures the duration of the intubation procedure under the trial’s operational definition. Timing a procedure can make a practical comparison more direct than relying only on a subjective rating, but interpretation depends on consistent start and stop rules, stopwatch use, and handling of cases that reach the time limit. The registry record describes the timing rules but does not report how observations at the 100-second limit were handled in the analysis or whether any participants reached that limit.

The posted summaries use medians and interquartile ranges. A median describes the middle of the observed distribution, while the interquartile range describes the span of the central half of observations. These summaries do not show the full distribution or establish how much overlap there was between individual participants. The registry does not report a confidence interval for the primary comparison, so the precision of an estimated between-group effect cannot be assessed from the reported p-value alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry summary describes a two-sided T-test at a significance level of 0.05 for comparing average time. A two-sided test evaluates departures in either direction: it does not assume in advance that one group must have a higher or lower average. The stated significance level is a decision threshold used in a testing procedure; it is not the probability that a conclusion is wrong. The posted primary outcome, however, is summarized by medians and interquartile ranges, and its reported analysis is Cox regression. The registry record does not report a full statistical analysis plan or explain the difference between the planned description and posted analysis.

What does a median and interquartile range describe?

In general, the median is the central value when observations are ordered. The interquartile range spans the middle half of the observations and conveys variability without requiring a symmetric distribution. It can be useful when a distribution is skewed or contains unusually long times. These descriptive summaries do not estimate the uncertainty in a treatment contrast. An interval around a group median and an interval around a between-group effect answer different questions; the posted primary results do not give a confidence interval for the contrast.

What does the reported p-value tell the reader?

In general, a p-value measures how unusual the observed data, or data more extreme, would be under a specified null model and its assumptions. It is not an effect size and does not show clinical importance. It also does not establish that two groups are alike when the result is not statistically significant. The primary p-value is reported as 0.19, but the record does not provide the model estimate or its uncertainty. A p-value without those quantities gives an incomplete account of magnitude and precision.

How should the Cox regression label be understood?

In general, Cox regression is commonly used to model time until an event while accounting for the timing of observations and, in some settings, censoring. Its interpretation depends on the event definition, model specification, and assumptions. The registry identifies Cox regression but does not report the coefficient, hazard ratio, confidence interval, event-handling details, or model covariates for this primary analysis. The endpoint’s time limit is stated, but how observations at that limit entered the model is not reported in the registry record. Consequently, readers cannot reconstruct the model-based result from the posted summaries.

What do the secondary comparisons contribute?

For three binary secondary outcomes, the posted results include simple unadjusted recalculations based on the arm-level counts, alongside sponsor-reported Cochran-Mantel-Haenszel analyses. In general, a risk difference describes a difference between proportions, while a risk ratio compares them as a ratio. Confidence intervals describe uncertainty around an estimate under the method used. The recalculations are not adjusted for other variables and are not substitutes for the sponsor’s reported analyses. The registry’s reported methods and values should be distinguished from these simple comparisons, especially where estimates or p-values differ.

The secondary results include confidence intervals for the recalculated comparisons and p-values for both recalculated and sponsor-reported analyses. Several intervals are wide and cross the value representing no difference on their respective scales. Such intervals indicate uncertainty; they do not prove that no effect exists. Sparse events can make estimates particularly imprecise. The registry does not state whether the sponsor’s analyses adjusted for specific factors, beyond identifying the Cochran-Mantel-Haenszel method, and does not report strata or adjustment details.

Why do planning illustrations need caution?

In general, a sample-size calculation estimates the number of participants needed under stated assumptions to have a chosen chance of detecting a specified effect at a chosen significance level. The planning illustrations associated with the binary outcomes use the observed effect as a starting point and show alternative fractions of that effect. They are not the original trial’s sample-size justification, do not establish the trial’s observed power, and should not be read as evidence that the trial was designed around those effects. The registry summary gives its own planned sample of fifty and a testing approach for the primary outcome, but does not report the underlying sample-size assumptions or justification in enough detail to assess them.

More generally, power is a property of a design under assumptions about the true effect and variability; it is not a post-study measure of whether a result is reliable. Planning from an observed effect can be unstable, particularly when estimates come from limited data. Smaller assumed effects require larger studies to detect under otherwise similar assumptions. This general principle explains the shape of planning exercises without converting them into evidence about the effects observed in this trial.

What can be concluded from the methods information?

The record identifies random assignment, parallel groups, a masking designation, primary timing rules, and a reported primary model. It does not provide enough information to evaluate every model assumption, the treatment of missing or capped times, or whether the analysis followed the stated original plan. A complete interpretation therefore combines the reported group summaries with careful attention to what the analysis does and does not disclose.

10. Analyses Reported by the Sponsor

The sponsor-reported primary analysis is identified as Cox regression and has a p-value of 0.19. The posted results give no model estimate or confidence interval for that analysis. The simple recalculations available for selected secondary outcomes do not constitute a recalculation of the primary time-to-intubation analysis, and they cannot be used to infer a primary effect estimate.

There is no reported discrepancy flag for this trial. Even so, the primary analysis cannot be independently reproduced from the posted medians and interquartile ranges: those summaries do not contain the participant-level timing information or all model details needed for a Cox regression. The study summary’s stated plan to compare average times with a two-sided T-test also differs from the posted median summaries and Cox regression label. The registry does not explain the relationship between those descriptions.

For the binary secondary outcomes, sponsor-reported Cochran-Mantel-Haenszel results and simple unadjusted recalculations are distinct analyses. Differences between them can arise because methods, assumptions, or adjustments differ; the record does not supply enough detail to identify the reason for each difference. The sponsor’s reported analyses should be treated as the trial’s own inferential results, while the recalculations are supplementary checks based only on posted group counts. Neither set should be presented as more precise than its estimates and confidence intervals warrant.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists several secondary outcomes in addition to the primary time measure. It does not report a multiplicity adjustment, a testing hierarchy, or a rule describing how secondary findings were to be interpreted if more than one comparison was made. In general, when many outcomes are tested, the chance of at least one apparently unusual result can increase. Without a stated strategy, the secondary p-values are best read as separate, exploratory comparisons rather than as a family of tests with controlled overall error.

Some named secondary outcomes have numerical results in the posted record, while results for Intubation Difficulty Score, Sore Throat Grade, and Number of Intubation Attempts are not reported in the registry record. The reason for their absence is not reported in the registry record. The information does not establish whether these outcomes were unmeasured, unavailable, or omitted from the posted results, so none of those explanations should be assumed.

The primary outcome results identify group sizes, medians, interquartile ranges, and a model-based p-value, but do not report a confidence interval or model estimate. The record does not report how missing primary observations, if any, were handled, or whether any participants were excluded from the analysis. It also does not identify an analysis population such as intention-to-treat or per-protocol for the posted results. The registry’s arm counts describe the participants contributing to the displayed summaries, but do not by themselves establish the full analysis-population rules.

For secondary outcomes, the posted participant counts differ by outcome in what they count as events, while the group denominators are reported. The registry does not provide a general missing-data policy or explain whether all randomized participants contributed to each outcome. In general, missingness can affect interpretation if the probability of an outcome being observed is related to group assignment or outcome status. No conclusion about the presence or impact of missing data can be drawn from the available record.

These omissions matter because a p-value or group summary is interpreted in light of the analysis population, missing-data handling, and multiplicity plan. The registry record does not report enough information to evaluate those issues fully.

12. 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.

The registry reports zero serious adverse events and zero other adverse events in each arm, among the 37 participants at risk in the fiberoptic group and 38 participants at risk in the GlideScope group. These are the counts recorded in the registry’s adverse-event categories. They describe the reported event totals for this trial and should not be taken to establish that no harm occurred.

Adverse-event counts depend on what was defined, collected, and reported. The record does not provide a list of serious event terms, and the number of deaths is not reported in the registry record. A zero count in a trial of this size cannot rule out uncommon events or quantify risks precisely. The registry also does not provide detailed event definitions, severity criteria, or information on duration of follow-up for adverse events.

Other outcomes, including hypoxaemia and trace bleeding, are reported separately as secondary endpoints. They should not be conflated with the general adverse-event categories. The serious and other event counts are therefore a limited description of recorded safety information, not a comprehensive account of all possible complications or a comparison that establishes equivalent safety.

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

The results describe a randomized comparison of two oral intubation techniques in this completed trial. For the primary outcome, the registry reports the median procedure time and interquartile range in each arm, along with a Cox regression p-value. This is evidence about the participants and analysis reported in this record; it is not a complete estimate of the size and precision of a between-group effect, because the primary model estimate and confidence interval are not reported.

A p-value that does not meet a conventional significance threshold does not prove equivalence, absence of a difference, or equal performance. Demonstrating equivalence or non-inferiority generally requires a prespecified margin and a design and analysis tailored to that question. Such a margin is not reported in the registry record. Conversely, the descriptive medians alone do not establish that one approach is faster overall or quantify how consistently any observed difference would apply to other participants.

The secondary outcomes add descriptive information about selected aspects of intubation and adverse events, but several named outcomes have no numerical results in the registry record. The available secondary comparisons are limited by small event counts, uncertainty, and the absence of a reported multiplicity plan. Zero recorded serious and other adverse events should not be interpreted as proof that either technique has no risk.

The registry also leaves important details unspecified, including the primary model estimate, the handling of missing observations and time-limit cases, and the analysis population. The stated planned analysis and posted analysis descriptions differ, without an explanation in the record. These limitations mean that the results should be read as a narrow report of observed outcomes and tests, not as a comprehensive evaluation of the techniques or a basis for conclusions beyond the trial’s setting and methods.

14. Why This Trial Matters Statistically

This trial illustrates why a reported p-value is not a complete statistical result. The primary outcome has descriptive summaries and a test result, but no model estimate or confidence interval. Readers can see the reported distribution summaries and the test’s level of evidence under its assumptions, but cannot assess the precision of a modeled primary contrast from the record. Separating effect size from statistical significance is essential when interpreting clinical comparisons.

It also illustrates the importance of consistency between a planned analysis and a posted analysis. The registry summary describes a comparison of average times using a T-test, whereas the posted primary summaries are medians and the analysis is identified as Cox regression. These methods address data in different ways, and the registry does not explain the change. Transparent reporting of the analysis plan, model specification, and effect estimate would make the result easier to evaluate and reproduce.

The trial also shows why a nonsignificant result is not synonymous with equivalence. A conclusion of similarity requires an explicit framework and sufficient precision, not simply a p-value above a threshold. The secondary outcomes reinforce the point: low event counts and wide uncertainty can leave substantial ambiguity even when the observed counts are small.

Finally, planning illustrations based on observed secondary effects are not evidence of the study’s original design assumptions or its achieved power. Keeping planning scenarios separate from observed findings prevents a post hoc calculation from being mistaken for prospective justification. Taken together, these statistical issues apply broadly to randomized procedural trials: clear estimands, prespecified analyses, complete outcome reporting, and uncertainty estimates are central to reliable interpretation.

15. 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.

The main trial-specific limitation in the posted primary results is the lack of a model estimate and confidence interval alongside the p-value. The group medians and interquartile ranges describe observed times but do not provide an interval for the primary comparison. The registry identifies Cox regression without reporting its coefficient, model covariates, event-handling details, or assumptions, which limits independent evaluation and reproducibility.

The study summary’s planned comparison of average times using a two-sided T-test differs from the posted median summaries and Cox regression analysis. The registry record does not explain why the descriptions differ or whether the posted analysis was prespecified. The time limit of 100 seconds is noted, but the record does not explain how reaching that limit affected analysis. It also does not report missing-data handling, exclusions, or the analysis population.

The posted enrollment is 75, while the study summary describes a plan to study fifty patients. The reason for that difference is not reported in the registry record. The arm sizes are relatively limited for evaluating uncommon events, and several secondary outcomes have few recorded events. The resulting secondary comparisons have uncertainty that limits precise interpretation. Results for Intubation Difficulty Score, Sore Throat Grade, and Number of Intubation Attempts are not reported in the registry record.

The registry describes single masking but does not identify who was masked or how. It states that intubators were required to have experience with both techniques, but does not report operator-level results or how experience was distributed. Patient characteristics, detailed eligibility criteria, and information needed to judge generalizability are not reported in the registry record. These gaps limit assessment of the trial’s context and of how broadly its findings might apply.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: GlideScope Video Laryngoscope Versus Fiberoptic Intubation — NCT01091948.
• Registry record last updated 2016-12-20; status last verified 2016-10.
• Results first posted 2016-12-20.
• 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.

19. Record Summary

NCT01091948 is a completed, randomized, parallel-group trial sponsored by The Cleveland Clinic. It compared oral fiberoptic intubation with GlideScope® Video Laryngoscope intubation and reported enrollment of 75. The primary endpoint was time to successful intubation in seconds, summarized by group medians and interquartile ranges. The sponsor-reported primary analysis is identified as Cox regression, with p = 0.19; an estimate and confidence interval are not reported.

The study summary describes a planned two-sided T-test of average times, while the posted primary summaries and analysis use different descriptions. Selected secondary outcomes and adverse-event counts are reported, but several named secondary measures lack numerical results. Missing-data handling, analysis-population definitions, multiplicity procedures, and important primary-model details are not reported in the registry record. The posted findings therefore provide a limited account of observed outcomes and their statistical uncertainty.