This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for RIFL (Rigid and Flexing Laryngoscope) vs. Fiberoptic Bronchoscope (NCT01965938), a randomized na study. The primary outcome is Time Until Proper Endotracheal Tube Placement.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01965938 |
| Phase | NA |
| Condition | Intubation; Difficult |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 41 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Vanderbilt University |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerned patients with potentially difficult airways. The registry describes eligibility examples as an oropharyngeal class of 3–4, BMI greater than 35, or a history of difficult intubation using direct laryngoscopy. It does not report the characteristics of the enrolled patients or how many qualified through each criterion.
Intervention
The intervention was the Rigid and Flexing Laryngoscope (RIFL). The registry describes advancing the endotracheal tube after visualizing the carina with the scope, then removing the scope. It does not report additional procedural details or operator experience.
Comparator
The comparison device was a flexible fiberoptic bronchoscope. The registry describes the same broad sequence: visualize the carina, advance the endotracheal tube, and remove the bronchoscope. The trial was randomized, parallel, and unmasked, so masking of participants or clinicians was not used.
Primary question
The primary endpoint was time until proper endotracheal tube placement, measured in seconds and confirmed by end-tidal carbon dioxide. The registry reports a median of 49 seconds for RIFL and 64 seconds for the fiberoptic bronchoscope. It does not report a primary between-group estimate, confidence interval, or test, so these summaries alone do not quantify the precision of a difference between devices.
3. Trial Design
The registry describes a randomized, parallel-group comparison of RIFL with a fiberoptic bronchoscope for intubation in patients with potentially difficult airways. Allocation was randomized, and masking was listed as none. The trial status is completed. Vanderbilt University is listed as sponsor; the registry records a start in 2012-09 and primary completion in 2013-07. The phase field is recorded as NA.
Enrollment is recorded as 41. For the primary endpoint, the registry gives an analysis group size of 20 for RIFL and 20 for the fiberoptic bronchoscope. It does not explain how the enrollment figure relates to those endpoint group sizes, or report participant flow, exclusions, withdrawals, or the analysis population. Those details should not be inferred from the group summaries.
The intervention descriptions specify bronchoscopy with the assigned device, visualization of the carina, advancement of the endotracheal tube, and removal of the scope. The endpoint description defines successful placement by confirmation of end-tidal carbon dioxide. The registry does not report further procedural standardization, operator training, or whether additional care differed between groups.
The listed secondary outcomes include successful intubation, attempts, glottic view, assistance maneuvers, lowest pulse oximetry saturation, and alternate device use. Detailed posted results are available for attempts and assistance maneuvers; results for the other listed outcomes are not reported in the registry record. No registered statistical analysis is 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
| Stage | RIFL (Rigid and Flexing Laryngoscope) | Fiberoptic Bronchoscope |
|---|---|---|
| STARTED | 21 | 20 |
| COMPLETED | 20 | 20 |
| NOT COMPLETED | 1 | 0 |
Reasons for not completing this period:
| Reason | RIFL (Rigid and Flexing Laryngoscope) | Fiberoptic Bronchoscope |
|---|---|---|
| Withdrawal by Subject | 1 | 0 |
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.
| Characteristic | Unit | RIFL (Rigid and Flexing Laryngoscope) | Fiberoptic Bronchoscope | Total |
|---|---|---|---|---|
| Participants analysed | 20 | 20 | 40 | |
| Age, Continuous | years | 50 (SD 15) | 49 (SD 12) | 49.5 (SD 14) |
| Gender: Female | Participants | 10 | 13 | 23 |
| Gender: Male | Participants | 10 | 7 | 17 |
| Mallampati Class (N): Class 1 | participants | 3 | 1 | 4 |
| Mallampati Class (N): Class 2 | participants | 2 | 3 | 5 |
| Mallampati Class (N): Class 3 | participants | 6 | 7 | 13 |
| Mallampati Class (N): Class 4 | participants | 9 | 9 | 18 |
| Anticipated Difficult airway: Yes | participants | 9 | 6 | 15 |
| Anticipated Difficult airway: No | participants | 11 | 14 | 25 |
6. Primary Endpoint
The registry lists the primary outcome as Time Until Proper Endotracheal Tube Placement, measured over usually <100 seconds.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | seconds |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is time until proper endotracheal tube placement, measured in seconds. Its description starts timing when the intubating scope is placed in the oral cavity and ends when proper tube placement is confirmed by end-tidal carbon dioxide. The description also defines successful intubation time by the scope passing the incisors and then being withdrawn past that point after successful intubation. The record does not explain how these two timing descriptions were reconciled in practice.
Time is a direct measure of the duration of the intubation process. In general, a continuous time measure can distinguish differences in duration that a simple success-or-failure outcome would not capture. The registry reports medians and interquartile ranges, which describe the central value and spread of the observed times without requiring a normal distribution assumption for the summary itself.
The reported median was 49 seconds with an interquartile range from 24 to 73 seconds for RIFL, and 64 seconds with an interquartile range from 40 to 120 seconds for the fiberoptic bronchoscope. The timeframe is described as usually <100 seconds, but the record does not explain how that phrase was applied to the endpoint. A median and interquartile range are descriptive; without a reported between-group estimate and its uncertainty, they do not establish the size or precision of a treatment contrast.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary results are descriptive summaries of intubation time. The registry reports a median of 49 seconds for RIFL, with an interquartile range of 24 to 73 seconds, and a median of 64 seconds for the fiberoptic bronchoscope, with an interquartile range of 40 to 120 seconds. The observed medians are not identical, but the registry does not report a primary between-group estimate, confidence interval, or p-value. It is therefore not possible to use the posted primary summaries to quantify the uncertainty around the contrast or to determine whether a specified statistical test supported a difference.
Interquartile ranges describe the middle half of the observed values within each group. They are not confidence intervals for a difference in group medians. Their overlap or non-overlap is not a substitute for a formal comparison. The record also does not report individual observations, a distributional analysis, or an adjusted estimate. Any interpretation should therefore stay at the level of the posted group summaries.
The secondary results include a mean number of attempts of 1.1 for RIFL and 1.2 for the fiberoptic bronchoscope. The posted unadjusted recalculation gives a mean difference of 0.1 and p = 0.443. For assistance maneuvers, the posted counts are 2 participants in the RIFL group and 16 in the fiberoptic bronchoscope group; the posted unadjusted recalculation gives a risk difference of 0.7 and p < 0.001. These are secondary comparisons, and no adjusted analyses are reported. They should not be treated as confirmation of the primary endpoint or as a substitute for a prespecified primary analysis.
The registry does not report a primary inferential analysis or explain why none is posted. It also does not describe a statistical analysis plan, handling of missing data, or analysis population. The enrollment figure and the group sizes shown for outcomes do not, by themselves, explain participant disposition. These omissions limit conclusions about how precisely the trial estimated differences and how representative the posted outcome data are of all enrolled participants.
9. Statistical Methods Explained
The record presents group summaries and selected unadjusted secondary comparisons. It does not report a full statistical analysis plan, so the methods distinguish the posted calculations from general statistical concepts.
What do the primary summaries tell us?
The primary endpoint is reported as a median with an interquartile range. A median is the middle value in an ordered set of observations. The interquartile range describes the interval from the lower to the upper quartile and contains the middle half of the observed values. These summaries are useful when values may be skewed or when a few long times could make an average less representative of a typical observation.
The posted medians are 49 seconds for RIFL and 64 seconds for the fiberoptic bronchoscope. Their interquartile ranges are 24 to 73 seconds and 40 to 120 seconds, respectively. These are separate within-group descriptions. A difference between medians would require a defined comparison and should not be constructed from the group summaries for this interpretation. The registry does not report a primary contrast, its confidence interval, or a test result.
What is a confidence interval?
General explanation: a confidence interval expresses uncertainty around an estimated quantity under a specified statistical method. For a between-group comparison, it can show the range of effect sizes compatible with the data and method. It is distinct from an interquartile range, which describes the spread of individual observations. The registry does not report a confidence interval for the primary endpoint. The posted intervals attached to secondary recalculations are not needed to establish what the primary time summaries mean.
How should the secondary comparisons be read?
The attempt outcome is a mean with a standard deviation in each group. The posted recalculation is an unadjusted mean difference of 0.1, with p = 0.443. The assistance outcome is a participant count in each group. Its posted unadjusted comparison is a risk difference of 0.7, with p < 0.001. These recalculations compare the posted summary data without adjustment for other variables. They do not show that the trial's sponsor specified these tests, and the registry reports no analyses under its reported analyses field.
General explanation: an unadjusted comparison does not account for possible covariates, stratification factors, or other design features unless those are built into the calculation. A p-value describes how surprising data at least as incompatible with a null hypothesis would be under the test's assumptions; it is not the probability that the null hypothesis is true, nor a measure of clinical importance. A small p-value for a secondary outcome does not repair the absence of a reported primary comparison.
What do the planning illustrations mean?
The registry includes sample-size planning illustrations based on observed secondary effects. The stated assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is a stated fraction of the observed effect. For attempts, planning for 100% of the observed effect gives 267 participants per arm for 80% power and 358 participants per arm for 90% power; planning for 75% gives 475 and 636 participants per arm, and planning for 50% gives 1,068 and 1,430 participants per arm. For assistance maneuvers, the corresponding figures are 7 and 9 participants per arm, 12 and 16 participants per arm, and 25 and 33 participants per arm.
These are planning illustrations, not observed power and not evidence that the completed trial had the stated power. They depend on the observed effect estimates, which may be imprecise, particularly in small groups. The record says the illustrations are not the trial's own design calculation. Its original sample-size justification is not reported in the registry record.
Why does over-dispersion matter in general?
General explanation: when counts vary more than a simple statistical model expects, standard errors from that model can be too small and intervals too narrow. Models may need to account for this extra variability. The posted primary time summaries do not include a model for over-dispersion, and the registry does not report a model-based analysis of attempts or assistance. It would be inappropriate to infer whether over-dispersion was assessed or addressed.
The record also does not explain missing-data handling, prespecified covariates, multiplicity control, or whether participants were analyzed according to randomized assignment. These omissions mean the posted calculations can be described, but cannot be assumed to represent a complete prespecified analysis.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists multiple secondary outcomes, including success, attempts, glottic view, assistance maneuvers, oxygen saturation, and alternate device use. It does not report how many hypotheses were treated as confirmatory, whether a hierarchy or multiplicity adjustment was prespecified, or whether secondary outcomes were intended to be exploratory. When several outcomes are tested, the chance of at least one apparently unusual result can increase. General statistical practice may address this through prespecified ordering or adjustment, but the registry does not report such a method.
No analyses are listed under reported analyses. The primary endpoint has group medians and interquartile ranges, but no reported primary test or comparison estimate. The secondary comparison calculations are unadjusted. The statistical analysis plan, including any planned covariate adjustment or interim analysis, is not reported in the registry record. Interim analyses should not be assumed to have occurred or not occurred.
Missing-data handling is also not reported. The registry does not describe whether any endpoint values were unavailable, how missing values were handled, or whether sensitivity analyses were conducted. It does not identify an intention-to-treat, per-protocol, or other analysis population. The enrollment record gives 41, while the outcome group summaries give 20 in each arm; the registry does not explain the relationship between those figures. Participant flow, reasons for any exclusions, and outcome-specific denominators beyond the posted group sizes are not reported.
These gaps matter because the strength of an estimate depends not only on its numerical value but also on how the analysis was planned and who contributed data. Without those details, the posted summaries and unadjusted recalculations can be described, but the completeness and prespecification of the analyses cannot be established.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| RIFL (Rigid and Flexing Laryngoscope) | 0 | 20 | 0.0% |
| Fiberoptic Bronchoscope | 0 | 20 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| RIFL (Rigid and Flexing Laryngoscope) | 2 of 20 |
| Fiberoptic Bronchoscope | 3 of 20 |
Most frequent non-serious adverse event terms
| Event term | Organ system | RIFL (Rigid and Flexing Laryngoscope) | Fiberoptic Bronchoscope |
|---|---|---|---|
| Oropharyngeal injuries | Injury, poisoning and procedural complications | 2 of 20 | 3 of 20 |
The registry reports zero serious adverse events among 20 participants at risk in the RIFL group and zero among 20 at risk in the fiberoptic bronchoscope group. This means no serious adverse events are recorded in either group in the posted safety figures. It does not establish that the risk is zero, especially because the groups are small and the registry provides no uncertainty estimate for these counts.
Deaths are recorded as null, not as zero. The number of deaths is therefore not reported in the registry record and should not be interpreted as evidence that none occurred. The record also gives other adverse-event counts of 2 for RIFL and 3 for the fiberoptic bronchoscope. It does not provide further event descriptions in the listed serious-event terms.
These figures describe what the registry reports; they do not support a precise comparison of safety between devices. The registry does not provide details about adverse-event definitions, severity assessment beyond the serious-event category, follow-up duration, or missing safety information. The absence of reported serious events should be read as a limited observation from this trial record, not as a guarantee about safety.
12. What the Result Does, and Does Not, Mean
The registry provides a randomized comparison of two airway devices in patients described as having potentially difficult airways. It reports the median time to confirmed tube placement and selected secondary outcome summaries. The observed primary medians were 49 seconds with RIFL and 64 seconds with the fiberoptic bronchoscope. Those values describe the recorded groups; they do not, by themselves, establish a reliable between-group effect or its precision.
The record does not report a primary comparison estimate, confidence interval, or p-value. It also does not report an analysis plan or explain the relation between overall enrollment and the outcome group sizes. As a result, readers cannot determine from this registry record how the primary analysis was specified, how missing data were handled, or whether the posted data include all randomized participants.
The secondary outcomes provide additional but incomplete information. Their unadjusted comparisons should be treated cautiously because there are multiple listed outcomes and no reported multiplicity strategy. Several listed outcomes do not have results reported in the registry record. The available safety figures record no serious adverse events in either group, but they are limited observations and deaths are not reported.
These results do not establish that either device is preferable, nor do they settle how the devices compare across patient groups or clinical settings. They describe a small randomized trial record with limited inferential reporting. The distinction between observed group summaries and a precise causal estimate is important: randomization is a design feature, but the registry information available does not provide the complete analysis needed to quantify the primary contrast or its uncertainty.
13. Why This Trial Matters Statistically
This trial illustrates why a randomized design and a reported primary comparison are different parts of statistical evidence. Random allocation is intended to support a fair comparison between groups, but readers also need a clearly reported estimate of the contrast and its uncertainty. Here, the primary outcome is summarized within each group, while a primary between-group estimate and inferential analysis are not reported in the registry record.
The example also shows why the form of a summary matters. Medians and interquartile ranges describe the observed distribution of time in each group. They are not confidence intervals for a treatment contrast. Treating the ranges as uncertainty intervals for the difference would confuse within-group variation with uncertainty about a comparison.
Secondary endpoints can provide useful context, but multiple unadjusted comparisons do not automatically form a coherent confirmatory analysis. The registry lists several outcomes, reports selected results, and gives no multiplicity strategy or registered analysis. The sample-size illustrations are based on observed secondary effects and explicitly are not the trial's own design calculations. They are planning scenarios, not evidence of achieved power or proof that the original design was adequate.
For clinical researchers and statisticians, the record is a practical reminder to report participant flow, analysis populations, missing-data rules, prespecified analyses, effect estimates, and uncertainty alongside descriptive summaries. Those elements help readers distinguish what the observed data say from what remains uncertain.
14. 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 record constrain interpretation. The primary endpoint is described with two timing formulations: time from first placement in the oral cavity to confirmation by end-tidal carbon dioxide, and time from the scope passing the incisors until withdrawal past the same point after successful intubation. The registry does not explain how these definitions were applied or reconciled. It also describes the timeframe as usually <100 seconds without explaining how that qualifier relates to the reported observations.
The group summaries are small, with 20 participants reported for each primary endpoint group, and the registry does not provide participant-level data or a primary comparison estimate. Although enrollment is recorded as 41, the record does not explain the difference between that figure and the outcome group sizes. Disposition, exclusions, and endpoint-specific missingness are not reported.
The trial is unmasked. The registry does not report whether outcome assessment was independently conducted or whether timing was assessed by someone unaware of assignment. It also does not report operator experience, procedural standardization beyond the brief intervention descriptions, or possible learning effects. These are not grounds to presume bias occurred, but they are relevant details that are absent from the registry record.
Finally, the available secondary results cover only part of the listed outcomes, and no analysis plan or multiplicity approach is reported. The registry does not provide enough detail to assess whether the posted comparisons were prespecified, whether adjustment was intended, or how missing observations were handled. Conclusions should remain limited to the posted descriptive summaries and recalculations.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: RIFL (Rigid and Flexing Laryngoscope) vs. Fiberoptic Bronchoscope — NCT01965938.
- Registry record last updated 2017-01-05; status last verified 2016-10.
- Results first posted 2017-01-05.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry identifies NCT01965938 as a completed, randomized, unmasked, parallel trial sponsored by Vanderbilt University. It records enrollment of 41 and compares the Rigid and Flexing Laryngoscope with a fiberoptic bronchoscope in patients with potentially difficult airways.
The primary endpoint is time until proper endotracheal tube placement. The registry reports medians of 49 seconds for RIFL and 64 seconds for the fiberoptic bronchoscope, with interquartile ranges, but no primary between-group analysis. Posted secondary results cover attempts and assistance maneuvers; several other listed outcomes have no results reported in the registry record. No registered analyses are listed, and the statistical plan, missing-data handling, and analysis population are not reported.