Endotrol-tracheal Tube Assisted Endotracheal Intubation During Video Laryngoscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Endotrol-tracheal Tube Assisted Endotracheal Intubation During Video Laryngoscopy (NCT01099969), a randomized na study. The primary outcome is Intubation Time.

2. Clinical Question

In practical statistical terms, the key questions are whether the mean intubation times differ across the device combinations and how precisely the available summaries estimate those differences. The trial record includes randomized allocation and four groups, each with 15 participants reported for the primary outcome. The registry does not explain the exact randomization procedure or identify who was masked. It also does not report a primary analysis plan or adjusted comparisons, so the pairwise results should be read as unadjusted summaries rather than as a complete account of a prespecified inferential analysis.

3. Trial Design

The registry record describes a completed randomized, single-masked, parallel-group study with an enrollment of 60. It lists the phase as NA. The record gives a start of 2010-03 and a primary completion of 2012-01. The sponsor was The University of Texas Health Science Center, Houston.

Four groups combined two videolaryngoscopes with two endotracheal-tube approaches. The GlideScope groups used either a non-styletted Endotrol tube or a regular tube with a GlideRite stylet. The McGrath groups used the same two tube approaches. The primary outcome summaries report 15 participants in each group. This arrangement allows readers to inspect the results for each combination, but the registry record does not describe a factorial analysis or state that the study was designed to estimate separate effects for tube type and laryngoscope type.

Single masking is recorded, but the identity of the masked individuals and the practical masking procedures are not reported in the registry record. The record does not give details of the random sequence, allocation concealment, eligibility criteria, recruitment setting, or participant flow. The protocol’s original sample-size justification, planned primary analysis, and any prespecified interim analyses are also not reported in the registry record.

The primary endpoint was continuous: intubation time in seconds, summarized as a mean and standard deviation for each group. The registry also lists Cormack and Lehane Grade of Laryngeal View as a secondary outcome. Although four outcome measures are recorded, the available secondary outcome listing names one outcome; details of the other measures and their results are not reported in the registry record. The record is marked completed, but that status alone does not describe adherence, missing observations, or deviations from the planned conduct.

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 Intubation Time, measured over time from insertion of the laryngoscope to detection of CO2 on the capnogram.

Intubation time measures elapsed time from insertion of the laryngoscope until CO2 is detected on the capnogram. It is recorded in seconds and summarized as a mean with a standard deviation. As a continuous measure, it describes the average time in each device group while the standard deviation conveys how spread out individual times were around that group mean.

Timing provides a measurable way to compare the intubation procedures. It captures the interval specified in the registry record, rather than a broader measure of safety or overall procedural success. The endpoint is also distinct from the listed secondary outcome, Cormack and Lehane Grade of Laryngeal View: one concerns elapsed time, while the other concerns the recorded laryngeal view grade. The registry does not explain how the view grade was assessed or provide its results in the posted outcome summaries described by the record.

For interpretation, the mean is a group-level summary, not a prediction of the time for an individual participant. A standard deviation describes variation within a group; it is not the uncertainty interval for the mean difference between groups. The reported mean differences and their confidence intervals address that comparative uncertainty, but they do not by themselves establish the clinical importance of a difference. A threshold for a clinically important change in intubation time is not reported in the registry record.

7. Results Posted in the Registry

• GlideScope With Styletted Regular ETT: mean 48.80 versus 60.20 on control; difference -11.40 (95% CI -34.92 to 12.12), standardized effect d = -0.35; z-test p = 0.342.
• McGrath With Non-styletted Endotrol ETT: mean 58.60 versus 60.20 on control; difference -1.60 (95% CI -24.82 to 21.62), standardized effect d = -0.05; z-test p = 0.893.
• McGrath With With Styletted Regular ETT: mean 40.70 versus 60.20 on control; difference -19.50 (95% CI -41.01 to 2.01), standardized effect d = -0.65; z-test p = 0.076.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, so the registry summarizes each group with a mean and standard deviation. A mean gives the arithmetic center of the observed times; a standard deviation describes how dispersed individual observations are around that center. These are different quantities: a standard deviation represents variability among observations, whereas a confidence interval for a mean difference represents uncertainty in the comparative estimate.

What does a mean difference represent?

Each pairwise comparison uses the GlideScope with non-styletted Endotrol group as the reference. The reported mean difference is the other group’s mean minus the reference group’s mean. A negative estimate therefore indicates a lower observed mean time in the named comparison group than in the reference group. For example, the estimate for GlideScope with a styletted regular tube is -11.4 seconds. This is a descriptive contrast of the posted group summaries; it should not be interpreted as a causal effect without the relevant analysis assumptions and conduct details.

The posted comparisons include pooled standard deviations and standardized effect estimates, as well as standard errors for the group means. A pooled standard deviation combines information about variability across the two groups being compared into a common spread estimate. A standardized effect expresses a mean contrast relative to that spread, which can make effects from measures on different scales easier to compare. The registry record does not report a protocol analysis explaining how these quantities were intended to be used.

How should the p-values be read?

A p-value describes how compatible the observed data are with a specified null model, under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of a difference. The posted values are unadjusted: they do not account for considering multiple comparisons. The registry record does not report the sponsor’s inferential analysis, a planned testing hierarchy, or the significance threshold for the primary outcome. The separate planning illustration uses a two-sided significance level of 0.05, but that is an assumption for that illustration, not evidence of the trial’s own analysis plan.

In general, confidence intervals show a range of estimates compatible with the observed data under the method used to construct them. For each comparison, the interval gives information about both direction and precision. An interval that includes zero is consistent with no mean difference, but it may also include differences in either direction. The confidence level and construction method for the posted intervals are not reported in the registry record, so they should be interpreted as the intervals shown rather than assigned an undocumented confidence level.

Why does variability matter?

When observations vary considerably within groups, a small group may estimate the underlying mean imprecisely. The standard deviations in these summaries describe that within-group variation, and the comparison intervals reflect uncertainty in the estimated contrasts. In general, greater variability makes it harder to distinguish a mean contrast from random variation unless the data are more informative in other ways. This is one reason that an estimate should be read together with its interval, rather than judged by its direction alone.

The posted statistics are based on group-level summaries. They do not show the distribution of individual times, identify unusual observations, or explain whether the measure was skewed. The registry record does not report whether model assumptions were checked or whether a transformation or robust method was considered. Those omissions matter because standard mean-based comparisons can be sensitive to distributional features, especially in small groups. This is a general methodological consideration, not a claim that a particular assumption was violated in this trial.

What does randomization contribute?

Random allocation is intended, in general, to reduce systematic differences between groups at assignment. The record labels the allocation randomized, but does not describe how the sequence was generated, how assignments were concealed, or whether all randomized participants were included in the posted summaries. The registry entry alone therefore does not establish how successfully randomization was implemented or how the analysis preserved its benefits.

The four arms combine laryngoscope and tube choices. A direct contrast between two arms changes the combination, and the available summaries do not provide a reported factorial model that separates the contribution of each device component. The contrasts should be understood as comparisons between the named combinations. The registry record does not report interaction testing or adjusted analyses.

Finally, no comparative analyses are listed in the registry record. The posted pairwise statistics can describe the available summaries, but no details are reported about model specification, missing-data handling, analysis population, or multiplicity adjustment. Those limits are relevant when moving from descriptive comparisons to broader claims.

10. Confidence Intervals and Precision

Precision concerns how tightly the data estimate a quantity. For the group means, the registry reports standard deviations, which describe variation among participants’ intubation times. For the pairwise mean differences, it reports intervals: -34.92 to 12.12 seconds for GlideScope with a styletted regular tube; -24.82 to 21.62 seconds for McGrath with a non-styletted Endotrol tube; and -41.01 to 2.008 seconds for McGrath with a styletted regular tube. The corresponding estimates were -11.4, -1.6, and -19.5 seconds.

Each interval includes zero, so the posted results do not pin down the direction of the mean difference. The intervals also span values on both sides of zero, indicating uncertainty that is important when considering the size of any possible difference. This does not demonstrate equivalence or prove that the groups have identical mean times. Establishing equivalence would require a prespecified margin and an analysis designed to assess it; such a margin and analysis are not reported in the registry record.

A confidence interval is generally a range of estimates compatible with the data and the method used. The registry record does not report the confidence level or the method used for these intervals. Therefore, the intervals can be described by their posted endpoints, but a confidence level should not be inferred from the record. The intervals also do not account for possible multiplicity unless the method explicitly does so; no multiplicity adjustment is reported.

These estimates are based on 15 participants per group, and the observed standard deviations indicate variation in the timing measure. The sample size and variability help explain why the intervals are broad, but the registry record does not report the original precision target or design assumptions. The interval width is a more direct guide to uncertainty than the point estimate alone. A clinically important difference threshold is also not reported, so the data cannot be judged against a stated threshold for practical importance.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total event counts. They are illustrations based on the observed effect, not the trial’s original design justification. The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect equal to the stated fraction of the observed effect. The original sample-size assumptions are not reported in the registry record.

The column for 80% power gives the planned number of participants per arm for a hypothetical study designed to have an 80% chance of detecting the specified effect under the planning assumptions, if that effect and assumptions hold. The 90% power column uses a higher target chance of detection. These are planning targets, not guarantees; actual performance depends on the true effect, variability, analysis, and study conduct.

Rows that plan for 75% or 50% of the observed effect consider smaller effects than the row based on 100% of the observed effect. Smaller effects are harder to distinguish from random variation, so they require more participants under the same assumptions. The illustration is especially sensitive to the observed effect: a small estimated contrast can produce very large planning figures, while an imprecise estimate does not necessarily indicate that the true effect is small.

These calculations are not observed power. They are hypothetical planning illustrations based on the observed effect and stated assumptions, and should not be read as a retrospective measure of how informative the completed trial was. The trial’s own sample-size rationale and original target are not reported in the registry record.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -11.400; pooled standard deviation σ = 32.861.
2. n = 2 × (1.96 + 0.842)² × 32.861² / -11.400² = 130.4, rounded up to 131 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -11.4                      # observed difference in means
sigma <- 32.8609190376654                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1099969)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 131 (80% power), 175 (90% power)
 75% of observed effect: n per arm = 232 (80% power), 311 (90% power)
 50% of observed effect: n per arm = 522 (80% power), 699 (90% power)
power.t.test: 131.4 
Simulated power at n = 131 per arm: 0.795 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome, intubation time, and one named secondary outcome, Cormack and Lehane Grade of Laryngeal View. It also reports three pairwise mean comparisons for the primary outcome. The p-values for those comparisons are identified as unadjusted. No method for controlling the chance of false-positive findings across multiple comparisons is reported in the registry record, and no testing hierarchy or primary contrast is specified.

Multiplicity arises when several hypotheses are tested. In general, considering more comparisons increases the opportunity for at least one apparently unusual result to occur by chance. An adjustment or prespecified testing strategy can address this issue, but the record does not state that one was used. The unadjusted p-values should therefore be treated as descriptive evidence for their individual contrasts, not as multiplicity-controlled confirmatory results.

The registry record lists no analyses. It does not report an analysis population, such as whether the posted outcomes include all randomized participants or only participants with a measured endpoint. It also does not describe participant flow, withdrawals, protocol deviations, or the handling of missing outcome values. The primary outcome summaries show 15 participants per arm, but those group counts do not establish how missing data were handled or whether any participants were excluded after randomization.

Methods for dealing with missing continuous outcomes can affect the estimated means and comparisons. In general, complete-case analysis, imputation, and model-based approaches rely on different assumptions. The record does not identify any such method, nor does it report sensitivity analyses. It is therefore not possible to assess from the registry entry whether missingness could have influenced the posted contrasts.

The record also does not describe covariate adjustment, model diagnostics, or an analysis plan for the four device combinations. The summaries support direct description of the posted group means and contrasts, but they do not fill in these methodological details. The sponsor’s analysis plan and analysis population are not reported in the registry record.

14. 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.

For each of the four groups, the registry reports 15 participants at risk for serious adverse events and zero serious adverse events. It also reports 15 participants at risk for other adverse events and zero other adverse events in each group. No serious adverse event terms are listed. These are the recorded counts for the groups in this entry; they are not estimates of risk for other settings or populations.

A zero count means that no event in that category was recorded in the stated group. It does not establish that the underlying event risk is zero. When event counts are low or absent, the data may still be compatible with risks that the study was not able to estimate precisely. The registry record does not give event definitions, surveillance procedures, follow-up duration for safety, or details about how adverse events were collected.

Deaths are not reported in the registry record. The absence of a reported death count should not be interpreted as a reported count of zero. The safety summaries are separate from the primary timing outcome and do not provide a comparative safety analysis or establish that one device combination is safer than another.

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

The posted data describe average intubation times for four combinations of videolaryngoscope and endotracheal tube. The observed group means range from 40.7 seconds to 60.2 seconds, and each group has a reported standard deviation. The pairwise estimates compare three combinations with the GlideScope and non-styletted Endotrol combination as the reference. Their confidence intervals all include zero and span differences in both directions.

These results do not establish that the combinations have equal mean times. Nor do they establish a definitive difference in mean time. The estimates are uncertain, and the registry record does not report a clinically important threshold against which to judge the size of a timing difference. A lower group mean is a descriptive feature of the posted summaries; it does not, on its own, demonstrate better overall performance or safety.

The stated study purpose concerns safety and efficacy, but the primary outcome is intubation time. The registry lists Cormack and Lehane Grade of Laryngeal View as a secondary outcome, without results in the posted outcome summaries described by the record. The adverse-event counts are zero in the recorded categories for each group, while death counts are not reported. These limited summaries do not establish broader safety, procedural success, or effectiveness.

The contrasts concern combinations of devices. They do not isolate an effect attributable only to the tube or only to the laryngoscope, and the registry record does not report an analysis that separates those components. It also does not report the original analysis plan, missing-data procedures, or multiplicity strategy. The findings should therefore be read as descriptive comparisons of the registered group summaries, with uncertainty, rather than as a complete confirmatory analysis.

General interpretation of randomized evidence also depends on how allocation was implemented, which participants were analyzed, and how outcomes were collected. The record labels the study randomized and single-masked, but does not provide the operational details needed to evaluate those aspects fully. The results are informative about the observations recorded in this trial, but they do not answer every question raised by the study’s broader stated purpose.

16. Why This Trial Matters Statistically

This trial presents a useful statistical distinction between an observed group difference and a well-resolved comparative result. The group means differ numerically, but the pairwise confidence intervals include zero and cover values in both directions. Readers can therefore see why a point estimate alone is insufficient: uncertainty around the estimate affects how confidently the data distinguish among possible mean differences.

The four arms also make clear that device comparisons can be comparisons of complete combinations. Each arm pairs a particular laryngoscope with a tube approach. Without a reported model that separates those components, a contrast between arms cannot be attributed solely to one device feature. This is a broadly important issue in interpreting studies that vary more than one component across treatment groups.

The trial also illustrates why outcome scope matters. Intubation time is a measurable continuous endpoint, while the stated study purpose includes safety and efficacy. A timing result does not stand in for every dimension of safety or success. The registry’s separate adverse-event counts and secondary outcome listing address different questions, and the information reported for those outcomes is limited.

Finally, the registry record does not report an analysis plan, missing-data approach, or multiplicity strategy. Such details help readers distinguish prespecified confirmatory analyses from exploratory comparisons and assess how much weight to give several unadjusted tests. The posted summaries still permit useful description of the observed means, variability, and uncertainty, but the reporting gaps limit the strength and scope of conclusions that can be drawn.

17. 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 registry record leaves important design and analysis details unreported. It does not specify eligibility criteria, recruitment setting, randomization procedures, allocation concealment, or who was masked. Single masking is recorded, but the practical masking arrangements cannot be evaluated from the entry. The record also does not provide participant flow or explain whether the posted outcome counts include all randomized participants.

The primary results are group-level means and standard deviations with pairwise comparisons. Individual-level distributions, potential outliers, and model checks are not described. No analysis population, missing-data method, covariate adjustment, or sensitivity analysis is reported. The comparative p-values are unadjusted, and a multiplicity strategy is not reported. These omissions make it difficult to assess the full inferential analysis behind the posted summaries.

All three reported pairwise intervals include zero, and the intervals span a range of possible mean differences. The registry record does not identify a clinically important timing threshold or report an equivalence design. Consequently, neither equivalence nor practical importance can be determined from the interval endpoints alone. The confidence level and interval construction method are also not reported.

The arms combine laryngoscope and tube approaches, and the record does not report a factorial or interaction analysis to distinguish their contributions. Although the stated purpose includes safety and efficacy, the primary outcome is time; secondary outcome results are not described in the posted summaries. The adverse-event entry lists zero events in the reported categories, but does not provide event definitions or surveillance details, and death counts are not reported in the registry record.

The original sample-size justification, protocol analysis plan, and any interim analyses are not reported in the registry record. Planning illustrations based on the observed effects cannot replace those original design details.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Endotrol-tracheal Tube Assisted Endotracheal Intubation During Video Laryngoscopy — NCT01099969.
• Registry record last updated 2018-06-04; status last verified 2018-05.
• Results first posted 2018-06-04.
• 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.

21. Record Summary

NCT01099969 is a completed randomized, single-masked, parallel-group study sponsored by The University of Texas Health Science Center, Houston. The record gives a start of 2010-03, primary completion of 2012-01, and enrollment of 60. It compares four combinations of GlideScope or McGrath videolaryngoscopy with either a non-styletted Endotrol tube or a regular tube with a GlideRite stylet.

The primary outcome is intubation time in seconds, from laryngoscope insertion to CO2 detection on the capnogram. Each group’s posted summary includes 15 participants. The three unadjusted pairwise mean-difference intervals include zero. Cormack and Lehane Grade of Laryngeal View is listed as a secondary outcome. Serious and other adverse-event counts are reported as zero for each group; death counts are not reported in the registry record.

The registry does not report the original sample-size rationale, the sponsor’s analysis plan, missing-data methods, or multiplicity strategy. The posted comparisons therefore describe the available summary statistics but do not supply a complete account of the planned analysis.