Red-Rubber Catheter to Facilitate Nasotracheal Intubation in Adult Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Red-Rubber Catheter to Facilitate Nasotracheal Intubation in Adult Patients (NCT03779984), a randomized na study. The primary outcome is The Number of Participants With Nasal Bleeding.

2. Clinical Question

3. Trial Design

The registry classifies this as a prospective randomized controlled trial with double masking and a crossover model. Enrollment was 112. The record lists 56 participants in the Red Rubber Catheter Group and 56 in the Standard Nasal Tracheal Intubation group for the primary outcome. These are the arm-specific counts recorded for that outcome; the registry's crossover label does not, by itself, supply enough detail to reconstruct the sequence or participant-level exposure pattern.

The study start date is 2019-05-31, the primary completion date is 2023-12-06, and the status is completed. The phase is listed as NA. The sponsor is University of Texas Southwestern Medical Center. The registry record does not report the setting, eligibility criteria beyond the broad adult population, allocation sequence generation, concealment procedures, or the specific masking arrangements.

The catheter method is described as attaching the red-rubber catheter securely to a nasal tracheal tube and introducing the rounded catheter end into a naris. In the standard group, the nasal tube is inserted into the nasal passage. The study summary says the comparison was intended to assess nasal bleeding, speed of intubation, and patient satisfaction. The primary posted result concerns nasal bleeding; the listed secondary result concerns severe epistaxis. Results for intubation time and patient satisfaction are not reported in the registry record.

Although the design is identified as crossover, details needed to assess how that design was implemented are not reported in the registry record. The timing and order of interventions, any washout procedures, and whether the posted comparison accounts for within-participant pairing are not reported. The original statistical analysis plan and the trial's initial sample-size assumptions are also not reported in the registry record.

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.

Population: A total of 112 participants enrolled to the study.

6. Primary Endpoint

The registry lists the primary outcome as The Number of Participants With Nasal Bleeding, measured over Within 5 minutes following the nasal tracheal intubation.

The primary endpoint is the number of participants with nasal bleeding within 5 minutes following nasal tube placement. It is a binary participant-level outcome: each participant either had nasal bleeding during the specified window or did not. The registry reports 22 participants with bleeding in the Red Rubber Catheter Group and 35 in the Standard Nasal Tracheal Intubation group, with 56 participants recorded in each arm.

This endpoint captures whether bleeding occurred soon after intubation, rather than measuring its volume, duration, or clinical consequences. The registry lists severe epistaxis as a separate secondary outcome, which distinguishes the occurrence of any recorded nasal bleeding from a more severe event. The brief study description also refers to assessing incidence and severity, but the primary endpoint itself is the count of participants with nasal bleeding within the stated timeframe.

For a binary outcome, arm-specific counts allow readers to compare how often the event was recorded in each group. The risk difference expresses the contrast in event proportions, while a confidence interval conveys uncertainty around that contrast. General statistical context: a short, explicitly defined observation window makes the endpoint's time frame clear, but conclusions are limited to events captured within that window and to the way bleeding was assessed. Further details about assessment procedures and missing outcome data are not reported in the registry record.

7. Results Posted in the Registry

• Red Rubber Catheter Group: 39.3% (22/56) versus 62.5% (35/56) on control; risk difference -23.2 percentage points (95% CI -41.2 to -5.2), risk ratio 0.63 (0.43–0.92); unadjusted two-proportion z-test p = 0.014.

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.

The Number of Participants With Severe Epistaxis

• 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:
  • Red Rubber Catheter Group: 1.8% (1/56) versus 1.8% (1/56) on control; risk difference 0.0 percentage points (95% CI -4.9 to 4.9), risk ratio 1.00 (0.06–15.59); unadjusted two-proportion z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Red Rubber Catheter Group and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcome concerns severe epistaxis within 5 minutes following nasal intubation. The registry records one participant with this outcome in each arm. The accompanying comparison has a zero risk difference, an interval that includes zero, and an unadjusted p-value of 1.0. This is an observed equality in the posted counts, not evidence that the underlying risks are identical.

In broad terms, the secondary result does not mirror the primary outcome's observed contrast: the primary bleeding counts differ between arms, while the severe-epistaxis counts are equal. That contrast is compatible with the outcomes representing different levels of severity. It does not establish a mechanism, and the low number of severe events limits the precision of that comparison. The primary and secondary outcomes therefore answer related but distinct questions.

The brief study description also refers to time to intubation and patient satisfaction as intended areas of assessment. Results for those measures are not reported in the registry record. The posted secondary outcome information is limited to severe epistaxis; no broader secondary-outcome pattern can be inferred from measures without posted results.

Unadjusted secondary results generally carry less weight than a result supported by a prespecified analysis plan and an explicit approach to multiple testing. General statistical context: testing several outcomes creates more opportunities for an apparently notable result to arise by chance, even when each test is considered separately. Adjustment or a hierarchy of outcomes can address that issue, but the registry record does not report a multiplicity plan. The secondary comparison should therefore be treated as descriptive and interpreted alongside its sparse event count and missing analysis details, not as independent confirmation of the primary finding.

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

• The Number of Participants With Severe Epistaxis

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary because it records whether a participant had nasal bleeding within a specified period. For this kind of outcome, an event count and the number assessed in each group describe the observed frequency. The registry reports 22 events among 56 participants in the Red Rubber Catheter Group and 35 among 56 in the standard group. The comparison is presented as a risk difference, which is the event proportion in one group minus the event proportion in the other, using the catheter group as the comparison arm against standard intubation.

What does the risk difference tell us?

The risk difference keeps the comparison on an absolute scale: it describes how far apart the two event proportions are. A negative estimate means the observed event proportion is lower in the catheter group under the stated comparison direction. General statistical context: an absolute difference can be useful when considering the size of an observed contrast, but it does not by itself establish a causal effect or explain why the groups differed.

The registry also posts a risk ratio and an odds ratio for the primary comparison. These are relative measures, unlike the absolute risk difference. General statistical context: a risk ratio compares event proportions, whereas an odds ratio compares event odds. Relative measures can communicate the same comparison on a different scale, and their numerical size should not be confused with the absolute number of participants affected. The registry record does not report an adjusted model or explain whether these measures were prespecified.

How should the p-value be read?

The posted unadjusted p-value for the primary comparison is 0.014. General statistical context: a p-value describes how unusual data at least as discrepant as the observed data would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it is not a measure of the size or practical importance of an effect. Because the value is unadjusted, it does not account for testing multiple outcomes or multiple analyses.

The registry does not report the statistical test used to obtain the p-value. It also does not state whether the analysis incorporates the crossover structure or a paired comparison. That omission matters because observations from the same participant across treatment periods may be related. General statistical context: accounting for within-participant dependence can affect standard errors and inference; treating related observations as independent when they are not can misstate uncertainty. The record does not permit a determination of how this issue was addressed.

What does the confidence interval add?

A confidence interval gives a range of values compatible with the observed data under the interval procedure and its assumptions. General statistical context: a narrower interval indicates greater precision, while a wider interval signals more uncertainty about the effect's magnitude. The posted primary interval lies below zero, consistent with a negative risk-difference estimate, but its exact construction and confidence level are not reported. The interval does not account automatically for unreported design features, selection, measurement issues, or multiple testing.

For severe epistaxis, the posted estimate is a risk difference of zero, and the interval includes zero. There is one recorded event in each arm. General statistical context: when event counts are sparse, estimates can be imprecise even when the observed counts match. A zero point estimate is not proof that the underlying groups are identical; the interval communicates that a range of nonzero differences remains compatible with the data.

What analysis details are unavailable?

The registry lists zero reported analyses for the primary outcome. For the secondary outcome, a comparison is posted, while the reported-analyses list is empty. The test specification, model, covariate adjustment, analysis population, handling of missing observations, and treatment of crossover sequence or period are not reported in the registry record. The original statistical analysis plan and the trial's initial sample-size justification are also not reported.

General statistical context: these details help readers judge whether analyses were planned in advance, whether the model matches the design, and how robust the conclusions may be. In crossover studies, period effects, sequence effects, and within-person correlation can be relevant. Their relevance does not establish that any such problem occurred in this trial; it identifies questions that the available record does not resolve.

The distinction between a posted estimate and a fully specified analysis is important. The summary counts and comparisons permit a straightforward description of the reported results. They do not reveal every analytic choice behind those results. The sponsor's analysis does not conflict with the posted recalculation, and the registry record does not flag a discrepancy. Even so, the unavailable analytic details limit independent assessment of the inferential procedure.

11. Confidence Intervals and Precision

The primary risk-difference confidence interval lies entirely below zero. This indicates that the interval, as posted, does not include a null difference. Its span nevertheless allows for a range of possible magnitudes, so the point estimate should not be read as exact. The registry record does not state the confidence level or the interval-construction method. Those details affect how a confidence interval should be interpreted, and their absence prevents a more specific methodological assessment.

General statistical context: a confidence interval is a way to represent uncertainty around an estimate under a statistical procedure and its assumptions. It is not a guarantee that the true effect lies within the particular interval, nor does it include every source of uncertainty. In particular, an interval does not automatically account for unreported missingness, measurement error, design complications, or selection among multiple outcomes.

The secondary severe-epistaxis interval is centered at a zero risk difference and extends both below and above zero. One participant in each arm had the event. With sparse events, the observed equality of counts does not imply high precision; the range of compatible differences remains substantial. The posted p-value is 1.0, but that value does not show that the groups are equivalent.

The primary outcome has more recorded events than the severe-epistaxis outcome, but precision still depends on the number and distribution of events, the design, and the analysis method. The registry's crossover classification makes the missing information about pairing especially relevant to assessing uncertainty. Because the record does not explain how the analysis handled the crossover structure, readers cannot determine whether the posted intervals fully reflect the design. The results should therefore be read as the posted estimates and uncertainty ranges, with the unavailable methods kept in view.

12. 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 participants and not total events. The illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It uses the observed effect as its reference and considers planning for 100%, 75%, or 50% of that observed effect. These are planning assumptions for an illustration; the original trial design assumptions are not reported in the registry record.

For planning for 100% of the observed effect, the illustration gives 72 participants per arm for 80% power and 96 participants per arm for 90% power. For planning for 75% of the observed effect, it gives 128 participants per arm for 80% power and 171 participants per arm for 90% power. For planning for 50% of the observed effect, it gives 285 participants per arm for 80% power and 381 participants per arm for 90% power.

In plain terms, the 80% column gives the illustrative per-arm size associated with an 80% chance of detecting the specified effect under the stated assumptions; the 90% column gives the corresponding size for a higher chance of detection. The calculation is not observed power for the completed trial. It is a planning illustration based on the observed effect, not a description of the trial's original design.

The progression across the scenarios illustrates a general planning principle: smaller effects require more participants to detect, all else equal. The curve should be read as a visual representation of how the planning size changes with the effect used for planning, under the listed assumptions. It does not establish that the study was designed around these values or that any particular sample size would guarantee a result.

13. 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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.625; treatment proportion p₁ = 0.393; average p̄ = 0.509.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.7070 = 1.3857.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6877 = 0.5788.
4. n = (1.3857 + 0.5788)² / (-0.2321)² = 71.6, rounded up to 72 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
p0 <- 0.625                          # control proportion
p1 <- 0.392857142857143                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3779984)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 72 (80% power), 96 (90% power)
 75% of observed effect: n per arm = 128 (80% power), 171 (90% power)
 50% of observed effect: n per arm = 285 (80% power), 381 (90% power)
power.prop.test: 71.6 
Simulated power at n = 72 per arm: 0.812 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report how multiplicity was handled. It does not specify whether the primary endpoint was the only confirmatory test, whether secondary endpoints were tested under a hierarchy, or whether any adjustment was planned for multiple outcomes or analyses. The primary p-value is explicitly unadjusted. The secondary p-value is also posted without a reported multiplicity procedure.

General statistical context: when multiple hypotheses are tested, the chance of at least one apparently unusual result can increase. Prespecified outcome hierarchies or statistical adjustments are common ways to address this, but their use cannot be assumed. The fact that the registry lists two outcome measures does not establish that these were the only outcomes collected or analyzed; other outcomes and their status are not reported in the registry record.

Missing-data procedures are not reported. The record does not state whether all randomized participants had outcome data, how unavailable measurements were handled, or whether any imputation or sensitivity analysis was used. The arm counts shown for the primary endpoint are 56 in each group, but those counts alone do not describe the flow of participants through a crossover trial or resolve whether any data were missing at another period or assessment.

The analysis populations are not reported in the registry record. It is not stated whether the posted comparison follows an intention-to-treat approach, a per-protocol approach, or another population definition. The record also does not explain how crossover sequence, period, or within-participant correlation was incorporated. These details are important for interpreting a randomized crossover comparison, but their absence does not establish that the analysis was incorrect.

The original statistical analysis plan, interim-analysis procedures, and sample-size justification are not reported. The planning illustration based on the observed effect is separate from those original design details. Without the prespecified plan and analysis-population definitions, readers cannot assess whether the posted results reflect all planned analyses or how decisions about missing data and multiple testing were made.

15. Safety Results

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

Deaths

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 serious adverse event figures separately for the two groups. In each group, 56 participants were listed as at risk for serious adverse events, and zero were listed as affected. The reported deaths are also zero in each group. For other adverse events, 56 participants were listed as at risk in each group and zero as affected. No top serious adverse-event terms are listed.

These are the safety figures reported in the registry record; they should not be read as a comprehensive account of every possible event unless the reporting definitions and collection procedures are known. The record does not describe the adverse-event ascertainment period, definitions, severity grading, or whether events were actively solicited. It also does not explain how safety reporting relates to the crossover periods.

General statistical context: zero recorded events does not prove that an event is impossible or that the approaches have identical safety profiles. It means that no affected participants were recorded in the listed categories in these registry results. The figures are descriptive and should be interpreted within the limitations of the reporting details available.

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

The posted results show fewer participants with nasal bleeding in the red-rubber-catheter group than in the standard-intubation group during the specified 5-minute window. The risk-difference estimate is negative, its confidence interval lies below zero, and the unadjusted p-value is 0.014. These statistics describe the observed comparison and its uncertainty under the posted analysis; they do not, by themselves, establish why the groups differed.

The severe-epistaxis counts are equal, with one recorded participant in each group. The associated interval includes zero and the unadjusted p-value is 1.0. This does not establish equivalence. Sparse events and the breadth of the interval leave uncertainty about the possible difference in this secondary outcome.

The trial's randomized, double-masked, crossover classification is relevant to how the result might be interpreted, but the registry does not report enough implementation or analysis detail to judge whether the posted comparison accounts for the crossover structure. The original analysis plan, missing-data methods, and analysis populations are not reported. The primary p-value is unadjusted, and multiplicity handling is not reported.

The registry summary describes intended assessments of time to intubation and patient satisfaction, but results for those measures are not reported in the registry record. The posted findings therefore do not answer whether the approaches differed on those measures. Nor do they address outcomes outside the stated nasal-bleeding time window, other patient groups, or circumstances not described in the record.

General statistical context: a result can be compatible with a difference without settling the magnitude, reproducibility, or broader relevance of that difference. Statistical evidence should be considered alongside design details, endpoint measurement, missing information, and the range of outcomes actually reported. These data support a focused description of nasal bleeding in the trial record, not a universal conclusion about intubation approaches.

17. Why This Trial Matters Statistically

This trial illustrates how a clinical comparison can produce different messages for an overall event and a more severe event. The primary endpoint counts any nasal bleeding within a defined short period, while the secondary endpoint counts severe epistaxis. The primary counts differ between the groups; the severe-event counts are equal and sparse. Keeping these outcomes distinct helps prevent an observation about any bleeding from being generalized to severity.

The registry identifies a crossover model, which highlights why the analysis must be understood in relation to the design. In a crossover study, observations from the same participant may be related across periods. General statistical context: this dependence can affect uncertainty estimates, and an analysis should reflect the structure of the data. The registry's classification makes this an important question, but the posted record does not explain how the comparison handled it.

The example also shows why p-values, effect estimates, and confidence intervals have different roles. The unadjusted p-value gives one form of evidence against a null model; the risk difference conveys the direction and absolute scale of the observed comparison; the interval communicates uncertainty around that estimate. None is a substitute for the others, and none addresses missing-data or multiplicity questions automatically.

Finally, the distinction between a planning illustration and a trial's actual design assumptions matters. The sample-size figures are based on the observed effect and stated planning assumptions. They are not the original sample-size justification and do not describe observed power. Recognizing that distinction helps readers avoid treating post-result planning calculations as evidence that the completed study was designed to detect a particular effect.

18. 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 several trial-specific questions unresolved. Although it identifies a crossover model, it does not report the sequence in which approaches were used, the timing of periods, any washout procedure, or how period and participant effects were handled. It is therefore not possible to determine from the record whether the posted comparison appropriately accounts for within-participant dependence.

Details about randomization and masking are limited to the labels randomized and double-masked. The method of sequence generation, allocation concealment, who was masked, and how masking was maintained are not reported in the registry record. Eligibility criteria, setting, and further information about the participants are also not reported beyond the adult population and the listed condition.

The record gives a defined primary outcome window but does not describe how nasal bleeding was assessed, who assessed it, or how severity was classified. Missing-data handling and analysis populations are not reported. The original statistical analysis plan, multiplicity approach, interim analyses, and trial-specific sample-size assumptions are also not reported.

The posted results include nasal bleeding and severe epistaxis, but the study summary also mentions time to intubation and patient satisfaction. Results for those measures are not reported in the registry record. The available outcomes therefore provide an incomplete account of the broader aims described in the summary. Safety reporting is likewise limited by the absence of information about collection periods and definitions.

These gaps do not demonstrate that a particular method was absent or that the trial was conducted improperly. They limit what can be independently assessed from the registry record and should be kept separate from the observed event counts and comparisons.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Red-Rubber Catheter to Facilitate Nasotracheal Intubation in Adult Patients — NCT03779984.
• Registry record last updated 2024-11-21; status last verified 2024-10.
• Results first posted 2024-11-21.
• 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.

22. Record Summary

The registry record describes a completed prospective randomized controlled trial, classified as double-masked and crossover, comparing red-rubber-catheter-guided nasotracheal intubation with standard nasal tube insertion in adults. Enrollment was 112, with 56 participants recorded in each arm for the primary outcome.

The primary endpoint was the number of participants with nasal bleeding within 5 minutes following nasal tube placement. The registry reports 22 such participants in the catheter group and 35 in the standard group. The posted risk difference is negative, with an unadjusted p-value of 0.014. For severe epistaxis, one participant was recorded in each group; the posted risk difference is zero and the unadjusted p-value is 1.0.

The record reports zero serious adverse events and zero deaths in each group. It does not report results for time to intubation or patient satisfaction, despite those measures appearing in the study summary. Details of crossover implementation, analysis populations, missing-data handling, multiplicity, and the original sample-size assumptions are not reported in the registry record.