The Laryngeal Mask Airway in Edentulous Geriatric Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Laryngeal Mask Airway in Edentulous Geriatric Patients (NCT02197377), a randomized na study. The primary outcome is First Attempt's Success Rate of Insertion.

2. Clinical Question

The study also set out to compare ease and time of insertion and oropharyngeal leak pressure. The registry lists oropharyngeal leak pressure as a secondary outcome, with a timeframe of before surgery. The primary outcome is a binary measure: whether insertion succeeded on the first attempt. That makes the main comparison a comparison of proportions, rather than a comparison of average insertion times or pressure measurements.

The clinical context described in the registry is that face-mask ventilation can be difficult in edentulous patients, and that a supraglottic airway device may be considered when facial contours make standard mask fitting difficult. The trial question is narrower than that broader context: it compares two named devices in the stated population. The registry record does not report a comparison with face-mask ventilation, nor does it provide results for ease or time of insertion as separate posted outcomes.

3. Trial Design

The registry describes a randomized, double-masked, parallel-group trial sponsored by Dokuz Eylul University. Its recorded enrollment is 60, and its status is completed. The record gives a start date of 2009-08 and a primary completion date of 2010-04. The phase is listed as not applicable. It does not report the method used to generate the allocation sequence or the procedures used to conceal it.

The two groups received the LMA Unique or the LMA Supreme. Arm descriptions state that both devices were fully deflated before insertion. They also describe using size 4 for patients weighing 50-70 kg and size 5 for those weighing 70-100 kg, followed by inflation to an intracuff pressure of 60 cm H2O. The record gives the same procedural description for both arms. Further detail about how the devices were inserted or how masking was maintained is not reported in the registry record.

The primary outcome was first-attempt insertion success after anaesthesia induction. The record lists oropharyngeal leak pressure as a secondary outcome, measured before surgery. Its primary-outcome description also mentions ease and time of insertion, but separate posted results for those measures are not reported. The registry states that three insertions failed in the Supreme group and that 27 patients were included in analysis. The posted arm summaries list 30 participants for Unique and 27 for Supreme. How the analysis population was defined beyond these statements is 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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Non parametric data between groups were analyzed with the X2-test, while parametric data were compared with unpaired t-test. P \< 0.05 was considered significant. 3 LMA insertion failed in Group LMA Supreme. Total 27 patients included analysis.

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 First Attempt's Success Rate of Insertion, measured over after anaesthesia induction.

First-attempt insertion success records whether the assigned airway device was inserted successfully on the first attempt after anaesthesia induction. It is a binary outcome: each participant either had a successful first attempt or did not. The registry presents the result as a percentage of participants in each group.

This endpoint is useful for a device comparison because it captures an immediate procedural outcome and can be expressed as the proportion of participants meeting the stated success criterion. A comparison of those proportions describes the observed difference in first-attempt success between the groups. It does not, by itself, summarize other aspects of insertion, such as ease or time, even though the registry’s primary-outcome description mentions those measures. Separate numerical results for ease and time are not reported in the registry record.

The endpoint is tied to the specific setting and population described in the record: edentulous elderly patients receiving anaesthesia. It should not be read as a measure of every aspect of airway management, or as evidence about populations or procedures not described in the record. The registry gives the measurement timeframe as after anaesthesia induction. It does not provide a more detailed operational definition of what counted as a successful insertion or how that determination was made.

7. Results Posted in the Registry

• Group LMA Supreme: 85.2% (23/27) versus 73.3% (22/30) on control; risk difference 11.9 percentage points (95% CI -8.9 to 32.6), risk ratio 1.16 (0.89–1.52); unadjusted two-proportion z-test p = 0.273.

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.

Oropharyngeal Leak Pressure

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Group LMA Supreme: mean 20.56 versus 17.10 on control; difference 3.46 (95% CI -0.38 to 7.30), standardized effect d = 0.47; z-test p = 0.077.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Group LMA Supreme and the control. The interval gives the range of effects that remain compatible with the data.

The registry posts one secondary endpoint: oropharyngeal leak pressure. Its group means follow the same numerical direction as the primary arm summaries, with a higher mean in the Supreme group. The secondary comparison remains uncertain, as its interval includes no mean difference. This offers a related but distinct view of device performance; it does not independently confirm the first-attempt insertion result.

The outcomes measure different properties. First-attempt success is a binary procedural result, whereas leak pressure is a continuous measurement. Similar direction across these measures can be noted, but it should not be treated as proof that one outcome validates the other. The record does not report a formal combined analysis or a prespecified interpretation linking the secondary measure to the primary endpoint.

Unadjusted secondary results generally carry less weight when several outcomes are examined, because looking across multiple comparisons increases the chance of finding an apparently notable result by chance. This is a general statistical concern, not a claim that a particular adjustment was required or performed in this trial. The registry does not report a multiplicity plan or an adjusted secondary analysis. The secondary endpoint should therefore be considered supportive and exploratory in interpretation, rather than a standalone basis for a firm conclusion.

The primary outcome description also mentions ease and time of insertion, but the registry lists no separate posted numerical results for those measures. The record therefore does not allow a complete assessment of all the aims described in the summary. The available secondary evidence is limited to the leak-pressure measure, and its uncertainty should be considered alongside the primary result and the inconsistencies in the primary reporting.

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

• Oropharyngeal Leak Pressure

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary, so its natural summary is the proportion of participants with first-attempt success in each group. A group percentage is easy to interpret, but the uncertainty around it depends on the number of observations and events contributing to the estimate. A comparative analysis can express the group contrast as a risk difference, a risk ratio, or an odds ratio. These measures use different scales, so they answer related but not identical questions.

A risk difference describes the difference between group proportions on the percentage-point scale. A risk ratio compares the proportions multiplicatively. An odds ratio compares the odds of success rather than the probabilities themselves. When success is common, an odds ratio can look farther from the null value than a risk ratio; the two should not be treated as interchangeable. The registry’s posted comparison includes these types of comparative estimates, but the primary percentage entries and the event counts used for the comparison do not align exactly for the Supreme group.

The registry’s primary-outcome description says that nonparametric data between groups were analyzed with an X2-test, while parametric data were compared with an unpaired t-test, and that P < 0.05 was considered significant. In general, a chi-square test assesses whether categorical outcomes are distributed differently between groups. An unpaired t-test compares means between independent groups under assumptions about the measurement and its distribution. The record does not identify which test was applied to each posted outcome, and it lists no reported analyses. The p-values attached to the posted comparisons are unadjusted recalculations, not a substitute for a documented sponsor analysis.

A p-value measures how incompatible 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, and it does not measure the size or clinical importance of an effect. A value above the stated significance threshold does not prove that groups are the same. It can reflect a small underlying difference, limited information, or both. Interpretation therefore requires the estimate and its confidence interval as well as the p-value.

For a continuous outcome such as oropharyngeal leak pressure, the registry gives a mean and standard deviation for each arm. The mean describes the average recorded measurement, while the standard deviation describes the spread of individual measurements around that average. The posted comparison is a mean difference. Its confidence interval describes uncertainty about that difference under the analysis assumptions. A mean comparison does not describe the full shape of the measurements, and the registry does not provide distributions or participant-level values.

The general role of a confidence interval is to show a range of effect estimates compatible with the data and the analysis method. A wide interval signals limited precision; an interval that crosses the null value includes both no difference and values on either side. For a difference measure, the null is no difference. For a ratio measure, the null is a ratio of one. The interval is not a guarantee that the true effect lies within its endpoints, nor does it account for unreported design or analysis choices.

Over-dispersion is a general issue for count outcomes when variability exceeds what a simple count model expects. It can make model-based standard errors too small if ignored. The outcomes posted for this trial are a binary insertion result and a continuous pressure measurement, not a count-rate endpoint; the registry does not report an over-dispersion model or any other model-based adjustment. More broadly, the record does not provide enough detail to assess model diagnostics, covariate adjustment, or whether assumptions were checked.

Randomization is intended to make groups comparable on average, but it does not remove uncertainty in a trial of limited size. Masking can reduce some forms of measurement or performance bias, though the registry record does not explain who was masked or how masking was implemented. The record states double masking, but the procedures and success of masking are not reported. The analysis population, handling of missing outcomes, and whether analyses followed assigned groups are also not reported in the registry record.

11. Confidence Intervals and Precision

Precision concerns how tightly the data locate an effect estimate. The primary comparison’s unadjusted p-value is 0.273, and its confidence interval crosses the null value of no difference. This means the data do not sharply distinguish a positive difference from no difference or a difference in the opposite direction. The interval should be read as a range of estimates compatible with the analysis, not as a set of equally likely values.

The arm summaries list 30 participants for Unique and 27 for Supreme. Although the registry records enrollment of 60, the posted analysis information states that three Supreme insertions failed and that 27 patients were included in analysis. The record does not fully explain how enrollment, failures, and analysis populations relate. Small group counts make estimates of proportions particularly sensitive to a small number of outcome classifications, and they limit the precision that can be expected.

The comparison is further complicated by the difference between the Supreme arm percentage and the event-count inputs used in the comparison calculation. Because the registry does not reconcile these entries, readers should not assume that every displayed summary is derived from precisely the same set of values. The stated comparison interval and p-value are useful for understanding uncertainty in that calculation, but they cannot resolve the underlying reporting mismatch.

For oropharyngeal leak pressure, the confidence interval for the mean difference spans values on either side of no difference. This likewise indicates uncertainty rather than a precise separation of group means. In general, an interval that includes the null does not prove no effect, while an interval that excludes it does not by itself establish clinical importance. The registry does not report a prespecified threshold for a clinically important difference.

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

The 80% power column represents the planned number of participants per arm for a design with an 80% chance of detecting the assumed effect under those planning assumptions, if that effect were the true one. The 90% power column represents a design with a 90% chance under the same conditions. These are planning concepts, not guarantees about a future result. The figures are displayed for the primary binary outcome and the secondary continuous outcome, so they should be interpreted in relation to the outcome and effect scenario to which each set applies.

Rows that plan for 75% or 50% of the observed effect assume a smaller effect than the row using 100% of the observed effect. Smaller effects are harder to distinguish from chance variation and therefore require more participants per arm to reach the same target power. These sample-size illustrations are not observed power: they do not describe the probability that this completed trial detected an effect after seeing its results. Rather, they show how planning requirements change under the stated hypothetical effect sizes and assumptions.

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 = 0.733; treatment proportion p₁ = 0.852; average p̄ = 0.793.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5734 = 1.1238.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5672 = 0.4774.
4. n = (1.1238 + 0.4774)² / (0.1185)² = 182.5, rounded up to 183 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 <- 0.733333333333333                          # control proportion
p1 <- 0.851851851851852                          # 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(2197377)
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 = 183 (80% power), 244 (90% power)
 75% of observed effect: n per arm = 343 (80% power), 458 (90% power)
 50% of observed effect: n per arm = 808 (80% power), 1,081 (90% power)
power.prop.test: 182.5 
Simulated power at n = 183 per arm: 0.808 (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 identifies first-attempt insertion success as the primary outcome and posts oropharyngeal leak pressure as a secondary outcome. It does not report a plan for controlling the chance of false-positive findings across outcomes, nor does it say whether any endpoint was treated as exploratory. When several hypotheses are tested, multiplicity can make an unadjusted p-value less persuasive as evidence; this is a general consideration. No multiplicity adjustment is reported in the registry record.

The primary-outcome description mentions ease and time of insertion in addition to first-attempt success, but separate results for ease and time are not posted. It is not reported whether they were prespecified endpoints, components of a broader endpoint, or measures not included in the final analysis. The record lists two outcome measures and one posted secondary outcome, but does not give a complete outcome-analysis plan.

The registry states that three insertions failed in the Supreme group and that 27 patients were included in analysis. It does not report whether these failures were excluded from the primary analysis, how they were classified for first-attempt success, or whether there were other missing observations. The analysis population, missing-data methods, and any sensitivity analyses are not reported in the registry record. Nor does the record state whether the analysis followed randomized assignment or used a different population.

These omissions matter because analysis choices can affect a binary endpoint, especially when failures and missing outcomes are involved. The arm summaries and comparison inputs should be read as posted, while recognizing that the registry does not fully explain their relationship. The record also does not report an interim-analysis plan, a stopping rule, or a detailed statistical analysis plan. No conclusion about those procedures can be drawn from the available registry information.

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’s adverse-event fields list zero serious adverse events, zero other adverse events, and zero deaths in both groups. The recorded numbers at risk are 30 for the LMA Unique group and 27 for the LMA Supreme group. No serious adverse-event terms are listed.

These figures describe the safety entries in the registry record. They should not be interpreted as proof that no adverse event occurred, since the record does not provide detailed definitions, collection procedures, follow-up duration, or a narrative account of safety monitoring. It also does not report whether all participants were assessed over the same period or how missing safety information was handled.

With no events recorded in these fields, the registry data do not permit a comparison of event rates between the devices. A zero count in a limited trial record is not evidence that the risk is absent. The results are best read as an absence of events recorded in the posted categories, rather than as a comprehensive demonstration of safety.

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

The posted primary summaries show a higher first-attempt success percentage for the LMA Supreme than for the LMA Unique. The unadjusted comparison, however, is imprecise and does not establish a clear difference. In addition, the Supreme arm percentage does not align exactly with the event counts used in the comparison calculation. The registry record gives no explanation for this discrepancy, so the numerical pattern should be interpreted cautiously.

The secondary leak-pressure results are also numerically higher for Supreme, but their uncertainty includes no mean difference. Taken together, the posted outcomes point in a similar direction, yet they do not provide precise evidence of a device difference. Similar direction across two measures is not the same as confirmation, especially when one result is secondary and no multiplicity plan is reported.

These findings apply to the population and procedures described in this registry record. They do not establish how either device compares in other patient groups, settings, or airway-management strategies. The record does not report a comparison with face-mask ventilation. Nor do the posted results answer the stated aims concerning ease and time of insertion, for which separate results are not available.

The safety fields contain no recorded adverse events or deaths, but the registry does not supply the detail needed to treat that as proof of no risk. The results also do not determine whether any observed difference would be clinically important; no clinical importance threshold is reported. The most defensible reading is that this completed randomized comparison offers limited and uncertain evidence about the listed outcomes, with a primary-outcome reporting mismatch that should remain visible in interpretation.

17. Why This Trial Matters Statistically

This trial is statistically instructive because the central result is not just a comparison of two percentages. Readers must consider the uncertainty around the comparison, the analysis population, and whether the group summaries agree with the values used to calculate the contrast. A numerical advantage in an arm summary is not enough to establish a precise or meaningful difference.

The registry also illustrates why confidence intervals and p-values answer different questions. The p-value summarizes compatibility with a null model under specified assumptions, while the interval displays a range of effect estimates compatible with the data. Neither measure resolves limitations in the underlying outcome reporting. Here, the primary comparison is uncertain, and its inputs do not align exactly with one arm’s posted percentage.

The secondary continuous measure adds context but not a definitive resolution. Its direction is similar to the primary summaries, while its interval remains compatible with no difference. Considering multiple outcomes without a reported multiplicity plan also calls for restraint in treating isolated results as confirmatory. These are general principles of trial interpretation applied to the record’s stated endpoints.

Finally, the registry emphasizes the difference between enrollment and the population described for analysis. It records enrollment of 60, while also noting insertion failures and 27 patients included in analysis for the Supreme group. Without a fuller account of missing data and analysis populations, readers cannot fully assess how exclusions or outcome classification may have shaped the estimates. Transparent reporting of these details is essential to evaluate the strength and reproducibility of a clinical trial’s findings.

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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

Several limitations are specific to the information recorded for this trial. First, the primary arm summary for the Supreme group and the event counts used in the comparison calculation do not align exactly. The registry record does not explain the difference. This makes it harder to reconcile the displayed primary results and limits confidence in treating them as a single consistent summary.

Second, the record notes three failed insertions in the Supreme group and says 27 patients were included in analysis, but does not explain how failures were handled in the primary endpoint or whether any other data were missing. Although the record lists enrollment of 60 and arm counts of 30 and 27, it does not describe the complete flow from enrollment through analysis. The analysis population and handling of missing observations are not reported.

Third, the posted trial information is limited for outcomes mentioned in the study aims. Separate numerical findings for ease and time of insertion are not reported, while leak pressure is the only posted secondary endpoint. The record does not provide a detailed definition of successful first-attempt insertion, an analysis plan, or a multiplicity strategy. It also does not describe who was masked or how masking was maintained.

Finally, the reported group sizes and broad uncertainty in the comparisons limit precision. Safety entries lack detailed collection and follow-up information. The record does not report a clinically important difference threshold or the trial’s original sample-size assumptions. These points limit interpretation of the posted results; they do not establish that unreported procedures or analyses were absent.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: The Laryngeal Mask Airway in Edentulous Geriatric Patients — NCT02197377.
• Registry record last updated 2018-10-19; status last verified 2017-12.
• Results first posted 2018-10-19.
• 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

NCT02197377 is a completed randomized, double-masked, parallel-group comparison of the LMA Unique and LMA Supreme in edentulous geriatric patients. The registry records enrollment of 60 and lists Dokuz Eylul University as sponsor. The primary outcome is first-attempt insertion success after anaesthesia induction; oropharyngeal leak pressure is the posted secondary outcome.

The arm summaries report first-attempt success percentages of 73.3% for Unique and 86.6% for Supreme, while the posted unadjusted primary comparison has p = 0.273 and an interval spanning no difference. The Supreme arm percentage does not align exactly with the comparison’s event-count inputs. The secondary comparison is also uncertain. No adverse events or deaths are recorded in the listed safety fields. Important details about the analysis population, missing data, multiplicity, and the discrepancy in the primary result are not reported in the registry record.