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 Evaluation of a Systematic Approach to Weaning From Mechanical Ventilation (NCT01482429), a non-randomized na study. The primary outcome is Mortality.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01482429 |
| Phase | NA |
| Condition | Weaning Failure, Complication of Respirator [Ventilator] |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 235 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Federal University of Uberlandia |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes an intensive care unit at a teaching hospital of the Federal University of Uberlandia. It lists Weaning Failure and Complication of Respirator [Ventilator] as conditions and identifies the primary outcome population as Overall. Specific eligibility criteria and patient characteristics are not reported in the registry record, so the intended patient group cannot be characterized more narrowly from this information.
Intervention
The intervention is a multidisciplinary weaning-ventilator protocol. The registry describes protocol-directed discontinuation of ventilation as based on a multidisciplinary protocol. Its stated objective is to assess a systematic approach to weaning in relation to time spent on the ventilator, complications of mechanical ventilation, and length of stay in critical care.
Comparator
The arm descriptions include Usual Care, in which discontinuation of ventilation was left entirely to physician discretion. The record also lists a Protocol-directed arm. However, it classifies the study as single group and non-randomized. It does not explain how these descriptions relate to the stated design or whether participants were enrolled concurrently, sequentially, or in another arrangement.
Primary question
The registered primary outcome is mortality, measured as participants, with the timeframe described as length of ICU stay (days). The broad objective concerns whether a systematic weaning approach changes ventilation duration, complications, and critical-care stay compared with physician judgment alone. The record does not report a mortality comparison, an effect estimate, or the results for the other stated objectives. Consequently, it does not establish whether mortality differed between care approaches.
3. Trial Design
The registry lists this study as completed, non-randomized, unmasked, and single group. It records enrollment of 235. The sponsor is the Federal University of Uberlandia. The listed start is 2011-01 and the primary completion is 2012-01. The study phase is recorded as NA.
The intervention is named Multidisciplinary weaning-ventilator protocol. The arm descriptions distinguish protocol-directed discontinuation from usual care, where decisions were left to physicians. At the same time, the registry classifies the overall model as single group. It does not explain this apparent mismatch, identify how participants were assigned to the described approaches, or report whether care approaches were observed in separate periods or concurrently. The comparison therefore cannot be reconstructed from the registry record alone.
Because the study is classified as non-randomized, it should not be interpreted as a randomized comparison. Even if results for both care approaches were available, differences might reflect factors other than the protocol, including patient characteristics, clinical circumstances, or changes in care over time. Whether the investigators measured or adjusted for such factors is not reported in the registry record.
The registry lists four outcome measures and two analyses, but their full identities, analysis methods, and results are not reported in the registry record. No protocol, detailed statistical analysis plan, sample-size justification, interim analysis plan, or account of how enrollment was divided among care groups is reported. Enrollment of 235 is an overall registry figure; it is not an arm-specific sample size or a mortality denominator.
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.
Care Usual
| Stage | Protocol-directed | Usual Care |
|---|---|---|
| STARTED | 0 | 269 |
| COMPLETED | 0 | 96 |
| NOT COMPLETED | 0 | 173 |
Reasons for not completing this period:
| Reason | Protocol-directed | Usual Care |
|---|---|---|
| Protocol Violation | 0 | 172 |
| Lost to Follow-up | 0 | 1 |
Protocol
| Stage | Protocol-directed | Usual Care |
|---|---|---|
| STARTED | 414 | 0 |
| COMPLETED | 139 | 0 |
| NOT COMPLETED | 275 | 0 |
Reasons for not completing this period:
| Reason | Protocol-directed | Usual Care |
|---|---|---|
| Protocol Violation | 275 | 0 |
Analysis population for the primary outcome, as defined in the registry: Overall
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 | Protocol-directed | Usual Care | Total |
|---|---|---|---|---|
| Participants analysed | 139 | 96 | 235 | |
| Age Continuous | years | 49.9 (SD 20.18) | 43.5 (SD 17.89) | 47.28 (SD 19.50) |
| Sex: Female, Male: Female | Participants | 38 | 33 | 71 |
| Sex: Female, Male: Male | Participants | 101 | 63 | 164 |
| Region of Enrollment: Brazil | participants | 139 | 96 | 235 |
6. Primary Endpoint
The registry lists the primary outcome as Mortality, measured over length of ICU stay (days).
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The registered primary endpoint is Mortality, with the unit stated as participants. In a participant-count outcome, the central quantity is the number of people who experienced the event during the specified observation period. To interpret that count as a comparison, readers also need the number of participants at risk in each relevant group and a clear definition of when mortality was assessed.
The registry gives the timeframe as length of ICU stay (days). This wording links assessment to the ICU stay, but it does not specify whether mortality means death in the ICU, death during a fixed follow-up period, or another definition. That operational definition is not reported in the registry record. The primary outcome population is listed as Overall.
Mortality is a binary outcome at the participant level: each person is classified according to whether the defined event occurred. Comparing counts alone can be misleading when group sizes differ, so analyses commonly relate event counts to the numbers of participants at risk and then estimate a contrast between groups. That is a general statistical principle, not a description of an analysis reported for this study. The registry record does not provide outcome counts, denominators, an effect estimate, or uncertainty for mortality. It therefore does not support a numerical estimate of the frequency of mortality or a comparison between the described approaches.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry’s stated objective is to evaluate a systematic, multidisciplinary approach to ventilator weaning against physician judgment alone. Its primary outcome is mortality among the overall population, with the timeframe described as length of ICU stay (days). The posted record does not report mortality counts, group denominators, an effect estimate, a confidence interval, or a test result. The direction and precision of any mortality comparison therefore cannot be described from the registry results.
The record lists 235 participants enrolled overall, but does not state how many received protocol-directed care or usual care. That total cannot substitute for the group-specific denominators needed to interpret event counts. Nor does an enrollment total by itself establish how many participants contributed data to a particular outcome. The four listed outcome measures and two analyses are not described in enough detail to identify their results or how they were conducted.
There is a design issue that matters for interpretation. The registry labels the study non-randomized and single group, yet describes protocol-directed and usual-care approaches. It does not explain the relationship between the single-group classification and the two care descriptions. Without that information, the structure of the intended comparison is unclear. If groups differed in patient mix, clinical severity, timing, or other factors, those differences could influence outcomes independently of the protocol. Whether such factors were assessed or addressed is not reported in the registry record.
The listed planning assumptions describe an illustration based on an observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. For time-to-event outcomes, the stated convention is total events using Schoenfeld; for other outcomes, it is participants per arm. These assumptions do not establish the trial’s original design or its actual statistical analysis. No observed effect or sample-size result is included in the registry information, so the planning illustration cannot be interpreted as evidence about the study’s findings or as observed power.
In statistical terms, the available record documents a study objective, a primary outcome label, and broad design information, but not the outcome evidence needed to quantify a treatment contrast. Absence of a reported estimate is not evidence that the approaches were equivalent, nor does it demonstrate that they differed. Any conclusion about mortality, ventilation duration, complications, or ICU stay would require results and methods not reported in the registry record.
9. Statistical Methods Explained
The study is classified as non-randomized and single group, while the care descriptions identify protocol-directed and usual-care approaches. This distinction is important. Random assignment, when used, is intended to make groups comparable on average at baseline. A non-randomized comparison does not have that design protection, so measured and unmeasured differences may affect the outcome contrast. The registry record does not report a randomization procedure, and its allocation classification is NON RANDOMIZED. It also does not explain how the single-group label relates to the two arm descriptions.
What a binary outcome comparison requires
Mortality is recorded as a participant count, which is a binary outcome format: an individual either meets the event definition or does not. For a meaningful group comparison, event counts need to be interpreted alongside the number of people observed in each group. A count without its denominator does not describe how common the event was among participants at risk. The registry record does not provide mortality counts or mortality denominators for the described care approaches.
A statistical analysis could express a contrast in several ways, such as a difference in event proportions or a relative measure. Those are general possibilities, not methods reported for this study. Each estimate has assumptions and answers the comparison on a different scale. The analysis actually used, including whether it adjusted for other characteristics, is not reported in the registry record. No mortality effect estimate or confidence interval is reported.
What uncertainty estimates communicate
In general, a confidence interval describes a range of values compatible with the data and the assumptions of a statistical procedure. Its width conveys precision: a wider interval indicates less precision than a narrower interval. It does not remove bias from a non-randomized design, correct incomplete outcome reporting, or prove that a particular value is true. A p-value, in general, describes how incompatible the observed data are with a specified null model under its assumptions; it is not the probability that the null hypothesis is true, and it does not measure clinical importance. These concepts can only be applied to the trial’s results if the estimates, uncertainty measures, and analytic details are reported. They are not reported for the primary outcome in the registry record.
Planning assumptions are not trial results
The stated planning illustration uses a two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. It is described as based on the observed effect, with the effect to detect set at a stated fraction of that observed effect. The record also says that time-to-event illustrations use the total number of events under Schoenfeld, while other illustrations use participants per arm. These are planning conventions, not evidence that participants were actually allocated equally or that these methods were used in the study’s final analysis.
A planning calculation based on an observed effect is conditional on that effect estimate and on the assumptions used to construct the illustration. It is not observed power. Because the observed effect and calculated planning values are not stated in the registry information, the planning assumptions alone cannot show what size of study was considered adequate or whether the completed study was informative. The trial’s own sample-size rationale is not reported in the registry record.
Why design and outcome definitions matter
For a non-randomized comparison, analysis may need to account for differences between care groups, but the appropriate approach depends on how the groups were formed and what information was collected. For example, adjustment cannot address unmeasured differences, and it can be misleading if important variables are measured poorly or handled incorrectly. The registry record does not report baseline characteristics, covariate adjustment, model specification, or sensitivity analyses. It is therefore not possible to assess whether the analysis addressed confounding.
The registered mortality timeframe is described as length of ICU stay (days), but the event definition and follow-up rules are not given. A clear definition matters because participants must be assessed over a comparable period, and different definitions can produce different event counts. How deaths after ICU discharge were handled, and whether follow-up was complete, are not reported in the registry record.
The record lists four outcome measures and two analyses but does not identify the additional outcomes or explain which analyses correspond to which endpoints. It also does not report a statistical analysis plan, missing-data method, or analysis population. Accordingly, the available design information supports a cautious description of the intended evaluation, but not a reconstruction or appraisal of the statistical methods used for the reported outcomes.
10. Exact Estimates for Each Arm
No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.
| Arm | Participants | Events | Observed % | Clopper-Pearson 95% CI | Wilson 95% CI | Bayesian 95% credible interval |
|---|---|---|---|---|---|---|
| Protocol-directed | 139 | 10 | 7.2% | 3.5% to 12.8% | 4.0% to 12.7% | 4.0% to 12.7% |
| Usual Care | 96 | 14 | 14.6% | 8.2% to 23.3% | 8.9% to 23.0% | 8.9% to 23.0% |
R code and output
arm <- c("Protocol-directed", "Usual Care")
n <- c(139, 96)
events <- c(10, 14)
for (i in seq_along(n)) {
ci <- binom.test(events[i], n[i])$conf.int # Clopper-Pearson exact interval
cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i]) # Bayesian, uniform Beta(1,1) prior
wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}
ARM Protocol-directed 139 10 7.2 3.5 12.8 4.0 12.7 4.0 12.7
ARM Usual Care 96 14 14.6 8.2 23.3 8.9 23.0 8.9 23.011. Multiplicity, Missing Data and Analysis Populations
The registry lists four outcome measures and two analyses. Their individual identities, ordering, and relationship to the analyses are not reported in the registry record. Although mortality is identified as the primary outcome, the record does not explain whether additional outcomes were considered secondary, how many comparisons were tested, or whether any adjustment for multiple testing was planned. Multiplicity can matter when several outcomes or contrasts are examined, because the chance of at least one apparently notable result can increase as the number of tests grows. That is a general statistical concern, not a finding about this study.
Missing-data handling is not reported in the registry record. The record does not say whether all enrolled participants were assessed for mortality, how losses to follow-up were handled, or whether any outcome values were unavailable. The total enrollment of 235 does not establish the number analyzed for mortality or any other outcome.
The analysis population is also not described. The registry does not report whether analyses included all enrolled participants, only participants with available outcome data, or a different defined group. Such distinctions can affect interpretation, especially in a non-randomized study where care received and inclusion in an analysis may be related to participant characteristics. The record does not provide enough information to determine how these issues were addressed.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a completed study evaluated a multidisciplinary ventilator-weaning protocol and described usual care as leaving discontinuation decisions to physicians. It identifies mortality as the primary outcome and gives the overall enrollment as 235. It also states an objective involving ventilation duration, mechanical-ventilation complications, and critical-care length of stay.
Those details describe the study question and its broad setting; they do not establish an outcome effect. Mortality counts, denominators, estimates, and uncertainty are not reported in the registry record. The results for the other stated objectives are also not reported in the information available. It is therefore not possible to say whether any outcome was more or less frequent under one approach, or how precisely a difference was estimated.
A missing result should not be read as a finding of no difference. Nor should the study’s completed status, enrollment total, or the presence of a planning illustration be treated as evidence that a particular effect was detected or excluded. Statistical interpretation requires the observed results, their denominators, and enough information about the analysis and design to judge the comparison.
The non-randomized, single-group classification and the two care descriptions also limit what can be inferred about comparability. The record does not explain how participants came to receive each approach. Even with outcome results, a difference between care groups would not automatically establish that the protocol caused the difference. Patient characteristics, clinical circumstances, or timing could also contribute. Whether the investigators accounted for such factors is not reported in the registry record.
The appropriate interpretation is therefore descriptive: the record documents an evaluation objective and a primary mortality endpoint, but does not report evidence that can quantify or resolve the outcome comparison.
13. Why This Trial Matters Statistically
This study raises a central statistical issue in clinical research: the distinction between a clinical objective and evidence capable of answering it. The registry describes a structured, multidisciplinary approach to ventilator weaning and a usual-care approach based on physician discretion. It identifies mortality as the primary endpoint, but does not report the counts or comparative estimates needed to evaluate that endpoint.
The design classification is also consequential. The record calls the study non-randomized and single group while describing two care approaches. Randomization is not the only way to learn from clinical data, but a non-randomized comparison needs a clear account of how groups were formed and what differences may have influenced outcomes. Without that account, it is difficult to distinguish an association between care approach and outcome from differences in the people or circumstances being compared.
Enrollment of 235 is useful context, but enrollment alone does not establish the precision of an outcome estimate. Precision depends on the number analyzed, the number of events, and the study design. Those details are not reported for mortality. A planning illustration based on an observed effect can help describe assumptions about future or target sample sizes, but it is distinct from the observed analysis and is not observed power.
For clinical research reporting, the record illustrates why outcome definitions, group denominators, effect estimates, uncertainty, analysis populations, and methods for missing data are important. Without them, readers cannot judge the magnitude or precision of a result, or assess how strongly the design supports a causal interpretation. Here, the registry supports a description of the research question and design labels, but not a statistical conclusion about the outcomes.
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.
The main limitation for interpretation is that the registry record does not report results for the primary mortality endpoint. It provides no mortality event counts, group-specific denominators, effect estimate, confidence interval, or test result. The stated objectives concerning time on the ventilator, complications, and critical-care length of stay likewise lack reported results in the available record.
The design description is internally difficult to reconcile: the study is classified as single group and non-randomized, while the arm descriptions distinguish protocol-directed care from usual care. How participants entered those care approaches is not reported in the registry record. This prevents a clear assessment of the comparison structure and the potential for confounding. Baseline characteristics and methods for adjustment are also not reported.
The endpoint description gives mortality as participants and the timeframe as length of ICU stay (days), but does not define the event or follow-up rules in greater detail. The registry does not report whether mortality was assessed only during ICU stay or over another period. It also does not state the analysis population, missing-data procedures, or whether all enrolled participants contributed to each outcome.
Although four outcome measures and two analyses are listed, their details and statistical methods are not reported. The registry does not provide the trial’s sample-size justification, interim analysis plan, or statistical analysis plan. Overall enrollment of 235 cannot resolve these omissions and should not be treated as the number analyzed in either care group.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of a Systematic Approach to Weaning From Mechanical Ventilation — NCT01482429.
- Registry record last updated 2013-03-04; status last verified 2013-01.
- Results first posted 2013-03-04.
- 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.
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18. Record Summary
NCT01482429 is a completed, non-randomized study sponsored by the Federal University of Uberlandia. The record lists a single-group model, no masking, and enrollment of 235. Its start is listed as 2011-01 and its primary completion as 2012-01. The study evaluates a multidisciplinary ventilator-weaning protocol, with an arm description contrasting protocol-directed discontinuation and usual care at physician discretion.
The registered primary outcome is Mortality, measured as participants, in the Overall population; its timeframe is described as length of ICU stay (days). The record lists four outcome measures and two analyses, but does not report the mortality results or identify the other outcome results in the available information. It also does not explain how the single-group classification relates to the two care descriptions. Thus, the registry establishes the study’s broad objective and design labels, but does not provide enough outcome or methods detail to interpret a comparative effect.