Change In Diaphragmatic Thickness Predicts Extubation Success: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Change In Diaphragmatic Thickness Predicts Extubation Success (NCT02656199), a registered phase not stated study. The primary outcome is Extubation Success.

2. Clinical Question

The title frames diaphragm thickness change as a predictor of extubation success, but a title is not evidence that prediction was demonstrated. Establishing predictive performance would require posted outcome data and a reported analysis connecting ultrasound measurements to subsequent extubation outcomes. Neither is available in this registry record. The clinical question can be identified from the study description; its answer cannot be determined from the posted results.

3. Trial Design

NCT02656199 is described as a prospective study evaluating diaphragm ultrasound measurements and their relationship to weaning from mechanical ventilation. The registry lists Albert Einstein Healthcare Network as the sponsor, a start date of 2015-01, primary completion on 2017-01-13, and a status of TERMINATED. The listed enrollment is 57. These entries describe the registered study but do not establish how many participants contributed usable measurements or outcomes.

The intervention is a procedure named Diaphragm Ultrasound. The arm description identifies one Main Cohort and says that all patients enrolled would undergo ultrasound after reaching a pressure support trial. There is no separate comparator arm described, and allocation is not stated. The record explicitly cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. No causal treatment contrast should be inferred from the design information.

The primary outcome is named Extubation Success, with a timeframe of 48 hours. Its description defines the intended measure as discontinuation from mechanical ventilation within 48 hours of ultrasound. Re-intubation is listed as a secondary outcome. Other operational details, such as criteria for a successful discontinuation and the precise timing or ascertainment procedures, are not reported in the registry record.

The record states that the principal investigator left the institution, attempts to make contact were unsuccessful, and no study data are available. The status is TERMINATED, but the reason for termination beyond the note about unavailable data is not reported in the registry record. The protocol, recruitment progress, analysis plan, and any changes made after study start are also not reported in the registry record. These absences limit what can be concluded about study conduct as well as outcomes.

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.

Before assignment: 0 participants analyzed. PI has left the institution. Efforts made to contact the PI were unsuccessful. No study data available.

Overall Study

Analysis population for the primary outcome, as defined in the registry: PI has left the institution. Efforts made to contact the PI were unsuccessful. No study data available.

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: PI has left the institution. Efforts made to contact the PI were unsuccessful. No study data available.

6. Primary Endpoint

The registry lists the primary outcome as Extubation Success, measured over 48 hours.

The primary endpoint is Extubation Success, described as discontinuation from mechanical ventilation within 48 hours of ultrasound. The 48-hour window links the ultrasound measurement to a near-term clinical outcome and defines the period during which the intended prediction was to be assessed. The record also lists re-intubation as a secondary outcome, but it does not give a detailed definition or timeframe for that outcome.

In general, an endpoint gives a study a defined outcome against which measurements or interventions can be evaluated. In a prediction study, a clearly specified outcome and follow-up window are important because predictive performance depends on what counts as an outcome and when it is assessed. Here, the stated endpoint provides a broad target, but the detailed criteria for discontinuation, handling of ongoing ventilation, and ascertainment of the outcome are not reported in the registry record.

No endpoint results, participant-level outcomes, summary statistics, or estimates of predictive performance are available. The registry description also does not report how the ultrasound measurement was converted into a predictor, whether a threshold was used, or how success was classified. As a result, the listed endpoint identifies the study’s intended question but does not establish how accurately diaphragm thickness change predicted extubation success.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What would a prediction analysis assess?

In general, a prediction analysis asks whether information available at a defined point helps anticipate a later outcome. For this study, the proposed predictor was a change in diaphragm thickness measured by ultrasound during the respiratory cycle, and the intended outcome was discontinuation from mechanical ventilation within 48 hours. An analysis would need to connect measurements made at the specified time to outcomes assessed during that follow-up window.

Prediction has several aspects. Discrimination describes whether a model or measurement tends to assign different predictions to people who experience the outcome and those who do not. Calibration concerns agreement between predicted probabilities and observed outcome frequencies. A threshold-based assessment may also be relevant if a particular measurement value is intended to classify people into predicted outcome groups. These are general concepts, not methods reported for this study. The registry record does not report which, if any, were used.

What does the record say about the analysis?

The registry lists zero analyses and states that no study data are available. It therefore provides no model specification, effect estimate, predictive performance measure, confidence interval, or p-value. It is not possible to assess statistical significance, precision, discrimination, calibration, or the practical consequences of any proposed threshold from the posted record. The absence of a registered analysis entry does not establish whether an analysis was conducted elsewhere; it establishes only that no analysis result is posted in this record.

The description raises the possibility that prediction could differ by pressure support level, contrasting lower and higher levels. A statistical evaluation of that question would need to define how pressure support is represented and how differences in prediction are assessed. The record does not report those definitions or an analysis of pressure support. It is therefore not possible to tell whether the proposed comparison was made or what it found.

Why are confidence intervals important?

In general, a confidence interval conveys the uncertainty around an estimated quantity under the assumptions of the analysis. A narrow interval can indicate greater precision than a wide one, although interpretation also depends on the study design, measurement quality, and whether the analysis assumptions are reasonable. A point estimate without an interval can obscure how uncertain the estimate is. Here, no estimate or confidence interval for the primary question is reported in the registry record, so neither the direction nor the precision of a possible association can be evaluated.

What can the planning assumptions tell us?

The stated planning illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; it describes detecting a stated fraction of an observed effect. For time-to-event illustrations, it uses a total number of events under the Schoenfeld approach; other illustrations are expressed as participants per arm. These are planning conventions, not evidence about the study’s actual analysis or design. The registry describes a single Main Cohort, does not state allocation, and does not report an observed effect from which a planning result could be interpreted. Any sample-size illustration is therefore not an observed power calculation and should not be mistaken for the enrollment or analysis plan used in this study.

In general, planning calculations depend on choices such as the target effect, statistical assumptions, outcome type, and allocation scheme. A calculation can illustrate the sample size associated with those choices, but it cannot establish that a study has a particular probability of detecting an effect after the data are collected. Observed power is not a substitute for an effect estimate and its uncertainty. The registry record does not report the study’s own sample-size justification, so the planning assumptions should not be attributed to the investigators.

Why does over-dispersion matter in general?

Over-dispersion occurs when observed variability is greater than a statistical model expects. If it is ignored, standard errors may be too small and intervals or tests may convey more certainty than the data warrant. That general issue can arise in some outcome models, but the registry record does not report a model, a dispersion assessment, or evidence that over-dispersion was relevant to this study. It cannot be used to infer which analysis would have been appropriate.

What is unavailable for independent assessment?

The record does not report the ultrasound acquisition and measurement protocol, measurement reliability, handling of repeated measurements, outcome-classification rules, or a statistical analysis plan. It also does not provide participant-level data, subgroup results, or performance estimates. These details matter because prediction results depend on consistent measurement, clear outcome definitions, appropriate handling of missing observations, and analysis choices specified in relation to the study question. Without them, readers cannot reproduce or independently scrutinize a prediction analysis. The missing details are not evidence that a particular method was or was not used; they are simply not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry names a primary outcome, Extubation Success within 48 hours, and lists Re-intubation as a secondary outcome. It also describes interest in prediction across pressure support levels. However, a multiplicity strategy, such as a hierarchy among outcomes or adjustment for multiple comparisons, is not reported in the registry record. No outcome-specific analysis results are posted, so the effect of any multiplicity approach cannot be evaluated.

Missing-data methods are not reported in the registry record. The stated note that no study data are available is a limitation of the registry information; it does not tell readers how many participants had missing measurements or outcomes, or how missing observations were handled in any analysis. Participant flow, reasons for missingness, and the number included in each outcome analysis are also not reported.

The analysis populations are not described. The registry does not say whether analyses were intended for all enrolled participants, only those with usable ultrasound measurements, or another defined group. It also does not report exclusions or whether participants were analyzed according to a prespecified rule. The listed enrollment of 57 cannot resolve these questions.

These omissions matter because outcome choice, missingness, and analysis-population definitions affect how a result should be interpreted. With no posted data or analyses, readers cannot determine whether results would have been sensitive to different handling choices. The record does not establish that any specific method was omitted in the study’s conduct; the relevant details are not reported in the registry record.

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

The registry supports a limited description of the study’s intent: it planned to evaluate whether ultrasound-measured change in diaphragm thickness could predict discontinuation from mechanical ventilation within 48 hours, and it raised the question of prediction at different pressure support levels. It also identifies a prospective design, a single Main Cohort, a listed enrollment of 57, and a secondary outcome of re-intubation.

It does not provide evidence that diaphragm thickness change did or did not predict extubation success. There is no posted outcome estimate, predictive performance measure, confidence interval, or analysis result. The title should not be read as a demonstrated finding. The registry record explicitly states that no study data are available.

Nor can the record establish how precise a possible estimate would have been, whether measurement or outcome classification was reliable, or whether a prediction rule would perform similarly in another group of patients. Those judgments require results and methodological detail that are not reported in the registry record. The listed enrollment alone cannot show the number of participants included in an analysis or the strength of any observed association.

The registry’s zero entries for adverse-event counts do not establish the absence of harm, particularly given the statement that study data are unavailable. Similarly, the TERMINATED status does not, on its own, reveal the full reason for termination or whether the study question was addressed outside the posted record. The appropriate interpretation is that the intended question is identifiable, but the posted registry information is insufficient to answer it.

12. Why This Trial Matters Statistically

This study is statistically relevant because it asks a prediction question rather than describing a randomized comparison of two treatment strategies. Prediction studies require a clear link between a measurement made at a defined time and a subsequent outcome. They also require evaluation of how well predictions distinguish outcomes and, where probabilities are produced, whether those predictions are calibrated. The registry record identifies the intended measurement and outcome window but does not report the analyses needed to judge predictive performance.

The description also raises a potentially important methodological issue: prediction may depend on the conditions under which a measurement is taken. In this case, the stated question concerns whether diaphragm thickness change retains predictive ability at higher pressure support levels or is useful only at lower levels. This is a question about the setting and transportability of a predictor, but no results or analytic details addressing it are posted.

The registry record is also a reminder that a registered research question and a published statistical result are different things. A title or objective can express a hypothesis without showing that it was supported. Here, the explicit statement that no study data are available prevents assessment of effect size, uncertainty, or reproducibility. The gap is not resolved by the listed enrollment, the study status, or the presence of an endpoint definition.

For biostatisticians and clinical researchers, the record highlights why complete outcome reporting and transparent analysis descriptions matter. Without data and methods, readers cannot assess whether a predictor has useful performance, whether apparent performance is precise, or whether conclusions depend on analytic choices. The study’s statistical importance lies in the design question it set out to address and in the limits of what can be learned from an incomplete results record—not in an inferential finding that is absent.

13. 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 primary limitation is that no study data are available in the registry record. The record attributes this to the principal investigator having left the institution and unsuccessful efforts to make contact. Consequently, no primary or secondary outcome results are posted, and the proposed prediction question cannot be evaluated.

The registry lists an enrollment of 57 but does not report participant characteristics, the number with completed ultrasound measurements, the number followed through the 48-hour outcome window, or the number included in any analysis. The status is TERMINATED, but details about recruitment, study conduct, and the circumstances of termination are not reported in the registry record beyond the note about unavailable data.

The study description identifies a single Main Cohort and no randomized comparator. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Thus, the record does not support a comparative treatment-effect interpretation. The detailed ultrasound protocol, measurement reproducibility, outcome criteria, pressure support definitions, and assessment procedures are not reported in the registry record.

The registry lists Re-intubation as a secondary outcome but gives no posted result or detailed outcome definition. It also reports zero adverse-event counts alongside the statement that study data are unavailable, so those entries cannot be treated as informative evidence of no events. Finally, no statistical analysis plan, missing-data approach, analysis population, or multiplicity strategy is reported. Together, these limitations mean that the registered question and broad design can be described, but neither the validity nor the precision of a potential result can be judged.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Change In Diaphragmatic Thickness Predicts Extubation Success — NCT02656199.
• Registry record last updated 2020-03-09; status last verified 2016-01.
• Results first posted 2020-03-09.
• 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.

17. Record Summary

NCT02656199, titled “Change In Diaphragmatic Thickness Predicts Extubation Success,” is registered as a prospective study of diaphragm ultrasound during a pressure support trial. Albert Einstein Healthcare Network is listed as sponsor. The record gives a start date of 2015-01, primary completion date of 2017-01-13, status TERMINATED, and enrollment of 57.

The intended primary outcome was Extubation Success, described as discontinuation from mechanical ventilation within 48 hours of ultrasound. Re-intubation is listed as a secondary outcome. The study description also proposed examining whether prediction differed between lower and higher pressure support levels.

The registry states that the principal investigator left the institution, contact efforts were unsuccessful, and no study data are available. No analysis results, estimates of predictive performance, or outcome summaries are reported in the registry record. The study’s predictive question therefore remains unanswered by the posted information.