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 Predictors of the Ability to Protect the Airway in Long-term Ventilated Patients (NCT01618240), a registered phase not stated study. The primary outcome is Muscle Strength.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01618240 |
| Phase | Phase not stated |
| Condition | Swallowing Disorder, Aspiration, Long Term Ventilation |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 30 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Massachusetts General Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned long-term ventilated subjects. The registry record lists swallowing disorder, aspiration, and long-term ventilation as conditions of interest, and reports enrollment of 30 participants. It does not report further eligibility details or describe the characteristics of the participants.
Intervention
The listed study activities were muscle strength measurement and ventilator use. The record describes assessment of muscle strength with the Medical Research Council (MRC) scale in tracheostomized patients. It does not describe a treatment intervention intended to change strength or airway function.
Comparator
No separate control group is described. The listed arm is “Long term ventilated subjects,” with muscle strength measurement and ventilator use. Allocation is not stated, and this is not a randomized comparison or a like-for-like control comparison.
Primary question
The investigators hypothesized that clinical muscle strength assessment using manual muscle testing predicts the ability to protect the airway during swallowing in long-term ventilated subjects. More specifically, they proposed that low strength is associated with difficulty clearing secretions from the peri-laryngeal area and with material entering the airway. These were hypotheses; the registry record does not report outcome results establishing whether the proposed associations were observed.
The airway-related measures described in the hypothesis include the valleculae and pyriform sinus residue scale (VPSR), with a value > 1, and the penetration-aspiration scale (PAS), with a value > 1. The investigators stated that these findings should predispose to endotracheal aspiration. The record does not report the observed VPSR or PAS results, or the number of participants with clinical aspiration.
3. Trial Design
This is a completed study record for NCT01618240, titled “Predictors of the Ability to Protect the Airway in Long-term Ventilated Patients.” The official title describes determining predictors of adequate upper airway function in long-term ventilated patients. Massachusetts General Hospital is listed as the sponsor. The recorded study start is 2011-01, and primary completion is recorded as 2012-04. Enrollment is 30.
The brief summary identifies this as the first part of a two-part study with the same IRB protocol number, labeled “A.” This registry record concerns that first part; it does not report results for the other part. The record lists one arm, “Long term ventilated subjects,” and lists muscle strength measurement and ventilator use as study activities. Allocation is not stated. There is no separate control arm described, so the design does not support a randomized treatment comparison.
The study question is framed around whether measured muscle strength predicts airway protection during swallowing. The primary outcome is titled “Muscle Strength,” and its description states that the MRC scale, with a range of 0–60, was used to evaluate the degree of muscle weakness in tracheostomized patients. The assessment timeframe is within 24 hours of fiberoptic endoscopic evaluation of swallow. A secondary outcome is the number of patients with muscle weakness, defined as MRC<48, who developed clinical aspiration.
The registry record lists two outcome measures but zero analyses. It does not report a statistical analysis plan, a sample-size justification, or a detailed protocol for measurement and analysis. The planning assumptions recorded for sample-size illustrations are not evidence that these were the trial’s original design assumptions. The status is completed, but completion status alone does not supply the missing outcome estimates or analysis results.
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
| Stage | Long-term Ventilated Subjects |
|---|---|
| STARTED | 30 |
| COMPLETED | 30 |
| NOT COMPLETED | 0 |
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: 30 long-term ventilated subjects were included (ventilated \> 10 days). Subjects had a Richmond Agitation Sedation score of \>0, had no delirium, had no abnormalities of the larynx or pharynx, and no history of chemotherapy or radiotherapy to the head/ neck, or of degenerative neurological disease.
| Characteristic | Unit | Baseline Population |
|---|---|---|
| Participants analysed | 30 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 23 |
| Age, Categorical: >=65 years | Participants | 7 |
| Age, Continuous | years | 55 (SD 14) |
| Sex: Female, Male: Female | Participants | 14 |
| Sex: Female, Male: Male | Participants | 16 |
| Region of Enrollment: United States | participants | 30 |
6. Primary Endpoint
The registry lists the primary outcome as Muscle Strength, measured over Within 24 hours of fiberoptic endoscopic evaluation of swallow.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is titled “Muscle Strength.” It concerns the degree of muscle weakness measured with the Medical Research Council (MRC) scale, which the record describes as ranging from 0–60. The stated population for the measurement is tracheostomized patients, and the assessment was to occur within 24 hours of fiberoptic endoscopic evaluation of swallow. The outcome unit is participants, and the listed parameter is a number. The registry record does not report a participant-level distribution, summary value, or count for this primary outcome.
The strength measure is relevant to the stated research question because the investigators hypothesized that clinical muscle strength assessment could predict airway protection during swallowing. Their more specific hypothesis linked low strength with inability to clear peri-laryngeal secretions and with material entering the airway. The record also defines a secondary outcome concerning participants with muscle weakness, using MRC<48, who developed clinical aspiration. That definition indicates how weakness was classified for the secondary outcome; it does not establish how many participants met the criterion.
In general, a prespecified endpoint gives a study a defined outcome to measure in relation to its research question. Here, the registry identifies muscle strength as the primary outcome, but does not report an analysis connecting the strength assessment to the airway-protection measures or aspiration. Thus the endpoint definition explains what was to be assessed, while the posted record does not provide the results needed to evaluate the proposed predictive relationship.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study’s question and outcome definitions, but does not post the primary or secondary outcome results. Although enrollment is recorded as 30 and the study status is completed, there is no reported MRC summary, no reported count of participants classified as weak, and no reported number of participants with clinical aspiration. The record also does not report observed VPSR or PAS results. Consequently, the registry record does not permit an estimate of the association between muscle strength and airway protection.
The hypothesis was that low clinical muscle strength would be associated with difficulty clearing secretions around the larynx and with material entering the airway. The record describes VPSR values > 1 and PAS values > 1 in stating that hypothesis. These threshold definitions are not outcome findings. They should not be read as showing that any participant had residue, penetration, aspiration, or a particular MRC score. No corresponding outcome counts or estimates are reported.
There is also no reported effect estimate, confidence interval, or p-value for the primary or secondary research question. In general, an effect estimate describes the magnitude and direction of an observed relationship, while a confidence interval conveys its statistical precision under the method used. Without such results, neither the size nor the precision of a strength–airway association can be assessed. The record’s listing of two outcome measures and zero analyses reinforces that no statistical result for those measures is posted in this registry record.
The study lists one group of long-term ventilated subjects rather than a randomized comparison. Its stated aim is predictive or associational, not a comparison of assigned treatments. Even if results were available, a relationship between strength and airway measures in this group would not by itself establish that changing strength causes a change in airway protection. The posted record provides no data from which to examine even that association, and it does not describe an external validation analysis.
The registry does report serious adverse events in the enrolled group: zero serious events among 30 at risk. It also reports zero other adverse events among 30 at risk. These are safety counts, not the missing endpoint results; they do not answer the primary question about muscle strength or the secondary question about clinical aspiration. The death count is not reported in the registry record. As with any recorded safety count, absence of reported events should be interpreted as a description of the record, not as proof that no risk exists.
The trial’s completed status and stated enrollment therefore need to be separated from evidence of an observed association. The record permits a description of the intended measurement, hypotheses, and recorded adverse-event counts, but not a conclusion about whether muscle strength predicted airway protection or how precisely such a relationship was estimated.
9. Statistical Methods Explained
The record frames the research question as whether muscle strength predicts airway protection in long-term ventilated subjects. It describes a single group and does not state an allocation method. There is no separate control group or randomized comparison. This design information matters because an association within a group is different from a contrast between assigned interventions. The registry record does not report a statistical analysis plan explaining how the proposed prediction question was to be tested.
What does the MRC measure contribute?
The primary outcome is named “Muscle Strength,” and the description states that the MRC scale, ranging from 0–60, was used to evaluate muscle weakness in tracheostomized patients. The assessment was scheduled within 24 hours of fiberoptic endoscopic evaluation of swallow. In general, a measurement scale records a characteristic according to defined values; an analysis must then specify how those values will be represented and related to other outcomes. The registry record does not say whether the primary analysis was to use individual MRC values, a summary, categories, or another representation. It provides no observed scores or summary statistics.
The secondary outcome uses a threshold definition: patients with muscle weakness are identified as MRC<48, and the outcome concerns those who developed clinical aspiration. In general, categorizing a measured scale can make a clinical question easier to express as an event count, but it also discards distinctions among values within each category. The registry record does not report the number meeting the weakness definition, the number developing clinical aspiration, or the statistical method intended to examine their relationship.
How should the airway measures be understood?
The hypothesis refers to clearing secretions from the peri-laryngeal area, assessed with the valleculae and pyriform sinus residue scale (VPSR), with a value > 1. It also refers to materials entering the airway, assessed with the PAS scale, with a value > 1. These descriptions identify thresholds used in the investigators’ hypothesis. They do not provide observed values, counts, or estimates. The record does not report how VPSR and PAS were to be modeled, whether they were separate endpoints in the analysis, or how they related to the secondary clinical aspiration outcome.
In general, a predictive analysis evaluates whether information about one measure helps anticipate another outcome. A test of association instead assesses whether measures vary together in the studied data. These are related but not interchangeable goals: a predictive claim is stronger when its performance is evaluated beyond the data used to develop the prediction. The registry record does not describe a prediction model, validation procedure, or statistical test, and it posts no analyses. It is therefore not possible to determine which approach was used or whether any predictive performance was assessed.
What can an estimate and its precision tell readers?
In general, an effect estimate expresses the size and direction of a relationship or contrast. A confidence interval describes statistical uncertainty around an estimate under the assumptions of the analysis. A narrow interval generally indicates greater precision than a wide interval, but precision does not establish that a relationship is causal or clinically important. The registry record reports no effect estimate or confidence interval for the primary question, the secondary outcome, VPSR, or PAS. It also reports no p-value. No numerical inference about association or precision can therefore be drawn from the posted outcomes.
In general, binary outcome analyses may compare event proportions or model the probability of an event, while scale outcomes may be analyzed using methods appropriate to their values and distribution. The record’s overall outcome classification does not supply a specific analysis method for the named MRC measure. No modeling family, covariate adjustment, handling of repeated or related measures, or assumption checking is reported. It would be inappropriate to infer any of these choices from the outcome labels alone.
What do the planning illustrations mean?
The recorded planning illustration assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. It specifies that time-to-event illustrations count total events, while other illustrations count participants per arm. These are planning conventions, not a description of the design reported for this single-group study. The registry record does not state that the trial used those assumptions or that it had two allocated arms.
In general, a sample-size calculation estimates how many observations would be needed under specified assumptions to detect a chosen effect with a chosen degree of statistical power. A planning illustration based on an observed effect is conditional on that effect estimate and its assumptions. It does not establish the original sample-size rationale, and it is not observed power. No sample-size justification for this study is reported in the registry record. The available study details also do not report an effect estimate from which the illustration’s practical implications could be assessed.
More broadly, statistical interpretation depends on the defined analysis population, endpoint rules, missing-data handling, and the analysis actually performed. The record reports enrollment but does not state the number analyzed for either outcome or explain whether every enrolled participant contributed outcome data. It lists zero analyses. As a result, general explanations of methods clarify what information would be relevant, but they cannot substitute for absent results or an unreported analysis plan.
10. Multiplicity, Missing Data and Analysis Populations
The record lists two outcome measures: the primary outcome of muscle strength and a secondary outcome concerning patients with muscle weakness (MRC<48) who developed clinical aspiration. It reports zero analyses. No multiplicity strategy is reported in the registry record, including whether or how any adjustment for examining multiple outcomes or airway measures was planned. In general, multiplicity refers to the added chance of at least one misleading statistical finding when several hypotheses are tested. Whether that issue arose in the analysis cannot be determined because no analyses are posted.
Missing-data procedures are not reported in the registry record. There is no account of missing MRC measurements, unavailable swallowing evaluations, incomplete aspiration assessments, or how any such observations would be handled. The number enrolled is 30, but the number contributing data to each outcome is not reported. Enrollment should not be treated as proof that all participants had complete data or were included in every analysis.
The analysis population is likewise not described. The registry record does not specify whether analyses were intended for all enrolled participants, only participants with evaluable measurements, or another defined group. It does not report exclusions or reasons for missing outcome information. These omissions limit assessment of possible selection effects and prevent reconstruction of the analysis population from the posted record.
In general, missing-data handling and analysis-population definitions are important because they clarify which observations support an estimate and what assumptions are required. Without those details, the record cannot establish whether outcome data were complete, how incomplete records affected the analysis, or whether the stated hypothesis was evaluated as planned. The endpoint definitions alone do not answer these questions.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Long-term Ventilated Subjects | 0 | 30 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Long-term Ventilated Subjects | 0 of 30 |
The safety record lists 30 long-term ventilated subjects at risk. It reports zero serious adverse events and zero other adverse events in that group. These figures describe what is recorded for the study group; they are not estimates of the primary muscle-strength outcome or the secondary clinical-aspiration outcome. The record does not provide further detail about event definitions, observation duration for safety, or how events were collected.
The death count is not reported in the registry record. A missing death count should not be interpreted as a reported count of zero. Likewise, the recorded zero adverse-event counts should not be expanded into a claim that no adverse events occurred outside what was captured in the registry record. The posted figures do not describe a comparison with another group, because no separate control group is listed.
In general, adverse-event counts are most informative when read alongside clear definitions, follow-up periods, and the population monitored. Such context is not reported. These safety figures therefore describe the registry entries, while leaving the study’s airway-protection question unanswered.
12. What the Result Does, and Does Not, Mean
The record’s main contribution is to identify a research question: whether clinical muscle strength assessment predicts airway protection during swallowing among long-term ventilated subjects. It specifies an MRC assessment within 24 hours of fiberoptic endoscopic evaluation of swallow and describes hypotheses involving peri-laryngeal secretion clearance, VPSR values > 1, PAS values > 1, and endotracheal aspiration. It also defines a secondary outcome using MRC<48 and clinical aspiration.
Those details describe what investigators proposed to measure and hypothesized. They do not show that low muscle strength was associated with residue, material entering the airway, or clinical aspiration. The registry record does not report MRC results, VPSR or PAS findings, aspiration counts, effect estimates, confidence intervals, or p-values. Thus it is not possible to assess the direction, magnitude, or precision of the proposed relationship from this record.
The single listed group and absence of a separate comparator also matter. This record does not describe a randomized comparison of treatments. Even an observed association in a single group would not, on its own, establish that muscle strength caused a change in airway protection. The record does not report a predictive model or validation assessment that would show how well strength measures forecast airway outcomes.
The enrollment of 30 and completed status provide context for the study record, but they do not replace outcome reporting. Similarly, the recorded zero serious adverse events and zero other adverse events are safety counts, not evidence about the primary research question. The death count is not reported in the registry record.
In general, a study question, outcome definition, and result are distinct pieces of evidence. Here, the first two are described, but the posted registry information does not include the results or analyses needed to answer the question. Any interpretation should therefore remain limited to the stated hypothesis, the recorded design, and the outcome definitions, without treating the hypothesis as a finding.
13. Why This Trial Matters Statistically
This study is statistically interesting because it frames muscle strength as a possible predictor of airway protection rather than as an intervention being compared with a control. That distinction shapes what an analysis would need to establish. A study can assess whether measurements are associated, while a claim that a measure reliably predicts outcomes requires evaluation of predictive performance. The registry record states the proposed relationship but does not report an analysis or validation procedure.
It also illustrates how endpoint definition affects interpretation. The primary outcome is muscle strength measured with the MRC scale, while the hypothesis concerns airway function during swallowing. The secondary outcome uses a threshold, MRC<48, alongside clinical aspiration. The registry record identifies thresholds for VPSR and PAS in its hypothesis as well. Defining measures and thresholds makes the question more specific, but without outcome counts and analysis details, readers cannot determine how those definitions were applied to observed participants.
Another statistical issue is the separation between planning and findings. The record contains assumptions for sample-size illustrations, including a two-sided significance level of 0.05, equal allocation between two arms, and normal approximation. Those assumptions do not describe the listed single-group study design, and the registry record does not identify them as the original trial’s design or sample-size justification. Planning illustrations should not be mistaken for observed results or for evidence that a study had adequate precision.
Finally, the registry lists two outcome measures but zero analyses. This makes transparent a central limitation of interpreting registry entries: a completed study with defined outcomes is not equivalent to a posted statistical result. The record allows readers to distinguish the research hypothesis from evidence actually reported, and to see why outcome estimates, uncertainty measures, analysis populations, and missing-data methods are needed for a statistical conclusion.
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 most consequential limitation for interpretation is that the registry record does not report results for the primary or secondary outcomes. There are no MRC summaries or counts, no reported VPSR or PAS findings, and no clinical aspiration count. It also reports zero analyses. The central proposed association between muscle strength and airway protection therefore cannot be evaluated from the posted record.
The design information is limited. One group of long-term ventilated subjects is listed, allocation is not stated, and there is no like-for-like control comparison. The record does not describe eligibility criteria in detail, participant characteristics, recruitment procedures, or the number of participants with evaluable outcome data. These details are not reported in the registry record and should not be inferred from the enrollment figure.
Measurement and analysis details are also incomplete. The primary outcome description identifies the MRC scale and assessment timeframe, while the hypothesis identifies VPSR and PAS thresholds. The record does not report how these measures were scored in practice, how missing or indeterminate measurements were handled, or what statistical model was planned. It does not report an analysis population, covariate strategy, or any validation approach for the predictive hypothesis.
The brief summary identifies this record as the first part of a two-part study under the same IRB protocol, labeled “A,” but it does not provide results for the other part. The planning assumptions recorded for sample-size illustrations should not be taken as the study’s original justification, and the record does not report that justification. Safety reporting is also limited: zero serious and zero other adverse events are recorded among 30 at risk, while the death count is not reported. These limitations constrain both the scientific interpretation and the ability to reproduce or audit an analysis.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Predictors of the Ability to Protect the Airway in Long-term Ventilated Patients — NCT01618240.
- Registry record last updated 2014-10-13; status last verified 2013-05.
- Results first posted 2013-08-27.
- 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
NCT01618240 is a completed, single-group study sponsored by Massachusetts General Hospital, with enrollment of 30. Its recorded start is 2011-01 and primary completion is 2012-04. The study concerns whether muscle strength predicts airway protection during swallowing in long-term ventilated subjects. The primary outcome is muscle strength measured with the MRC scale, and the secondary outcome concerns patients with weakness (MRC<48) who developed clinical aspiration.
The registry record lists two outcome measures and zero analyses. It does not report outcome results, statistical estimates, confidence intervals, p-values, an analysis population, missing-data methods, or a sample-size justification. It reports zero serious adverse events and zero other adverse events among 30 at risk; the death count is not reported. The record identifies hypotheses and measurement definitions, but does not provide the findings needed to assess the proposed association.