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 Electric Muscle Stimulation for Patients With Chronic Respiratory Failure (NCT01930643), a randomized na study. The primary outcome is Ventilator-free Days.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01930643 |
| Phase | NA |
| Condition | Chronic Respiratory Failure, Critical Illness Myopathy |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 13 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Mackay Memorial Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerned adults with mechanical ventilation for more than 14 days. Its conditions were chronic respiratory failure and critical illness myopathy. The registry summary describes the clinical context as patients who may remain dependent on ventilator support after acute respiratory failure because of critical-illness weakness and underlying diseases. It states that 5-20% of patients with acute respiratory failure would depend on ventilator support more than 14 days; this is background in the record, not a result of this trial. The enrolled total was 13.
Intervention
The experimental arm received electric muscle stimulation (EMS) for both quadriceps, using a programmed middle-frequency device identified as HELEX 573. The regimen was 32 minutes per day, 5 time per week. These are the intervention details recorded for the study; information about adherence or the amount of stimulation actually received by each participant is not reported in the registry record.
Comparator
The control arm received a routine passive rehabilitation program. The registry record does not give further detail about that program or whether its components were standardized. The trial was randomized, parallel, and had no masking. It therefore set out to compare the EMS program with passive rehabilitation without masking participants or study personnel.
Primary question
The primary outcome was cumulative ventilator-free days during the 28 days following intervention. The clinical question was whether the observed distribution of ventilator-free days differed between participants assigned to EMS and those assigned to routine passive rehabilitation. The registry record presents arm-level medians and inter-quartile ranges, but no inferential comparison or estimate of the difference between arms is reported.
3. Trial Design
This was a randomized controlled trial with a parallel-group design. The registry record identifies the study as not masked and lists an enrollment of 13. Seven participants are reported in the EMS arm and six in the control arm. The planned population was adults receiving mechanical ventilation for more than 14 days, in the context of chronic respiratory failure and critical illness myopathy.
The EMS arm was described as receiving programmed middle-frequency stimulation to both quadriceps for 32 minutes per day, 5 time per week. The comparator was routine passive rehabilitation. The brief summary states the investigators’ hypothesis that EMS would improve muscle strength and shorten ventilator days; that statement describes the study rationale, not an established effect. Grip power is listed as a secondary outcome.
The study start date is 2013-08-21, and primary completion is recorded as 2015-06. Its status is TERMINATED. The reason for termination, the timing and circumstances of the decision, and whether the study stopped before its planned enrollment or follow-up are not reported in the registry record. The planned enrollment target and the basis for choosing it are also not reported in the registry record.
The record identifies Mackay Memorial Hospital as the sponsor. It does not describe the random sequence generation, allocation concealment, details of eligibility beyond the summary, or the statistical analysis plan. The phase is listed as NA. These missing details limit how fully the trial conduct can be assessed from the registry record alone.
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 | Electric Muscle Stimulation(EMS) | Control |
|---|---|---|
| STARTED | 7 | 6 |
| COMPLETED | 7 | 6 |
| NOT COMPLETED | 0 | 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.
| Characteristic | Unit | Electric Muscle Stimulation(EMS) | Control | Total |
|---|---|---|---|---|
| Participants analysed | 7 | 6 | 13 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 1 | 1 | 2 |
| Age, Categorical: >=65 years | Participants | 6 | 5 | 11 |
| Age, Continuous | years | 82 (74 to 83) | 73.5 (66 to 75) | 75 (73 to 82) |
| Sex: Female, Male: Female | Participants | 3 | 5 | 8 |
| Sex: Female, Male: Male | Participants | 4 | 1 | 5 |
| Region of Enrollment: Taiwan | participants | 7 | 6 | 13 |
6. Primary Endpoint
The registry lists the primary outcome as Ventilator-free Days, measured over 28 days.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | day |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint was cumulative ventilator-free days during the 28 days following intervention. It combines information about being alive and free from ventilator support across a defined follow-up period, as specified by the registry description. In general, ventilator-free days can provide a clinically interpretable summary of both ventilation duration and time without ventilation. The registry record does not give a full operational definition, including how deaths, recurrent ventilation, or partial days were handled, so those details should not be assumed.
The reported endpoint is summarized by a median and an inter-quartile range for each arm. The EMS arm had a median of 6 days, with an inter-quartile range of 0 to 17. The control arm had a median of 0 days, with an inter-quartile range of 0 to 19. The arm sizes were 7 and 6, respectively. The inter-quartile range describes the central part of the observed distribution; it is not a confidence interval for the median or for a treatment contrast.
This endpoint was selected as the primary outcome while grip power was listed as a secondary outcome. The registry record does not explain why ventilator-free days were selected, how the endpoint was adjudicated, or whether its analysis accounted for death or other competing events.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary-outcome summaries are medians of 6 ventilator-free days in the EMS arm and 0 days in the control arm during the 28-day period. Their inter-quartile ranges are 0 to 17 and 0 to 19, respectively. The reported arm sizes are 7 and 6. These are descriptive summaries of the participants included in each arm; they do not establish the size or statistical uncertainty of a difference between treatment assignments.
The overlap in the reported inter-quartile ranges is substantial. That observation is descriptive and should not be treated as a formal test. A median is a measure of the center of a distribution, while the inter-quartile range reflects its spread. Neither quantity by itself gives a confidence interval for a between-arm effect. The registry record does not report a confidence interval, p-value, hazard ratio, or other inferential comparison for this endpoint. It also records no posted analyses.
The number of participants is small, and the endpoint summaries alone cannot show whether any apparent separation between arm medians reflects a reproducible difference or sampling variability. In small randomized trials, individual participant outcomes can have a strong influence on summaries. Random allocation is a design feature intended to support fair comparisons, but it does not eliminate uncertainty, particularly when enrollment is limited.
The registry status is TERMINATED. The reason for termination and whether it was related to the observed outcomes are not reported in the registry record. It would therefore be inappropriate to infer a reason for stopping or to interpret the termination as evidence about the intervention. The record also does not describe whether all randomized participants completed the 28-day outcome assessment.
The results do not support a confident causal conclusion about the effect of EMS on ventilator-free days. There is no reported inferential estimate to quantify the contrast, and no uncertainty interval to indicate its precision. The posted summaries are useful as a record of what was observed in these enrolled participants, but they should be interpreted as descriptive rather than as proof of benefit, lack of benefit, or equivalence.
9. Statistical Methods Explained
The reported primary outcome is a quantitative measure summarized by medians and inter-quartile ranges. Those statistics describe the center and spread of the observed arm-specific values. The registry record supplies an arm-level median and inter-quartile range, but not the participant-level outcome distribution. The summaries therefore do not reveal how values were distributed within the ranges or whether particular observations had a large influence on the median.
What does a median describe?
In general, the median is the value at the center of an ordered set of observations. It is less sensitive than the mean to unusually high or low values. That can be useful when a clinical outcome has a skewed distribution, but the median does not describe all aspects of that distribution. Two groups can have the same median and different spreads or shapes; conversely, different medians do not by themselves establish a statistically reliable group difference.
How should the inter-quartile range be read?
In general, the inter-quartile range marks the central half of the observed values, from the first quartile to the third quartile. It describes variability among participants, not uncertainty about the estimated median. A confidence interval has a different role: it represents the precision of an estimated quantity under a statistical procedure. No confidence interval for either median or for a between-arm contrast is reported in the registry record.
What does randomization contribute?
In general, randomization assigns participants to groups by chance and is intended to reduce systematic differences between groups at the start of a trial. It supports causal interpretation when the allocation process is implemented as planned and the analysis appropriately accounts for participants’ assignments. The registry record identifies the study as randomized, but does not describe sequence generation, concealment, or the analysis population. Those details are not reported in the registry record, so the randomization process cannot be fully evaluated from the posted information.
Why does a small study require caution?
With few participants, the observed outcomes can be sensitive to individual values, and estimates can be imprecise. This is a general statistical consideration, not a claim about any particular participant in this trial. The enrolled total was 13, with 7 in the EMS arm and 6 in the control arm. Because no standard error or confidence interval is reported, the precision of the arm summaries and of any underlying contrast cannot be quantified from the registry results.
What does the endpoint classification imply?
The registry characterization treats the endpoint as a time-to-event outcome, while the posted arm summaries present ventilator-free days as medians and inter-quartile ranges. General time-to-event methods can account for the timing of events and, in some settings, incomplete follow-up. A hazard ratio is one possible summary from such analyses, but its interpretation depends on the event definition and modeling assumptions. No sponsor-reported hazard ratio or other inferential estimate is reported in the posted results. The record also does not specify censoring rules, event definitions beyond the outcome description, or how death was handled.
Why can no comparison be recalculated?
The registry record does not report an inferential analysis for the two-arm median-time endpoint. A difference between medians is not enough to reconstruct a valid statistical comparison: the participant-level distribution and the analysis method matter, as do the definitions of follow-up and missing observations. The record explicitly indicates that values are missing or not estimable for a two-arm comparison for this median-time endpoint. No recalculated comparison should therefore be treated as an available result.
In general, a p-value addresses compatibility between observed data and a specified null model; it does not measure the probability that a treatment works. A confidence interval communicates a range of values compatible with the data and method, subject to assumptions. Neither is reported for the primary comparison. The absence of these statistics means that the precision and strength of evidence for a group contrast cannot be assessed from the posted results. It does not mean that the groups were identical.
The registry record lists grip power as a secondary outcome, but does not provide an outcome result for it in the registry record for this analysis. The record identifies two outcome measures and no analyses. It does not describe a statistical plan, adjustment for baseline values, treatment of repeated measurements, or a model for the primary outcome. No such methods should be attributed to the investigators based on the arm summaries alone.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists ventilator-free days as the primary outcome and grip power as a secondary outcome. It identifies two outcome measures, but no analyses are reported. A strategy for handling multiplicity—such as controlling the chance of false-positive findings across several outcomes or time points—is not reported in the registry record. Because no inferential results are posted, there is no reported set of outcome tests from which to assess how multiplicity was handled.
Information about missing outcomes is also not reported in the registry record. The record does not state whether all randomized participants had primary-outcome data, how any missing values were handled, or whether follow-up differed between arms. It does not describe an intention-to-treat analysis, a per-protocol analysis, or another analysis population. The arm sizes reported with the primary summaries are 7 for EMS and 6 for control, but those figures alone do not establish how participants with missing data, if any, were treated.
The statistical analysis plan, including any prespecified primary contrast, adjustment variables, or interim analyses, is not reported in the registry record. No interim-analysis procedure should be inferred from the terminated status. The reason for termination and any relation to outcome monitoring are not reported in the registry record.
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 |
|---|---|---|---|
| Electric Muscle Stimulation(EMS) | 0 | 7 | 0.0% |
| Control | 0 | 6 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Electric Muscle Stimulation(EMS) | 0 of 7 |
| Control | 0 of 6 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Electric Muscle Stimulation(EMS) | 0 of 7 |
| Control | 0 of 6 |
The registry reports no serious adverse events among the 7 participants at risk in the EMS arm and none among the 6 participants at risk in the control arm. It also reports no other adverse events in either arm and no deaths. These figures describe the safety events recorded for the listed groups; they are not evidence that the risk of an adverse event is absent.
When event counts are zero in a small study, the data provide limited information about how often uncommon harms might occur. The number of participants and the duration and completeness of safety follow-up matter when interpreting such counts. The safety observation period, definitions used for adverse events, and procedures for collection or adjudication are not reported in the registry record. The record lists no serious adverse-event terms.
These safety figures should be read as counts observed in this trial, not as a definitive comparison of safety between EMS and control. No inferential safety analysis or uncertainty interval is reported. Zero recorded events in these arms cannot establish that either intervention is free of risk.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, unmasked, parallel-group trial compared electric muscle stimulation with routine passive rehabilitation in a small group of adults requiring prolonged mechanical ventilation. It reports arm-level medians and inter-quartile ranges for cumulative ventilator-free days during the 28 days following intervention. The EMS arm median was 6 days, with an inter-quartile range of 0 to 17; the control arm median was 0 days, with an inter-quartile range of 0 to 19.
Those summaries describe observed outcomes but do not supply an estimate of the treatment contrast with statistical uncertainty. No p-value, confidence interval, hazard ratio, or other inferential comparison is reported. The results therefore do not establish that EMS caused a difference in ventilator-free days. They also do not establish that the groups were equivalent or that any difference is absent. Lack of an inferential result is not the same as evidence of no effect.
The trial’s stated hypothesis concerned muscle strength and ventilator days, and grip power is listed as a secondary outcome. The registry record does not report a grip-power result in the registry record for this analysis. It likewise does not report details sufficient to determine how deaths, incomplete follow-up, or missing endpoint data were handled.
The trial was terminated, but the reason and its relationship, if any, to study results are not reported in the registry record. The posted safety counts include no serious adverse events, other adverse events, or deaths in the listed groups, but the small enrollment and unreported safety follow-up details limit what those counts can establish. Overall, the record offers a descriptive account of a limited number of participants, not a conclusive estimate of efficacy or safety.
13. Why This Trial Matters Statistically
This trial illustrates a common statistical distinction between a visible difference in descriptive summaries and a reliable estimate of a treatment effect. The posted medians differ, but the registry record does not report a formal between-arm analysis or an interval expressing uncertainty. Without that information, readers cannot assess how precisely the trial estimates the effect or whether the observed arm summaries are compatible with a range of possible underlying effects.
It also highlights why endpoint definitions matter. Ventilator-free days may summarize an important clinical course, but interpretation depends on how ventilation, death, recurrent ventilation, and incomplete follow-up are treated. The registry description identifies a 28-day period, yet the operational rules and analysis details are not reported in the registry record. Statistical summaries cannot compensate for uncertainty about what was measured.
The randomized design is relevant because it aims to make treatment groups comparable, but randomization alone does not guarantee a precise result. Enrollment was 13, and the study is listed as terminated. The record does not state the reason for termination, the planned enrollment target, or the rationale for the study size. This makes it especially important to distinguish the descriptive results from any unsupported claim of certainty.
Finally, zero recorded adverse events in small groups illustrate that observed counts and the underlying risk are not interchangeable. The trial provides a record of what was reported among enrolled participants, while leaving important questions about precision, analysis, and follow-up unanswered. These are useful lessons for interpreting small clinical trials and registry results generally.
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 enrolled total was 13, with 7 participants in the EMS arm and 6 in the control arm. This small enrollment limits the amount of information available for estimating differences and makes arm-level summaries potentially sensitive to individual outcomes. The registry record does not report a statistical comparison, confidence interval, or other measure of precision for the primary endpoint.
The study status is TERMINATED, but the reason for termination is not reported in the registry record. Planned enrollment, sample-size justification, and whether the study reached its intended recruitment target are not reported. The termination status alone does not show why the study stopped or whether the results influenced that decision.
The registry identifies the trial as randomized and unmasked, but does not describe random-sequence generation, allocation concealment, or blinding of outcome assessment. It also does not provide detailed eligibility criteria beyond the brief summary, or explain the practical delivery and adherence to the EMS and passive rehabilitation programs. These gaps make it difficult to assess how the study was conducted and how closely the recorded intervention descriptions match participants’ actual treatment.
The primary endpoint is described as cumulative ventilator-free days during the 28 days following intervention, but the detailed event rules are not reported. The record does not explain how death, recurrent ventilation, partial days, or missing measurements were handled. It also does not describe analysis populations, missing-data methods, or the prespecified statistical plan. No inferential comparison is posted, and no grip-power result is reported in the registry record for this analysis. The safety observation period and adverse-event collection methods are not reported either.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Electric Muscle Stimulation for Patients With Chronic Respiratory Failure — NCT01930643.
- Registry record last updated 2019-07-08; status last verified 2019-04.
- Results first posted 2019-07-08.
- 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
NCT01930643 is a randomized, unmasked, parallel-group trial sponsored by Mackay Memorial Hospital. It studied electric muscle stimulation for patients with chronic respiratory failure and critical illness myopathy. The record lists an enrollment of 13, with 7 participants in the EMS arm and 6 in the control arm. EMS was described as quadriceps stimulation using a programmed middle-frequency device; the control was routine passive rehabilitation.
The primary outcome was cumulative ventilator-free days during the 28 days following intervention. The reported medians were 6 days for EMS and 0 days for control, with inter-quartile ranges of 0 to 17 and 0 to 19, respectively. Grip power was listed as a secondary outcome. No inferential analyses are reported. The study began on 2013-08-21, primary completion is recorded as 2015-06, and status is TERMINATED. The reason for termination and key statistical and outcome-handling details are not reported in the registry record.