Acute Effects of a Flutter Device in COPD: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Acute Effects of a Flutter Device in COPD (NCT01832961), a randomized na study. The primary outcome is Airways Resistance (IOS).

2. Clinical Question

The clinical question concerns an acute physiological response, not a long-term change in COPD. The registry describes a randomized crossover design, in which participants may receive more than one intervention, but it does not report the intervention sequence, the timing between intervention periods, or the primary comparison used for analysis. Those details are important for understanding precisely what contrast the investigators intended to estimate.

The trial also included flutter exercises combined with a bronchodilator. The registry lists this intervention but does not give a corresponding arm description or state how the bronchodilator was incorporated into the primary analysis. It therefore does not establish whether the principal question was flutter versus sham, flutter with versus without bronchodilator, or another comparison.

The study population was restricted by the stated respiratory and medical exclusions. The registry record does not give further demographic or clinical characteristics, such as age, baseline COPD severity, or prior device use. Results, if available elsewhere, would need to be interpreted in relation to the study’s specific eligibility criteria and acute measurement setting.

3. Trial Design

The registry identifies this as a randomized, unmasked, crossover study of a flutter device in COPD. It records enrollment of 15 and lists three device-based interventions: flutter valve exercises, flutter-sham exercises, and flutter exercises with a bronchodilator. The trial status is completed. The registry gives a start date of 2013-04 and a primary completion date of 2013-12.

In general, randomization assigns treatment order or treatment allocation by chance, while a crossover design measures responses under more than one intervention in the same participant. This can make within-participant comparisons informative because each participant can serve as their own reference. However, valid interpretation depends on the actual sequence, adequate separation between intervention periods when needed, and appropriate handling of period and carryover effects. The sequence, washout arrangements, and any period-effect analysis are not reported in the registry record.

The record identifies masking as none. Readers should therefore not assume that participants or study personnel were unaware of which device or exercise condition was used. The record does not specify who performed the measurements or whether outcome assessors were masked.

The registry describes flutter-valve and flutter-sham sessions as 30 minutes of breathing exercises. It also defines the primary outcome measurement schedule as baseline, after breathing exercises with a flutter or flutter-sham device, and after 20 minutes of rest. It notes that no data were collected for the flutter-sham control group after 20 minutes of rest. The precise timing and measurement schedule for the bronchodilator intervention are not reported in the registry record.

The registry does not report the allocation sequence, sample-size justification, planned statistical model, or analysis population. Although it states enrollment, that number alone does not describe how many participants contributed usable measurements to each outcome or comparison. The trial is listed as completed, but the registry record does not include numerical primary outcome results with which to assess the size or precision of any treatment contrast.

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.

First Intervention

Washout

Second Intervention

Third Intervention

Analysis population for the primary outcome, as defined in the registry: Patients with COPD, without upper respiratory tract infection or treatment with antibiotics within 4 weeks prior the study; without acute dyspnea or hemoptysis, and no recent history of rib fractures or pneumothorax. In the Flutter-sham Control group after 20 minutes of rest - no data was collected.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Airways Resistance (IOS), measured over Baseline test, after breathing exercises with flutter or flutter-sham device and after 20 minutes of rest.

The primary endpoint is airways resistance measured by impulse oscillometry, reported in kPa/L/s. The registry specifies that the outcome is a mean with standard deviation and describes measurements at baseline, after breathing exercises with a flutter or flutter-sham device, and after 20 minutes of rest. It also states that no flutter-sham control data were collected after the rest period.

In general, impulse oscillometry measures aspects of the mechanical resistance encountered as air moves through the respiratory system. It uses oscillations during breathing rather than relying solely on a forced blow. The study description motivates this measurement by noting that standard spirometry assesses larger-airway function and may not assess small airways, which are relevant to COPD. That rationale explains why the investigators selected an oscillometry-based outcome; it does not establish that any particular device changes resistance.

A mean describes the average measured value within a group or condition, while a standard deviation describes the spread of individual measurements around that mean. These summaries can help characterize a continuous outcome, but they do not by themselves show the estimated difference between interventions or the uncertainty around that difference. A confidence interval for a contrast, a test result, and the underlying outcome summaries are not reported in the registry record.

The missing post-rest measurement for the flutter-sham control condition limits the set of comparisons that can be made across all stated time points. The registry record does not explain why those measurements were not collected or how the missing condition was handled analytically. Interpretation should therefore remain tied to the measurements actually described, without assuming a complete set of repeated observations.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization and crossover are features of the trial design; they are not, on their own, a complete statistical analysis plan. In general, random allocation helps prevent systematic differences in treatment assignment, while crossover designs permit comparisons of more than one condition within a participant. Such designs require careful attention to the order in which conditions occur and to whether an earlier condition could influence a later measurement. The registry record does not report the intervention sequence, washout arrangements, or planned method for accounting for period or carryover effects.

What does a mean and standard deviation describe?

The primary outcome is identified as a mean of a continuous measure, with standard deviation as its dispersion measure. In general, the mean describes the central average of observed values, and the standard deviation describes how widely individual values vary around that average. A standard deviation is not the same as the standard error: the former describes variability among measurements, while the latter concerns the precision of an estimated mean. The registry record does not report numerical means or standard deviations for the primary outcome.

For a treatment comparison, the estimated difference between conditions is usually more directly relevant than either condition’s mean alone. A confidence interval around that difference conveys a range of values compatible with the data under the analysis assumptions. In general, a narrow interval indicates greater precision than a wide interval. Neither a contrast estimate nor its confidence interval is reported for airways resistance in the registry record, so the effect size and precision cannot be evaluated.

Why does the crossover structure matter?

In general, a crossover analysis should respect the fact that measurements from the same participant are related. Treating repeated observations as if they came from unrelated people can misrepresent uncertainty. Analyses may account for participant-level pairing and may consider period or sequence effects, depending on the design. The registry record does not identify the statistical model, the unit of analysis, or how within-participant correlation was handled. It also does not provide enough detail to establish whether each participant completed every intervention condition.

The listed measurement schedule includes baseline, post-exercise, and post-rest observations. These are repeated time points, but the registry record does not state whether the primary analysis compared change from baseline, post-exercise values, or another summary. It also does not report how multiple measurements within a participant were combined or modeled. Those choices affect the meaning of an estimate and should not be inferred from the endpoint description alone.

How should missing measurements be considered?

The registry explicitly says that no data were collected for the flutter-sham control group after 20 minutes of rest. This is a structurally absent measurement condition as described in the record; it should not be treated as an observed value or assumed to be zero. In general, missing-data methods depend on why observations are unavailable and on the analysis objective. The registry record does not give a reason for the absent measurements or describe any imputation, exclusion, or sensitivity analysis.

The record lists enrollment and gives adverse-event group counts, but it does not report the number of participants with usable primary-outcome measurements at each time point or the analysis population. In general, an intention-to-treat analysis includes participants according to randomized assignment, while a per-protocol analysis uses criteria based on treatment adherence or protocol completion. The registry record does not identify either approach, so the population underlying any primary result cannot be determined.

What can significance testing and planning calculations establish?

In general, a p-value describes how surprising data at least as incompatible with a specified null hypothesis would be under that hypothesis and the analysis assumptions. It does not measure the probability that a treatment effect is real, and it does not describe the clinical importance or precision of an estimate. No primary-outcome p-value is reported in the registry record.

The registry describes planning illustrations based on a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects expressed as fractions of an observed effect. These are planning assumptions, not evidence of the trial’s original sample-size justification. The registry record does not report numerical planning estimates. Such illustrations, when presented, are hypothetical participant requirements under stated assumptions and are not observed power or a retrospective measure of whether the trial detected an effect.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and several secondary outcomes: exhaled nitric oxide, forced expiratory volume at 1 second, forced vital capacity, cough, secretion volume, and secretion purulence score. It also reports 8 outcome measures and 5 analyses. The relationship between those counts, outcomes, time points, and planned comparisons is not reported in the registry record.

In general, testing multiple outcomes, time points, or contrasts creates multiplicity: the more statistical questions addressed, the greater the chance of obtaining a seemingly unusual result by chance if each is interpreted independently. Common approaches include prespecifying a primary contrast, adjusting for multiple testing, or treating secondary analyses as exploratory. The registry record does not report a multiplicity adjustment, a testing hierarchy, or which analyses were confirmatory.

The record describes a missing post-rest measurement for the flutter-sham control group. It does not report why those data were not collected, whether other measurements were missing, or how missing observations were handled. No analysis population or participant flow for the primary outcome is reported in the registry record. Therefore, the amount and pattern of missing primary-outcome data beyond the stated uncollected condition cannot be assessed.

In general, missing-data assumptions matter because estimates can depend on whether absent observations differ systematically from observed ones. A complete-case analysis, imputation method, or sensitivity analysis would each require information about the data and assumptions. None is described in the registry record. The record also does not report a statistical analysis plan, interim analyses, or whether the reported outcome analyses followed a prespecified strategy. These absences prevent a full assessment of how multiplicity and missingness were addressed.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry reports serious adverse events, other adverse events, and deaths separately for Flutter Exercises, Flutter-sham, and Flutter+Bronchodilator. For each listed group, 15 were reported at risk for serious adverse events and 0 were reported as affected; the same at-risk and affected figures are reported for other adverse events. Deaths are recorded as 0 in each group. No top serious-event terms are listed.

These are descriptive registry counts. They do not, by themselves, show whether the groups differed in safety, establish the cause of an event, or rule out harms that were not recorded. The record does not provide event definitions, a detailed observation period, severity grading beyond the serious-versus-other distinction, or information about how events were collected. It also does not report a statistical comparison of adverse events.

The study is described as a crossover trial, but the registry presents safety figures by intervention group. It does not explain whether those figures represent randomized assignment, exposure to each condition, or another counting method. They should therefore be read as the registry’s reported group summaries rather than as a basis for reconstructing the trial’s safety analysis.

Zero recorded events means that none were reported in these registry summaries; it is not proof that an intervention has no risk. Safety interpretation also depends on the number of participants observed, follow-up duration, and completeness of event ascertainment. The registry record does not provide enough detail to assess those factors fully.

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

This trial addresses an acute physiological question: whether airways resistance measured by impulse oscillometry differs in relation to flutter-device breathing exercises, sham exercises, or rest. Its randomized crossover design and stated outcome schedule indicate an effort to compare responses under different conditions. The registry record does not report the numerical primary-outcome results, so it does not establish the direction, size, or precision of a difference.

The result therefore cannot be interpreted as evidence that the device did or did not change airways resistance. No numerical comparison, confidence interval, or primary-outcome test result is reported in the registry record. A missing result is not a finding of no effect, and it is not evidence that two conditions are equivalent.

The trial’s endpoint is a physiological measure rather than a reported long-term clinical outcome. In general, a change in a measured physiological variable does not automatically establish a meaningful change in symptoms, daily function, disease course, or other outcomes. The registry lists secondary measures such as spirometry, cough, and secretion characteristics, but it does not report their numerical results either. No broader clinical conclusion can be drawn from the endpoint description alone.

The record lists a third intervention combining flutter exercises and a bronchodilator, but does not report its primary-outcome results or explain its role in the main contrast. It also notes that the flutter-sham control group had no measurement after 20 minutes of rest. Those features limit what can be inferred about comparisons across interventions and time points from the registry description.

The study’s eligibility criteria define a specific COPD population and exclude several clinical circumstances. In general, findings from a restricted sample may not apply to people who would not have met those criteria. The registry does not give additional participant characteristics that would help assess generalizability. The appropriate conclusion is limited: the record describes the trial question and measurement plan, but does not report enough outcome data to judge the observed response.

13. Why This Trial Matters Statistically

This study is statistically interesting because it combines a randomized crossover design with repeated measurements of a continuous physiological outcome. In general, a crossover structure can make within-participant contrasts useful, but it also requires analysis that accounts for paired observations, intervention order, and potential carryover. The registry record identifies the design but does not report how those issues were handled.

The outcome schedule raises a second design consideration. Measurements were described at baseline, after breathing exercises, and after 20 minutes of rest, but the record states that the flutter-sham control group had no post-rest data. Missing a condition at a planned time point can restrict the contrasts available and complicate interpretation of time-related changes. The reason for the uncollected measurements and their treatment in the analysis are not reported in the registry record.

The trial also illustrates why an endpoint definition is not a substitute for an effect estimate. The record names airways resistance, its unit, and its measurement method, but does not report means, standard deviations, contrasts, or confidence intervals. Without those results, neither the size of an observed response nor its precision can be assessed. A design and outcome description alone cannot answer the clinical question.

Finally, the registry lists several secondary outcomes and multiple analyses. In general, a clear prespecified analysis strategy helps readers distinguish a primary test from exploratory comparisons and understand how multiple testing was addressed. The statistical plan and multiplicity approach are not reported in the registry record. This makes the record useful for identifying the methodological questions that matter, while leaving the trial’s primary statistical findings unavailable for evaluation.

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 registry record provides limited information for interpreting the trial beyond its design and endpoint description. It does not report numerical primary or secondary outcome results, treatment contrasts, confidence intervals, or p-values. Consequently, the magnitude and precision of any observed response cannot be assessed.

Important crossover details are absent. The intervention sequence, period structure, washout arrangements, and methods for addressing period or carryover effects are not reported in the registry record. The record also does not specify the primary contrast or explain how the third intervention, flutter with bronchodilator, fits into that contrast.

The measurement schedule is incomplete for at least one stated condition: no post-rest data were collected for the flutter-sham control group. The reason for this is not reported. The record does not explain how the missing condition was handled analytically or provide a participant flow showing available primary-outcome measurements at each time point.

The registry does not report the statistical analysis plan, analysis population, sample-size justification, or multiplicity strategy. It also lacks additional characteristics of participants that could help readers judge how closely the enrolled population resembles other COPD populations. The stated eligibility restrictions are useful, but they do not fully describe the sample.

Safety summaries report zero serious adverse events, other adverse events, and deaths in each listed group, but the event-collection procedures, follow-up duration, and detailed definitions are not reported. These limitations mean that the registry record supports a description of the planned question and selected design features, but not a comprehensive assessment of efficacy, precision, safety, or generalizability.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Acute Effects of a Flutter Device in COPD — NCT01832961.
• Registry record last updated 2020-02-27; status last verified 2020-02.
• Results first posted 2020-02-27.
• 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.

18. Record Summary

The registry record describes a completed randomized, unmasked crossover study of acute flutter-device effects in COPD. Enrollment is listed as 15. The interventions are flutter valve exercises, flutter-sham exercises, and flutter exercises with a bronchodilator. The primary endpoint is mean airways resistance measured by impulse oscillometry in kPa/L/s.

The record describes measurements at baseline, after flutter or flutter-sham breathing exercises, and after 20 minutes of rest; it states that no post-rest data were collected for the flutter-sham control group. It also lists secondary outcomes involving exhaled nitric oxide, spirometry, cough, and secretion measures. Numerical results for the primary and secondary outcomes, along with the primary statistical contrast and analysis plan, are not reported in the registry record.

Safety summaries report 0 serious adverse events, 0 other adverse events, and 0 deaths for each listed intervention group. The study began in 2013-04 and reached primary completion in 2013-12. The registry record describes the study question and design but does not provide enough outcome information to assess the estimated effect or its precision.