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 Testing of a Valsalva Assist Device (VAD) in Healthy Volunteers Performing a Valsalva Manoeuvre (NCT03298880), a na na study. The primary outcome is Assessing Heart Rate During the Supine and Modified VM and Assessing Heart Rate While Using the VAD and Manometer.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03298880 |
| Phase | NA |
| Condition | SVT, Vagal Bradycardia |
| Allocation | Not applicable (single group) |
| Design model | Sequential |
| Masking | None (open label) |
| Enrollment | 75 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Exeter |
| Results posted | Yes |
2. Clinical Question
The study asks whether heart-rate responses differ when healthy volunteers perform supine or modified Valsalva manoeuvres using a Valsalva Assist Device (VAD) or a standard manometer. It also concerns whether the device can deliver the intended strain and whether the manoeuvre is associated with the expected physiological response described in the registry record: lowered heart rate.
Population
Healthy volunteers performing repeated Valsalva manoeuvres. The registry lists SVT and vagal bradycardia as conditions, but describes the study participants as healthy volunteers rather than patients being treated for those conditions.
Intervention
A Valsalva Assist Device, which provides resistance to exhalation, used for supine and modified manoeuvres. The registry also describes repeated manoeuvres across the device and manometer procedures.
Comparator
A standard manometer used during supine and modified manoeuvres. The allocation is listed as NA, and the study is not described as a randomized, like-for-like comparison.
Primary question
How does heart rate during and after the manoeuvre vary by posture modification and by use of the VAD versus the manometer? The registry describes heart-rate measurement but does not report the condition-specific estimates or a statistical comparison.
This is a physiological device-testing question, not a clinical treatment comparison. The intended focus is whether the device can provide strain and how heart rate responds during the manoeuvres. The registry also identifies strain duration and peak sustained pressure as secondary outcomes. Those outcomes address device performance, while the heart-rate outcome describes a physiological response. Without reported group or condition estimates, the registry record does not establish the size, precision, or direction of any differences between procedures.
3. Trial Design
The registry describes a completed, sequential study sponsored by the University of Exeter. Enrollment is listed as 75. The participants are described as healthy volunteers, and the arm description refers to repeated Valsalva manoeuvres. The listed procedures include a supine VAD manoeuvre, a supine manometer procedure, a modified VAD manoeuvre, and a modified manometer procedure. The registry calls these “Four VM's” and says the procedures are repeated.
Allocation is listed as NA, masking as none, and the model as sequential. This is therefore not described as a randomized trial with masked assignment. The registry record does not explain the sequence in which participants received procedures, whether that sequence was fixed or varied, or how order effects were handled. It also does not set out a separate parallel control group. The procedures should not be interpreted as randomized arms or as independent groups in a conventional treatment comparison.
The primary outcome timeframe is listed as 3 minutes, described as 4 repetitions of 45 seconds. The registry describes heart-rate assessment during supine and modified manoeuvres and while using the VAD and manometer. It also lists secondary outcomes on achieving a 15-second strain duration and on peak sustained pressure. The registry does not report the observed results for these outcomes or explain whether every volunteer completed every procedure.
The study status is completed. The start and primary-completion dates are listed as 2017-11-01 and 2018-02-05, respectively. Phase is recorded as NA. A detailed protocol, sample-size justification, and full statistical analysis plan are not reported in the registry record.
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 | Four VM's |
|---|---|
| STARTED | 75 |
| COMPLETED | 75 |
| 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.
| Characteristic | Unit | Four VM's |
|---|---|---|
| Participants analysed | 75 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 75 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 26.19 (19 to 55) |
| Sex: Female, Male: Female | Participants | 45 |
| Sex: Female, Male: Male | Participants | 30 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United Kingdom | participants | 75 |
6. Primary Endpoint
The registry lists the primary outcome as Assessing Heart Rate During the Supine and Modified VM and Assessing Heart Rate While Using the VAD and Manometer, measured over 3 minutes (4 repetitions of 45 seconds).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | beat per minute |
| Endpoint classification | not reduced to a single comparison |
The registered primary outcome concerns heart rate during supine and modified Valsalva manoeuvres, with procedures using the VAD and a manometer. The registry describes measuring the longest RR interval—the interval between successive R waves—during the 15 seconds of the manoeuvre and the 15 seconds afterwards, using a 3-lead ECG. It also describes measuring baseline heart rate during the 15 seconds before the manoeuvre. Heart rate in beats per minute is derived from the RR interval.
Heart rate is used as a physiological measure of the response to a Valsalva manoeuvre. The registry's rationale refers to evaluating lowered heart rate, and the outcome description links the ECG measurement to that response. RR interval and heart rate are related measures: a longer interval between beats corresponds to a lower rate. The registry does not, however, report the resulting estimates by procedure or specify a single contrast that would summarize the primary question.
The outcome is reported as a mean with a full range. Its description says that a higher number is better and gives a minimum of 25.9 and a maximum of 33.6, but does not clarify how those values map to specific procedures or whether they represent an overall range or a particular result. They should not be treated as a comparison between the VAD and manometer. Condition-specific means, uncertainty estimates, and the statistical comparison are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study question and describes how heart rate was intended to be measured. It does not report the primary outcome estimates for the VAD and manometer procedures, the supine and modified manoeuvres, or a statistical contrast among them. Consequently, the relative heart-rate response cannot be characterized from the record's reported results. The value range mentioned in the endpoint description is not assigned to particular procedures and is not enough to identify a difference or its direction.
The record also does not report confidence intervals, p-values, or other uncertainty measures for the primary outcome. A point estimate alone would describe an observed value; uncertainty measures would help show how precisely an estimate is known and how compatible the data are with a range of possible effects. Without estimates and uncertainty, the precision and statistical evidence for any difference are not assessable from the registry record.
The design description matters for interpretation. Allocation is listed as NA, masking as none, and the model as sequential. The arm description refers to repeated procedures rather than a randomized parallel-group comparison. Responses within a participant could be related across procedures, and the order of procedures could matter. The registry does not report how the sequence was set or whether the analysis accounted for within-participant dependence or possible order effects. It would therefore be inappropriate to read the study as a randomized comparison or to infer that each procedure was evaluated in a separate, comparable group.
The secondary outcomes address device performance: the percentage of participants achieving a 15-second strain duration and peak sustained pressure. Their outcome titles are listed, but their observed estimates and comparisons are not reported in the registry record. The primary endpoint alone would not answer every question about whether the device achieved the intended strain.
The safety record lists no serious events and 17 other events among the group for which 75 were at risk. These counts are descriptive registry entries; they do not provide event types, timing, relation to a procedure, or comparative safety estimates. They cannot establish whether event rates differed between procedures.
The record lists two analyses and three outcome measures, but it does not provide the analysis methods or identify which comparisons those analyses cover. Neither a statistically significant finding nor evidence of equivalence can be inferred from the absence of reported estimates. The appropriate conclusion is that the registry describes a device-testing study and its intended measurements, while the posted results do not give enough detail to quantify or test the primary comparison.
9. Statistical Methods Explained
Statistical interpretation depends on distinguishing the study's design description, its measurements, and its reported results. The registry describes a sequential study with repeated manoeuvre procedures, but does not provide a full statistical analysis plan. The methods below explain how common statistical ideas would apply in general; they do not assert that the investigators used any particular method unless it is explicitly described in the record.
What does a mean with a full range tell a reader?
A mean gives a summary of observed values, while a full range reports the lowest and highest values in the set being summarized. The range communicates the span of the observations, but it does not show how values are distributed within that span. A range can be affected by extreme observations and does not, on its own, quantify uncertainty in the mean. The registry lists the primary parameter as a mean with a full range and gives a minimum of 25.9 and a maximum of 33.6 in the outcome description. It does not identify those bounds by procedure or provide the corresponding condition-specific means. The record therefore does not support a direct comparison of heart rate across procedures.
Why does the repeated, sequential design matter?
In a repeated-measures design, the same participant may contribute measurements under more than one procedure. Those measurements are often statistically related because they come from the same person. A method that treats every measurement as independent can misrepresent uncertainty when within-person correlation is present. A paired analysis or a model that accounts for participant-level dependence can be appropriate in general, depending on the design and data structure. The registry does not report the analysis method, the sequence of procedures, or how repeated observations were handled.
Sequence can also matter. If participants complete procedures one after another, fatigue, learning, recovery, or carryover could influence later measurements. These are general design considerations, not claims that such effects occurred in this study. The registry's sequential label does not by itself establish whether procedure order was fixed, counterbalanced, or randomized. It does not report whether order effects were evaluated.
How should uncertainty be understood?
A confidence interval is a general way to express the precision of an estimated quantity. It gives a range of values compatible with the data and the method used to construct the interval. A narrow interval indicates greater precision than a wide interval, but it does not establish clinical importance by itself. A p-value, in general, measures how unusual data at least as incompatible with a specified null hypothesis would be under that hypothesis and the statistical model. It does not measure the probability that the null hypothesis is true, and it does not show the size or practical importance of an effect. The registry record does not report confidence intervals or p-values for the primary outcome.
For a device comparison, effect estimates should be accompanied by uncertainty and tied to a clearly stated contrast. A comparison might concern a difference between procedures, a change from baseline, or another defined quantity. These answer different questions. The primary outcome description mentions baseline heart rate and measurements during and after manoeuvres, but the registry does not state a single contrast or provide the corresponding estimates. No contrast should be reconstructed from the descriptive text alone.
What do the planning assumptions mean?
The record includes a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It describes the target effect as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed findings and not observed power. The record does not give a trial-specific sample-size justification or explain how the study's sequential, repeated-procedure design relates to the illustration's equal-allocation assumption. A calculation based on an assumed effect does not show that the trial had adequate precision for its actual comparisons.
In general, over-dispersion means that variability in the data exceeds what a chosen model expects. Ignoring it can make standard errors too small and confidence intervals too narrow. Whether over-dispersion is relevant depends on the outcome and model; the registry does not report a model or diagnostic assessment. Likewise, the record does not say whether the primary outcome was adjusted for baseline heart rate or other variables. No adjustment method should be attributed to the study without that information.
The registry lists two analyses and three outcome measures, but does not describe the hypotheses, model specifications, missing-data approach, or analysis populations. Those omissions limit the ability to assess whether the statistical methods matched the repeated-measures design and whether the reported evidence would be robust to alternative reasonable analyses. The posted record does not provide results sufficient to evaluate those questions.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures and two analyses, but does not describe how the analyses map to outcomes, which comparisons were planned, or whether any outcome was designated for a particular confirmatory test beyond the primary outcome title. It does not report a multiplicity procedure. When several outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase; general approaches include prespecifying a primary contrast, adjusting significance thresholds, or treating secondary analyses as exploratory. The record does not indicate which, if any, approach was used.
The primary outcome describes comparisons involving posture and device, but the registry does not specify the exact statistical contrast or whether interaction between these factors was assessed. It also does not say whether baseline heart rate was used as a covariate or how repeated measurements were incorporated. These analysis details are not reported in the registry record.
Missing-data handling and analysis populations are also not reported in the registry record. It is not stated whether all enrolled volunteers completed every manoeuvre, how incomplete ECG traces were handled, whether any observations were excluded, or whether analyses used all available measurements or a defined subset. The registry record therefore does not permit assessment of potential bias due to missing or excluded data. It also does not provide enough information to determine whether the reported analysis population matched enrollment.
These are reporting gaps, not proof that the investigators failed to plan or perform the relevant analyses. They mean that readers cannot verify from the registry record how multiplicity, incomplete observations, or repeated measurements were handled.
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 |
|---|---|---|---|
| Four VM's | 0 | 75 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Four VM's | 0 of 75 |
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 |
|---|---|
| Four VM's | 17 of 75 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Four VM's |
|---|---|---|
| headache | Nervous system disorders | 17 of 75 |
The adverse-event entry lists 75 participants at risk for serious events and 0 serious events. For other events, it lists 75 at risk and 17 affected. These are the registry's recorded counts for the group titled “Four VM's.” The registry does not list serious-event terms, and it does not describe the types of the other events in the information.
These entries should be read as descriptive counts, not as a comparison of the VAD with the manometer. The record does not assign events to a particular procedure, report when they occurred, state whether an event was judged related to a device or manoeuvre, or provide separate event counts by procedure. It also does not explain how repeated procedures were handled when recording events. The counts therefore cannot identify a procedure-specific risk or establish a difference in safety between the device and manometer.
A recorded count of 0 serious events means that none were entered in this registry category for the listed group; it does not prove that a procedure has no risk. The entry for 17 other events is not interpretable as a particular type of harm without event descriptions. The registry record does not report additional detail needed for a fuller safety assessment.
12. What the Result Does, and Does Not, Mean
This study addresses a relevant measurement and device-performance question: whether a VAD can provide resistance during Valsalva manoeuvres and how heart rate responds under different procedures. Its registered outcomes include heart-rate assessment, strain duration, and peak sustained pressure. The record identifies healthy volunteers as the study population and describes repeated supine and modified manoeuvres using a VAD or manometer.
What the posted record does not establish is the size or precision of any difference between these procedures. It does not report condition-specific heart-rate estimates, confidence intervals, p-values, or the observed results for the listed secondary outcomes. The minimum and maximum mentioned in the primary outcome description are not linked to particular conditions, so they cannot be used to infer which device or manoeuvre produced a higher or lower response.
The record also does not establish equivalence or non-equivalence between the VAD and standard manometer. Those conclusions require a defined comparison and suitable estimates with uncertainty; a lack of reported comparative results is not evidence that procedures are alike. Nor does this healthy-volunteer device-testing record demonstrate a clinical effect in people with SVT or vagal bradycardia. Those terms appear as listed conditions, while the described participants are healthy volunteers.
Accordingly, the registry supports a description of the study's purpose, procedures, and intended measures, but not a conclusion about the magnitude, statistical significance, or clinical importance of the primary comparison. The safety counts are likewise limited to descriptive entries and do not provide procedure-specific estimates.
13. Why This Trial Matters Statistically
Device studies often need to answer more than whether a physiological measurement changes. They may also need to establish that a device can deliver a specified manoeuvre or pressure consistently. This record reflects that distinction: the primary outcome concerns heart rate, while the secondary outcomes concern achieving a 15-second strain duration and peak sustained pressure. Separating device performance from physiological response helps clarify what each outcome can address.
The design also highlights a statistical issue common in procedural studies. When the same volunteer performs multiple manoeuvres, observations from different procedures may be linked within the person. The sequence can matter as well. A clear account of procedure order and analysis is important for understanding whether a comparison reflects the device, posture, repetition, or other features of the procedure. The registry identifies a sequential model but does not provide those details.
Another important distinction is between a study's stated purpose and its reported evidence. The record describes a prototype and the intended measurements, but does not include the primary estimates or uncertainty needed to judge the size and precision of a comparison. A carefully defined outcome is valuable, but readers also need transparent results and a statistical contrast that matches the design.
The planning illustration has a different role from observed evidence. Sample-size calculations can inform future planning under stated assumptions, but they do not replace outcome estimates or demonstrate observed power. Overall, this record is a useful example of why design details, outcome reporting, and uncertainty all matter when evaluating a device study.
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 leaves several trial-specific questions unresolved. Although it labels the study sequential and describes repeated manoeuvres, it does not specify the procedure order, how order was determined, or whether every volunteer completed every procedure. It does not report whether measurements were paired or how dependence among repeated observations was handled. These details are important for interpreting comparisons in a repeated-procedure study.
The primary outcome description includes baseline, during-manoeuvre, and post-manoeuvre measurements, but does not specify the exact primary contrast. It also states that a higher number is better while describing a heart-rate measure in a study rationale focused on lowered heart rate. The record does not clarify how this direction statement should be applied to the different measurements or procedures. The stated minimum and maximum are not assigned to conditions, and condition-specific results are not reported.
Secondary outcomes are named, but their estimates and comparisons are not included in the registry information described. The record does not report the statistical model, adjustment methods, missing-data handling, analysis populations, or multiplicity approach. It also does not provide confidence intervals or p-values for the primary outcome. These gaps prevent an assessment of precision and make it difficult to evaluate whether the analysis reflected the design.
The safety listing provides counts without event descriptions or procedure-specific attribution. Finally, the sample-size information is described as a planning illustration, not as the trial's own design justification. These limitations concern what is reported in the registry record; they do not establish what may have been specified or analyzed outside that record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Testing of a Valsalva Assist Device (VAD) in Healthy Volunteers Performing a Valsalva Manoeuvre — NCT03298880.
- Registry record last updated 2021-06-10; status last verified 2021-06.
- Results first posted 2021-06-10.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT03298880 is a completed, sequential study sponsored by the University of Exeter, enrolling 75 healthy volunteers. The registry describes repeated supine and modified Valsalva manoeuvres using a Valsalva Assist Device or standard manometer, with masking listed as none and allocation as NA.
The primary outcome concerns heart rate measured with a 3-lead ECG. Secondary outcomes concern achieving a 15-second strain duration and peak sustained pressure. The registry record does not report condition-specific primary estimates, uncertainty measures, or the statistical comparison. It also does not describe the detailed analysis plan, missing-data handling, or the procedure sequence. Safety entries list 0 serious events and 17 other events among the group for which 75 were at risk; event types and procedure-specific attribution are not reported.