Tourniquets Increase Proximal Pressure: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Tourniquets Increase Proximal Pressure (NCT05324306), a na na study. The primary outcome is Systolic Blood Pressure During Application of the CAT Tourniquets.

2. Clinical Question

The question is a physiological proof-of-concept question, not a direct test of outcomes during cardiac arrest. The study description proposes that restricting peripheral blood flow might route limited oxygenated blood toward the heart and brain during CPR. However, the participants described for this study are healthy humans, and the primary endpoint is arm-measured systolic blood pressure. The record does not report measurements of coronary or cerebral perfusion, CPR performance, survival, or neurologic outcomes. Therefore, the registered question concerns a change in a blood-pressure measure under the study procedure, rather than whether the proposed approach improves outcomes after cardiac arrest.

3. Trial Design

This is a completed, single-group study, with allocation listed as not applicable and masking listed as none. The intervention was application of CAT tourniquets to both lower extremities. Participants had baseline blood pressure measured in their upper extremities, then had blood pressure measured again in the upper extremities after tourniquet deployment. The sequence was repeated 3 times. The record describes the primary outcome as the average of those repetitions.

The design uses participants as their own reference: the post-deployment measurement is interpreted in relation to the baseline measurement rather than to measurements in a separate untreated group. That structure can address whether blood pressure changes across the recorded procedure. It does not provide a randomized, concurrent comparison with participants who did not receive tourniquets. The registry record does not report a washout procedure, the order of measurements beyond baseline followed by application, or whether the baseline was remeasured before each repetition.

Each tourniquet application lasted 5 minutes, and participants rested 3-5 minutes between repetitions. The registry lists enrollment of 27. Its brief description says the investigators planned to recruit 30 healthy participants; it does not explain the difference between that planned recruitment and the listed enrollment. The record gives a start date of 2022-02-01, a primary completion date of 2023-06-01, and status of completed.

The record does not report a randomization method, allocation concealment, a sample-size justification, or a detailed statistical analysis plan. It lists no analyses. Thus, the design and measurement sequence can be described, but the statistical approach used to summarize or test the blood-pressure changes is 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

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 Systolic Blood Pressure During Application of the CAT Tourniquets, measured over the average of 3 repetitions is reported; the duration of each tourniquet application was 5 minutes and participants rested 3-5 minutes between each repetition.

The primary endpoint is systolic blood pressure measured in the arms during application of the CAT tourniquets to the lower extremities. It is reported in mmHg, with the average of 3 repetitions identified as the summary measure. The endpoint description defines successful application in normal physiology in healthy humans as a minimum increase in blood pressure of 10 mmHg.

Systolic blood pressure is the pressure recorded during the heart’s contraction. In this study it serves as a proximal, measurable physiological marker during the intervention. The proposed rationale is that occluding peripheral circulation could change pressure in a more proximal location. The endpoint therefore addresses whether an arm blood-pressure measure changes during the tourniquet procedure; it is not a direct measure of blood flow to the heart or brain.

A prespecified target can make the intended interpretation clearer: the record identifies 10 mmHg as the minimum increase that would meet its endpoint definition. But a definition of success is not itself evidence that the target was reached. The registry record does not report baseline values, post-application values, the observed change, variability, or the proportion meeting that target. It also does not report how the endpoint was analyzed statistically.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a single-group, before-and-after measurement procedure. Its primary endpoint uses systolic blood pressure measured in the arms, with the average of 3 repetitions reported as the intended summary. The record does not provide outcome values or an analysis for that endpoint. The statistical concepts below explain how such data are generally interpreted; they do not describe analyses reported for this study.

What does a within-participant comparison mean?

In a within-participant comparison, each participant’s measurement after an intervention is considered in relation to that participant’s own baseline. This can be useful when people differ in their usual blood pressure, because a person’s baseline provides a reference for that person rather than relying only on a comparison between different groups. The study’s described sequence follows this general structure: measure arm blood pressure at baseline, apply tourniquets to both lower extremities, and measure arm blood pressure again.

A before-and-after comparison does not, by itself, show that the intervention caused a change. General statistical consideration: pressure can vary over time, and measurement conditions or repeated procedures can influence observed readings. A control group measured over the same period can help distinguish changes associated with the intervention from changes that would have happened otherwise. This record does not describe a separate control group. It also does not report whether the analysis accounted for the repeated measurements or for possible period or carryover effects.

Why average repeated measurements?

Averaging repeated readings is a common way to summarize measurements when the goal is to reduce the influence of short-term measurement variability. Here, the record says the average of 3 repetitions is reported. An average can make the endpoint easier to summarize, but it does not show how much the readings differed from one repetition to another. A measure of variability, the individual readings, or a plot of their distribution can help readers assess whether the average represents a consistent pattern or conceals variation.

General statistical consideration: measurements from the same participant are related, so they should not ordinarily be treated as if they came from unrelated people. Analyses of repeated measurements may account for that dependence directly. The registry record does not report whether such an analysis was used, or whether the endpoint was analyzed only as an average per participant.

What would an estimate and confidence interval show?

An estimated change would describe the size and direction of the observed difference between the post-deployment measurement and baseline. A confidence interval would express the uncertainty around that estimate under the assumptions of the analysis. A narrower interval indicates greater precision, while a wider interval indicates less precision. A confidence interval is not a guarantee that the true value lies within its limits; it is a statistical summary whose interpretation depends on the study design and analysis assumptions.

The registry record does not report an estimated change or a confidence interval. It also does not report a p-value. These omissions mean that readers cannot assess either the magnitude of the recorded change or its statistical uncertainty from the registry record. A p-value, if reported, would not by itself convey the size or practical importance of a change; it would need to be considered alongside an estimate, its uncertainty, the endpoint definition, and the design.

How should the threshold be understood?

The endpoint description identifies a minimum increase of 10 mmHg as the criterion for successful application. This is a stated target for interpreting the endpoint, not a result. A complete report would need to show the observed measurements and explain how the target was evaluated. For example, readers would need to know whether the criterion applies to an average change, how participant-level measurements were summarized, and how uncertainty was considered. Those details are not reported in the registry record.

What can sample-size planning show?

Sample-size calculations are planning tools that estimate the amount of information needed to detect a specified effect under stated assumptions. They are not outcome findings and do not establish that a study has detected an effect. A planning calculation based on an observed effect is especially distinct from a justification documented before the study: it uses an effect estimate as an input and describes a hypothetical design under assumptions. The registry record does not report the study’s own sample-size justification or a statistical analysis plan. Any planning illustration should therefore be read as an illustration, not as evidence about the study’s observed result or as observed power.

General statistical consideration: planning calculations depend on assumptions about the effect of interest, outcome variability, significance level, allocation, and analysis. If these assumptions are not appropriate, the calculation may not describe the performance of a future study. The registry record does not report a protocol-level sample-size rationale or the observed endpoint statistics needed to evaluate such assumptions.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure: systolic blood pressure during application of the CAT tourniquets. It does not list any analyses. The record does not report whether additional outcomes were tested, whether multiple comparisons were planned, or how multiplicity would be handled. A multiplicity adjustment can be relevant when several outcomes, time points, subgroups, or statistical tests are examined, because repeated testing can increase the chance of a seemingly notable result arising by chance. Whether that issue applies to the analysis cannot be determined from the registry record.

The record describes 3 repetitions and says the average is reported, but does not explain how missing or unusable readings would be handled. It does not report how many participants contributed endpoint data, whether any measurements were missing, or whether any participants were excluded from the endpoint analysis. The listed enrollment is 27, but enrollment alone does not establish the analysis population or the completeness of the outcome data.

The registry record does not describe an intention-to-treat population, a per-protocol population, or another analysis set. In a single-group physiological measurement study, the distinction between participants enrolled, participants who completed the procedure, and participants included in an endpoint analysis can matter for interpreting the summary. The record does not provide those details.

It also does not report a prespecified approach to outliers, deviations from the procedure, or adjustment for repeated measurements. These are not necessarily problems with the study; they are aspects of analysis and reporting that cannot be evaluated without further information. The absence of an analysis description limits assessment of how the endpoint was summarized and how uncertainty was handled.

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 for the group titled “Application of Tourniquets on Lower Extremities.” It lists 27 participants at risk for serious adverse events and 0 affected. It also lists 27 at risk for other adverse events and 0 affected, with 0 deaths. No serious adverse-event terms are listed.

These figures describe what is recorded in the registry for this group. They should not be read as proof that no adverse effects occurred. A zero count means that no affected participants are reported in that category in this record; it does not establish that an event was impossible, that all possible events were captured, or that there was no risk. The record does not provide event definitions, the method or completeness of adverse-event collection, or a narrative of safety monitoring.

The reported safety figures also do not establish how well the findings apply outside the study population. The study description concerns healthy participants undergoing a brief tourniquet procedure, not patients receiving CPR. Safety in another population or clinical context is not assessed by these counts. The record does not report additional safety analyses or a comparison group.

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

The record describes a physiological study of arm systolic blood pressure before and after CAT tourniquets were applied to both lower extremities in healthy participants. It defines a minimum increase of 10 mmHg as the endpoint criterion and specifies that the average of 3 repetitions is reported. These details clarify the intended measurement and its interpretation.

The registry record does not report the observed blood-pressure measurements, the estimated change, or uncertainty around an estimate. It therefore does not establish whether the primary endpoint changed in the expected direction or whether the stated threshold was met. The record lists no analyses, so there is no posted statistical result to interpret.

The study’s rationale proposes that occluding peripheral vasculature could influence blood distribution during CPR and ultimately affect heart and brain perfusion. The registered measure is arm systolic blood pressure in healthy participants. It is not a direct measurement of coronary perfusion, cerebral perfusion, survival, or neurologic outcome. The registry record does not report results for those clinical outcomes.

General statistical consideration: an observed change in a surrogate or physiological measure can motivate further study, but it does not automatically demonstrate a change in a downstream clinical outcome. The strength of any inference depends on the endpoint, design, quality and completeness of measurement, and the analysis. Here, the absence of posted endpoint results prevents assessment even of the size and precision of the physiological change. The study description provides a rationale and a measurement plan, not evidence in the registry record about whether the proposed effect was observed.

13. Why This Trial Matters Statistically

This study is statistically notable for the gap between a clearly described physiological question and the absence of posted outcome analyses. The registry identifies a primary endpoint, a measurement location, a repetition scheme, and a threshold for success. Those features help define what the investigators intended to measure. But without the observed values and an analysis, readers cannot judge the size, direction, or precision of the result.

The single-group, within-participant structure also illustrates an important design distinction. Comparing a participant with their own baseline can be useful for detecting a change across a procedure, but it does not offer the same protection against time-related or measurement-related alternatives as a concurrent control group. The record identifies no separate control group and no randomized comparison. That design context matters when interpreting any before-and-after finding, if one is reported elsewhere.

The endpoint sits at an early point in the proposed chain of evidence. Arm systolic blood pressure is a measurable physiological quantity; it is not itself a measure of CPR effectiveness or patient outcome. Statistical reporting should preserve that distinction and avoid extending conclusions beyond the measured outcome and study population.

Finally, the record demonstrates why reporting the analysis population, missing-data handling, variability, and uncertainty is important. The planned repetition and averaging clarify the intended summary, but do not reveal the consistency of the underlying readings. Transparent results would allow readers to evaluate both the estimate and its limitations. In this record, those details are not reported in the registry record.

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 principal limitation for statistical interpretation is that the registry record does not report primary endpoint results. It provides no baseline or post-tourniquet systolic blood-pressure values, estimated change, measure of variability, confidence interval, or p-value. The stated threshold of 10 mmHg cannot be evaluated without those findings.

The design is single-group, with baseline serving as the reference and no separate control group described. This limits the ability to distinguish a change associated with tourniquet application from changes related to time, repeated measurement, or other conditions. Masking is listed as none, and the record does not describe steps to reduce measurement or observer influences.

The registry record does not report participant characteristics, detailed eligibility criteria, or the number of participants with complete endpoint data. It lists enrollment of 27, while the study description says the investigators planned to recruit 30; the reason for the difference is not reported in the registry record. Missing-data procedures, exclusions, protocol deviations, and analysis populations are also not reported.

The endpoint is a proximal physiological measure in healthy participants. The record does not report direct measurements of coronary or cerebral perfusion, or clinical outcomes after cardiac arrest. Findings about the registered endpoint, if available elsewhere, would not by themselves establish effects on those outcomes.

Finally, no statistical analyses or detailed analysis plan are listed. The registry record does not explain how repeated readings, potential outliers, or uncertainty were handled. These reporting gaps limit reproducibility and make it impossible to assess the statistical result from the record alone.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Tourniquets Increase Proximal Pressure — NCT05324306.
• Registry record last updated 2024-07-18; status last verified 2024-07.
• Results first posted 2024-07-18.
• 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

NCT05324306 is a completed, single-group study titled “Tourniquets Increase Proximal Pressure.” It investigated arm systolic blood pressure before and after CAT tourniquets were applied to both lower extremities in healthy participants. The procedure was repeated 3 times, with an average of the repetitions identified as the primary outcome summary. The endpoint definition specifies a minimum increase of 10 mmHg.

The registry lists enrollment of 27 and reports 0 serious adverse events, 0 other adverse events, and 0 deaths in the intervention group. It does not report primary endpoint values, an effect estimate, uncertainty, or statistical analyses. The record therefore describes the study question and procedure, but does not show whether the stated blood-pressure target was reached.