Comparison Between a Novel Proning Pillow System and Standard Pillows: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison Between a Novel Proning Pillow System and Standard Pillows (NCT05149989), a na na study. The primary outcome is Peak Chest and Pelvis Interface Pressures.

2. Clinical Question

The clinical motivation described in the record is the use of proning for people receiving intensive care, and the concern that prolonged pronation can contribute to pressure sores at support locations. The study itself, however, involved healthy NHS staff rather than patients in intensive care. Its primary measurement was interface pressure, not pressure sores, patient comfort, oxygenation, or other clinical outcomes. Those distinctions matter when interpreting what the study could address: pressure readings can describe loading at the measured locations under the study conditions, but they are not themselves evidence of a change in patient outcomes.

3. Trial Design

This was a completed, single-group study with an enrollment of 50. The record lists the allocation as NA, masking as NONE, and the model as SINGLE GROUP. It describes the participants as being proned on standard and proning pillows. The study title and aim describe a comparison of the two pillow types, but the record does not establish that participants were randomly assigned or that the conditions formed a like-for-like control comparison.

The registry lists the study start as 2022-02-21 and primary completion as 2022-03-10. The sponsor was Liverpool University Hospitals NHS Foundation Trust. The phase is listed as NA. The study status is COMPLETED. These administrative details describe the registry record; they do not add information about the procedures used to collect or analyse pressure measurements.

Participants were healthy subjects, described in the summary as healthy NHS staff. That differs from the intensive-care patients who motivate the study in the background. The registry says the population was analysed in separate male and female groups, with male (20) and female (30), but it does not report how those groups were defined beyond that description or provide outcome results for either group.

The record does not report the sequence in which participants used each pillow type, whether the same participants contributed measurements under both conditions, how long each condition lasted, or whether any rest or repositioning occurred between measurements. It does list a primary endpoint timeframe of 10 minutes. Without further protocol detail, those design features should not be inferred from the stated comparison or the single-group label. The record also lists no statistical analyses. Consequently, the intended comparison can be described, but the method used to estimate it cannot be reconstructed from the registry entry.

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

Analysis population for the primary outcome, as defined in the registry: Population was analysed in two separate groups: male (20) and female (30)

5. Baseline Characteristics

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

Population: NHS staff

6. Primary Endpoint

The registry lists the primary outcome as Peak Chest and Pelvis Interface Pressures, measured over 10 minutes.

The primary endpoint is titled Peak Chest and Pelvis Interface Pressures. It concerns the maximum pressure values measured by two pressure mats: one placed in the chest region and one in the pelvis region. Pressure is expressed in mmHg, and the stated timeframe is 10 minutes. The registry identifies the parameter as a mean and the dispersion measure as an inter-quartile range.

Interface pressure is a measurement of the contact loading between a person and the supporting surface at the instrumented locations. Comparing chest and pelvis readings is relevant to the study’s stated aim because those are the regions supported by the pillows and identified in the record’s rationale about pressure sores. The measurement can therefore characterize pressure under the conditions in which the mats and pillows were used.

It is important to distinguish the endpoint from a clinical event. A peak pressure measurement is not a count of pressure sores, nor does the record identify it as a direct measure of their occurrence. The registry record does not report the pressure values, comparisons, or uncertainty estimates. It also does not describe how the maximum was calculated from the mat readings, whether chest and pelvis were treated as separate outcomes in the analysis, or how measurements within participants were handled. Those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods should be interpreted in light of the actual design and posted results. The registry identifies the model as SINGLE GROUP, allocation as NA, masking as NONE, and the number of analyses as zero. It also describes participants as being proned on standard and proning pillows. These registry entries identify an intended comparison, but they do not specify the statistical model or the way observations from the pillow conditions were related. The registry record does not report an analysis plan or any completed endpoint analysis.

What does the endpoint summary mean?

The endpoint is a pressure measurement in mmHg, with the parameter listed as mean and dispersion listed as inter-quartile range. A mean describes the arithmetic average of observations. An inter-quartile range describes the spread of the middle portion of a distribution. These summaries answer different questions: the mean characterizes an average level, while the inter-quartile range conveys how observations are distributed around the center. Reporting both can help readers understand a set of measurements, but it does not by itself establish a difference between conditions.

The endpoint description refers to maximum values from pressure mats in the chest and pelvis regions and gives a timeframe of 10 minutes. The record does not explain whether the maximum was summarized separately by region, how observations within the timeframe were reduced to a participant-level value, or how the two pillow conditions were compared. Those are important analytical choices, because a maximum, an average over time, and a participant-level summary do not represent the same feature of the measurement process.

Why does the comparison structure matter?

In general, a comparison can be analysed differently depending on whether measurements come from independent groups or from the same participants under multiple conditions. Measurements from the same person are often related, while measurements from different people may be treated as independent only when the design and assumptions justify that approach. The record does not report the order of pillow use or confirm whether each participant contributed measurements under both conditions. It therefore does not support a claim that a paired, independent-group, or other specific analysis was used.

Random allocation can help balance factors that might otherwise differ between comparison groups, but the registry lists allocation as NA and explicitly notes that this is not a randomized comparison. That does not prove that the measurements are unusable; it does mean that the record does not support an interpretation based on randomized assignment. Differences in measurement conditions or participant characteristics could be relevant, and the registry does not report procedures for addressing them.

What would uncertainty estimates tell readers?

In general, a confidence interval gives a range of values compatible with the observed data under the assumptions of the analysis. Its width reflects statistical precision: a narrower interval indicates greater precision than a wider interval, while an interval that includes values in different directions may leave the direction of the effect uncertain. A p-value, when used, addresses compatibility of data with a specified statistical null model; it does not measure the size or clinical importance of an effect. No confidence intervals or p-values are reported for this endpoint in the registry record, so no such interpretation can be made for the study.

The mean and inter-quartile range listed as the endpoint summaries are not substitutes for a contrast and its uncertainty. To assess a comparison, readers would need results for the relevant pillow conditions, a clearly defined contrast, and an uncertainty estimate based on the design. The registry record does not report those elements. General statistical explanations describe how such quantities are interpreted; they do not imply that the study calculated them.

How should the planning illustration be read?

The record describes sample-size calculations as planning illustrations based on a fraction of the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It distinguishes total event counts for time-to-event calculations from participants per arm for other calculations. This description concerns planning illustrations, not the study’s own design or its observed results. The record does not report a sample-size justification for the trial itself. Such illustrations are not observed power and cannot establish whether the study was adequately sized for its actual design or endpoint.

More generally, planning calculations depend on assumptions about the effect to detect, variability, analysis method, and design. If those assumptions differ from the trial’s circumstances, a planning figure may not describe the precision of the collected data. Here, the absence of posted endpoint results and analyses means readers cannot evaluate the observed precision from the registry record.

Finally, over-dispersion is a general statistical concern when observed variability exceeds what a chosen model assumes. In general, ignoring over-dispersion can make uncertainty estimates too small and evidence appear more precise than it is. The registry does not report a count model or over-dispersion assessment for this continuous pressure endpoint, so that concern should not be presented as a method used or a problem identified in this study.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint involves pressure measurements at the chest and pelvis, and the registry describes separate male and female population groups. It does not report whether chest and pelvis were analysed as separate endpoints, whether subgroup comparisons were planned, or how multiple statistical tests would be handled. The number of analyses is listed as zero. Accordingly, the registry record does not provide a multiplicity strategy or results that would show how multiple comparisons affected interpretation.

In general, multiplicity arises when several hypotheses or outcomes are tested. The more comparisons made, the greater the chance of finding an apparently notable result by chance if each test is interpreted without regard to the others. Statistical plans may address this by identifying a primary comparison in advance or by adjusting interpretation across tests. The registry entry does not report such decisions, so no specific multiplicity procedure should be inferred.

Missing-data methods and analysis populations are also not reported in the registry record. The enrollment is 50, and the record describes male (20) and female (30) groups, but it does not state whether all enrolled participants contributed usable measurements, whether any data were missing, or how incomplete measurements would be handled. The record does not report an intention-to-treat or per-protocol population, nor does it define an analysis set. Because allocation is listed as NA and the model as SINGLE GROUP, familiar randomized-trial population labels should not be assumed to apply.

These omissions limit assessment of bias and precision. If measurements were unavailable for some participants or conditions, the way those observations were handled could affect the estimated comparison. Without counts and a stated method, readers cannot assess that possibility from this registry entry.

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 lists one group, titled Proning, with 50 participants at risk. It reports 0 participants affected by serious adverse events, 0 affected by other adverse events, and 0 deaths. No top serious adverse event terms are listed. These are the safety figures posted for the group.

Zero reported events should be read as the registry’s recorded count, not as proof that no event was possible or that the intervention is free of risk. The entry does not report how adverse events were defined, how actively they were sought, the observation period for safety, or whether the figures refer to events attributed to a particular pillow condition. It also does not provide safety results separately for standard pillows and the novel system.

The population consisted of healthy subjects, as described in the study summary, rather than the intensive-care patients discussed in the rationale. The safety counts therefore describe this study group and should not be treated as a general estimate for other populations or settings. With no additional event details or comparative analysis reported, the figures should be interpreted narrowly as the counts entered in the registry record.

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

The record identifies a focused measurement question: whether peak interface pressure at the chest and pelvis differs when healthy subjects are prone on a novel pillow system versus standard pillows. It also records the intended measurement locations, unit, timeframe, and population grouping. This provides context for the study’s aim and the type of data it was meant to collect.

What the record does not provide is the result of that measurement question. There are no posted pressure estimates, contrasts, uncertainty intervals, or statistical tests, and the registry lists no analyses. Consequently, readers cannot determine the direction or size of any difference, or how precisely it was estimated. No conclusion about similarity or difference between pillow types follows from the absence of posted results.

The endpoint is an interface-pressure measure, not a pressure sore outcome. The study rationale discusses pressure sore concerns, but the primary endpoint does not directly count sores or establish whether they occurred less or more often. The record does not report clinical outcomes in patients receiving intensive care. Even a pressure difference, if reported, would need to be interpreted as a measured pressure difference under the study conditions, not automatically as a change in patient outcomes.

The study is also described as a single-group, nonrandomized comparison, with allocation listed as NA. The registry does not give enough procedural information to reconstruct how pillow conditions were ordered or how observations were linked. That limits what can be said about the comparison’s design and analysis. The appropriate conclusion is therefore bounded: the registry describes an intended comparison of pressure measurements in healthy subjects, but does not report results that answer the comparative question.

13. Why This Trial Matters Statistically

This study matters statistically because it illustrates the distinction between a clearly stated measurement aim and a result that can be evaluated. The registry identifies a pressure endpoint, the locations measured, the unit, and the timeframe. Those details help define what investigators intended to observe. But without outcome estimates and analysis results, the scientific question remains unanswered in the registry record.

The design description is also important. The record calls the model SINGLE GROUP, lists allocation as NA, and notes that this was not a randomized comparison. A comparison of conditions can still be informative, but the design determines which sources of variation and potential bias need attention. Since the order of pillow use and the relationship between measurements are not described, readers cannot identify an appropriate analysis or assess whether the comparison controlled for relevant differences.

The distinction between a surrogate measurement and a clinical outcome is central. Interface pressure can characterize loading at specified body regions, while pressure sores are clinical events. The rationale links the measurement to a clinical concern, but pressure measurements alone do not establish an effect on that outcome. The registry reports no pressure sore results and no patient outcomes.

Finally, the record demonstrates why registration details and posted results serve different purposes. Enrollment, study status, endpoint definitions, and adverse-event counts describe aspects of the conduct and reporting. They do not replace the numerical outcome estimates needed to assess effect size and precision. For statistical interpretation, a transparent report of the observations, analysis population, comparison method, and uncertainty would be needed. Those results and methods 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 most direct limitation is that the registry record does not report the primary outcome results or any statistical analyses. It therefore offers no numerical basis for estimating the pressure difference between pillow types or its precision. The listed endpoint definition is not enough to establish what the observed measurements showed.

The study population also limits the scope of interpretation. The summary describes healthy NHS staff, whereas the clinical rationale concerns people in intensive care who are proned. The record does not report patient data or outcomes in that clinical population. Any relevance of measurements in healthy subjects to intensive-care patients is not established by the registry entry.

The comparison is not described as randomized: allocation is NA, and the record notes that the arms are not a like-for-like control comparison. The registry does not report the order of pillow conditions, whether participants were measured under both conditions, or how the measurements were made comparable. Without those details, potential design-related influences on a comparison cannot be evaluated.

Other procedural details are also absent, including eligibility criteria beyond the healthy-subject description, the pressure mat procedures, the handling of repeated readings, and the analysis population. Missing-data methods, a multiplicity plan, and a statistical analysis plan are not reported in the registry record. The record also does not report a trial-specific sample-size justification. These gaps prevent a full assessment of measurement validity, bias, and statistical precision.

Finally, the primary endpoint is pressure, not pressure sores or other patient outcomes. The study’s stated rationale does not change the endpoint’s scope. The registry record does not establish that pressure measurements predict or alter clinical events.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison Between a Novel Proning Pillow System and Standard Pillows — NCT05149989.
• Registry record last updated 2024-08-22; status last verified 2022-06.
• Results first posted 2024-08-22.
• 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

NCT05149989 is a completed study titled “Comparison Between a Novel Proning Pillow System and Standard Pillows.” The sponsor was Liverpool University Hospitals NHS Foundation Trust. The record lists an enrollment of 50 and describes healthy NHS staff proned on standard and novel proning pillows. The study aimed to compare peak chest and pelvis interface pressures, measured in mmHg over a timeframe of 10 minutes.

The model is listed as SINGLE GROUP, allocation as NA, and masking as NONE. The primary endpoint summary specifies a mean and inter-quartile range. The record describes male (20) and female (30) population groups but lists zero analyses and reports no pressure outcome estimates or statistical comparisons.

The safety record lists 50 at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths in the Proning group. The registry record does not report additional safety definitions or comparative safety results. Overall, it documents the study’s intended pressure measurement and basic design details, but not the numerical findings needed to assess the pillow comparison.