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 CPR Quality Between Flexible Stretcher and Standard Stretcher in OHCA (NCT02527694), a non-randomized na study. The primary outcome is Comparison of Percentage of Chest Compression Fraction Between Before- and After-phase Groups.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02527694 |
| Phase | NA |
| Condition | Out-of-hospital Cardiac Arrest |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 49 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Seoul National University Hospital |
| Results posted | Yes |
2. Clinical Question
Population
Patients with out-of-hospital cardiac arrest who receive prehospital resuscitation and are transported to hospital by ambulance. The record does not report further eligibility criteria or patient characteristics.
Intervention
Transport on a flexible EMS stretcher cart with mechanical CPR during transport. The description also includes elevator transport when applicable.
Comparator
Transport on a standard stretcher cart with manual CPR, following the current standard protocol used by EMS providers.
Primary question
How does chest compression fraction compare between the groups during total prehospital resuscitation time? The record’s primary outcome title describes a comparison between before- and after-phase groups, while the group descriptions identify standard and flexible stretcher approaches.
The clinical question concerns CPR delivery during transport, rather than a direct comparison of the stretcher alone. The flexible-stretcher group also receives mechanical CPR, whereas the standard-stretcher group receives manual CPR. Any observed group difference would therefore reflect the combined care approaches recorded for the groups; the record does not isolate the contribution of the stretcher from the CPR method.
The registry describes a non-randomized study. Consequently, the groups may differ in ways other than the transport and CPR approach, and the record does not establish that those differences were controlled. It also does not report outcome values, so the direction or size of any difference in chest compression fraction cannot be described from the registry record. CPR duration is listed as a secondary outcome, but its results are not reported in the registry record.
3. Trial Design
This was a completed, parallel-group, non-randomized study sponsored by Seoul National University Hospital. The registry reports an enrollment of 49. The listed condition is out-of-hospital cardiac arrest. The study began in 2015-09, with primary completion in 2015-12.
One group is described as receiving transport on a flexible EMS stretcher cart and mechanical CPR during transport to hospital. The description includes elevator transport when applicable as well as transport in the moving ambulance. The comparison group is described as using a standard stretcher cart and manual CPR during transport, under the current EMS provider protocol. Masking is listed as none.
Because allocation was non-randomized, the comparison should not be read as if participants had been assigned by chance to otherwise exchangeable groups. The registry record does not report how patients entered each group, whether the groups corresponded to distinct calendar periods, or what factors informed allocation. Although the primary outcome title refers to before- and after-phase groups, the arm descriptions use standard and flexible stretcher group labels. The record does not explain this difference in terminology.
The record identifies two outcome measures and lists CPR duration as a secondary outcome. It does not provide outcome values, an analysis population, or entries describing statistical analyses. It lists no study phase beyond “NA.” The registry record does not report further information on eligibility criteria, recruitment procedures, follow-up, or the statistical plan. These omissions limit assessment of how the planned comparison was implemented and how its results should be interpreted.
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 | Flexible Stretcher Cart Group | Standard Stretcher Cart Group |
|---|---|---|
| STARTED | 20 | 29 |
| COMPLETED | 10 | 21 |
| NOT COMPLETED | 10 | 8 |
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: During the before-phase, 29 OHCAs were treated and transported by EMS crews. After serial exclusion, 21 patients were eligible for the final analysis. During the afterphase, 20 OHCAs were eligible for enrollment. After serial exclusion, 10 cardiac arrests received mechanical chest compressions on reducible stretchers during hospital transport
| Characteristic | Unit | Standard Stretcher Cart Group | Flexible Stretcher Cart Group | Total |
|---|---|---|---|---|
| Participants analysed | 21 | 10 | 31 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 10 | 4 | 14 |
| Age, Categorical: >=65 years | Participants | 11 | 6 | 17 |
| Age, Continuous | years | 66 (58 to 73) | 66 (60 to 74) | 66 (58 to 74) |
| Sex: Female, Male: Female | Participants | 8 | 2 | 10 |
| Sex: Female, Male: Male | Participants | 13 | 8 | 21 |
| Region of Enrollment: South Korea | Participants | 21 | 10 | 31 |
6. Primary Endpoint
The registry lists the primary outcome as Comparison of Percentage of Chest Compression Fraction Between Before- and After-phase Groups, measured over During the total prehospital resuscitation time.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | Percentage of chest compression fraction |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the percentage of chest compression fraction during total prehospital resuscitation time. The registry defines chest compression fraction as the proportion of CPR time spent providing compressions. It reports the endpoint summary measure as a median with an inter-quartile range.
Chest compression fraction describes how much of the CPR period is spent actively delivering compressions rather than in pauses. As a general statistical point, this kind of measure can help describe the continuity of compressions during resuscitation. A median is a measure of the center of a distribution that is less influenced by extreme observations than a mean. The inter-quartile range describes the middle portion of the observed values and gives information about their spread.
The endpoint is relevant to the recorded comparison because CPR is delivered during ambulance transport in both groups, using different stretcher and CPR approaches. However, the registry record does not report the group medians or inter-quartile ranges, nor does it report a between-group estimate or uncertainty interval. The endpoint’s measurement unit is described as a percentage, but no endpoint result is available in the registry record. Therefore, the size, direction, and precision of any difference cannot be assessed from this record. CPR duration is listed separately as a secondary outcome, but its measurement details and results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a comparison of CPR quality during ambulance transport, with chest compression fraction as the primary endpoint. It does not report the observed chest compression fraction in either group or a statistical comparison between them. As a result, there is no reported estimate from which to describe whether the recorded groups differed, how large any difference was, or how precisely it was estimated.
The non-randomized allocation is central to interpreting the study. In a randomized comparison, assignment by chance is intended to reduce systematic differences between groups. That protection is not established by the design recorded. General statistical reasoning indicates that group differences in outcomes may reflect differences in patient characteristics, circumstances of care, provider practice, or other factors, in addition to the stretcher and CPR approach. The registry record does not report whether such factors were measured or adjusted for.
The comparison also combines two components: the flexible stretcher approach is paired with mechanical CPR, while the standard stretcher approach is paired with manual CPR. Any group contrast would not, by itself, distinguish an effect associated with the stretcher from an effect associated with the CPR method. The record does not describe a design that separates these components.
The primary outcome title refers to before- and after-phase groups, but the arm descriptions use standard and flexible stretcher labels. The record does not explain whether these terms refer to the same grouping structure or how the groups were defined. This leaves uncertainty about the exact comparison represented by the primary outcome title.
The adverse-event information lists zero serious events and zero other events in each of the two named groups, with 29 at risk in the Standard Stretcher Group and 20 at risk in the Reducible Stretcher Group. These entries describe what the registry reports; they do not establish that all relevant events were captured or that the approaches have equivalent safety. The deaths fields are not populated with a count.
In short, the record supports a description of the study question, design, endpoint definition, and adverse-event entries. It does not provide endpoint results, inferential statistics, or enough information to establish a causal comparison. Any conclusion about the observed CPR quality difference would require results and analysis details not reported in the registry record.
9. Statistical Methods Explained
The registry identifies the primary measure as median chest compression fraction with an inter-quartile range. It does not report an inferential analysis, confidence interval, or statistical test. The methods below explain how these statistical concepts generally relate to an endpoint of this type; they should not be taken as a description of analyses performed in this study.
Why report a median and inter-quartile range?
General: a median indicates the central point of an ordered set of observations. Half of the observations lie on either side of the median, subject to ties. An inter-quartile range describes the span between the central quartiles and gives a sense of the spread among observations. These summaries can be useful when values are skewed or when unusually high or low values might pull a mean away from the typical observation.
Reporting a median and inter-quartile range does not, by itself, show how different two groups are. Readers need the group-specific summaries and a clearly defined contrast to understand the observed difference. An uncertainty interval around a group contrast would also help show which values remain compatible with the data under the chosen analysis. None of those outcome results is reported in the registry record.
What does non-randomized allocation imply?
General: random allocation helps make groups comparable in expectation with respect to measured and unmeasured characteristics. A non-randomized comparison does not have that design-based safeguard. If patient or care characteristics differ between groups, those differences can influence the endpoint as well as the assigned approach. Statistical adjustment can sometimes address measured differences, but it cannot automatically eliminate bias from unmeasured factors or from inadequate measurement.
The registry record does not report which characteristics were collected, whether adjustment was planned or performed, or how allocation occurred. It also does not provide an adjusted or unadjusted effect estimate. The primary outcome title’s before-and-after wording adds a further interpretive issue: if groups corresponded to different phases, changes in practice or circumstances over time could be relevant. The record does not state that this was the allocation mechanism, so that possibility cannot be resolved from the registry description.
Why does the combined intervention matter?
The recorded approaches differ in both stretcher and CPR method. The flexible EMS stretcher group receives mechanical CPR, and the standard stretcher group receives manual CPR. General: when several features change together, a group contrast estimates the difference between the combined approaches rather than isolating the effect of one feature. A design that varies one component while holding the others comparable, or an appropriate analysis with adequate data and assumptions, would be needed to separate component-specific contributions. The registry record does not report such a design or analysis.
What can a confidence interval add?
General: a confidence interval is an uncertainty summary for an estimate under a specified statistical method and its assumptions. It can indicate whether the estimate is precise or compatible with a broad range of possible values. It does not by itself remove confounding, correct biased measurement, or prove that a treatment effect is absent when an interval includes a null value. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be evaluated.
What is the role of the planning assumptions?
The record describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. These are stated as assumptions for planning illustrations, not as the study’s own design justification or analysis plan. The registry record does not report a sample-size justification or calculated planning values. Such illustrations are not observed power, and they do not establish that a study was adequately powered for its actual comparison.
More generally, power calculations depend on assumptions about the effect to detect, variability, allocation, and analysis method. If the target effect is defined as a fraction of an observed effect, the planning result depends on that observed estimate and may not represent a clinically meaningful target. The record does not report an independently chosen target effect or its rationale. No new power or sample-size calculation can be inferred from the information recorded.
Finally, the registry lists two outcome measures but zero analysis entries. That does not identify what statistical work may or may not have been undertaken outside the registry; it means the registry record does not document those analyses. The endpoint summary, group comparison method, handling of missing observations, and any adjustment strategy are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies a primary outcome and lists CPR duration as a secondary outcome. It reports two outcome measures, but no analysis entries. A multiplicity strategy for interpreting more than one outcome or more than one statistical comparison is not reported in the registry record. It is therefore not possible to tell whether any adjustment for multiple testing was planned or used, or how the primary and secondary results were intended to be interpreted together.
General: when several hypotheses are tested, the chance of obtaining at least one apparently notable result can increase. Prespecifying a primary outcome and a limited set of analyses can help clarify which result is central; adjustments or other strategies may also be considered depending on the aims. The record does not report such details beyond identifying the primary endpoint and the secondary outcome.
Missing-data methods and the amount or pattern of missing outcome data are not reported in the registry record. Without that information, readers cannot assess whether observations were incomplete, how any incomplete records were handled, or whether missingness could have affected the comparison. Analysis populations, such as which participants were included in the primary endpoint analysis, are also not reported.
The record does not describe exclusions after enrollment, the timing of outcome measurement for each participant, or whether all enrolled participants contributed to the outcome analysis. These details matter because a reported summary may depend on who was included and how incomplete measurements were treated. No assumptions about missingness, exclusions, multiplicity correction, or analysis populations can be attributed to this study from the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Standard Stretcher Group | 0 | 29 | 0.0% |
| Reducible Stretcher Group | 0 | 20 | 0.0% |
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 |
|---|---|
| Standard Stretcher Group | 0 of 29 |
| Reducible Stretcher Group | 0 of 20 |
The registry lists adverse-event entries for the Standard Stretcher Group and the Reducible Stretcher Group. The Standard Stretcher Group has 29 at risk, with 0 serious events and 0 other events recorded. The Reducible Stretcher Group has 20 at risk, with 0 serious events and 0 other events recorded. These are registry entries, not a complete safety analysis.
The deaths fields are not reported with numerical counts. The record also does not describe how adverse events were defined, collected, monitored, or attributed, or the period over which they were assessed. It does not report whether every participant was assessed for each event type or how missing safety information was handled.
General: a zero count in a registry entry means that no events are recorded for that category and group in that entry. It does not establish that the true event risk is zero, that no events went unrecorded, or that groups have equivalent safety. A comparative safety assessment would require adequate event ascertainment and an analysis that accounts for the study design and uncertainty. Since allocation was non-randomized, these entries should not be interpreted as a causal comparison between approaches. The group label “Reducible Stretcher Group” appears in the safety information; the record does not explain its relationship to the flexible EMS stretcher wording elsewhere.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the study was designed to compare CPR delivery during ambulance transport using two approaches: a flexible EMS stretcher with mechanical CPR and a standard stretcher with manual CPR. Its primary endpoint is chest compression fraction during total prehospital resuscitation time, summarized as a median and inter-quartile range. It also lists CPR duration as a secondary outcome.
The record does not report the primary endpoint values or the secondary outcome results. It therefore does not show whether the groups had similar or different chest compression fractions, nor does it provide an estimate of the size or precision of a difference. Without those results, no conclusion about the observed CPR quality comparison can be drawn from the registry record.
Even if outcome values were available, the non-randomized design would require cautious interpretation. General: an association between a care approach and an outcome in a non-randomized study may reflect differences between groups as well as the approach itself. Here, the two recorded approaches also differ in CPR method as well as stretcher type, so the design does not isolate the effect of either component.
The adverse-event entries report zero serious and zero other events in each named group, but the record does not supply the information needed to establish completeness of event collection or comparative safety. The deaths fields do not contain reported counts. These entries should be read as registry reporting, not as proof that an approach has no risks.
The study matters as a documented clinical comparison of equipment and CPR delivery during transport. Its registry entry is insufficient to establish effectiveness, lack of effectiveness, equivalence, or safety. Those judgments would require outcome results, statistical methods, and fuller information about allocation, analysis populations, missing observations, and event ascertainment, which are not reported in the registry record.
13. Why This Trial Matters Statistically
CPR during ambulance transport presents a setting in which the care process and the transport equipment are considered together. The registry record makes that combined comparison explicit: the flexible EMS stretcher approach is paired with mechanical CPR, while the standard stretcher approach is paired with manual CPR. This is statistically important because the comparison cannot separate the contributions of those components.
The study also illustrates why design information matters alongside an endpoint definition. Chest compression fraction is defined as the proportion of CPR time spent providing compressions, and its median and inter-quartile range are specified. But a defined outcome is not enough to interpret a study: readers also need group results, an estimate of the contrast, uncertainty, and a clear account of how groups were formed and analyzed. Those results and details are not reported in the registry record.
Non-randomized allocation makes the distinction between an observed group difference and a causal effect especially relevant. General: group comparisons can be influenced by factors associated with both the chosen approach and the outcome. Without a reported allocation process and analysis strategy, it is difficult to assess the extent to which such factors were addressed.
The registry wording also demonstrates the value of consistent group labels. The primary outcome title refers to before- and after-phase groups, while the arm descriptions refer to stretcher approaches. The safety entries use “Reducible Stretcher Group.” The record does not explain how these descriptions relate. Clear, consistent terminology would help readers determine exactly which groups and time periods are being contrasted.
Thus, the statistical importance of this trial record lies both in its clinical question and in the limits of what its public information can support. It documents a potentially relevant comparison, but not the results needed to quantify or interpret the endpoint contrast.
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 of the registry record is that it does not report primary or secondary outcome results. No group-level chest compression fraction summaries, between-group estimate, uncertainty interval, or CPR duration result is reported. The statistical significance and precision of any endpoint comparison therefore cannot be assessed.
The non-randomized allocation leaves potential for differences between groups that could influence the outcome. The record does not describe the allocation process or report whether patient characteristics, care circumstances, or other potential confounders were measured and accounted for. The primary outcome title’s reference to before- and after-phase groups is not reconciled with the stretcher-based group descriptions.
The approaches differ in both stretcher and CPR method: the flexible EMS stretcher group receives mechanical CPR, while the standard stretcher group receives manual CPR. The record does not describe a comparison that separates those elements. Masking is listed as none, and the record does not explain whether outcome measurement could be influenced by knowledge of group assignment.
Further limitations include the absence of reported eligibility details, patient characteristics, analysis populations, missing-data information, and statistical analysis methods. Multiplicity handling is not reported despite the listing of a primary and a secondary outcome. Adverse-event entries have no accompanying description of ascertainment or completeness, and death counts are not reported. The registry record also uses differing group terminology without explaining the relationship among the labels. These omissions constrain both reproducibility and interpretation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: CPR Quality Between Flexible Stretcher and Standard Stretcher in OHCA — NCT02527694.
- Registry record last updated 2019-01-15; status last verified 2018-12.
- Results first posted 2018-11-05.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
This completed, non-randomized, parallel-group study compared approaches to CPR during ambulance transport for out-of-hospital cardiac arrest. The flexible EMS stretcher cart group received mechanical CPR; the standard stretcher group received manual CPR. The record reports enrollment of 49 and lists chest compression fraction as the primary endpoint, measured during total prehospital resuscitation time and summarized by median and inter-quartile range. CPR duration is listed as a secondary outcome.
Outcome results and statistical analyses are not reported in the registry record. The record lists zero serious and zero other adverse events in both named safety groups, while death counts are not reported. The primary outcome title uses before- and after-phase wording, which the record does not reconcile with the group descriptions. Non-randomized allocation and the combined changes in stretcher and CPR method limit causal interpretation.