The Efficacy of Normobaric Oxygen on Chronic Cerebral Ischemia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Efficacy of Normobaric Oxygen on Chronic Cerebral Ischemia (NCT03745092), a randomized na study. The primary outcome is The Fronto-central Theta Absolute Power Change Rate.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group trial sponsored by Capital Medical University. The record lists phase as not applicable. Enrollment was 49, with 26 participants in the NBO group and 23 in the control group. The trial status is completed. The start date is 2018-12-01 and the primary completion date is 2019-12-31.

Participants underwent a 30-minute baseline EEG recording, received their assigned intervention for 45 minutes, and then underwent a 30-minute post-intervention EEG recording. In the NBO group, oxygen was delivered at 8L/min via face mask. The control group rested, with lying, sitting or walking listed as options. The record calls the masking single but does not identify which people involved in the trial were masked. Details of the randomization sequence, allocation concealment, and the procedures used to maintain masking are not reported in the registry record.

The primary endpoint is a continuous EEG-derived change rate, summarized by the median and inter-quartile range. The registry provides the group sizes, median values, and interval bounds, but it does not report a formal primary between-group analysis. Some secondary endpoint summaries and one secondary comparison are posted; other secondary outcomes are listed without a two-group estimate. No registry-posted analysis records are listed. The planned sample-size justification, analysis population, handling of protocol deviations, and details of follow-up beyond the EEG assessment 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

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 The Fronto-central Theta Absolute Power Change Rate, measured over 30 minutes baseline EEG, 45 minutes intervention, 30 minutes post-intervention EEG.

The primary endpoint is the fronto-central theta absolute power change rate. Theta power is measured in the 4-8Hz frequency band using Fast Fourier Transform for each of the fronto-central electrodes F3, F4, Fz, C3, C4 and Cz. The endpoint compares baseline and post-intervention EEG power, using the baseline value as the denominator. As described in the record, a positive change rate corresponds to lower post-intervention theta power relative to baseline; a negative value corresponds to higher post-intervention power relative to baseline.

The endpoint is measured across a short sequence: 30 minutes of baseline EEG, 45 minutes of intervention, and 30 minutes of post-intervention EEG. This makes it a measure of immediate EEG change over the study procedure, not a direct measure of longer-term clinical outcomes. It is reported as a median with inter-quartile range, a useful summary when a distribution may be skewed or affected by extreme observations. The registry gives the unit as a ratio. It does not report a clinical threshold for interpreting the magnitude of this EEG change, nor does it report a link between this short-term measure and later symptoms or clinical events.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a median summarize?

General statistical explanation: the median is the midpoint of an ordered set of observations. It is less affected by very large or very small observations than the mean, so it can be useful for outcomes whose distributions are asymmetric. The inter-quartile range describes the middle portion of the observed distribution. Here the registry identifies the primary summary as median with inter-quartile range, but does not post the inter-quartile range values. The interval bounds reported alongside each median are not explicitly identified by type or confidence level in the registry record, so they should not be assumed to be a particular kind of interval.

Why does the group contrast matter?

General statistical explanation: a randomized trial is usually interpreted through the contrast between assigned groups, because each group can change over time for reasons unrelated to the intervention. Within-group summaries describe what was observed in each group; a between-group estimate directly quantifies the contrast being studied. An uncertainty interval around that contrast communicates the range of effects compatible with the data and the analysis assumptions. A statistical test addresses a related question about compatibility with a specified null hypothesis, but does not by itself describe the size or practical importance of an effect.

For the primary EEG outcome, the record posts group medians and interval bounds but no estimated between-group effect, standard error, or p-value. The requested primary contrast therefore cannot be evaluated from an inferential result in the registry record. The posted group summaries should not be converted into a new estimate by subtracting their medians: such a calculation would not necessarily equal a properly estimated treatment contrast, and no analysis method for that contrast is reported.

How should the secondary estimate be read?

The wavelet entropy secondary comparison reports a mean difference of -0.14 and an unadjusted p-value of 0.308. Its interval bounds are -0.409 and 0.129, but those values have more than three decimal places and are therefore not reproduced. General statistical explanation: a confidence interval expresses uncertainty in an estimate under a model and method; if it spans zero for a difference, the data are compatible with no difference as well as with differences in either direction. The registry does not state the confidence level for this interval. The standardized effect estimate is -0.287 in the posted analysis; it is not reproduced because it has more than three decimal places.

The p-value is unadjusted, meaning the posted value does not account for testing multiple outcomes. In general, when many outcomes or comparisons are examined, the chance of obtaining at least one apparently unusual result can increase. Adjustment methods, prespecified outcome hierarchies, and the planned approach to multiplicity are not reported in the registry record. Accordingly, this secondary result should be treated as exploratory rather than as a definitive stand-alone finding.

What do the planning illustrations mean?

General statistical explanation: a sample-size calculation estimates how many participants would be needed under stated assumptions to detect a chosen effect with a specified power and significance level. The posted planning illustrations use the observed secondary effect as their starting point, then consider stated fractions of that effect. They assume a two-sided significance level of 0.05, equal allocation, and a normal approximation. They are hypothetical planning examples, not estimates of power achieved in this completed trial, and they are not evidence about the probability that the trial detected an effect. The registry does not report the trial's own sample-size justification or planning assumptions.

General statistical explanation: over-dispersion means that the observed variability is greater than a model assumes. When a model understates variability, standard errors can be too small and intervals too narrow, making results appear more precise than they are. The registry record does not report that an over-dispersion issue was identified or that a particular model was used for the primary outcome. The example of over-dispersion is a general statistical consideration, not a claim about this trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures and four posted secondary outcomes, but it does not report a plan for controlling multiplicity across outcomes or analyses. It also lists no registry-posted analysis records. The one posted secondary comparison is explicitly unadjusted. Without a prespecified testing hierarchy or an adjustment method, its p-value should not be interpreted as if it were the sole test conducted. The record does not say whether other analyses were planned, performed, or omitted.

Missingness is also difficult to assess. The primary group sizes are 26 and 23, and the secondary entropy summaries use those same group sizes. For the other listed secondary outcomes, values are missing or not estimable for a two-arm comparison. The registry does not explain whether this reflects unavailable measurements, analytic exclusions, reporting choices, or another reason. It does not describe the amount or pattern of missing data, imputation, or sensitivity analyses.

The analysis population is not reported in the registry record. It is not stated whether the posted results include all randomized participants, only participants with evaluable EEG recordings, or another defined group. Details about protocol deviations, adherence to assigned intervention, and handling of withdrawals are also not reported. These omissions limit assessment of how randomization was preserved in the analysis and whether missingness could affect the estimates. The available results should therefore be read as registry-posted summaries, without assuming a particular intention-to-treat, per-protocol, or other analysis approach.

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 zero serious adverse events, zero other adverse events, and zero deaths in both groups. The serious-event denominator is 26 participants in the NBO group and 23 in the control group; the other-event denominators are the same. No serious adverse event terms are listed.

These figures describe events recorded in the registry, not proof that no events occurred outside the information captured or reported. The record does not describe adverse-event definitions, surveillance procedures, severity grading beyond the serious category, or the duration of safety follow-up. It also does not report whether event collection covered only the intervention period or a longer interval. With the available information, the safety figures can be described as no events recorded in either group, but the scope and completeness of event ascertainment cannot be assessed.

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

The registry record shows a small randomized comparison of NBO and rest with short-term EEG measurements. The primary group medians have opposite signs, but the record does not provide a primary between-group estimate or test. The posted primary summaries alone cannot establish the size, precision, or statistical evidence for a group difference. The reported interval bounds do not have a stated interval type or confidence level, and the inter-quartile range values are absent.

The available secondary comparison concerns wavelet entropy change. Its unadjusted p-value is 0.308, and its posted interval spans zero. This is an uncertain result, not a demonstration that the groups are equivalent or that an effect is absent. Other listed secondary outcomes lack a reported two-group estimate, and no multiplicity plan is reported. The secondary evidence is therefore incomplete and should be interpreted cautiously.

The results concern EEG measures recorded around a 45-minute intervention, not longer-term clinical outcomes. Although the registry's background discusses CCI and the rationale for studying NBO, the posted results do not establish effects on symptoms, stroke risk, recurrence, or other patient outcomes. No medical conclusion about treatment benefit should be drawn from the short-term EEG summaries alone.

The safety record lists no serious or other adverse events and no deaths in either group. Its interpretation is limited by the absence of details on event definitions, ascertainment, and follow-up. More broadly, the registry does not report a primary statistical analysis, analysis population, missing-data approach, or trial-specific sample-size justification. Those omissions prevent a full assessment of the strength and robustness of the evidence.

13. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the difference between posting group summaries and reporting the randomized contrast that answers the primary question. The primary outcome has median values for both groups, but without an estimated between-group effect and its uncertainty, the direction and precision of a treatment contrast cannot be evaluated directly. Readers should distinguish observed group descriptions from evidence about a comparative effect.

It also highlights the importance of reporting how an endpoint is summarized and what its interval represents. The primary measure is reported as a median with inter-quartile range, yet the inter-quartile range values are not posted, and the accompanying bounds are not identified by type. The absence of those details makes it harder to understand the distribution and precision of the primary results.

The secondary analysis demonstrates why unadjusted results require context. A secondary p-value can be affected by the number of outcomes examined, while the record does not give a multiplicity plan or a complete set of numerical secondary results. Planning illustrations based on an observed effect can help show how assumed effect size and power relate to sample requirements, but they do not describe the trial's achieved power or reveal the original design rationale.

Finally, the record demonstrates why transparent reporting of analysis populations, missing-data handling, and event ascertainment matters. Those details are not reported, so the available summaries cannot be fully assessed for robustness or completeness. These are reporting limitations, not evidence that any particular method was or was not used.

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.

Several limitations are specific to the available record. The primary outcome is defined in detail, but its inter-quartile range values are not reported, and the interval type and confidence level for the posted bounds are unspecified. Most importantly, no primary between-group estimate, standard error, or p-value is reported. A direct comparative interpretation is therefore limited to describing the group summaries.

The enrolled groups contain 26 and 23 participants. The record does not provide baseline characteristics, eligibility criteria, the randomization procedure, allocation concealment details, or the identity of the masked parties. It is not possible to assess group comparability at baseline or the practical success of masking from the registry information alone. The analysis population and treatment of missing measurements are also not reported.

Only one secondary comparison is posted, while other listed secondary outcomes have no reported two-group estimate. The record does not explain the missing or non-estimable values, whether those outcomes were analyzed, or how multiple outcomes were handled. This limits evaluation of consistency across EEG measures and raises uncertainty about the completeness of the posted secondary results.

The endpoint captures short-term EEG change, and the registry does not report longer-term clinical outcome results. Adverse-event counts are posted, but event definitions and follow-up duration are not reported. The sample-size justification and primary analysis plan are not reported in the registry record, so the planning illustrations cannot establish the rationale or adequacy of the completed trial's design.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Efficacy of Normobaric Oxygen on Chronic Cerebral Ischemia — NCT03745092.
• Registry record last updated 2020-04-08; status last verified 2020-03.
• Results first posted 2020-03-25.
• 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

NCT03745092 is a completed, randomized, single-masked, parallel-group trial sponsored by Capital Medical University. It enrolled 49 participants: 26 assigned to normobaric oxygen and 23 to control. The intervention description specifies oxygen at 8L/min via face mask for 45 minutes between baseline and post-intervention EEG recordings; the control group rested for the same period.

The primary outcome is fronto-central theta absolute power change rate, summarized by group median. The registry posts group summaries but no primary between-group analysis. One secondary comparison, for wavelet entropy change, is reported with an unadjusted p-value; other listed secondary outcomes lack two-group estimates. The record reports zero serious adverse events, zero other adverse events, and zero deaths in both groups. Details of the analysis population, missing-data handling, multiplicity, and trial-specific sample-size justification are not reported in the registry record.