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 Preoxygenation Using THRIVE Versus Facemask in Parturients (NCT03772574), a randomized na study. The primary outcome is Preoxygenation Duration.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03772574 |
| Phase | NA |
| Condition | Preoxygenation |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 91 |
| Arms in the primary outcome | 3 |
| Lead sponsor | University of British Columbia |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes parturients undergoing preoxygenation. The primary outcome description refers to tidal-volume breathing with either THRIVE or facemask preoxygenation. Further eligibility details, participant characteristics, and the clinical setting are not reported in the registry record, so the target population cannot be characterized more narrowly from this record.
Intervention
One arm used THRIVE preoxygenation: tidal-volume breathing with the OptiFlow system applied at 100% oxygen. The registry also lists a THRIVE and Facemask arm, but does not describe how the two devices were combined or used in sequence. Additional details of the THRIVE procedure are not reported in the registry record.
Comparator
The Standard Facemask arm used tidal-volume breathing through a face mask set at 100% oxygen. The registry lists both a THRIVE arm and a THRIVE and Facemask arm alongside this comparator. It does not clearly specify which pairwise contrast was designated as the primary comparison or how the combined arm was implemented.
Primary question
The primary outcome is the duration, in minutes, to achieve end-tidal oxygen (EtO2) of at least 90% after tidal-volume breathing, with a maximum timeframe of 8 minutes. The registry describes the study aim as determining preoxygenation duration using THRIVE and facemask. Results for the primary outcome are posted for Standard Facemask, while results for both THRIVE arms are missing.
3. Trial Design
The registry record describes a randomized, single-masked, parallel-group trial sponsored by the University of British Columbia. The study is marked completed, with enrollment of 91. Its recorded start date is 2018-12-01 and its primary completion date is 2019-07-15. The registry lists phase as not applicable.
Three arms are listed: Standard Facemask, THRIVE, and THRIVE and Facemask. The intervention descriptions specify tidal-volume breathing at 100% oxygen for the facemask and THRIVE arms; the THRIVE description names the OptiFlow system. Details of the combined arm are not reported in the registry record. Although the allocation is randomized and the model is parallel, the identity of the person or people masked is not reported in the registry record.
The primary outcome is preoxygenation duration, measured in minutes, to reach EtO2 of at least 90%, with a maximum timeframe of 8 minutes. The posted Standard Facemask result has an analysis count of 40. The THRIVE and THRIVE and Facemask primary-outcome results have analysis counts of 20 each, but their outcome estimates are missing. The registry does not explain why the arm counts for this outcome differ from enrollment.
Eight secondary outcomes are listed: the proportion reaching the EtO2 threshold at time points from 3 minutes through 8 minutes, comfort score, and acceptability score. The registry record does not post results for these secondary outcomes. It also does not report a statistical analysis plan, the methods used to generate the posted confidence interval, or how the three arms were intended to be compared.
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.
Before assignment: 91 patients provided informed consent in order to reach the recruitment goal of 80 patients. This is the reason for the discrepancy mentioned in the comments.
Overall Study
| Stage | Standard Facemask | THRIVE | THRIVE and Facemask |
|---|---|---|---|
| STARTED | 42 | 25 | 24 |
| COMPLETED | 40 | 20 | 20 |
| NOT COMPLETED | 2 | 5 | 4 |
Reasons for not completing this period:
| Reason | Standard Facemask | THRIVE | THRIVE and Facemask |
|---|---|---|---|
| Protocol Violation | 2 | 0 | 0 |
| Discomfort | 0 | 5 | 4 |
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 | Standard Facemask | THRIVE | THRIVE and Facemask | Total |
|---|---|---|---|---|---|
| Participants analysed | 40 | 20 | 20 | 80 | |
| Age, Continuous | years | 35.5 (SD 4.3) | 35 (SD 4.1) | 35 (SD 4.4) | 35.3 (SD 4.2) |
| Sex: Female, Male: Female | Participants | 40 | 20 | 20 | 80 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 | 0 |
| Race and Ethnicity Not Collected | Participants | — | — | — | 0 |
| Region of Enrollment: Canada | participants | 40 | 20 | 20 | 80 |
| Gravidity | Pregnancies | 2 (2 to 3) | 2 (2 to 4) | 2 (2 to 2) | 2 (2 to 3) |
| Parity | births | 1 (0 to 1) | 1 (0 to 1) | 1 (0 to 1) | 1 (0 to 1) |
| Gestational age | weeks | 38.6 (SD 1.0) | 38.7 (SD 1.1) | 39.1 (SD 0.6) | 38.8 (SD 0.92) |
| Baseline respiratory rate | breaths/min | 11.9 (SD 3.7) | 14.5 (SD 4.1) | 13.3 (SD 3.1) | 12.9 (SD 3.8) |
| Baseline End Tidal Oxygen (ETO2) | Percent of oxygen in expired breath | 15.7 (SD 1.2) | 15.7 (SD 0.9) | 15.8 (SD 1.0) | 15.7 (SD 1.1) |
| Baseline Heart Rate | bpm | 74.4 (SD 10.8) | 76.1 (SD 9.7) | 75.2 (SD 13.9) | 75.1 (SD 11.3) |
| Baseline Oxygen Saturation (SPO2) | percent of hemoglobin carrying oxygen | 98.0 (SD 1.5) | 98.4 (SD 1.4) | 98.5 (SD 1.4) | 98.2 (SD 1.4) |
| BMI | kg/m^2 | 29.1 (SD 3.7) | 29.5 (SD 4.8) | 30.4 (SD 3.8) | 29.5 (SD 4.0) |
6. Primary Endpoint
The registry lists the primary outcome as Preoxygenation Duration, measured over Maximum 8 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | minutes |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is the duration required to reach end-tidal oxygen (EtO2) of at least 90% during tidal-volume breathing with preoxygenation. It is recorded in minutes, with a maximum timeframe of 8 minutes. The registry frames the endpoint as a comparison of preoxygenation using THRIVE and facemask oxygenation in parturients.
EtO2 is the oxygen concentration measured at the end of expiration. In general, a threshold-based duration endpoint captures how long it takes for a measured value to reach a specified level. It differs from a single measurement at a fixed time: the endpoint concerns the time taken to reach the target, subject to the stated observation limit. The registry does not explain the rationale for choosing the 90% threshold or the 8-minute limit.
The endpoint is reported as a continuous measure with a mean and a 95% confidence interval. In general, a mean summarizes the average duration in a group, while a confidence interval conveys uncertainty around an estimated mean. Neither quantity alone establishes a difference between treatment groups; that requires a defined group contrast and its estimate. The posted record gives a mean of 3.6 minutes for Standard Facemask, with a 95% confidence interval from 3.3 to 6.7. The corresponding estimates for the THRIVE and THRIVE and Facemask arms are not reported in the registry record.
The registry also lists secondary outcomes based on the proportion reaching the threshold at specified time points, along with comfort and acceptability scores. Those outcomes could describe aspects of performance and participant experience, but their results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary-outcome result is for the Standard Facemask arm: the mean preoxygenation duration is 3.6 minutes, with a 95% confidence interval from 3.3 to 6.7. This is a group-level estimate for the listed arm. It is not a direct estimate of the difference between Standard Facemask and either THRIVE arm.
Primary-outcome estimates for the THRIVE arm and the THRIVE and Facemask arm are missing. Without those estimates, the registry record does not support a numerical comparison of mean duration across the listed arms. It also does not post a treatment-effect estimate, a confidence interval for a between-arm contrast, or a p-value for the primary outcome. The registry record does not state which pairwise contrast was the primary comparison.
In general, a confidence interval describes the uncertainty associated with an estimate under the statistical method used to construct it. The interval around the Standard Facemask mean is not itself a comparison interval: it does not show how the mean differs from the THRIVE results. A confidence interval also should not be read as a range containing every participant’s duration. The registry does not report the distribution of individual durations or the method used to calculate this interval.
The reported endpoint is limited to achieving the EtO2 target within a maximum timeframe of 8 minutes. The registry does not state how participants who did not reach the target within that timeframe were handled in the mean, or how any such observations were represented. It is therefore not possible to determine from the record whether the estimate reflects all randomized participants or a subset with an observed duration.
The arm analysis counts are 40 for Standard Facemask, 20 for THRIVE, and 20 for THRIVE and Facemask. The record does not explain these counts or reconcile them with enrollment of 91. They should be read as the reported counts for the primary-outcome entries, not as proof of the number randomized to each arm or the number included in every analysis.
The record lists eight secondary outcomes but does not post their results. It gives no estimates for the proportions reaching the target at the listed time points, and no comfort or acceptability scores. Consequently, neither those outcomes nor the primary-outcome entries establish whether one approach had a shorter duration or different participant ratings. The appropriate interpretation is limited to the Standard Facemask estimate and the specific gaps in the registered results.
9. Statistical Methods Explained
Outcome type and summary
The primary outcome is a continuous measure expressed in minutes and summarized by a mean. In general, continuous outcomes can take a range of values rather than belonging to a simple category. A mean describes the average of the observations included in an analysis. It does not, on its own, describe the spread of individual values or whether observations are concentrated near the mean. A standard deviation or another measure of spread is not posted for the primary outcome.
The endpoint has a threshold: time until EtO2 reaches at least 90%. A duration endpoint can be analyzed in different ways, depending on the data structure and analysis plan. For example, an analysis might compare average recorded durations or account for participants who do not reach the threshold during observation. The registry record identifies the outcome as a mean and gives a maximum timeframe of 8 minutes, but does not report how observations that did not reach the threshold were handled. The method used for the primary analysis is not reported in the registry record.
Confidence intervals
The Standard Facemask mean is reported with a 95% confidence interval from 3.3 to 6.7. In general, a confidence interval gives a range of estimates compatible with the observed data under the method’s assumptions. Its width reflects statistical uncertainty as well as features of the analysis, including the amount and variability of usable data. It is not a description of the full range of participant outcomes, and it does not directly quantify a difference between arms unless the interval is calculated for that difference.
The registry does not report the formula, distributional assumptions, or other details used to calculate this interval. The interval should therefore be read as the registry’s posted uncertainty estimate, without assuming a particular analysis procedure. No confidence intervals are posted for the other arms.
Randomization and group comparisons
Random allocation is recorded, and the trial is described as parallel group. In general, randomization is intended to make treatment groups comparable with respect to factors measured and unmeasured at baseline, on average. It does not guarantee that the groups are identical in a particular trial. A parallel design assigns participants to groups that receive their assigned intervention rather than making the comparison within the same participant.
The record lists three arms, but does not state the planned primary contrast or explain the combined THRIVE and Facemask procedure. A between-arm result requires estimates for the relevant arms and a specified comparison. Since primary-outcome estimates are missing for the THRIVE arms, the registry’s posted mean for Standard Facemask cannot answer whether its duration differs from either of those arms.
Secondary outcomes and multiple comparisons
The listed secondary outcomes include proportions reaching the EtO2 threshold at 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, and 8 minutes, as well as comfort and acceptability scores. In general, when a study examines multiple outcomes or contrasts, the chance of observing an apparently notable result by chance can increase if each is tested separately without accounting for multiplicity. A statistical plan may specify which outcomes are primary, how secondary outcomes will be interpreted, and whether any adjustment is used.
The registry record does not report a multiplicity strategy, the analysis methods for the secondary outcomes, or results for those outcomes. It is not possible to determine whether any planned adjustments were made. The secondary outcomes should not be treated as evidence of an effect when their estimates are absent.
Missing estimates and analysis counts
For the primary outcome, the registry gives analysis counts of 40 for Standard Facemask and 20 each for THRIVE and THRIVE and Facemask, but gives estimates only for Standard Facemask. The record does not explain why those counts differ from enrollment of 91, whether they refer to randomized participants or outcome-specific observations, or why the other estimates are missing. The reasons for missing outcome results are not reported in the registry record.
In general, missing outcome data can affect both precision and the interpretation of a group estimate. The impact depends on how much information is missing, why it is missing, and how the analysis treats missing observations. None of those details is stated for this trial. No analysis population definition, such as an intention-to-treat population, is reported in the registry record.
Planning illustrations
Any sample-size calculations associated with the registry are planning illustrations rather than observed trial results. In general, such illustrations use assumptions about the effect to detect, the significance level, allocation, and statistical approximation. They do not show the probability that this completed trial detected an effect, and they do not substitute for a reported trial analysis. The record says the illustration is based on a fraction of the observed effect, but the missing arm results mean that a reader cannot verify the underlying observed contrast from the posted primary-outcome entries. The trial’s own sample-size justification and design calculations are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome and eight secondary outcomes. The secondary outcomes comprise the proportion reaching EtO2 of 90% at time points from 3 minutes through 8 minutes, plus comfort and acceptability scores. Results for these secondary outcomes are not reported in the registry record. The record does not describe whether the analyses were intended to be confirmatory or exploratory, whether particular secondary outcomes had priority, or whether adjustments for multiple testing were planned.
In general, multiplicity matters when many statistical comparisons are made: without a prespecified approach, isolated findings can be difficult to distinguish from chance patterns. A statistical analysis plan can define which comparisons are central and how secondary findings should be interpreted. Such a plan is not reported in the registry record, so no conclusion can be drawn about the handling of multiplicity.
The primary outcome is also incomplete in the posted results. A mean and confidence interval are available for Standard Facemask, but estimates for the THRIVE and THRIVE and Facemask arms are missing. The registry does not explain why these results are absent, how many participants lacked outcome data, or how any missing observations were handled. The reported primary-outcome analysis counts are 40, 20, and 20 for the three listed arms, respectively; their relationship to enrollment of 91 is not explained.
The analysis populations are not described. In general, an analysis population definition clarifies which randomized participants are included and how deviations, withdrawal, or missing measurements are treated. The record does not identify an intention-to-treat, per-protocol, or other analysis population, and it does not report exclusions or reasons for missingness. These omissions limit assessment of potential bias and of how representative the posted estimate is of all randomized participants.
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 Facemask | 0 | 42 | 0.0% |
| THRIVE | 0 | 25 | 0.0% |
| THRIVE and Facemask | 0 | 24 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Standard Facemask | 0 of 42 |
| THRIVE | 0 of 25 |
| THRIVE and Facemask | 0 of 24 |
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 Facemask | 0 of 42 |
| THRIVE | 0 of 25 |
| THRIVE and Facemask | 0 of 24 |
The registry reports serious adverse events for three groups. For Standard Facemask, 42 participants were at risk and zero were affected; for THRIVE, 25 were at risk and zero were affected; and for THRIVE and Facemask, 24 were at risk and zero were affected. The record also reports zero other adverse events and zero deaths in each of these groups.
These are counts as recorded in the registry. A count of zero affected participants means no events were recorded in the relevant category for the listed group; it does not establish that an event is impossible or that no event could occur outside the recorded observation and reporting process. In general, safety counts depend on how events were defined, collected, and reported, as well as on the number of participants observed.
The primary-outcome analysis counts differ from the safety counts, and the registry does not explain the relationship between these populations. The safety entries do not provide event descriptions, event timing, severity beyond the serious-versus-other categories, or details of follow-up. No serious adverse event terms are listed. These entries should therefore be read as the reported event counts, not as a complete account of every aspect of safety monitoring.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, single-masked, parallel-group trial compared preoxygenation approaches in parturients and was marked completed. The listed approaches were Standard Facemask, THRIVE, and THRIVE and Facemask. The primary outcome was duration to reach EtO2 of at least 90%, measured in minutes within a maximum timeframe of 8 minutes.
The posted primary-outcome result is limited to Standard Facemask: mean duration 3.6 minutes, with a 95% confidence interval from 3.3 to 6.7. This describes the estimate and its reported uncertainty for that arm. It does not tell the reader how the THRIVE arms performed, and it is not a treatment-effect estimate. The registry’s missing arm estimates prevent a direct assessment of differences in duration from the posted results.
The record also lists secondary outcomes about reaching the EtO2 target at specified time points, comfort, and acceptability, but their results are not reported. The registry does not give the primary comparison, analysis plan, analysis population, handling of missing outcomes, or rationale for the sample size. These gaps mean the statistical evidence cannot be reconstructed or fully evaluated from the record alone.
In general, a completed trial designation indicates the registry status, not that every planned result is posted or that a particular conclusion follows. Likewise, an arm-specific estimate is not evidence of a comparative effect unless the relevant group estimates and an appropriate contrast are available. The registry entries should be interpreted as a partial account of the trial’s results rather than as a complete comparative analysis.
13. Why This Trial Matters Statistically
This trial illustrates a basic distinction in clinical-trial interpretation: an outcome estimate for one group is not the same as a comparison between groups. The Standard Facemask mean and its confidence interval give information about that arm’s recorded preoxygenation duration. But the intended scientific question concerns approaches to preoxygenation, and the THRIVE-arm estimates needed to interpret that comparison are not reported in the registry record.
The record also lists three arms while its brief study aim refers to THRIVE and facemask preoxygenation. The third, combined arm makes clarity about the planned contrast especially important. A well-defined comparison tells readers which groups are being contrasted and which result addresses the primary question. That comparison is not specified in the registry record.
Another statistical issue is the link between enrollment and outcome analysis. Enrollment is 91, while the listed primary-outcome analysis counts are 40, 20, and 20. The record does not explain these counts or the absence of estimates for two arms. Clear reporting of analysis populations and missing data is important because readers need to know who contributed to each estimate and how incomplete measurements were handled.
The registry also lists several secondary outcomes without posting their results or describing how multiple analyses were addressed. In general, this information helps distinguish the primary question from exploratory analyses and supports a measured interpretation of secondary findings. Together, these features make the record useful for understanding the trial’s design and registered outcome, while also showing why complete arm-level results and analysis details are necessary for a comparative statistical interpretation.
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 posted results is that primary-outcome estimates are available only for Standard Facemask. The THRIVE and THRIVE and Facemask results are missing, so the recorded mean cannot be used to quantify a between-arm difference. The registry does not explain why those estimates are absent.
Although enrollment is 91, the primary-outcome counts are 40 for Standard Facemask and 20 for each THRIVE arm. The record does not explain the relationship between these figures, identify the number randomized to each arm, or state whether the analysis counts represent participants with an observed outcome. The amount and reasons for missing outcome data, and the methods used to handle it, are not reported in the registry record.
The trial has three listed arms, but the registry does not specify the primary pairwise comparison or describe the procedures for the combined THRIVE and Facemask arm. The person or people masked are not identified. Other potentially relevant design details, including eligibility criteria, participant characteristics, and the statistical analysis plan, are not reported in the registry record.
The primary outcome is capped at a maximum timeframe of 8 minutes, but the record does not explain how participants who fail to reach the EtO2 threshold within that timeframe are included in the mean analysis. The method used to calculate the confidence interval is also not stated. Secondary outcomes are listed without posted results, and multiplicity handling is not described. These limitations constrain interpretation of both the available arm estimate and the trial’s intended comparative question.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Preoxygenation Using THRIVE Versus Facemask in Parturients — NCT03772574.
- Registry record last updated 2022-05-24; status last verified 2022-05.
- Results first posted 2022-05-24.
- 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
The registry record describes a completed randomized, single-masked, parallel-group trial sponsored by the University of British Columbia, with enrollment of 91. It lists Standard Facemask, THRIVE, and THRIVE and Facemask arms. The primary outcome is duration in minutes to reach EtO2 of at least 90%, within a maximum timeframe of 8 minutes.
For Standard Facemask, the posted mean is 3.6 minutes with a 95% confidence interval from 3.3 to 6.7. Primary-outcome estimates for the two THRIVE arms are missing. Eight secondary outcomes are listed, but their results are not reported in the registry record. The registry does not state the primary group comparison, analysis plan, analysis populations, or how missing outcomes were handled.