Detecting Post-Operative Respiratory Depression in Children: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Detecting Post-Operative Respiratory Depression in Children (NCT01843933), a randomized na study. The primary outcome is Abnormal ETCO2 Values, Abnormal Pulse Oximetry Values, and Staff Interventions.

2. Clinical Question

The clinical motivation described in the record is that residual effects of general anesthesia and medicines given for pain can contribute to breathing problems in recovery. Pulse oximetry and nursing assessments are described as current monitoring practices; capnography measures exhaled carbon dioxide and provides a continuous assessment of respiration. The trial's stated objectives were to determine whether capnography detects breathing problems faster and more often than traditional monitors, and to determine whether adding capnography to routine monitoring has an effect. The available outcome description does not report a comparative estimate or specify a separate result for detection speed.

The record identifies the condition as respiratory depression. It does not report the trial's age eligibility criteria, the specific surgical procedures represented, or other population characteristics. Those omissions limit how specifically the question can be applied to particular groups of children or recovery settings.

3. Trial Design

The registry identifies NCT01843933 as a completed, randomized, parallel-group trial sponsored by Yale University. It lists enrollment as 211 and gives the trial start as 2013-06 and primary completion as 2014-12. The phase is listed as NA. The record describes no masking: staff could view the capnography output in the intervention group, while staff in the comparator group were blinded to that output.

Both groups received standard monitoring. In the intervention group, capnography was added to standard practice and its output was viewable to staff. In the comparator group, the monitor collected and recorded data, but staff were blinded to its output. This design makes access to the capnography information the stated difference between the groups; the record does not describe other differences in care or specify how staff acted on monitor readings.

The primary outcome is described as the number of participants with abnormal ETCO2 values, abnormal pulse oximetry values, and staff interventions during the post-operative period. The observation window ran from entry into the PACU until discharge; the record gives an average time of 1 hour. The outcome description defines mild, moderate, and severe events and interventions, rather than reducing them to a single event category in the available record.

Although the trial is marked completed, its primary outcome results are not reported in the registry record. The record lists one outcome measure and zero analyses. It does not report an analysis population, participant flow, arm-specific outcome counts, a treatment-effect estimate, or a confidence interval. It also does not report the randomization procedure, allocation concealment, sample-size justification, or details of the statistical analysis plan. These aspects of design and analysis therefore cannot be evaluated from the 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

Reasons for not completing this period:

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 Abnormal ETCO2 Values, Abnormal Pulse Oximetry Values, and Staff Interventions, measured over Post operative period (From entering the PACU until discharge. Average time is 1 hour).

The primary endpoint is titled “Abnormal ETCO2 Values, Abnormal Pulse Oximetry Values, and Staff Interventions.” Its unit is participants, and its measure is described as a number. The observation period extends from PACU entry until discharge, with an average time of 1 hour. The endpoint groups observations into mild, moderate, and severe events or interventions.

The definitions include oxygen desaturation thresholds measured by pulse oximetry, abnormal ETCO2 patterns, apnea, airway obstruction, and staff responses such as stimulation, airway repositioning, airway adjunct use, assisted ventilation, and reversal medication. These categories reflect both monitored respiratory findings and responses to them. They are relevant to the trial's question because the intervention is intended to make capnography information available to staff during recovery.

As a general statistical point, a participant-level endpoint can describe how many people experienced an event, rather than how many times an event occurred. However, the registry record does not clarify whether a participant could be counted in multiple categories, how repeated events were handled, or whether categories were combined for analysis. The record also does not give outcome counts or a comparison between arms, so the endpoint's observed frequency and any difference between monitoring approaches are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record identifies the study as randomized and parallel-group. In a randomized trial, allocation is intended to create groups that can be compared without choosing treatment according to participants' characteristics. Randomization does not guarantee that every characteristic is balanced, and the method used to generate or conceal allocation is not reported in the registry record. A parallel design means the comparison is between groups assigned to different monitoring approaches, rather than a crossover in which participants receive both approaches in sequence.

What does the lack of masking imply?

The trial is listed as having no masking. The intervention description says staff could view capnography output in one group, while comparator staff were blinded to that output. That difference is part of the intended contrast, but awareness of group assignment can also affect staff behavior and the recording of interventions. This is a general methodological consideration, not a finding that such influence occurred in this trial. The record does not describe safeguards for outcome assessment or specify who determined whether events met the endpoint definitions.

How should the endpoint structure be understood?

The listed outcome combines abnormal monitor values and staff interventions, with separate mild, moderate, and severe definitions. These are not necessarily interchangeable kinds of outcomes: a monitor threshold is an observed signal, while stimulation or airway support is a response. As a general principle, combining different event types can make a single summary difficult to interpret unless the combination rule is clear. The registry record does not state whether the categories were analyzed separately, combined, or ranked, and does not report a participant-level definition for handling multiple events.

The outcome unit is participants, which suggests a count of people with an event rather than a rate of repeated events, but the record does not clarify the counting rules. For example, it does not state whether a person with more than one event category would be represented once or in multiple category counts. No arm-level endpoint counts or effect estimates are reported, so it is not possible to reconstruct an unadjusted comparison from the record.

Why can uncertainty and event frequency matter?

As a general concept, an effect estimate describes the observed contrast between groups, while a confidence interval conveys uncertainty around that estimate under a specified method. A narrow interval indicates greater precision than a wide interval, but neither interval width nor an estimate's direction can be assessed without reported results. Neither a confidence interval nor a test result for this endpoint is reported in the registry record.

For binary outcomes, methods often compare the proportion of participants with an event, or model event status directly. The choice depends on the outcome definition, design, and analysis plan. Those choices cannot be identified because the registry does not report an analysis plan or results. When events can recur, analyses of event counts or rates may require methods that account for variability beyond a simple count model. This general issue cannot be resolved from the record, which describes a participant-count outcome but gives no repeated-event analysis details.

What analysis details are unavailable?

The record lists zero analyses and does not report a primary-outcome estimate, confidence interval, or significance test. It does not identify whether analysis was by assigned group, whether any adjusted analysis was planned, or how missing outcomes were handled. It also does not report an analysis population or the number of participants with outcome data. These details are important because exclusions, missing observations, and analysis choices can affect interpretation of a randomized comparison.

The sample-size assumptions described in the record refer to planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. The record also says that the effect to detect is a stated fraction of the observed effect, and distinguishes participant-per-arm illustrations from total-event illustrations for time-to-event outcomes. However, the primary outcome is not reduced to one comparison, and the registry does not report sample-size illustration results for this endpoint. These assumptions are not evidence of the trial's original design justification or its observed power. The trial's own sample-size justification and statistical plan are not reported in the registry record.

As a general matter, planning calculations depend on a clearly defined target effect and endpoint. Where an endpoint includes multiple categories, a planning calculation requires a decision about which comparison it targets. Since the registry does not state that decision or report the calculated illustrations for this endpoint, no power or sample-size conclusion for the trial can be drawn from the record.

10. Multiplicity, Missing Data and Analysis Populations

The primary endpoint description includes several event and intervention categories, divided into mild, moderate, and severe levels. The stated objective also asks whether capnography detects problems faster and more often. Testing or estimating several outcomes can raise multiplicity concerns: as a general statistical principle, examining many comparisons can increase the chance that at least one appears notable by chance if no adjustment or hierarchy is used. The registry record does not report a multiplicity strategy, a hierarchy of outcomes, or which category-level comparisons were prespecified for analysis.

The record lists one outcome measure, but its description contains multiple components and thresholds. It does not say whether these were intended as separate endpoints, a composite, or descriptive categories within one measure. It also does not report a result for the detection-speed objective. Without those specifications, the scope of the planned comparisons cannot be determined.

Missing-data handling is not reported in the registry record. There is no account of participants lacking endpoint measurements, how such measurements were handled, or whether follow-up through PACU discharge was complete. The analysis population is also not reported. In particular, the available adverse-event denominators should not be assumed to define the primary-outcome analysis population.

The registry lists zero analyses and does not provide an analysis plan. It therefore does not state whether participants were analyzed according to randomized assignment, whether any participants were excluded, or whether any model adjustments were made. These are uncertainties about reporting; they do not establish that data were missing or that any particular analysis choice was made.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The serious adverse-event entries list 0 events among 98 at risk in the standard-monitoring group blinded to capnography, and 0 among 103 at risk in the group with capnography viewable. The other adverse-event entries also list 0 events, with the same at-risk counts for the respective groups. These are the registry's recorded safety figures.

Zero recorded events means the registry fields show no events in those categories for the stated at-risk groups. It does not establish that the trial had no other clinical events, nor does it describe the primary respiratory endpoint. The record does not provide definitions or reporting details for the serious and other adverse-event categories in the posted adverse-event fields, so the scope of those categories cannot be further characterized.

Death counts are null for both groups and are not reported in the registry record. A null entry should not be read as a zero count. The at-risk counts in the safety fields are not identified as the denominator for the primary outcome, and should not be used as a substitute for unreported endpoint data.

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

This record describes a completed randomized trial comparing standard monitoring alone, with capnography output hidden from staff, against standard monitoring with capnography output viewable to staff. It gives clinically specific definitions for abnormal oxygenation and ETCO2 values and for staff interventions during recovery. These details establish what the investigators intended to observe, but do not establish what the comparison found.

The primary outcome results are not reported in the registry record. Consequently, the record cannot show whether one group had more or fewer participants meeting any event definition, whether staff interventions differed, or whether capnography identified problems faster. It also cannot establish the precision or statistical significance of an effect. No treatment benefit or lack of benefit can be inferred from the absence of results.

The zero serious and other adverse-event counts are limited to the registry's safety entries and their stated denominators. They should not be treated as evidence about all possible safety outcomes or as a substitute for primary-outcome reporting. Death counts are not reported in the registry record.

As a general interpretation principle, a trial's result depends on the outcome definition, analysis population, handling of missing data, and statistical method as well as on the numerical estimate. Those elements are not available for the primary endpoint. The appropriate conclusion is therefore about the limits of the record: it documents the design and intended measurements, but does not report the comparative clinical findings needed to determine what the observed data show.

13. Why This Trial Matters Statistically

This trial addresses a measurement question as well as a monitoring question. Capnography was used in both groups to collect and record data, but staff could view its output only in the intervention group. The comparison therefore concerns the availability of that information alongside standard monitoring, rather than simply whether a capnography device was present.

Statistically, that distinction matters because an endpoint can include both physiological observations and staff actions. If staff can see a monitor signal, that information may be relevant to both whether an event is recognized and whether an intervention is recorded. The registry's definitions make this connection visible, but the results and analysis rules needed to assess it are not reported.

The endpoint also spans a range of event severities and includes several types of findings and responses. This makes clear outcome specification important: a participant-level summary, category-specific counts, and repeated-event summaries answer different questions. The record does not state which of these summaries was used or report estimates for any of them.

The trial is therefore statistically informative as an example of why monitoring studies need transparent endpoint definitions and reporting of comparisons, uncertainty, analysis populations, and missing-data handling. The registry supplies detailed event thresholds and identifies a randomized design, but does not report the primary results. The clinical question is recognizable; its answer cannot be evaluated from the posted outcome information.

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.

Important limitations arise from missing result and analysis information in the registry record. The primary outcome is described in detail, but no event counts, between-group estimate, confidence interval, or significance test is reported. The record also lists zero analyses. As a result, neither the direction nor the size nor the precision of the primary comparison can be assessed.

The outcome includes multiple levels and types of events and staff interventions. The record does not explain how multiple events in one participant were counted, whether categories were combined, or how competing event types were handled. It also does not report an operational definition of detection speed or a result for the stated faster-detection objective.

The record does not report participant characteristics, age eligibility, surgical case mix, group-specific primary-outcome populations, participant flow, or completeness of observation. The enrollment is listed as 211, while adverse-event fields give at-risk counts of 98 and 103; the record does not explain the relationship between those safety denominators and the primary-outcome population. No conclusion about attrition or missingness follows from those entries alone.

Details of sequence generation, allocation concealment, outcome assessment, the statistical analysis plan, sample-size justification, and any interim analyses are not reported in the registry record. The trial is listed as unmasked, and staff access to capnography differed by group, but the record does not describe how that might have affected outcome ascertainment or intervention recording. These reporting gaps limit appraisal of both the analysis and the generalizability of any result, even though the trial is marked completed.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Detecting Post-Operative Respiratory Depression in Children — NCT01843933.
• Registry record last updated 2016-02-24; status last verified 2016-01.
• Results first posted 2016-02-24.
• 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.

18. Record Summary

NCT01843933 is a completed randomized, parallel-group trial sponsored by Yale University. It compared standard monitoring with capnography output hidden from staff against standard monitoring with capnography output viewable to staff. Enrollment is listed as 211; the trial start is 2013-06 and primary completion is 2014-12.

The primary outcome concerns participants with abnormal ETCO2 values, abnormal pulse oximetry values, or staff interventions during the PACU stay, with mild, moderate, and severe definitions. The registry record does not report primary-outcome results, analyses, or an analysis population. Safety entries report zero serious and zero other adverse events in each group; death counts are not reported in the registry record.