Comparative Analysis of CO2 Monitoring Methods in Patients With CF Undergoing General Anesthesia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparative Analysis of CO2 Monitoring Methods in Patients With CF Undergoing General Anesthesia (NCT03734822), a na na study. The primary outcome is Accuracy of CO2 Levels.

2. Clinical Question

This is a measurement-comparison question rather than a treatment-effect question. The aim is to assess how measurements from different methods relate to a reference measurement taken in the same clinical setting. Simultaneous measurement can make the comparison more direct by limiting the influence of changes in the patient's condition between measurement times. That is a general feature of paired measurement designs, not evidence that any method agreed closely with ABG in this study.

The registry record identifies cystic fibrosis and general anesthesia as the clinical context. It does not describe a control group of patients without cystic fibrosis, nor does it identify randomized treatment groups. The question therefore concerns measurement performance in the enrolled population, not whether one anesthetic or monitoring strategy improves a clinical outcome.

The primary outcome is titled “Accuracy of CO2 Levels” and is defined using mean CO2 levels in mmHg, with standard deviation as the stated dispersion measure. However, no means, standard deviations, agreement estimates, or outcome analyses are reported in the registry record. The magnitude and precision of any differences between the monitoring methods therefore cannot be assessed from the registry information.

3. Trial Design

The registry describes a completed, single-group study sponsored by Nationwide Children's Hospital. It lists 47 participants as enrolled and gives the condition as cystic fibrosis. The listed start date is 2016-03-10, and the primary completion date is 2017-12-20. The phase is listed as NA. These registry fields describe the study record; they do not establish when individual measurements were taken beyond the stated outcome timeframe.

The study compares measurements rather than assigning participants to separate monitoring strategies. The registry lists allocation as NA, masking as NONE, and the model as SINGLE GROUP. Its arm description is “Cystic fibrosis patients undergoing general anesthesia.” The record explicitly indicates that the arms are not a like-for-like control comparison. Accordingly, the listed monitoring methods should be understood as measurement methods used in the same clinical context, not as randomized arms.

The brief summary says that EtCO2 is monitored through the endotracheal tube during general anesthesia and that TCO2, capillary CO2, and ABG are also used in other healthcare settings. It states that the purpose was to perform all four measurements simultaneously during general anesthesia. The primary outcome description focuses on EtCO2, Cap-CO2, and TCCO2 compared with ABG immediately following induction of anesthesia. The registry does not describe further measurement timing, instrument details, or the operational definition used to judge accuracy.

The trial status is COMPLETED, but completion status alone does not mean that outcome results are available. The record lists one outcome measure and zero analyses. It does not report a statistical analysis plan, a sample-size justification for the study, or details of interim analyses. Information on participant flow, exclusions, and the number contributing to the primary outcome is 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 Accuracy of CO2 Levels, measured over Immediately following induction of anesthesia.

The primary endpoint is titled “Accuracy of CO2 Levels.” It concerns mean CO2 levels, expressed in mmHg, immediately following induction of anesthesia. The outcome description specifies comparison of EtCO2, capillary CO2, and transcutaneous CO2 with ABG, which the registry identifies as the gold standard. Standard deviation is the listed measure of dispersion for the continuous outcome.

Comparing monitoring methods with a reference measurement can help describe whether a method tends to give readings that differ from the reference and how variable those readings are. This is a general explanation of measurement comparison. Accuracy is not fully characterized by a mean alone: a mean difference can describe average bias, while the distribution of paired differences can show how widely individual readings vary. The registry record does not specify which agreement statistics were planned or used, and it reports no such estimates.

The stated timeframe is immediately following induction of anesthesia. The brief summary says the measurements were intended to be made simultaneously, which is relevant because the clinical state can change over time. The record does not provide observed values, the number of paired readings, or the degree of missingness. Therefore, it is not possible to determine from the registry whether any monitoring method had closer agreement with ABG, or how precisely any comparison was estimated.

The summary also refers to identifying a method with the least amount of patient risk. The primary endpoint description, however, is a comparison of CO2 levels, not a defined risk outcome. The record does not describe a risk measure linked to the monitoring methods or report a comparative estimate of risk.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a continuous primary outcome measured in mmHg and states that the summary parameter is the mean, with standard deviation as the dispersion measure. It also describes three non-ABG methods compared with ABG. The record does not report an analysis method, effect estimate, confidence interval, or test result. The explanations below are general statistical context for understanding this type of measurement question, not a description of analyses confirmed in the registry.

What does a mean describe?

For a continuous measurement, the mean summarizes the average value across observations. It can describe the central level of readings in a group or the average of paired differences between methods, depending on what is calculated. The standard deviation describes how spread out individual values are around their mean. Neither statistic alone describes how well two methods agree for individual patients. Two methods can have similar overall means while differing substantially for particular paired observations.

Why pair measurements?

When two methods are measured on the same participant at the same time, each participant can serve as their own measurement comparison. A paired analysis uses the within-participant difference between methods. This can reduce the effect of between-person variation on the comparison, because the methods are assessed under similar circumstances for each person. The study summary says the measurements were intended to be simultaneous. The registry does not report whether every participant had a complete set of measurements or how paired observations were handled in an analysis.

What does agreement mean?

Correlation describes whether two measurements tend to move together; it does not, by itself, show that they give similar values. For example, two methods may rank participants similarly while one method is systematically higher or lower. Agreement assessment therefore commonly examines paired differences, including their average and spread. A confidence interval for the mean difference can express uncertainty about average bias. Limits of agreement can describe the range within which individual differences are expected to fall under the analysis assumptions. These are general approaches. The registry does not report that these statistics were specified or calculated.

How does a confidence interval help?

A confidence interval conveys the precision of an estimated quantity, such as the average difference between a monitoring method and ABG. It is not a guarantee that the true value lies inside that particular interval. Its interpretation depends on the study design, the data, and the statistical procedure. A p-value, by contrast, is a measure of how incompatible the observed data are with a specified null hypothesis under the test assumptions; it does not measure the size or clinical relevance of a difference. No confidence intervals or p-values for the primary endpoint are reported in the registry record.

Why can variability matter?

General statistical context: measurements may show more variability than a simple normal model anticipates. In count outcomes, over-dispersion means that variability exceeds the level assumed by a basic count model and can make standard errors too small if ignored. The primary endpoint in this study is continuous rather than a count, and the registry does not report an over-dispersion analysis. For continuous paired measurements, the relevant concern is whether the distribution of differences and the chosen model support the assumptions used for estimates and uncertainty intervals. The registry does not report diagnostic checks or distributional assumptions for the outcome analysis.

What can planning calculations tell us?

The record describes sample-size illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. Such calculations are planning illustrations, not observed findings and not observed power. They are conditional on their assumptions and on the effect used as a reference. The record's study model is single-group, with multiple measurements, rather than a two-arm allocation. Consequently, an equal-allocation, two-arm illustration should not be mistaken for the study's actual design or a report of the number enrolled per monitoring method. Specific sample-size illustration values are not reported in the registry record.

What is missing for interpretation?

To interpret the measurement comparison statistically, readers would need observed paired results, the number of complete measurement sets, the defined agreement estimand, and an uncertainty measure. Details of missing-data handling and the analysis population would also help establish which participants contributed to each estimate. The registry lists zero analyses and reports none of these primary-outcome details. Without them, statistical significance, effect magnitude, agreement, and precision cannot be assessed.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure and zero analyses. It does not report whether multiple comparisons among EtCO2, capillary CO2, and transcutaneous CO2 were planned, how they would be prioritized, or whether any adjustment for multiple testing was specified. Because the registry does not report outcome tests or p-values, the impact of multiplicity on statistical conclusions cannot be assessed.

Missing-data methods are not reported in the registry record. The record gives an enrollment of 47, but it does not state how many participants had each measurement, how many had all four measurements, or whether any observations were excluded. It also does not describe reasons for missing measurements or methods for handling them. The enrollment count therefore cannot be assumed to equal the endpoint analysis count.

Analysis-population definitions are not reported. The registry does not specify whether the primary analysis included all enrolled participants, only those with complete measurements, or another set of participants. There is no description of exclusions, protocol deviations, or sensitivity analyses. The single-group measurement design also means that randomized treatment-analysis populations are not described in the record.

These omissions matter because the number and pattern of complete paired measurements can affect both the estimate and its precision. This is general statistical context, not a claim about what happened in this study. Without participant-level flow, missingness information, and a defined analysis population, readers cannot determine how broadly any eventual estimate would apply to those enrolled.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry lists 47 participants at risk in the cystic fibrosis group. It reports 0 serious adverse events, 0 other adverse events, and 0 deaths for that group. These are the event figures recorded for the listed group.

Zero recorded events should be read narrowly: the registry reports no events in those categories among the participants counted at risk. It does not show whether each participant completed every measurement, whether adverse events were actively assessed over a specified period, or whether events were attributed to a particular monitoring method. Those details are not reported in the registry record.

The study summary describes measurement methods used during general anesthesia and states an aim of identifying the method with the least amount of patient risk. The record does not provide a method-specific safety comparison or define an outcome for measuring risk. The adverse-event figures therefore do not establish comparative risk across EtCO2, TCO2, capillary CO2, and ABG. They are registry safety counts, not an estimate of the relative safety of the methods.

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

The registry record describes an investigation of CO2 monitoring in patients with cystic fibrosis undergoing general anesthesia. Its stated measurement question is whether EtCO2, capillary CO2, and transcutaneous CO2 provide readings that agree with ABG immediately following induction of anesthesia. The summary says the measurements were intended to occur simultaneously, and the record identifies ABG as the gold standard for comparison.

What the record does not establish is the result of that comparison. It contains no reported primary-outcome means, standard deviations, paired differences, agreement estimates, confidence intervals, or statistical tests. It is therefore not possible to determine from the registry whether the methods produced similar readings, how large any discrepancies were, or how precisely a comparison was estimated.

The study is described as single-group and non-randomized, with allocation listed as NA and masking as NONE. The measurements are not separate treatment arms in a like-for-like randomized comparison. This means the record should be read as a measurement study, not as evidence that choosing one monitoring method changes a clinical outcome. The registry also does not provide a comparative patient-risk estimate, despite mentioning risk as part of the study purpose.

The enrollment figure of 47 is not a substitute for the number of participants with complete paired measurements. That number, the analysis population, and missing-data handling are not reported. The completed status indicates the study record is marked complete, but it does not supply the missing outcome estimates.

In general, clinical interpretation of a measurement study depends on both the size of differences and their uncertainty, as well as the intended use of the measurements. Those considerations require results and analysis details absent from this registry record. The appropriate conclusion is limited: the study was designed to compare several CO2 monitoring methods with ABG in a specific anesthesia setting, but the registry information does not permit a conclusion about comparative accuracy, agreement, or safety.

13. Why This Trial Matters Statistically

Measurement studies address a different statistical problem from trials that compare treatments. Their central question is whether alternative methods produce values sufficiently similar to a reference for a particular setting and purpose. Describing the design correctly helps prevent measurement comparisons from being interpreted as randomized evidence about patient outcomes.

This study has a focused clinical context: patients with cystic fibrosis undergoing general anesthesia. It lists EtCO2, TCO2, capillary CO2, and ABG, and describes simultaneous measurements. The primary outcome specifically names three methods compared with ABG immediately following induction. These details clarify the intended comparison and the point in care at which it was meant to occur.

Statistically, the distinction between association and agreement is important. Two methods can be associated without giving interchangeable readings. A useful comparison generally needs paired differences and an assessment of their variability, together with uncertainty around the estimates. These are general principles; the registry does not report such analyses for this study.

The record also illustrates why enrollment and completion status alone do not answer questions about evidence strength. The enrollment is 47 and the status is COMPLETED, but no primary outcome results, analysis population, or missing-data description are reported. Without these, readers cannot assess precision, completeness of paired measurements, or the robustness of the comparison.

Finally, the record's planning assumptions should be kept separate from the described design and from observed results. A hypothetical two-arm, equal-allocation planning illustration does not convert a single-group measurement study into a randomized trial, and it does not show observed power. The statistical value of the record is therefore chiefly its clear statement of a measurement question and its limits: the design is described, but the estimates needed to answer that question are not reported.

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 main limitation for statistical interpretation is that the registry record does not report primary outcome results. Means and standard deviations are specified as the outcome summary, but no values are given. There are also no paired differences, agreement estimates, confidence intervals, or test results. Accuracy and precision therefore cannot be evaluated.

The outcome description and brief summary are not identical in their method lists. The summary describes all four measurements as simultaneous, while the primary outcome specifically names EtCO2, Cap-CO2, and TCCO2 as compared with ABG. The record does not explain whether each comparison was analyzed or how the measurements were operationally defined. It also does not give instrument details or further timing beyond immediately following induction of anesthesia.

Although 47 participants are listed as enrolled, the number with complete measurements is not reported. The registry does not describe participant flow, analysis populations, exclusions, missingness, or missing-data methods. It is thus unknown whether all enrolled participants contributed to the intended comparisons.

The record lists a single-group model and no masking. It does not report an analysis plan, interim analyses, a study sample-size justification, or methods for handling multiple comparisons. The sample-size assumptions described in the record use equal allocation between two arms, which is not the described single-group measurement structure; specific illustration results are not reported in the registry record.

Finally, the purpose mentions patient risk, but no method-specific risk endpoint or comparative risk analysis is reported. The safety counts are not linked to individual monitoring methods. These limitations restrict conclusions to the study's stated intent and registry design, rather than any claim about comparative accuracy or safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparative Analysis of CO2 Monitoring Methods in Patients With CF Undergoing General Anesthesia — NCT03734822.
• Registry record last updated 2019-03-14; status last verified 2019-03.
• Results first posted 2019-03-14.
• 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

NCT03734822 is a completed, single-group study sponsored by Nationwide Children's Hospital, with 47 participants listed as enrolled. The population is patients with cystic fibrosis undergoing general anesthesia. The registry lists a start date of 2016-03-10 and a primary completion date of 2017-12-20.

The stated purpose is to compare CO2 monitoring methods performed simultaneously during general anesthesia. The primary outcome is mean CO2 level in mmHg immediately following induction, with EtCO2, capillary CO2, and transcutaneous CO2 compared with ABG. Standard deviation is the listed dispersion measure.

The record reports 0 serious adverse events, 0 other adverse events, and 0 deaths in the listed group of 47 at risk. It lists one outcome measure and zero analyses. Primary outcome estimates, participant flow, analysis populations, missing-data methods, and comparative risk results are not reported in the registry record.