Pulmonary Function Using Non-invasive Forced Oscillometry: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pulmonary Function Using Non-invasive Forced Oscillometry (NCT03346343), a na na study. The primary outcome is Area Under the Reactance Curve (AXR).

2. Clinical Question

In general, an observational measurement study can describe how a physiological measure varies across clinical groups or over time. Its findings do not by themselves establish that a disease category caused a difference in lung function, or that a treatment caused a change. The registry's stated purpose includes both measurement and response to treatments, but the record does not report a treatment-effect estimate or a specific comparative analysis. The central interpretive question is therefore whether AXR measurements are reported for the intended infant groups and time period, and how complete and precise those measurements are. The record does not provide the numerical outcome values needed to answer that question.

3. Trial Design

The registry describes a prospective observational study titled “Pulmonary Function Using Non-invasive Forced Oscillometry Respiratory Testing.” Its model is single group, allocation is listed as not applicable, and masking is listed as none. The phase field is also not applicable. These entries distinguish this study from a randomized, masked trial designed to estimate a treatment contrast. The listed sponsor is the University of Alabama at Birmingham.

The registry lists an enrollment of 600. That entry is not itself a report of how many participants contributed to a particular outcome, nor does it establish that all listed participants had usable AXR measurements. The study status is active, not recruiting. The listed start date is 2017-12-06, and the primary completion date is 2024-10-21.

The intervention entry is non-invasive forced airway oscillometry, classified as a device. The arm description says lung function is analyzed in preterm infants and term infants with and without lung disease, using cross-sectional and longitudinal comparisons. It also names an aim concerning lung function in term and preterm infants without lung disease, with an anticipated group size stated in the registry. A further aim is incomplete in the record, so its full description is not reported in the registry record.

In general, a prospective observational design can collect measurements according to a planned follow-up structure without assigning participants to treatments. Cross-sectional comparisons describe differences between groups at a point or period of assessment; longitudinal comparisons concern measurements over time. Neither design feature guarantees that every participant has repeated measurements, and the registry record does not report the actual analysis population or follow-up completeness. It also does not report a protocol-level statistical plan, eligibility details, or how group membership was determined. The group labels in the adverse-event record should not be interpreted as randomized treatment assignments.

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 Area Under the Reactance Curve (AXR), measured over 40 weeks' postmenstrual age or discharge until 2 years.

The primary endpoint is area under the reactance curve, abbreviated AXR, with units of cmH2O/L. The registry describes AXR as an overall measure of reactance of the respiratory system, quantified by oscillometry. It specifies the summary parameter as the mean and the dispersion measure as the standard deviation. The stated timeframe is 40 weeks' postmenstrual age or discharge until 2 years.

In general, a physiological endpoint can provide a quantitative description of organ function that may be compared across clinical groups or measured over time. Oscillometry is the measurement approach named in this record; AXR is the particular summary measure selected as primary. A mean describes the central level of a continuous measurement, while a standard deviation describes variability among measurements around that mean. These summaries are most informative when their participant counts, measurement timing, and handling of repeated observations are also clear.

The record does not report the actual AXR means, standard deviations, sample counts for the primary outcome, or a numerical comparison. It also does not explain why AXR was selected over the other listed outcomes. Therefore, the endpoint definition can be described, but its observed distribution, precision, and relationship to clinical outcomes cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on the design and the way measurements are summarized. This study is registered as observational, single group, with allocation not applicable and masking none. Those design labels mean that the registry does not describe random assignment to competing treatments. The stated comparisons concern infant groups defined by term or preterm status and lung-disease status, as well as cross-sectional and longitudinal observations. In general, randomization can balance measured and unmeasured factors on average between assigned groups; observational comparisons do not have that design protection. An observed association should therefore be described as an association unless the analysis and assumptions support a stronger interpretation.

What does a mean and standard deviation convey?

The registry specifies the mean as the summary parameter for AXR and the standard deviation as its dispersion measure. In general, the mean gives the arithmetic average of a continuous measurement, while the standard deviation describes how spread out individual measurements are around that average. A mean alone does not describe the shape of a distribution. The standard deviation is not the standard error: the standard deviation describes variation among observations, whereas the standard error concerns the precision of an estimated mean and depends on the analysis and available data. The registry record does not report AXR means, standard deviations, standard errors, or confidence intervals.

A confidence interval is, in general, a range produced by a statistical method to express uncertainty around an estimate. Its width reflects both variability and information in the analyzed data, along with the method used. It is not a guarantee that an individual measurement will fall within the interval, nor does it directly establish clinical importance. No confidence interval for the primary outcome is reported in the registry record, so the precision of an AXR estimate cannot be judged from this record.

How should group comparisons be understood?

The registry mentions cross-sectional and longitudinal comparisons. In general, a cross-sectional comparison contrasts measurements across groups at a particular assessment, while a longitudinal analysis examines measurements across time. Repeated observations from the same infant are related rather than independent. Statistical methods for longitudinal data generally need to account for that within-infant correlation; treating repeated measurements as unrelated can make uncertainty estimates misleading. The registry record does not report which model, if any, was used for repeated observations, how measurement times were represented, or how within-infant correlation was handled.

Clinical group comparisons can also differ in their composition. In general, confounding occurs when factors associated with both group membership and the measured outcome contribute to an apparent association. Adjustment can address measured factors under appropriate assumptions, but cannot automatically remove unmeasured confounding. The record does not report an adjusted analysis, covariate set, or comparison-specific estimate. The group descriptions alone are not enough to determine whether any observed difference would reflect disease status, other participant characteristics, or differences in measurement and follow-up.

What do the registry's planning assumptions mean?

The registry includes a planning illustration framework based on a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of an observed effect. The record says these are planning illustrations computed from an observed effect, not the study's own design. Such assumptions are conventionally used to illustrate the sample size needed for a future comparison under specified conditions. They do not describe observed power, do not establish that the current study was planned as a two-arm trial, and do not show that the assumptions match this single-group observational design. No particular sample-size justification for this study is reported in the registry record.

For a continuous outcome, a planning calculation generally depends on the target difference, variability, significance level, allocation, and desired power. Altering the target effect changes the required information. A planning result is not a finding about the present study and cannot substitute for an outcome estimate or its uncertainty. The record's stated framework also assumes equal allocation between two arms, while the registered model is single group. Accordingly, those planning assumptions should be read only as illustrations, not as descriptions of the study's observed comparisons.

Why does over-dispersion matter?

In general, over-dispersion means that variation in the observed data exceeds what a statistical model expects. If a model assumes less variation than the data contain, standard errors can be too small and confidence intervals too narrow, making results appear more precise than warranted. Appropriate modeling or robust uncertainty estimates may help, depending on the data structure. The registry record does not report an over-dispersion assessment or a model for the AXR outcome, so no claim about this issue can be made for the study.

More broadly, statistical methods are only interpretable alongside the analysis population, outcome definitions, measurement schedule, and missing-data approach. The registry reports five outcome measures and zero analyses. It does not report a statistical analysis plan, named models, covariate adjustments, interim analyses, or a multiplicity procedure. These omissions prevent a methods-based appraisal of how estimates were produced. General statistical principles explain what such methods would address, but they cannot fill gaps in the registry record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Bronchopulmonary Dysplasia at 36 Weeks", "Infant Respiratory Distress Syndrome", "Preterm no RDS/BPD", "Control")
n   <- c(123, 221, 93, 145)
m   <- c(733, 599, 495, 385)
sp  <- c(257, 212, 159, 198)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Bronchopulmonary Dysplasia at 36 Weeks  123  733.000  257.000  687.127  778.873
CARM  Infant Respiratory Distress Syndrome  221  599.000  212.000  570.895  627.105
CARM  Preterm no RDS/BPD  93  495.000  159.000  462.254  527.746
CARM  Control  145  385.000  198.000  352.499  417.501

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures, including AXR as the primary measure and secondary measures named R7-20, R7, X7, and longer-term pulmonary outcomes. Considering several outcomes can raise a multiplicity issue: in general, the more hypotheses examined, the greater the chance that at least one result appears unusual by chance if each is judged separately. Methods such as prespecifying a primary endpoint or adjusting inference across multiple tests can address different aspects of this problem. The registry record does not report a multiplicity strategy, a hierarchy among secondary outcomes, or outcome-specific analysis methods.

The record reports no analyses, and it does not report numerical results for the listed outcomes. It is therefore not possible to assess whether all planned outcomes were analyzed, whether any were omitted, or how results across outcomes were interpreted. Interim analyses and stopping rules are not reported in the registry record.

Missing-data handling is also not reported in the registry record. In general, missing measurements can reduce precision and can bias estimates if the likelihood of having an observed measurement is related to the outcome or participant characteristics. The impact depends on why data are missing and on the analytic approach. The registry does not state how missing AXR values, incomplete follow-up, or repeated measurements were handled.

The analysis populations are not described. The enrollment entry does not identify the number included in each outcome analysis, and the registry record does not report outcome-specific denominators or exclusions. These details are necessary for judging how much information supports an estimate and to whom it may apply.

12. 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 adverse-event counts separately for bronchopulmonary dysplasia at 36 weeks, infant respiratory distress syndrome, preterm no RDS/BPD, and control. In each listed category, the record gives zero serious adverse events, zero other adverse events, and zero deaths. It also reports the at-risk count separately for serious and other events within each category.

These are event counts recorded in the registry, not evidence of a randomized comparison between treatments. The study is observational and single group, and the listed categories describe clinical groups rather than assigned device and control arms. The zero entries indicate that no events are recorded in those fields for those categories; they do not prove that the device or measurement procedure has no risks. Interpretation depends on the event definitions, observation period, completeness of reporting, and the number actually followed for safety. Those details are not reported in the registry record.

The registry identifies oscillometry as a non-invasive measurement approach, but the adverse-event entries alone cannot establish comparative safety or exclude uncommon harms. They should be read as the registry's reported event counts within the listed categories, not as a treatment-effect estimate.

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

The record establishes that the study is intended to measure pulmonary function in term and preterm infants with and without pulmonary disease using non-invasive forced airway oscillometry. It identifies AXR as the primary outcome, defines its units as cmH2O/L, specifies the mean and standard deviation as the summary and dispersion measures, and gives a timeframe extending from 40 weeks' postmenstrual age or discharge until 2 years. These details clarify what the study set out to measure.

The record does not report numerical AXR findings. It therefore does not show the average measurement in any group, the variability among infants, the size of any group difference, or how precise an estimate may be. It also does not provide a numerical treatment-response result. The stated purpose mentions response to treatments given to newborn infants with lung diseases, but no treatment assignment or comparative treatment analysis is reported in the registry record.

In general, a descriptive measurement study may help characterize physiological data and identify patterns for future study. Describing a pattern is different from establishing its cause. Since the registry identifies an observational single-group design, a comparison among disease categories should not be treated as proof that disease status caused a measurement difference. Nor can the record establish that a treatment caused a change in AXR.

The listed enrollment of 600 does not indicate how many infants contributed to each outcome or time point. Without outcome-specific sample counts, missing-data details, and analysis methods, the completeness and precision of any estimate cannot be evaluated. The adverse-event entries report zeros for the specified event categories, but those counts do not constitute a controlled safety comparison.

Accordingly, the registry record supports a description of the study's aim, design, population categories, and intended primary measurement. It does not support a conclusion about the observed AXR values, the direction or size of group differences, the effectiveness of a treatment, or the comparative safety of an intervention.

14. Why This Trial Matters Statistically

This study is statistically relevant because it focuses on measuring respiratory physiology in infants whose clinical groups include prematurity and several newborn pulmonary conditions. It uses a non-invasive oscillometry approach and specifies AXR as its primary continuous measure. In general, studies that characterize physiological measurements can help clarify how a measure varies across populations and over time, and can inform the design and interpretation of later research.

The registry also describes both cross-sectional and longitudinal comparisons. Those aims raise important analytic questions: whether group comparisons account for differences in participant characteristics, whether repeated measurements are modeled as correlated observations, and whether follow-up is sufficiently complete to support conclusions over time. These are general methodological considerations; the registry record does not report how they were addressed.

The distinction between a measurement study and a randomized treatment trial is central. The record is observational and single group, so its design is suited to describing measurements and associations rather than providing an automatically unbiased treatment contrast. The stated interest in response to treatments makes clear why interpretation needs the underlying analysis details, including treatment exposure definitions and methods for addressing differences between infants. Those details are not reported in the registry record.

The primary endpoint is explicitly defined, but numerical findings are absent. This illustrates a broader statistical point: a precise outcome definition is essential, yet it is not enough to evaluate a result. Estimates, uncertainty, analysis populations, and missing-data handling are also needed. Without them, readers can understand the measurement target and study framework but cannot judge the magnitude or precision of the observed findings.

15. 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 registry record leaves several trial-specific details unavailable for statistical assessment. It does not report numerical AXR results, outcome-specific sample counts, confidence intervals, or p-values. The enrollment entry cannot establish how many infants contributed usable measurements at a given assessment. The full description of one listed aim is incomplete, and the specific eligibility criteria and group-classification procedures are not reported in the registry record.

The intended timeframe is given as 40 weeks' postmenstrual age or discharge until 2 years, but the schedule and timing of individual measurements are not described. The record does not report how repeated measurements were analyzed, whether comparisons were adjusted for participant characteristics, or how measurement quality and incomplete follow-up were handled. These omissions limit assessment of both precision and potential bias.

The observational single-group design also limits causal interpretation. The registry describes clinical categories and a control category, but not random allocation. A contrast among such groups may reflect differences beyond the disease category or measurement itself. The record does not report a causal analysis or adjustment strategy that would address this concern.

Although five outcomes are listed, the record reports no analyses, and the numerical results for primary and secondary outcomes are not reported in the registry record. No multiplicity procedure, interim analysis plan, statistical analysis plan, or specific sample-size justification is reported. The planning framework described in the registry uses assumptions for illustrative two-arm calculations, which are not a description of this registered single-group study's design.

Finally, the adverse-event fields list zero events for the specified categories, but event definitions, monitoring procedures, and the safety observation period are not reported. These registry entries cannot support a comprehensive safety assessment.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pulmonary Function Using Non-invasive Forced Oscillometry — NCT03346343.
• Registry record last updated 2026-01-27; status last verified 2025-10.
• Results first posted 2026-01-27.
• 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.

19. Record Summary

NCT03346343 is a prospective observational study of non-invasive forced airway oscillometry in term and preterm infants, including infants with and without pulmonary disease. The registry identifies a single-group model, no masking, and allocation as not applicable. It lists an enrollment of 600 and identifies the University of Alabama at Birmingham as sponsor.

The primary outcome is AXR, measured in cmH2O/L, with the mean and standard deviation specified as summary measures. The timeframe is 40 weeks' postmenstrual age or discharge until 2 years. The registry lists five outcome measures and no analyses. Numerical primary and secondary outcome findings, analysis methods, missing-data handling, and multiplicity procedures are not reported in the registry record.

The adverse-event entries report zero serious events, zero other events, and zero deaths in each listed clinical category. These are registry counts, not randomized safety comparisons. Overall, the record defines a pulmonary-function measurement study but does not provide the numerical results needed to assess the observed AXR levels or their precision.