Nasal Noninvasive NAVA in the Very Low Birth Weight Infant: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Nasal Noninvasive NAVA in the Very Low Birth Weight Infant (NCT01785563), a na na study. The primary outcome is Change in Partial Pressure of Carbon Dioxide on Capillary Blood Gas.

2. Clinical Question

The study asks whether nasal noninvasive neurally adjusted ventilatory assist (NIV-NAVA) is associated with a change in carbon dioxide in the blood of very low birth weight infants after a 2-hour period. The registry describes infants who were stable on their existing mechanical breathing support before transition to the study intervention. Its stated purpose focuses on whether carbon dioxide decreases; the primary endpoint is described more generally as a difference between measurements, and the registry does not report the direction convention for that difference.

The registry lists change in fraction of inspired oxygen as a secondary outcome. Numerical outcome results, including the carbon dioxide change, are not reported in the registry record. The clinical question can therefore be described, but the posted record does not establish the size, precision, or direction of any observed change.

3. Trial Design

The registry describes a completed, single-group device study with an enrollment of 40. Its intervention is nasal NIV-NAVA, a form of noninvasive ventilation that responds to the infant's breathing effort. The brief summary describes electrical sensors on a feeding tube detecting the diaphragm's effort to inhale; the ventilator then supplies additional airflow through a nasal cannula. Infants transition from their current ventilation mode, except that those already receiving nasal NIV-NAVA have an increase in the NAVA level.

This is not a parallel-group controlled trial. Allocation is recorded as not applicable, masking is listed as none, and the trial model is single group. The registry's own note cautions that the arms are not a like-for-like control comparison. The before-and-after measurements are therefore observations within the intervention period, not a randomized contrast between groups. Changes over time cannot, on this design alone, be separated from other influences that may coincide with the intervention.

The registry lists the phase as not applicable, the status as completed, a start date of 2013-02, and a primary completion date of 2018-12-31. These record details describe study registration and status; they do not show when individual infants were assessed or how long enrollment took. The planned study period for the primary endpoint is 2 hours. Further details about recruitment, eligibility criteria beyond the brief description, site conduct, protocol deviations, or the timing of enrollment are not reported in the registry record.

The registry includes planning assumptions for a hypothetical two-arm sample-size illustration: two-sided significance level 0.05, equal allocation between arms, normal approximation, and an effect defined as a stated fraction of the observed effect. Those assumptions are not a description of the single-group intervention design. No planning illustration values are included in the record summarized for this study, and they should not be read as a sample-size justification for the trial or as observed power.

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 Change in Partial Pressure of Carbon Dioxide on Capillary Blood Gas, measured over 2 hours.

The primary endpoint is the change in partial pressure of carbon dioxide (pCO2) measured on capillary blood gas. The unit is mm Hg, the summary measure is the mean, and the registry identifies standard deviation as the measure of dispersion. The endpoint compares a capillary blood gas measurement obtained within 6 hours of study with a measurement taken immediately after the 2-hour study period.

Carbon dioxide is the gas described in the study summary as being exhaled. The proposed ventilation mechanism responds to an infant's effort to breathe and supplies additional airflow. Measuring blood pCO2 before and after the intervention period gives investigators an objective physiological measure for assessing whether carbon dioxide changed during that period. The brief summary frames the intended question as whether pCO2 decreases; however, the registry's endpoint wording specifies a difference without stating which subtraction order or sign convention was used. That convention matters when interpreting whether a positive or negative value represents a decrease.

The registry does not report the endpoint's observed mean change, standard deviation, confidence interval, or test result. It also does not report individual measurements, the number of infants with analyzable paired measurements, or how measurements outside the stated timing windows were handled. Thus the endpoint definition and rationale are available, but the actual magnitude and precision of the change cannot be assessed from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary endpoint summarized as a mean, with standard deviation as the dispersion measure. It defines change using two capillary blood gas measurements: one obtained within 6 hours of study and another immediately after the 2-hour study period. The record does not state the subtraction order, the statistical test, or the model used to analyze the endpoint. No numerical analysis result is reported.

What does a mean change represent?

In general, a mean change condenses a set of individual changes into an average. It can make the overall direction and scale of a group response easier to describe, but it does not show the pattern for every participant. Individual measurements may vary around the mean, and some changes may differ from the average in size or direction. The registry identifies the mean as the summary parameter, but does not provide the resulting value for pCO2.

For a before-and-after endpoint, each observed change depends on the paired measurements and on the convention used to subtract one from the other. Reversing the order reverses the sign while leaving the underlying pair of measurements unchanged. That is why the registry's unspecified sign convention limits interpretation of an increase or decrease, even if a numerical change were available. The record also does not report whether every enrolled infant contributed both measurements to the endpoint analysis.

What does standard deviation describe?

In general, standard deviation describes how dispersed individual observations are around their mean. It is not the same as the uncertainty in the estimated mean. Uncertainty in a mean is often conveyed with a confidence interval, which describes a range of values compatible with the data and analysis assumptions. A confidence interval is useful because it shows both the estimated effect and the degree of precision, rather than only whether a test crosses a threshold. No standard deviation, confidence interval, or other uncertainty estimate for the primary endpoint is reported in this registry record.

For repeated measurements, variation can arise within participants as well as between participants. The relationship between an infant's earlier and later measurements affects the variability of changes. The registry does not report a correlation, a repeated-measures model, or other details about how paired observations were handled. It is therefore not possible to reconstruct an analysis or determine whether a particular method accounted for the paired nature of the measurements.

What can a p-value establish?

In general, a p-value assesses how compatible data are with a specified null model under the assumptions of a statistical test. It does not measure the probability that a treatment works, the size of an effect, or the probability that the null hypothesis is true. A p-value also does not replace an estimate with an interval: a result can be estimated imprecisely even when a test produces a threshold-based classification. No p-value or test specification for the primary outcome is reported in the registry record.

The registry includes planning assumptions for a sample-size illustration, including a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect for that illustration is a stated fraction of the observed effect. These are planning conventions, not evidence that the study used a two-arm design. The actual study is listed as single group, and the registry warns that its arms are not a like-for-like control comparison. Planning illustrations are not observed power, and they cannot substitute for the primary result or its uncertainty.

Why does the study design affect interpretation?

In general, a randomized concurrent control group helps distinguish changes associated with an intervention from changes that might occur over time for other reasons. In a single-group before-and-after study, the within-participant timing can be useful for describing change, but there is no randomized comparison to estimate what would have happened over the same period without the intervention. The registry identifies allocation as not applicable and masking as none. The record does not report a statistical adjustment intended to address time-related or other alternative explanations.

Standard deviation is appropriate as a description of spread for a continuous measure, but the analysis must still define the outcome, the analysis population, and the treatment of incomplete measurements. Those details are not reported in the registry record. The primary outcome's observed mean, dispersion, and inferential analysis are also absent, so no independent recalculation is possible from the stated information.

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("Nasal Non-Invasive NAVA Group")
n   <- c(27)
m   <- c(0.019)
sp  <- c(0.037)
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  Nasal Non-Invasive NAVA Group  27  0.019  0.037  0.004  0.034

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures: the primary change in pCO2 and the secondary change in fraction of inspired oxygen. Considering more than one outcome can raise a multiplicity question because testing several hypotheses can increase the chance of at least one apparently positive finding under a set of null hypotheses. In general, a prespecified testing hierarchy or adjustment can address that concern, but the registry record does not report a multiplicity strategy, outcome hierarchy beyond primary and secondary labels, or a statistical analysis plan.

The registry records no analysis entries. This means the record does not give analysis details or results; it does not establish whether analyses took place outside the registry. The number of participants with usable primary or secondary outcome data is not reported. The registry's overall enrollment is 40, but enrollment alone does not identify how many contributed complete blood gas measurements or were included in any particular analysis.

Methods for handling missing observations, including exclusions, imputation, or sensitivity analyses, are not reported in the registry record. The analysis population is not described, and the primary endpoint population field is blank. The record does not say whether the endpoint was analyzed for all enrolled infants, for infants who completed both measurements, or using another rule.

These omissions limit both reproducibility and interpretation. Without a stated analysis plan, it is unclear which comparisons were prespecified, how multiple outcomes were treated, or how incomplete measurements could affect estimates. No assumptions about those procedures can be inferred from the endpoint definition alone.

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's adverse-event entry lists the Nasal Non-Invasive NAVA Group with 27 participants at risk in the serious-event category and 0 affected. It also lists 27 at risk in the other-event category and 0 affected, along with 0 deaths. No serious-event terms are listed.

These are the figures recorded for the adverse-event entry; they do not describe a comparison with a separate control group. The registry does not explain in this record how adverse events were defined, what observation period was used for safety reporting, or how the at-risk counts relate to overall enrollment. The enrollment figure of 40 should not be substituted for the category-specific at-risk figures.

A recorded zero means no affected participants are entered for that category in the registry entry. It does not establish that an event is impossible, that all potential events were captured, or that the intervention has no risk. With no control group and limited reporting detail, the entry cannot quantify a relative safety difference. The safety figures should be read as registry counts, not as a complete account of clinical safety.

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

This study matters as a registry record of a short-term physiological assessment of nasal NIV-NAVA in very low birth weight infants. It specifies a 2-hour intervention period and a primary measure based on capillary blood gas pCO2. It also describes how the device responds to breathing effort and how infants transition from their current ventilation mode, including a NAVA-level increase for infants already receiving nasal NIV-NAVA.

The record does not report the primary outcome result. It therefore does not show whether pCO2 changed, how large any change was, how variable individual changes were, or how precisely the average was estimated. The stated study aim of assessing a decrease is not itself evidence that a decrease occurred. The record also does not report the secondary outcome result for change in fraction of inspired oxygen.

The design places an important boundary on interpretation. This is a single-group study, not a randomized comparison with a concurrent control group. A before-and-after change could describe what happened during the study period, but the design cannot by itself establish what would have happened over the same period without the intervention. The registry's own note cautions against treating the listed arms as a like-for-like comparison.

The adverse-event entry records 0 affected for serious events and 0 deaths, with no serious-event terms listed. These counts are useful as a description of the registry entry, but they do not establish absence of risk or support a comparative safety estimate. Additional detail about the safety observation period and event ascertainment is not reported in the registry record.

Accordingly, the record supports understanding the intended clinical question, endpoint, intervention, and design. It does not support a conclusion about the magnitude or direction of the measured response, its statistical precision, or causal effects. These limits are especially important when distinguishing a study objective from an observed result.

14. Why This Trial Matters Statistically

The statistical value of this record lies in how clearly it identifies a focused physiological endpoint and the timing of its measurement. pCO2 is specified as a continuous outcome measured on capillary blood gas, summarized by a mean with standard deviation, and assessed across a 2-hour period. That definition helps readers understand what the investigators intended to observe rather than relying only on a broad description of respiratory support.

The design is equally important statistically. A single-group before-and-after structure can describe change over time, but it does not create the randomized counterfactual comparison that would help isolate an intervention effect. The registry explicitly identifies the study as single group and warns that the arms are not a like-for-like control comparison. This makes design-aware language essential: an observed change, if reported, would not automatically be a causal effect.

The entry also illustrates why result reporting must include estimates and uncertainty, not just an endpoint definition or a stated study aim. Without the mean change, dispersion, and a precision measure, readers cannot assess the magnitude or reliability of the primary result. The absence of recorded analysis details also leaves questions about paired measurements, missing observations, and the analysis population unresolved.

Finally, the registry's hypothetical two-arm sample-size assumptions should be kept separate from the actual single-group design. Planning calculations are not observed findings or observed power. Distinguishing planning conventions, design, endpoint, and results prevents a statistical illustration from being mistaken for evidence about the intervention.

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 main trial-specific limitation is the single-group design. There is no concurrent control group or randomized contrast, so a before-and-after difference cannot by itself separate an intervention-associated change from other changes occurring during the same period. The registry itself notes that the arms are not a like-for-like control comparison.

The primary outcome description does not state the subtraction order for the difference between the blood gas measurements. That omission makes the sign of any change ambiguous unless clarified elsewhere. The earlier sample is defined as occurring within 6 hours of study, while the later sample is taken immediately after the 2-hour period; the record does not provide more detail about the actual timing or consistency of measurements.

Numerical primary and secondary outcome results are not reported in the registry record. Nor are confidence intervals, standard deviations, p-values, or analysis methods for the primary endpoint. The analysis population, number of paired measurements, missing-data procedures, protocol deviations, and multiplicity approach are also not reported. These gaps prevent assessment of the estimate, its precision, and the robustness of any analysis.

The adverse-event entry contains registry counts but does not describe event definitions, ascertainment, or the observation period. The enrollment of 40 and the adverse-event at-risk entries are not interchangeable denominators. The record also does not report a statistical analysis plan or explain how the two-arm sample-size illustration relates to the single-group study. These limitations restrict both reproducibility and the scope of conclusions that can be drawn from the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Nasal Noninvasive NAVA in the Very Low Birth Weight Infant — NCT01785563.
• Registry record last updated 2022-06-09; status last verified 2022-05.
• Results first posted 2022-06-09.
• 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

NCT01785563 is a completed, single-group device study titled “Nasal Noninvasive NAVA in the Very Low Birth Weight Infant.” The registry lists an enrollment of 40, no masking, and a 2-hour intervention period involving nasal NIV-NAVA. The primary endpoint is change in pCO2 on capillary blood gas, summarized as a mean with standard deviation. Change in fraction of inspired oxygen is listed as a secondary outcome.

The primary and secondary outcome results, analysis methods, analysis population, and missing-data procedures are not reported in the registry record. The adverse-event entry records 0 affected for serious events and 0 deaths. The design is not a randomized comparison, and the registry cautions against treating its arms as like-for-like controls. The record defines the research question and measurement approach, but does not provide enough outcome information to assess the observed change or its precision.