Diaphragm Pacing in Individuals With Spinal Cord Injuries: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Diaphragm Pacing in Individuals With Spinal Cord Injuries (NCT04179799), a registered phase not stated study. The primary outcome is Change in Electromyogram (EMG).

2. Clinical Question

3. Trial Design

This completed study, NCT04179799, is titled “Diaphragm Pacing in Individuals With Spinal Cord Injuries.” Its official title describes diaphragm stimulation after human spinal cord injury and its effects on respiratory neural drive and function. The sponsor is the University of Florida. The registry record gives a start date of 2020-01-10 and a primary completion date of 2022-08-20. Enrollment was 6.

The intervention was a device, intramuscular diaphragm pacing. The described participants had acute, traumatic cervical spinal cord injuries; the record identifies a Cervical SCI group. It does not describe a randomized comparison, and allocation is not stated. The registry record also cautions that the arms are not a like-for-like control comparison. A pacer-off breathing condition is described for EMG recording, but this is a measurement condition rather than evidence of an independent control group.

The primary outcome was change in electromyogram, measured in mV, over the stated timeframe from baseline up to 24 hours. The protocol description says diaphragm EMGs would be recorded across time during non-stimulated respiration and alongside respiratory-function assessments. The posted primary outcome description is more limited: data were not obtained from 3 participants, and quiet-breathing data were recorded from 3 of 6 participants 24 hours after pacing use.

The registry lists 3 outcome measures and 0 analyses. It does not report a numerical primary outcome result, a statistical analysis plan, or a sample-size justification for the study. The available record supports describing the study’s aim, intervention, and extent of primary-outcome data, but not reconstructing unreported design or analysis details.

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

Analysis population for the primary outcome, as defined in the registry: Data not obtained from 3 participants. Data recorded during quiet breathing from 3 of 6 participants, 24hrs after use of diaphragm pacing.

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 Electromyogram (EMG), measured over Baseline up to 24 hours.

The primary endpoint is change in electromyogram (EMG), measured in mV. A diaphragm EMG records electrical activity associated with neuromuscular activation. In this study, the stated purpose was to assess diaphragm activation using electrodes implanted for stimulation, and the outcome description says recordings could be compared across time. The endpoint was therefore selected to characterize diaphragm activation, while respiratory assessments were also part of the project description.

The stated timeframe is baseline up to 24 hours. The recording description specifies non-stimulated respiration, with the diaphragm pacer turned off, and the posted data description identifies quiet breathing 24 hours after pacing use. These details distinguish the measurement condition from active stimulation itself: the outcome is an EMG measurement taken with the pacer off, not a count of pacing events.

For a continuous measure, a mean can describe the average value or average change, while a standard deviation can describe variation among observations. Those are general interpretations of the listed measure and dispersion type; the registry record does not provide the actual EMG values, mean change, or standard deviation. Without those quantities, the magnitude and variability of the recorded EMG cannot be assessed from the record. The outcome description also reports that data were not obtained from 3 participants, so the described recordings cover only 3 of 6 participants.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary outcome: change in diaphragm EMG, measured in mV. It lists the parameter as a mean and the dispersion measure as a standard deviation. These labels indicate how results could be summarized, but the registry record does not report the actual mean, standard deviation, or a numerical change estimate. There are no analyses listed.

What does a mean describe?

As a general statistical concept, a mean gives a central summary of measured values. For a change outcome, it could summarize the average change across participants with recorded measurements. The meaning of a mean depends on what observations are included and how change is defined. The outcome description says recordings were intended to be compared across time, but the registry record does not report the calculation used to define change or the results at each time point. It therefore is not possible to interpret an average change from the record.

What does a standard deviation describe?

As a general concept, a standard deviation describes the spread of observations around their mean. It is not the same as a confidence interval: a confidence interval expresses uncertainty about an estimate, while a standard deviation describes variability in the observed data. Neither the standard deviation nor a confidence interval for the EMG result is reported in the registry record. With only the description of the measure and dispersion type, the observed variability and precision cannot be assessed.

Why does the recording condition matter?

The primary outcome description says EMGs were recorded during non-stimulated respiration, with the diaphragm pacer turned off, and that recordings were intended to permit comparisons across time. It also describes quiet-breathing measurements 24 hours after pacing use. These are details about how the outcome was measured. They do not themselves establish a comparison between separate treatment groups, and they do not provide a result for the intended time comparison. General statistical interpretation of repeated measurements depends on knowing the observations at each time and how their within-participant relationship is handled; those analysis details are not reported in the registry record.

What can a confidence interval contribute?

In general, a confidence interval gives a range of values compatible with an estimate under a specified statistical method. Its width helps readers assess precision, while its location helps assess the direction and plausible magnitude of an effect. A confidence interval is not reported for this primary outcome. No estimate or interval should be inferred from the enrollment count or from the fact that recordings were obtained from 3 participants.

How should planning calculations be understood?

The study’s sample-size illustration is described as a planning exercise computed from the observed effect, rather than the trial’s own design. Its stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration considers detecting a stated fraction of the observed effect. For outcomes other than time-to-event outcomes, its results are expressed as participants per arm; time-to-event illustrations use a total event count under the Schoenfeld method.

These are general planning assumptions, not evidence that the study enrolled the number of participants needed for a particular power target. The record does not report the trial’s own sample-size justification, and the study is not described as a randomized comparison with two like-for-like arms. Any planning illustration should therefore be read as conditional on its assumptions, not as observed power or as proof that the primary outcome was tested with adequate precision. General power calculations address the chance of detecting an assumed effect under specified conditions; they do not replace a reported effect estimate and its uncertainty.

Finally, over-dispersion is a general issue for count outcomes when variability exceeds what a basic count model expects. It is not the measure identified as primary in this record, which is a continuous EMG outcome. No count-model method or over-dispersion assessment is reported. This distinction matters because statistical methods should follow the outcome’s scale and distribution rather than be assumed from the study’s clinical topic.

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("Cervical SCI")
n   <- c(3)
m   <- c(-0.0031)
sp  <- c(0.043)
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  Cervical SCI  3  -0.003  0.043  -0.110  0.104

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and identifies change in EMG as the primary outcome. It lists 0 analyses. The record does not report whether the other outcomes were secondary, how they were ordered, or whether any method was planned to account for testing multiple outcomes. Multiplicity is a general statistical concern: when several hypotheses are tested, the chance of at least one apparently notable result can increase. Whether and how to address that concern depends on the analysis plan, which is not reported in the registry record.

Missing primary outcome data are explicitly noted. The record says data were not obtained from 3 participants and that quiet-breathing recordings were recorded from 3 of 6 participants 24 hours after pacing use. It does not report why those data were unavailable, whether missingness was related to participant characteristics or measurements, or how missing data were handled in an analysis. No imputation, sensitivity analysis, or other missing-data method is described in the registry record. Without those details, the potential effect of missing data on an estimate cannot be assessed.

The analysis population is also not reported in the registry record. It is therefore unclear whether any intended analysis would have included all enrolled participants, only those with recorded EMG data, or another defined group. This uncertainty is distinct from the simple count of available recordings: a count alone does not specify the population used for an estimate.

The record does not report interim analyses, a statistical analysis plan, or a sample-size justification. These omissions do not establish that particular procedures were or were not carried out; they mean the registry record does not document them. With no analyses listed and no numerical primary result, there is no basis to assess multiplicity adjustments, missing-data sensitivity, or the analysis population’s influence on the reported treatment estimate.

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 lists a Cervical SCI group with 6 participants at risk for serious adverse events and 0 recorded as affected. For other adverse events, it likewise lists 6 at risk and 0 affected. Deaths are listed as 0. No serious adverse-event terms are listed.

These are the recorded counts for the stated group. They describe what the registry reports; they do not demonstrate that no adverse events of any kind occurred outside the categories or reporting scope captured in the record. Nor do zero affected participants establish that an intervention is free of risk. Counts from a group of this size also provide limited information about the range of possible event rates in a broader population. No additional safety analysis or explanatory detail about ascertainment is reported in the registry record.

Serious and other adverse events are separate categories in the record, so the two sets of counts should be read as distinct listings rather than combined into a new total. The absence of listed serious-event terms means the registry does not name a specific serious event in this record. It does not supply information about event definitions, follow-up completeness, or how safety events were collected. Safety interpretation should therefore remain descriptive and limited to the posted counts.

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

The available record supports a narrow description: a completed study enrolled 6 people with acute, traumatic cervical spinal cord injuries, used intramuscular diaphragm pacing, and intended to assess diaphragm EMG and respiratory function. The primary outcome description identifies quiet-breathing EMG recordings from 3 of 6 participants 24 hours after pacing use and states that data were not obtained from 3 participants.

Those observations do not provide a reported numerical effect. No EMG values, mean change, standard deviation, confidence interval, or p-value appear in the registry record, and 0 analyses are listed. It is therefore not possible to state how large or variable the observed EMG measurements were, whether the primary measure changed over time, or how precisely any change was estimated. A treatment effect should not be inferred from the study’s aim or from the existence of a recorded outcome.

The design information also constrains interpretation. The registry does not describe a like-for-like control comparison, and allocation is not stated. A pacer-off recording condition is described, but that is not a separate comparison group. The record does not provide results that allow a causal comparison between pacing and an alternative condition.

These limitations do not make the study question unimportant; they define what the posted information can answer. The record documents the planned measurement and a subset of recordings, but it does not provide enough numerical evidence for an estimate of effect or a conclusion about statistical uncertainty. It also does not establish that the intervention does or does not improve respiratory function. Any interpretation should remain within the scope of the available measurements and the missing outcome and analysis information.

14. Why This Trial Matters Statistically

This study raises a statistical question that is especially clear when the planned measure and the posted data are considered separately. The primary endpoint is continuous diaphragm EMG, intended to characterize neuromuscular activation across time. Yet the registry record describes recordings from 3 of 6 participants and reports no numerical outcome estimate or analysis. For readers, that distinction between a clearly stated measurement objective and an unreported estimate is central to evidence interpretation.

The study also illustrates why recording conditions and comparison structures need careful description. The pacer-off quiet-breathing condition is a way of measuring EMG, while the record does not identify a like-for-like control group. Without reported results at the relevant time points and a description of how within-participant measurements were analyzed, a reader cannot assess the intended change over time. A clinical hypothesis alone is not a statistical result.

Missing outcome data are another important feature: data were not obtained from 3 participants. A transparent count helps readers recognize that the available measurements do not cover the full enrollment, but the record does not explain why the data are missing or how they were handled. Such details matter because an estimate based on available measurements can be difficult to interpret when the analysis population and missing-data approach are unknown.

Finally, the record distinguishes the study from a conventional randomized comparison: allocation is not stated, and the arms are not a like-for-like control comparison. These features limit comparative claims, while the absence of posted analyses prevents assessment of effect size and precision. Statistically, the main lesson is to separate study rationale, measurement availability, design, and reported evidence rather than treating them as interchangeable.

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 primary limitation for interpreting this study is that the registry record does not report the numerical EMG outcome. It identifies the measure, unit, timeframe, and recording condition, but gives no observed value, mean change, standard deviation, confidence interval, or p-value. The record lists 0 analyses, so no inferential result is available to interpret.

Data were not obtained from 3 participants; the posted description says recordings were made in 3 of 6 participants. The reason for unavailable data, the handling of missingness, and the analysis population are not reported in the registry record. The available description also does not provide time-specific values needed to understand the stated comparison across time.

The study is not described as a randomized comparison, allocation is not stated, and the registry says the arms are not a like-for-like control comparison. The pacer-off measurement condition should not be treated as a participant control group. These details limit the scope for comparative interpretation.

The registry lists 3 outcome measures but does not report a multiplicity approach or analysis plan. It also does not report interim analyses or a sample-size justification for the study. The sample-size illustration is described as a planning exercise, not the trial’s own design; its assumptions should not be mistaken for evidence of observed power. The enrollment of 6 further means the record concerns a small group, but no additional precision or generalizability estimate can be calculated from the information reported. These limitations leave the study question identifiable while making the reported statistical evidence insufficient for estimating the primary outcome’s magnitude or precision.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Diaphragm Pacing in Individuals With Spinal Cord Injuries — NCT04179799.
• Registry record last updated 2024-05-30; status last verified 2024-05.
• Results first posted 2024-05-30.
• 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

NCT04179799 is a completed University of Florida study titled “Diaphragm Pacing in Individuals With Spinal Cord Injuries.” The official title describes diaphragm stimulation after human spinal cord injury, with a focus on respiratory neural drive and function. The registry gives a start date of 2020-01-10, a primary completion date of 2022-08-20, and enrollment of 6.

The intervention was intramuscular diaphragm pacing in people with acute, traumatic cervical spinal cord injuries. The primary outcome was change in diaphragm EMG, measured in mV, over baseline up to 24 hours. The outcome description reports quiet-breathing recordings 24 hours after pacing use from 3 of 6 participants and says data were not obtained from 3 participants.

The registry lists 3 outcome measures and 0 analyses. It does not report a numerical EMG result or an inferential analysis. It lists 0 participants affected by serious adverse events, 0 affected by other adverse events, and 0 deaths among 6 at risk in the Cervical SCI group. These safety counts are descriptive and do not replace outcome or comparative analyses.