Assessment of the Capability of PulmoVista 500 to Continuously Monitor Changes of Ventilation Over Time: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessment of the Capability of PulmoVista 500 to Continuously Monitor Changes of Ventilation Over Time (NCT03076983), a registered phase not stated study. The primary outcome is Monitoring Capabilities of PulmoVista 500.

2. Clinical Question

The study’s stated purpose is to examine whether PulmoVista 500 can detect changes in global and regional ventilation. The primary endpoint focuses on the relationship between the ventilator’s volume signal and the device’s global impedance signal. This is a monitoring-capability question: it concerns correspondence between two curves, rather than a comparison of clinical outcomes between randomized treatment groups.

The record also lists secondary outcomes concerning regional ventilation, tidal volumes, end-expiratory lung volumes, safety events, and clinical helpfulness assessed by questionnaire. The presence of these outcomes indicates a broader assessment than the primary curve-correlation measure alone. However, numerical results for these outcomes are not reported in the registry record. The registry therefore describes the questions the study set out to assess, but does not provide results sufficient to judge the observed magnitude or precision of the primary relationship.

3. Trial Design

The study is registered as an assessment of the capability of PulmoVista 500 to continuously monitor changes of ventilation over time. The sponsor is Drägerwerk AG & Co. KGaA. The record gives an enrollment of 80 and describes a device intervention, lung monitoring with PulmoVista 500. The study status is completed. Its recorded start date is 2017-05-30, and its primary completion date is 2018-04-12.

Two groups are described. ICU Patients are patients currently on or scheduled for ventilator care in the intensive-care-unit. OLV Patients are patients scheduled for elective surgery receiving one-lung ventilation. These groups represent different clinical contexts, and the registry explicitly notes that they are not a like-for-like control comparison. Allocation is not stated. The record does not establish that participants were randomly assigned, nor does it describe a randomized comparison.

The primary endpoint is recorded for Day 1 and is a continuous measure: the mean cross-correlation coefficient between the ventilator volume curve and the global impedance curve from PulmoVista 500. The record identifies standard deviation as the dispersion measure. The primary analysis population is described as an intention-to-treat collective, defined by availability of impedance waveforms and parallel volume waveforms during ventilation, allowing the endpoint to be evaluated.

The registry lists six outcome measures and names secondary assessments of regional ventilation, tidal volumes, end-expiratory lung volumes, safety events, and clinical helpfulness by questionnaire. Details of the questionnaire questions are referred to in the outcome-measure description, but further numerical results are not reported in the registry record. The registry record does not report the statistical analysis plan, sample-size justification, or an allocation procedure. It also does not give numerical results for the primary endpoint.

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: A Intention-to-Treat (ITT) collective was used as analysis population. The intention-to-treat collective comprises all patients for which both, the impedance waveforms and parallel to them volume waveforms have been generated during ventilation,so that the primary endpoint can be evaluated.

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 Monitoring Capabilities of PulmoVista 500, measured over Day 1.

The primary endpoint is the mean cross-correlation coefficient, R, between the volume curve from the ventilator and the global impedance curve from PulmoVista 500 on Day 1. The registry describes R as a measure of the relationship between the two curves. Correlation coefficients can range from −1 to 1: values indicate the direction and strength of a curve relationship, with the interpretation depending on the sign and magnitude.

The calculation accounts for a possible phase shift, or delay, between the signals. The record explains that the ventilator signal may be transmitted to PulmoVista 500 with a delay. Rather than using only a same-time-point correlation, the calculation evaluates correlations across a narrow range of lags, from −15 to 15, and takes the maximum correlation as the cross-correlation coefficient. This makes the endpoint responsive to a relationship that is present even if the signals are not perfectly synchronized.

This measure is relevant to the stated monitoring question because it quantifies how closely changes in the ventilator volume curve correspond to changes in the global impedance curve. It is a signal-agreement measure, not by itself a direct measure of whether a change in monitoring improves a clinical outcome. The record specifies a mean and standard deviation, but the numerical mean and standard deviation are not reported in the registry record. The endpoint’s observed magnitude and precision therefore cannot be assessed from the registry information available.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is a continuous correlation statistic. The registry identifies the endpoint as the mean of the cross-correlation coefficient, with standard deviation as the dispersion measure. A mean describes the average value of a continuous measure across the analyzed observations. A standard deviation describes how spread out individual observations are around that average. Neither quantity is reported numerically for this endpoint in the registry record, so the center and spread of the observed values cannot be evaluated.

What does cross-correlation measure?

In general, correlation describes how two measured signals vary in relation to one another. A positive correlation means the signals tend to move in the same direction, while a negative correlation means they tend to move in opposite directions. A value nearer zero indicates less linear association. The registry states that R ranges from −1 to 1. This scale gives the possible values of the statistic, not the trial’s actual result. Correlation also does not establish that one signal causes the other to change.

The endpoint uses cross-correlation rather than a single correlation at matching time points. As a general matter, two signals may reflect related changes but appear shifted in time. Allowing a lag can capture that delayed relationship. The registry says that the calculation evaluates the correlation coefficient across lags from −15 to 15 and selects the maximum value. The record attributes the possible delay to transmission of the ventilator signal to PulmoVista 500. It does not report additional details about signal processing beyond this description.

Why use a lagged measure?

Accounting for a phase shift can be useful when the monitoring signal and reference signal do not line up exactly in time. If a meaningful delay exists, a correlation calculated only at simultaneous points could understate the relationship between the curves. Searching over a specified lag range addresses this timing issue. Taking the maximum, however, means the endpoint represents the strongest correlation found in that search range, rather than a correlation at a single prespecified time alignment. Interpretation should therefore follow the registry’s definition of the endpoint.

Correlation is a measure of association between curves, not an agreement statistic that necessarily shows the signals have the same scale or identical values. Two signals can move together while differing in their absolute levels or variability. The primary endpoint therefore addresses the correspondence of changes as quantified by the stated cross-correlation method. It does not, on its own, establish clinical usefulness, accuracy for every individual measurement, or an effect on patient outcomes. Those broader questions require evidence beyond a correlation coefficient.

What does the analysis population mean?

The registry calls the primary analysis population an intention-to-treat collective. It defines this collective as patients for whom both impedance waveforms and parallel volume waveforms were generated during ventilation, so that the primary endpoint could be evaluated. In general, an intention-to-treat approach aims to retain participants according to their original assigned group. Here, however, allocation is not stated, and the record’s operational definition centers on the availability of paired waveforms. The registry does not explain how participants without evaluable paired waveforms were handled, or whether any other analysis population was used.

Pairing the two waveforms is necessary for the stated correlation calculation, because the endpoint relates measurements from both signals. If one of the signals is unavailable or unusable, the paired endpoint cannot be calculated as described. Missing-data rules, the amount of missing waveform data, and any sensitivity analyses are not reported in the registry record. The listed analysis population definition should therefore not be taken as a complete account of missing-data handling.

How should precision be assessed?

For a continuous endpoint, an estimate is more informative when accompanied by an indication of its uncertainty. In general, a confidence interval communicates uncertainty around an estimated quantity, while the standard deviation describes variability among observations. These are different concepts: the standard deviation reflects spread in the observed measurements, whereas a confidence interval concerns uncertainty in an estimated parameter. The registry specifies a standard deviation as the dispersion measure but does not report a numerical estimate, confidence interval, or other precision measure for the primary endpoint.

The study record lists no analyses. It does not report a hypothesis test, a model, covariate adjustment, or a statistical plan for the primary endpoint. These details are not reported in the registry record, so it is not possible to describe whether the mean was estimated with a particular model or whether subgroup or adjusted analyses were performed.

The record also includes planning illustrations based on the observed effect. These are planning calculations, not observed power. Their stated assumptions include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. The registry does not report the design’s sample-size justification. Such illustrations should be understood as conditional planning quantities rather than proof of the probability that this completed study detected an effect.

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("ICU Patients", "OLV Patients")
n   <- c(54, 25)
m   <- c(0.9692, 0.9093)
sp  <- c(0.0627, 0.1351)
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  ICU Patients  54  0.969  0.063  0.952  0.986
CARM  OLV Patients  25  0.909  0.135  0.854  0.965

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures. It identifies the primary endpoint as monitoring capability and lists secondary outcomes concerning regional ventilation, tidal volumes, end-expiratory lung volumes, safety events, and clinical helpfulness assessed by questionnaire. The registry record does not report a statistical plan for handling multiple outcomes or multiple comparisons. It does not state whether any multiplicity adjustment was used, or identify a hierarchy or testing sequence among the outcomes.

As a general statistical issue, examining several outcomes can increase the chance that at least one result appears noteworthy by chance when each is tested separately. Methods for controlling this issue depend on the study questions and analysis plan. Since the registry does not report such a plan or inferential results, the degree to which multiplicity was considered cannot be determined.

The primary analysis population is described as an intention-to-treat collective comprising patients with both impedance waveforms and parallel volume waveforms generated during ventilation, making the primary endpoint evaluable. This specifies the stated eligibility for the primary analysis but does not explain the extent of missing waveform data or how incomplete observations were handled. Missing-data methods, exclusions after enrollment, and sensitivity analyses are not reported in the registry record.

The registry does not report a statistical analysis plan, a sample-size justification, interim analyses, or analysis results. The record lists no analyses. It therefore does not permit an assessment of whether the planned analyses were prespecified, how missing observations affected estimates, or whether additional analyses were performed. The absence of these details in the registry record should be distinguished from evidence that the procedures were not used.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cardiac arrest (4.0%), post procedural swelling (3.6%), respiratory failure (3.6%), vascular graft complication (1.8%), cardiogenic shock (1.8%).

The registry reports serious adverse events for ICU Patients and OLV Patients. In the ICU Patients group, 55 were listed as at risk and 7 as affected by serious adverse events. In the OLV Patients group, 25 were listed as at risk and 1 as affected. The registry also reports other adverse events: 55 at risk and 2 affected in ICU Patients, and 25 at risk and 12 affected in OLV Patients. No deaths are reported for either group.

These are group-level event counts as recorded in the registry. The record does not explain whether an affected participant could have experienced more than one event, how events were classified, or whether the at-risk figures represent the full enrolled groups for each safety measure. The terms listed among the serious events include Cardiac arrest (4.0%), Post procedural swelling (3.6%), Respiratory failure (3.6%), Vascular graft complication (1.8%), Cardiogenic shock (1.8%), and Haemodynamic instability (1.8%). The record does not specify the denominator for these listed percentages in the safety summary.

The presence of an event in the registry does not establish that it was caused by PulmoVista 500. The record does not provide event-level timing, attribution, severity criteria, or a comparison with a control group. The groups also differ in clinical context and are not a like-for-like control comparison. These figures should therefore be read as reported safety counts, not as evidence of a causal device effect.

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

The registry record describes a study intended to assess whether PulmoVista 500 can monitor changes in global and regional ventilation. Its primary measure is the cross-correlation between a ventilator volume curve and a global impedance curve, with a phase shift taken into account. This identifies the statistical question addressed: whether the two signals show a relationship under the specified lagged correlation calculation.

The record does not report the numerical mean cross-correlation coefficient or its standard deviation. It also does not report a confidence interval or a statistical test. As a result, the posted results in the registry record do not establish the observed strength, direction, or precision of the primary relationship. The theoretical range of the correlation coefficient describes the scale, not the study finding.

The endpoint is a measure of signal association. In general, association between two curves does not prove that their values agree exactly, that one signal accurately captures every clinically relevant change, or that using a monitor changes care or patient outcomes. Those conclusions require appropriate data and analyses beyond the endpoint definition. The listed secondary outcomes broaden the intended assessment, but their numerical results are not reported in the registry record.

The group descriptions cover ICU patients receiving or scheduled for ventilator care and patients scheduled for elective surgery receiving one-lung ventilation. Allocation is not stated, and the groups are explicitly not a like-for-like control comparison. Any group contrast should not be interpreted as a causal estimate of the device’s effect.

The safety figures report affected counts in each group, and no deaths are reported. They do not establish whether events were related to the device. Overall, the registry provides a description of the study question, endpoint, analysis population, and safety counts, but not the numerical primary efficacy result needed to characterize the observed monitoring relationship.

14. Why This Trial Matters Statistically

This study raises a useful statistical distinction between measuring a device signal and evaluating a clinical intervention. The primary endpoint is a relationship between two time-varying curves: ventilator volume and PulmoVista 500 global impedance. The cross-correlation method accommodates a delay between signals, making timing part of the definition of the statistic rather than treating the curves as if they were necessarily synchronized.

That design makes endpoint definition especially important. The record explains that correlations are assessed across lags from −15 to 15 and that the maximum is selected. Readers can therefore understand what the statistic is intended to capture. Yet a clear definition is not enough to assess the finding: the numerical mean and standard deviation are not reported in the registry record, and there is no confidence interval or hypothesis-test result. Statistical interpretation requires both a well-defined measure and its observed estimate with an indication of precision.

The study also illustrates why clinical context matters when interpreting groups. ICU Patients and OLV Patients are described as different populations in different care settings. Allocation is not stated, and the registry notes that the arms are not a like-for-like control comparison. A difference between groups would not automatically represent a device effect, even if numerical group results were available.

The record includes several secondary questions, such as regional ventilation and clinical helpfulness, alongside safety reporting. Without results and a reported plan for multiple outcomes, the breadth of the assessment cannot be translated into a quantitative conclusion. The record is informative about the monitoring question and the chosen method, while leaving the central numerical evidence unavailable for statistical appraisal.

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.

A central limitation of the registry record is that it does not report the numerical primary endpoint result. The mean cross-correlation coefficient and standard deviation are specified as the planned summary, but their values are not reported in the registry record. A confidence interval and primary hypothesis-test result are also not reported. This prevents assessment of the observed relationship and its precision.

The record describes two clinically different groups: ICU Patients and OLV Patients. It states that allocation is not stated and that the arms are not a like-for-like control comparison. The record therefore does not support interpreting a contrast between these groups as a randomized or causal estimate. It also does not describe a separate control intervention.

The endpoint depends on paired waveforms and uses the maximum correlation over a specified lag range. The record provides this central calculation description, but additional details about signal quality, waveform exclusions, or the handling of unusable signals are not reported in the registry record. The analysis population requires both impedance and parallel volume waveforms, while the amount and handling of missing waveform data are not reported.

The registry lists secondary outcomes, but their numerical results are not reported. A statistical plan for multiplicity, covariate adjustment, subgroup analyses, and interim analyses is not reported in the registry record. The sample-size justification is also not reported. The record lists no analyses, so it is not possible to assess which analyses were conducted or how their results were evaluated.

The safety information gives counts and selected serious-event terms, but definitions, event attribution, and further context are not reported. These limitations concern what can be concluded from the registry record; they do not establish what information may exist outside it.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Assessment of the Capability of PulmoVista 500 to Continuously Monitor Changes of Ventilation Over Time — NCT03076983.
• Registry record last updated 2019-11-27; status last verified 2019-11.
• Results first posted 2019-10-18.
• 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

NCT03076983 is a completed device study sponsored by Drägerwerk AG & Co. KGaA, with an enrollment of 80. The record gives a start date of 2017-05-30 and a primary completion date of 2018-04-12. It assesses PulmoVista 500 monitoring in ICU Patients and OLV Patients.

The primary endpoint is the mean cross-correlation coefficient between the ventilator volume curve and the PulmoVista 500 global impedance curve on Day 1. The calculation accounts for a phase shift by assessing correlations across lags from −15 to 15 and selecting the maximum. The primary analysis population is described as patients with both waveform types available during ventilation.

The registry lists secondary assessments of regional ventilation, tidal volumes, end-expiratory lung volumes, safety events, and clinical helpfulness. Numerical primary and secondary outcome results, the statistical analysis plan, and the sample-size justification are not reported in the registry record. The record reports serious and other adverse-event counts by group, with no deaths reported.