Non-invasive Tidal Volume Monitoring Using the Linshom Respiratory Monitoring Device: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Non-invasive Tidal Volume Monitoring Using the Linshom Respiratory Monitoring Device (NCT03279458), a non-randomized na study. The primary outcome is Tidal Volume of Each Breath Was Measured Using the Same Breathing Mask CPAP Apparatus Combined With Respiratory Monitoring Device Allowing for Simultaneous Recording..

2. Clinical Question

The clinical motivation described in the record is the challenge of monitoring inadequate ventilation outside critical care settings. It notes that oxygen saturation can be less sensitive to depressed respiration when supplemental oxygen is administered, while carbon dioxide may rise gradually and remain undetected without blood-gas measurement. The study focuses on a measurement question: whether the device can provide a non-invasive estimate of tidal volume under the stated experimental conditions. It does not, on the available record, establish performance in other settings or report how the device compares with other monitoring approaches.

3. Trial Design

This was a completed, non-randomized, single-group study sponsored by the University of Mississippi Medical Center. The registry lists enrollment of 40. Its primary outcome description says that thirty participants successfully completed the experiment. The record does not explain the difference between enrollment and completion, nor does it describe the reasons for non-completion.

Volunteers breathed through a CPAP face mask fitted with the Linshom device and were instructed to breathe normally on room air. The device recorded thermistor-tracing excursions, while a ventilator measured tidal volume concurrently. Thus, the central design feature was simultaneous measurement during the same breathing experiment, rather than allocation to separate device and control groups. The ventilator measurement serves as the comparator for assessing the Linshom-derived measurement; it should not be read as a randomized control arm.

The primary outcome timeframe is 5 minutes. The outcome is described in milliliters and is characterized as a least-squares mean with a 95% confidence interval. The registry record does not report the numerical estimate, confidence interval, or detailed analysis model. The study start and primary completion dates are both 2017-09-08, and the status is completed.

Masking is listed as none, and allocation is listed as non-randomized. The record does not report a separate randomized assignment process, a blinding procedure, or a protocol rationale for the enrollment target. It also does not report participant demographics, the number of evaluable breaths, or details about the conditions under which the ventilator and device signals were processed. Those omissions limit the extent to which the recorded design can be assessed or generalized.

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: Thirty participants successfully completed the experiment, which involved breathing through a CPAP mask in order to have the Linshom device record excursions of the thermistor tracings while the ventilator concurrently measured tidal volume.

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 Tidal Volume of Each Breath Was Measured Using the Same Breathing Mask CPAP Apparatus Combined With Respiratory Monitoring Device Allowing for Simultaneous Recording., measured over 5 minutes.

The primary endpoint concerns tidal volume for each breath, measured with the CPAP mask apparatus while the respiratory monitoring device recorded at the same time. The ventilator posted a tidal-volume measurement for comparison with the value estimated indirectly by the Linshom device from temperature changes. The stated timeframe is 5 minutes, and the measurement unit is ml. The registry labels the reported parameter a least-squares mean and specifies a 95% confidence interval.

Tidal volume is relevant to this study because the stated research question is whether the temperature-based signal can track the volume of air moved with breathing. Comparing readings obtained concurrently makes it possible to examine whether the device-derived values correspond to ventilator measurements under the experimental conditions. That is a measurement-performance question, not a comparison of clinical outcomes or a test of whether using the device changes patient care.

The record does not provide the least-squares mean, its confidence interval, or the underlying paired readings. It therefore does not show the direction or magnitude of any difference between methods, nor does it quantify the precision of the estimate. Details such as the exact calculation used to derive each device-based volume and the handling of repeated breaths are not reported in the registry record. Without those results and methods, the endpoint definition alone cannot establish how closely the device tracked ventilator-measured tidal volume.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes the primary outcome as a least-squares mean with a 95% confidence interval. It does not report the numerical estimate or interval, and it does not give enough information to reconstruct the statistical analysis. The explanations below describe general statistical concepts, not additional procedures confirmed for this study.

What does a least-squares mean represent?

In general, a least-squares mean is a model-based estimate of an average. It can account for covariates or features of a statistical model, unlike a simple arithmetic average. Its interpretation depends on the model specification, variables included, and the population or conditions to which the estimate is standardized. Those details are not reported in the registry record, so the label alone does not reveal how the estimate was obtained or what adjustments, if any, were made.

For a device-measurement question, an average can summarize the readings but may not describe the full pattern of agreement. Two methods can have similar average values while differing substantially for individual readings. Conversely, a consistent average offset may coexist with a strong relationship across observations. General assessment of measurement performance can therefore involve both average differences and the spread of differences, as well as the relationship between paired values. The registry record does not report which such summaries, beyond the stated primary outcome, were calculated.

What does a confidence interval tell the reader?

In general, a confidence interval describes uncertainty around an estimate using a specified method and assumptions. A narrower interval indicates greater precision for the estimated quantity under those assumptions; a wider interval indicates greater uncertainty. The interval is not a guarantee that the true value lies within its limits, and it does not replace inspection of the estimate itself. The record names a 95% confidence interval but does not state its endpoints. Its precision and substantive implications therefore cannot be assessed from the registry entry.

Confidence intervals also depend on the data structure. If readings are repeated within participants, those readings may be correlated. Treating correlated observations as independent can make uncertainty appear smaller than it is. General approaches can account for within-participant dependence, for example through participant-level summaries or models that represent clustering. The statistical method used for this study, including whether repeated readings were modeled or summarized, is not reported in the registry record.

Why is concurrent measurement useful?

General measurement studies often compare methods applied under similar conditions to the same underlying event. Concurrent recording can reduce differences caused by changes in the subject’s state between measurements. In this study, the record says the ventilator measured tidal volume while the Linshom device recorded thermistor excursions during the same breathing experiment. That setup supports a paired measurement question. The entry does not provide the paired observations or describe how the device’s temperature signal was converted into a tidal-volume estimate beyond noting a computer algorithm.

Correlation and agreement are not interchangeable. In general, correlation describes how values vary together; it does not show that values are close in absolute terms. Agreement asks how far the readings from methods differ and whether those differences are acceptably small for a specified use. A high correlation may occur even when one method is systematically offset from another. The registry record does not report a correlation coefficient, agreement limits, an acceptable-error criterion, or the result of any such analysis. No conclusion about these properties should be inferred from the outcome title alone.

What analysis details are needed?

A statistical analysis plan would ordinarily clarify the precise primary estimand, the model and its assumptions, the unit of analysis, how repeated observations are handled, and how incomplete data are treated. It could also describe any transformations, exclusion criteria, or sensitivity analyses. These details help readers determine whether the reported estimate answers the stated question and whether its uncertainty is appropriately calculated. Such a plan and these specifications are not reported in the registry record.

General checks for a continuous measurement analysis may consider the distribution of paired differences, influential observations, and whether variability changes across the range of measurements. If variability increases with the magnitude of the readings, a single average difference may not characterize performance consistently. Over-dispersion, broadly, means that observed variability exceeds what a model assumes; accounting for it can be important because standard errors and confidence intervals depend on an appropriate variance model. The record does not report diagnostic checks or evidence of over-dispersion, so these are considerations for interpreting methods, not claims about this experiment.

The record states a primary endpoint and a confidence-interval form, but it does not report a test statistic or p-value. A p-value, in general, measures how incompatible data are with a specified null model under its assumptions; it is not a measure of the size or practical importance of a measurement difference. For method comparison, the estimated difference and its uncertainty are often more directly useful than a significance test alone. The posted results do not contain those numerical quantities.

Planning calculations, when displayed, should be understood as illustrations rather than evidence about what was observed. The registry notes that its planning illustration is based on the observed effect under stated assumptions, including a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also says the effect to detect is expressed as a fraction of the observed effect. Such calculations do not supply an observed result, do not establish the study’s original design rationale, and are not observed power. The registry record does not report a sample-size justification from the study’s original protocol.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and one analysis. That description does not establish the full analysis plan or show whether additional outcomes, exploratory analyses, or alternative measurement summaries were considered. A multiplicity adjustment, if any, is not reported in the registry record. In general, testing or estimating many outcomes can increase the chance of selectively emphasizing a favorable finding; prespecification and transparent reporting help readers understand this risk. The available entry does not permit an assessment of whether multiplicity was a concern or how it was handled.

Missing-data information is also limited. The outcome description says thirty participants successfully completed the experiment, while enrollment is listed as 40. The registry record does not explain why some enrollees did not complete the experiment, whether measurements were partly available for those participants, or how incomplete observations were handled. It does not state whether the primary analysis included all enrolled participants, only those with complete measurements, or another analysis population. The number of breaths contributing to the endpoint is not reported.

These omissions matter because incomplete measurement records can affect both the estimated average and its uncertainty, particularly if completion is related to the measurement process or participant characteristics. General approaches include describing the extent and reasons for missingness, specifying the analysis population, and assessing whether conclusions are sensitive to assumptions about unobserved values. The registry does not report such analyses or assumptions. No claim about the impact of missing data can therefore be made from the posted record.

The analysis plan, any interim analyses, and rules for selecting among analysis populations are not reported in the registry record. The record identifies the primary endpoint, but the available description is not sufficient to confirm how completely the stated analysis was prespecified or how all available observations were used.

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 reports serious adverse events for the Linshom and Maquet Ventilator entries. For each entry, the number at risk is 40, the serious adverse-event count is 0, and deaths are 0. The other-adverse-event count is also 0 for each entry. No serious-event terms are listed.

These are the posted counts, not evidence that an event was impossible or that the device has been shown to be free of risk. A zero count in a record means that no events were reported in that category for the listed group; it does not quantify the chance of an event beyond the observations recorded. The registry does not describe how adverse events were solicited, monitored, defined, or adjudicated, and it does not provide event narratives.

The group labels should not be interpreted as randomized treatment arms. The study is described as non-randomized and single-group, with ventilator measurements recorded concurrently as a comparator. The safety entries do not create a like-for-like controlled safety comparison. They also do not provide enough detail to assess whether all participants who began the experiment contributed to safety follow-up or how long follow-up lasted. Follow-up duration and those monitoring details are not reported in the registry record.

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

The record describes a study intended to evaluate whether a non-invasive temperature-based signal can track tidal volume during breathing through a CPAP mask. It reports concurrent collection of thermistor excursions from the Linshom device and tidal-volume measurements from a ventilator. This provides the basic context for a measurement comparison in the experimental setting.

However, the registry record does not report the numerical primary outcome estimate or its 95% confidence interval. It therefore does not show the size, direction, or precision of the observed result. Without those values, readers cannot determine how closely the Linshom-derived measurements corresponded to ventilator measurements in this experiment. The outcome description and device rationale are not substitutes for the measured result.

Even with a reported estimate, findings from this design would pertain to the participants and conditions studied unless supported by evidence in other settings. The record describes volunteers breathing through a CPAP face mask on room air, with measurements collected over the stated 5-minute timeframe. It does not report participant characteristics or establish how the device performs in other clinical environments, among different populations, or during conditions beyond the experiment.

The study also addresses measurement rather than patient outcomes. The registry does not report whether using the device changed clinical decisions, prevented complications, or affected health outcomes. No such conclusion follows from the stated purpose or endpoint. Likewise, zero recorded adverse events in the listed categories should be read as reported counts, not as proof of no risk.

The appropriate conclusion from the posted record is limited: it documents a completed experiment designed to compare a device-derived tidal-volume measure with concurrent ventilator readings, but omits the primary numerical result. The evidence needed to judge measurement accuracy, agreement, and precision is therefore not reported in the registry record.

13. Why This Trial Matters Statistically

This study raises a useful statistical distinction between detecting a respiratory signal and validating a measurement. A device may generate a signal that varies with breathing, but the clinical measurement question is whether values derived from that signal correspond closely enough to a reference measurement for the intended purpose. General statistical assessment therefore needs more than a description of the instrument or an average alone; it needs estimates of the relationship and uncertainty, with methods suited to paired and potentially repeated observations.

The concurrent measurement design is relevant because the two readings were collected during the same breathing experiment. That structure can support paired comparisons, which focus on within-observation differences rather than treating each method’s readings as unrelated. But the record does not report the paired results or describe how repeated breaths within participants were handled. The design’s statistical strengths cannot be fully evaluated without those details.

The distinction between association and agreement also matters. General correlation summaries can indicate whether methods move together, but do not by themselves show whether their readings are close. In a monitoring context, systematic offsets and the range of individual differences may be as important as an average relationship. The registry does not report those measures or an acceptable level of measurement error.

Finally, the distinction between a completed experiment and a reported result is important. The record identifies the outcome definition, unit, timeframe, and stated confidence-interval format, but omits the estimate and interval. Without the numerical outcome, statistical interpretation cannot move from design description to a judgment about observed performance. This makes transparent outcome reporting central to the value of a measurement study.

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.

Several limitations are specific to the information recorded for this study. The principal limitation is that the registry record does not report the primary endpoint estimate or its 95% confidence interval. It also does not provide paired readings, a measure of agreement, or a numerical summary of the relationship between the Linshom-derived values and ventilator measurements. The central measurement question therefore cannot be answered from the posted results.

The record states that thirty participants successfully completed the experiment, while enrollment was 40, but does not explain non-completion or specify the analysis population. It does not report participant characteristics, the number of breaths included, the approach to within-participant repeated observations, or missing-data procedures. These gaps prevent assessment of representativeness and of how the analysis accounted for the data structure.

The design is non-randomized and single-group. The ventilator is a concurrent measurement comparator, not a randomized control arm. The registry does not report blinding, measurement-processing details, an acceptable-error threshold, or the full statistical model. It also does not describe validation in other populations or settings. The stated breathing conditions are limited to volunteers using a CPAP face mask on room air during the experimental timeframe.

Finally, safety reporting is limited to the listed event counts. Definitions, ascertainment procedures, and follow-up duration are not reported in the registry record. These limitations concern what can be concluded from the registry entry; they should not be taken as evidence that unreported procedures or analyses did not occur.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Non-invasive Tidal Volume Monitoring Using the Linshom Respiratory Monitoring Device — NCT03279458.
• Registry record last updated 2018-07-05; status last verified 2018-07.
• Results first posted 2018-07-05.
• 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

This completed study, sponsored by the University of Mississippi Medical Center, evaluated whether the Linshom Respiratory Monitoring Device could track tidal volume using temperature-based thermistor excursions. Volunteers breathed through a CPAP mask on room air, while a ventilator measured tidal volume concurrently. The record lists enrollment of 40 and says thirty participants successfully completed the experiment.

The primary outcome is described in ml as a least-squares mean with a 95% confidence interval over 5 minutes. The registry record does not report the estimate, interval, or other numerical results needed to assess agreement or precision. It also does not explain non-completion or provide detailed analysis methods.

The study is non-randomized and single-group; ventilator measurements are a comparator, not a randomized control group. Serious adverse events, other adverse events, and deaths are recorded as 0 in both listed entries, with 40 at risk in each. The available record supports a description of the measurement setup, but not a conclusion about the device’s observed performance.