Comparison of Tissue Oxygenation Measurement Using Multimodal Devices: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Tissue Oxygenation Measurement Using Multimodal Devices (NCT05784103), a na na study. The primary outcome is Device-wise Comparison of Tissue Oxygenation Measurement.

2. Clinical Question

3. Trial Design

The registry record describes a completed, single-group device-measurement study with an enrollment of 20. It lists the study start as 2022-03-09 and primary completion as 2022-07-07. The stated aim was to assess accuracy, reliability, and usability of several oxygen measurement modalities in healthy volunteers. The study description says measurements would be made at the same site and compared.

The four measurement approaches are SFDI, TCOM, an Apple Watch Oxygen Sensor, and a pulse oximeter. The listed device interventions are Clarifi Modulum, Perimed PeriFlux 5000, Apple Watch Oxygen Sensor, and Innovo iP 900AP. The primary outcome timeframe is Visit 1, up to 2 hours in duration. The arm description also characterizes the measurements as occurring during a single study visit.

Allocation is listed as NA, and masking is listed as NONE. The study model is SINGLE GROUP. These registry fields do not describe a randomized allocation or a masked comparison. The device observations therefore do not form a randomized treatment-versus-control comparison. In particular, the record does not identify a separate control arm or state that one device served as a reference standard.

The official title refers to measurements before, during, and after hyperemic events. The primary outcome description says four devices were used to measure tissue oxygen saturation in healthy volunteers, but the registry record does not provide a detailed measurement protocol or explain how the timing of each device reading was synchronized. The planned procedure, including device placement and event sequence, is not reported in the registry record beyond the brief description.

The registry record lists three outcome measures and zero analyses. It does not report a statistical analysis plan, the actual number of observations available for each outcome, or numerical primary outcome results. Completion status indicates the study is recorded as completed; it does not by itself provide evidence about the quality, completeness, or agreement of the device measurements.

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: The Apple watch and the Pulse Oximeters are the devices designed to measure blood oxygenation based on the blood pulses occurring in the blood vessels when there is actual flow. At the time of occlusion there is no blood vessels pulsating, so the data were measured zero.

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.

Population: All 20 participants were taken for baseline. Before the occlusion was considered baseline and after the occlusion was compared before occlusion as baseline for each patient.

6. Primary Endpoint

The registry lists the primary outcome as Device-wise Comparison of Tissue Oxygenation Measurement, measured over Visit 1, up to 2 hours in duration.

The primary outcome is titled “Device-wise Comparison of Tissue Oxygenation Measurement.” It concerns a continuous measurement expressed as percentage of oxygen and is specified as a mean with standard deviation. The stated timeframe is Visit 1, up to 2 hours in duration. The description says four devices measured tissue oxygen saturation in healthy human volunteers.

A mean gives the central value of the recorded measurements, while a standard deviation describes how spread out those measurements are around the mean. Those summaries can help describe typical readings and variability, but they do not by themselves show whether two devices agree for individual participants. Agreement can require examining paired device readings, their differences, and the distribution of those differences. The registry record does not report such results or specify an agreement criterion.

The outcome population note points out that the Apple Watch and pulse oximeter are designed to measure blood oxygenation using blood pulses. It says that at the time of occlusion there are no pulsating blood vessels and that the data were measured as zero. Such zeros are part of the stated measurement context and could affect a mean and its variability. The registry record does not report how many measurements were taken during occlusion, how the zero values were handled in analysis, or whether the primary summaries include measurements from all event phases.

The purpose of measuring oxygenation with multiple modalities is to compare their recorded values. However, the registry record does not include the observed means or standard deviations, nor does it identify a primary device pair or a threshold for acceptable agreement. The endpoint definition alone therefore explains what was intended to be measured, not what the study found.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is continuous: oxygen saturation is expressed as a percentage of oxygen, with the primary summary specified as a mean and standard deviation. The registry record does not report the numerical values for those summaries. The concepts below explain how such measurements are generally analyzed; they do not describe analyses confirmed for this study.

What does a mean describe?

A mean is a measure of the center of a set of observations. For a device, it can describe the average reading across the observations included in the analysis. Its interpretation depends on which participants, device readings, and event phases were included. For example, a mean that combines readings from different phases of an event answers a different descriptive question from a mean calculated separately for each phase. The registry record does not say whether the primary summaries were separated by phase or combined.

A standard deviation describes the spread of observations around their mean. It is not the uncertainty in the estimated mean. The uncertainty of a mean is commonly described with a confidence interval, which gives a range of values compatible with the data and analysis assumptions. A confidence interval would help communicate precision, but no such interval is reported in the registry record. Neither a mean nor a standard deviation alone shows whether individual device readings are close to one another.

Why does pairing matter?

The study description says that a cohort of volunteers would be assessed with multiple devices at the same site. When different devices measure the same participant, their readings are paired. A paired analysis evaluates within-participant contrasts rather than treating every device reading as if it came from an unrelated person. Pairing can account for the fact that a participant’s readings across devices may share characteristics. The registry record does not report whether the device readings were matched in this way in an analysis, or how timing differences between devices were handled.

For a device comparison, a useful general quantity is the difference between two readings made under comparable conditions. The average of those differences can describe systematic offset, while the spread of individual differences can describe how variable agreement is. A confidence interval for the average difference communicates its precision. A formal test of whether an average difference is distinguishable from zero is not the same as a demonstration of practical agreement: a small estimated offset can still coexist with substantial variation among individual readings. The registry record does not report device differences, confidence intervals, or a prespecified acceptable range.

What do the zero readings imply?

The outcome population note states that the Apple Watch and pulse oximeters rely on blood pulses and that, during occlusion, there are no pulsating vessels and the data were measured as zero. In general, zero values can affect a continuous outcome’s mean and distribution. If measurements include multiple phases, the proportion and timing of zero readings may matter to the summary. A distribution with a concentration of zeros may also be poorly represented by a mean and standard deviation alone. The record does not report how many zero readings occurred, how they were represented in the analysis, or whether the outcome was analyzed separately by event phase. These issues cannot be resolved from the stated endpoint description.

Over-dispersion is a general concern when data vary more than an assumed statistical model allows. It is especially discussed for count outcomes, but the broader lesson is that model assumptions should match observed variability and dependence. This study’s primary outcome is described as continuous, and the registry record does not report a fitted model or diagnostics. There is therefore no basis for saying whether over-dispersion was present or whether a particular model was used.

What do significance tests and intervals contribute?

A significance test assesses how compatible the data are with a specified null hypothesis under the chosen model. Its p-value does not measure the probability that a device is accurate, nor does it quantify the size or practical importance of a difference. A confidence interval gives an uncertainty range for an estimate under the analysis assumptions. For device comparisons, reporting the estimate and interval is generally more informative than a p-value alone. The registry record lists no analysis results, p-values, or confidence intervals, so none can be interpreted.

The sample-size assumptions describe a planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They say that the effect to detect is a stated fraction of the observed effect. Such calculations are planning exercises: they ask what sample size would be needed under specified assumptions. They do not describe the number of participants actually analyzed, establish the original rationale for enrollment, or measure observed power. The registry record does not report a sample-size justification, and the assumed two-arm allocation does not match the listed single-group design description. No numerical planning estimates or observed effect are reported in the registry record.

Finally, interpreting any statistical comparison would require knowing the analysis population, handling of missing readings, device synchronization, and the chosen comparison method. Those details are not reported in the registry record. The statistical concepts above provide a framework for reading possible results, not a substitute for the missing numerical estimates and methods.

10. Multiplicity, Missing Data and Analysis Populations

The study lists three outcome measures, while the primary outcome description focuses on a device-wise comparison. The registry record does not identify the other outcome measures in the available details, specify which comparisons were prespecified as primary, or report a statistical plan for handling multiple comparisons. When several devices, event phases, or outcomes are compared, the chance of obtaining at least one apparently unusual result can increase. General approaches to multiplicity include defining a limited set of primary contrasts in advance or adjusting the interpretation of multiple tests. Which approach, if any, was used is not reported in the registry record.

The record lists zero analyses. It does not report hypothesis tests, confidence intervals, estimates, or a model. It is also not possible to determine whether results were intended to be descriptive, inferential, or both. The lack of a reported analysis plan means the reader cannot assess whether the comparisons were selected before or after examining the measurements.

The registry record does not report missing-data counts, reasons for missing readings, or the number of participants with measurements usable for each device or event phase. It does not say whether missing values were excluded, imputed, or handled by another method. Those details matter because device failure, incomplete measurements, or differences in data availability could make the set of observations differ across devices. No such issue should be assumed to have occurred, but its handling is not reported in the registry record.

The record describes a single-group study but does not define an analysis population, such as all enrolled participants or those with complete device measurements. It also does not report whether any participants or measurements were excluded from outcome summaries. These omissions limit assessment of the completeness and comparability of the measurements.

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 adverse-event record lists four device-specific groups: SFDI Measurement of Oxygen Saturation, PeriFlux 5000 for Transcutaneous Oxygen Partial Pressure, Apple Watch Oxygen Sensor for Arterial Oxygenation, and A Pulse Oximeter for Arterial Oxygenation. For each listed group, the record gives 20 as at risk for serious adverse events and 0 affected; it also gives 20 at risk for other adverse events and 0 affected. Deaths are recorded as 0 for each group. No serious adverse-event terms are listed.

These figures describe what the registry record reports; they do not establish that no unrecorded events occurred or that the devices have no safety risks. The record does not explain the event-collection procedure, the definitions used for serious and other adverse events, or whether the adverse-event groups represent separate participant sets. The group entries should therefore be read as device-specific reporting, not added together to infer a total number of participants.

The study description concerns healthy volunteers and a single visit, but the adverse-event listing does not provide event narratives or timing. It also does not state whether any event led to a measurement being stopped or omitted. The zero counts are registry-reported observations, not a guarantee of safety beyond the study conditions.

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

The registry record establishes that a completed study was designed to measure oxygen saturation using SFDI, TCOM, an Apple Watch Oxygen Sensor, and a pulse oximeter in healthy volunteers. The stated purpose was to compare measurement outcomes and assess accuracy, reliability, and usability. The record also identifies a continuous primary outcome, a mean with standard deviation, and a visit timeframe of up to 2 hours.

It does not report the primary outcome values, the number of usable observations for each device, or statistical analyses. As a result, it cannot show which device recorded higher or lower values, how variable the readings were, whether paired device readings agreed, or how precisely any differences were estimated. It also cannot establish accuracy against a reference standard, because the registry record does not identify a reference method or report a validation analysis.

The design description is a single-group measurement study rather than a randomized comparison of treatment groups. The devices are measurement modalities, not assigned therapies in a controlled efficacy comparison. The study aim and completion status do not demonstrate that a device is reliable, accurate, usable, or suitable for any particular clinical purpose.

The stated zero readings during occlusion require context: the outcome description says pulse-based devices had no pulsating vessels at that time and that the data were measured as zero. Without details about event phases, the handling of zeros, or outcome summaries, readers cannot know how those observations influenced any planned comparison.

Thus, the record is informative about the question and broad design, but insufficient for judging comparative performance. Numerical results, analysis methods, missing-data information, and a clear account of any reference standard are not reported in the registry record.

13. Why This Trial Matters Statistically

Comparing measurement devices raises a different statistical question from comparing treatments. The central issue is whether readings from different instruments are sufficiently similar for the intended measurement context. Group averages can be a starting point, but similarity of averages does not guarantee close agreement for individual readings. Paired comparisons and the spread of within-participant differences are often important when the same people are measured by multiple devices.

This study’s design description makes that issue relevant: participants were to have oxygenation measured with multiple modalities at the same site. The record’s note about pulse-based devices during occlusion adds another measurement consideration. A device may be responding to a condition in which its usual signal is absent, and a recorded zero can affect summaries. A useful analysis would need to make clear which measurement phases are being compared and how those readings enter the endpoint.

The registry record does not report the estimates needed to evaluate these questions. That absence is statistically important. A study aim is not a result, and a completed status does not replace reporting effect estimates, uncertainty, and analysis methods. Without those details, readers cannot distinguish small systematic offsets from broad participant-level disagreement or assess whether findings are precise.

The case also illustrates why planned comparisons and analysis populations should be explicit in multi-device studies. The record lists three outcome measures and zero analyses, but does not describe multiplicity handling or missing readings. Those details help readers understand which comparisons were intended and whether measurements can be compared fairly across devices.

The statistical importance of this study therefore lies in the measurement question it poses, while its registry record leaves the empirical answer unresolved. The record does not support a ranking of the devices or a conclusion about measurement agreement.

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.

The registry record gives limited detail about the measurement procedure. Although the official title refers to measurements before, during, and after hyperemic events, the record does not report the event protocol, the timing and synchronization of device readings, or the number of readings collected at each phase. These details are important when comparing instruments that may not capture data in the same way or at the same moment.

The enrolled population is described as healthy volunteers above the age of 18, including males and females with different skin colors. The record does not provide the distribution of participant characteristics or results by skin color, sex, or other subgroups. It therefore does not support subgroup comparisons or conclusions about populations beyond those described. The generalizability of measurements to people with illness is not established by the registry information.

The primary outcome is identified as a mean with standard deviation, but the record does not report numerical results, paired differences, uncertainty intervals, or a reference standard for accuracy. It also does not state how device agreement or reliability would be defined. Without an analysis plan and estimates, the stated aims cannot be evaluated statistically.

The endpoint note says that pulse-based measurements were recorded as zero during occlusion because there were no pulsating blood vessels. The record does not explain whether these values were included in the primary summaries, analyzed separately, or treated in another way. It also does not report missing-data handling or device-specific measurement availability.

Finally, the registry record lists no analyses and does not report a sample-size justification. Its separate planning assumptions describe equal allocation between two arms, whereas the study is described as single-group. The record does not reconcile these details. These limitations leave the actual comparative findings and their precision unreported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Tissue Oxygenation Measurement Using Multimodal Devices — NCT05784103.
• Registry record last updated 2023-11-29; status last verified 2023-11.
• Results first posted 2023-11-24.
• 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

The registry record describes a completed, single-group study of oxygen saturation measurement in healthy volunteers, with an enrollment of 20. Four modalities were named: SFDI, TCOM, an Apple Watch Oxygen Sensor, and a pulse oximeter. The primary outcome is a device-wise comparison of tissue oxygenation, expressed as a mean with standard deviation during Visit 1, up to 2 hours in duration.

Allocation is listed as NA, masking as NONE, and the study model as SINGLE GROUP. The record lists three outcome measures and zero analyses. It reports zero serious adverse events, zero other adverse events, and zero deaths in each listed device-specific adverse-event group.

Numerical primary outcome results, device comparisons, analysis methods, missing-data handling, and a sample-size justification are not reported in the registry record. The study question and measurement context are described, but comparative performance cannot be evaluated from the reported information.