This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Aerosol Particle Concentrations Among Different Oxygen Devices for Spontaneous Breathing Patients With Tracheostomy (NCT04654754), a randomized na study. The primary outcome is Aerosol Particle Concentrations With Size of 1-3 Micrometer at 1 Foot Away From the Patient.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04654754 |
| Phase | NA |
| Condition | Transmission, Patient-Professional |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 12 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Jie Li |
| Results posted | Yes |
2. Clinical Question
Population
Spontaneous-breathing patients with tracheostomy. The registry describes the concern that particles from the airway may enter room air because the airway is directly open to it. Enrollment was 12. Participant characteristics beyond this description are not reported in the registry record.
Intervention
The device configurations include a high-flow, high-humidity oxygen device with a tracheostomy adapter; a large-volume nebulizer with a trach collar; a Venturi adapter with a trach collar; a large-volume nebulizer with a T-piece and filter; and a high-flow, high-humidity device with a scavenger or surgical mask. The record describes the first as providing heated, humidified high-flow gas, the Venturi arrangement as providing oxygen without humidification, and the added filter, scavenger, or mask as intended to reduce surrounding particle concentrations.
Comparator
The registry describes comparisons among oxygen-device configurations. It calls the large-volume nebulizer with cool aerosol and trach collar the conventional device commonly used for humidification in this population. The relative ordering, sequence, and specific paired comparisons are not reported in the registry record.
Primary question
The primary question concerns aerosol particle concentrations of size 1-3 micrometer in room air at 1 foot from the patient, measured 5 minutes after using a device. The stated purpose is to use these concentrations to reflect potential transmission risk. The outcome is an environmental particle measurement, not a direct measurement of infection or transmission. Numerical primary-outcome results are not reported in the registry record.
3. Trial Design
The registry identifies this as a randomized, single-masked, crossover trial, with a status of completed and enrollment of 12. The title likewise describes a randomized crossover trial. The registry lists a start date of 2020-12-23 and a primary completion date of 2021-07-16. Phase is recorded as not applicable. The condition is transmission between patients and professionals.
A crossover design generally means that a participant receives or is assessed under more than one study condition, so comparisons can potentially use measurements from the same person under different conditions. This is a general explanation of the design type, not a confirmation of the exact procedures used in this study. The record does not report the order in which devices were used, whether order was randomized for each participant, the duration of exposure, any washout period, or how repeated measurements were summarized for analysis.
The arm descriptions cover several configurations, including humidified and non-humidified oxygen delivery and configurations with an added filter, scavenger, or surgical mask. The intervention listing names the high-flow high-humidity oxygen device with tracheostomy adapter, while the arm descriptions give details for the other configurations. The number and structure of randomized sequences, and how the listed configurations map to assigned conditions, are not reported in the registry record.
The primary endpoint is a median concentration of particles in a specified size range and at a specified distance, five minutes after device use. The registry also lists patient comfort as a secondary outcome and indicates seven outcome measures overall. The methods used to collect comfort data and the other listed outcome measures are not reported in the registry record. Although the trial is marked completed, numerical outcome results and an analysis are not reported in the registry record.
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.
LVN With T-piece and a Filter
| Stage | Spontaneous Breathing Patients With Tracheostomy |
|---|---|
| STARTED | 12 |
| COMPLETED | 12 |
| NOT COMPLETED | 0 |
High-flow High-humidity With Adapter
| Stage | Spontaneous Breathing Patients With Tracheostomy |
|---|---|
| STARTED | 12 |
| COMPLETED | 12 |
| NOT COMPLETED | 0 |
LVN With Trach Collar
| Stage | Spontaneous Breathing Patients With Tracheostomy |
|---|---|
| STARTED | 12 |
| COMPLETED | 12 |
| NOT COMPLETED | 0 |
Venturi With Trach Collar
| Stage | Spontaneous Breathing Patients With Tracheostomy |
|---|---|
| STARTED | 12 |
| COMPLETED | 12 |
| NOT COMPLETED | 0 |
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.
| Characteristic | Unit | Spontaneous Breathing Patients With Tracheostomy |
|---|---|---|
| Participants analysed | 12 | |
| Age, Continuous | years | 50.5 (SD 16.6) |
| Sex: Female, Male: Female | Participants | 6 |
| Sex: Female, Male: Male | Participants | 6 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Aerosol Particle Concentrations With Size of 1-3 Micrometer at 1 Foot Away From the Patient, measured over 5 minutes after using the device.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Inter-Quartile Range |
| Unit | particles/m3 |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the concentration of aerosol particles sized 1-3 micrometer in room air, measured 1 foot away from the patient 5 minutes after using the device. Its unit is particles/m3. The registry specifies the median and inter-quartile range as the summary form. The target is therefore a local environmental particle concentration at a stated distance and time, rather than a count of infections, a direct estimate of person-to-person transmission, or a clinical outcome in the patient.
The rationale in the registry is that particles generated by patients with a tracheostomy may disperse into room air and could reflect transmission risk. Measuring the concentration near the patient can describe particle presence under different device arrangements. As a general statistical point, an environmental measure may be useful for comparing conditions while remaining an indirect proxy for a downstream event. A change in a proxy does not by itself establish a change in infection risk; that would require evidence connecting the measured concentration to transmission.
Using a median and inter-quartile range is a way to describe the distribution without relying on the mean and standard deviation. In general, the median gives the central value in an ordered set of observations, while the inter-quartile range describes the spread of the middle portion. This can be useful when measurements are skewed or affected by unusually high readings. The registry does not report the observed median or inter-quartile range for any device configuration, nor does it describe the instrument, sampling procedure, or handling of repeated measurements.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the question and the intended measurement, but it does not provide the numerical primary-outcome findings. The primary endpoint is aerosol particle concentration for particles sized 1-3 micrometer, expressed in particles/m3, at 1 foot from the patient and 5 minutes after device use. The planned descriptive summary is the median with inter-quartile range. The record does not report those summaries by device, a comparison estimate, a confidence interval, or a significance test. Consequently, the posted record does not support a numerical account of how particle concentrations differed among the configurations.
The registry describes the study as randomized and crossover. In general, randomization can reduce systematic differences in the assignment of conditions, and crossover comparisons may account for stable participant characteristics when the same participant experiences multiple conditions. Those potential advantages depend on the actual assignment and measurement procedures. The sequence of device use, washout arrangements, treatment-period details, and analysis approach are not reported in the registry record. Without those details, the design label alone is not enough to assess whether period effects, carryover, or within-participant correlation were handled appropriately.
The purpose described by the investigators is to use particle concentration as a reflection of transmission risk. That is an indirect interpretation. Even if concentration results were available, particle measurements at a particular distance and time would not directly establish whether a person was infected or whether transmission occurred. The registry does not report infection outcomes or a measured transmission event. It also does not report a validated relationship between the particle endpoint and transmission.
The record lists patient comfort as a secondary outcome, but no comfort results are reported. It indicates seven outcome measures overall, yet the numerical findings and analysis details for those measures are not reported in the registry record. The trial is marked completed, but completion status does not supply the missing estimates or establish the direction, size, or precision of any device comparison.
Statistical precision cannot be judged without the outcome estimates and measures of uncertainty. In general, a confidence interval describes a range of values compatible with the data and a specified statistical procedure; its width conveys precision, not the probability that a particular treatment effect is true. No confidence intervals are reported in the registry record. There is likewise no reported test statistic or p-value from which to assess evidence against a null hypothesis.
The enrollment was 12. That figure alone does not show how many observations contributed to each device-specific estimate, whether any measurements were missing, or how precise a comparison would be. Those details are not reported in the registry record. The posted record therefore supports a description of the trial question, design labels, endpoint definition, and listed safety counts, but not a conclusion about the comparative particle concentrations or their clinical implications.
9. Statistical Methods Explained
The registry labels the study randomized, single-masked, and crossover. These labels describe broad features rather than a complete statistical plan. The record does not specify who was masked, the allocation procedure, the condition sequence, or the analysis model. Such details matter because a crossover study produces measurements under multiple conditions, often from the same participant. Those measurements are generally correlated rather than independent.
What does a crossover comparison require?
In general, a crossover analysis needs to account for the fact that observations from the same participant share characteristics. A within-participant comparison can remove some stable differences between people, but it does not automatically handle changes over time or effects carried from one condition into another. Period effects can arise if measurements change over the course of a study regardless of device. Carryover can arise if a prior condition affects a later measurement. The sequence of conditions, washout procedures, period-specific measurements, and any adjustment for period or carryover are not reported in the registry record.
Randomization in a crossover trial may refer to assignment of treatment order, but the record does not explain what was randomized or how. It is therefore not possible to determine from the registry entry whether the order of device use was randomized, balanced, or incorporated into an analysis. The record also does not describe the unit of analysis or whether repeated particle readings were aggregated before comparison.
What does the endpoint summary convey?
The registry defines the primary outcome as a median with inter-quartile range. In general, the median is a measure of location that is less affected by extreme observations than the arithmetic mean. The inter-quartile range describes the spread of the middle half of ordered observations. Reporting these summaries can be informative when data have a skewed distribution or occasional large values. However, a median and inter-quartile range do not, by themselves, quantify the uncertainty in a comparison between devices.
Particle concentrations may vary across time and measurement location. This is a general consideration for environmental measurements, not a statement about the observed data in this trial. The endpoint specifies a location 1 foot from the patient and a measurement time 5 minutes after device use. The record does not report the sampling duration, the equipment, the number of readings, or whether measurements were repeated at multiple times or positions. It also does not say whether the primary endpoint is a single measurement, an average of readings, or another summary at the participant level.
Why can distribution shape matter?
General statistical methods assume or accommodate different patterns in data. A mean-based analysis may be sensitive to unusually large measurements when the distribution is strongly skewed. A rank-based or other robust approach can be less dependent on a particular distributional shape, but each method targets a specific quantity and has assumptions of its own. In a crossover setting, a method must also account for the pairing or repeated observations. The registry record does not identify the planned or performed method, so it is not possible to determine how distribution shape or within-participant dependence was addressed.
Over-dispersion is a general term for variability greater than a chosen model would expect. When present, a model that assumes too little variability can understate uncertainty and make results appear more precise than warranted. Whether over-dispersion is relevant depends on the measurement and analysis model. The registry does not report a model or diagnostics, so no assessment of over-dispersion can be made for this trial.
How should uncertainty be interpreted?
In general, an estimate describes the magnitude of an observed quantity, while a confidence interval communicates its uncertainty under a specified method. A narrow interval indicates greater precision than a wide interval, but neither the estimate nor interval alone establishes practical importance. A hypothesis test addresses compatibility with a null value under its assumptions; a p-value is not the probability that the null hypothesis is true. These are general explanations. The registry record does not report an estimate, confidence interval, test, or p-value for the primary endpoint.
Statistical significance and clinical or operational importance are different questions. For this study, the endpoint is an environmental particle concentration intended to reflect possible transmission risk. Even a precise comparison of particle concentrations would need separate evidence to establish what magnitude of change, if any, is meaningful for transmission or patient-professional exposure. No such threshold or validation is reported in the registry record.
What is absent from the analysis record?
The registry indicates zero analysis entries. No prespecified statistical model, contrast, covariate adjustment, handling of repeated measures, missing-data approach, or analysis population is reported in the registry record. It is also not reported whether an interim analysis occurred. These omissions prevent evaluation of whether the reported endpoint was analyzed as planned or whether analytical choices were made after examining the data.
In general, a statistical analysis plan clarifies the primary comparison, the scale of analysis, the treatment of repeated observations, and the method for handling incomplete data. It also helps distinguish confirmatory analyses from exploratory ones. Without a reported plan or analysis, the trial's design labels and outcome definitions do not establish how evidence was quantified. No recalculated result or sample-size illustration can be interpreted as an observed trial finding because the registry record contains no reported primary outcome estimates.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists seven outcome measures and identifies patient comfort as a secondary outcome, in addition to the stated primary endpoint. It does not report a multiplicity strategy, such as whether any adjustment was planned for testing several outcomes or comparisons. The specific hypotheses and device-to-device contrasts are also not reported in the registry record. Without this information and without reported test results, the degree to which multiplicity could affect interpretation cannot be assessed.
As a general statistical principle, conducting multiple tests can increase the chance of at least one apparently unusual result when all null hypotheses are true. Methods that control family-wise error or false discovery rate address different goals, and the appropriate approach depends on the prespecified question. This general point does not imply that any particular method was used in this study. No method is reported in the registry record.
The registry does not report missing-data counts, reasons for missingness, or a method for handling incomplete measurements. In general, missing observations can affect estimates if the likelihood of missingness is related to the measurement or condition. In a crossover study, incomplete periods may also affect which within-participant comparisons are available. The registry does not state whether every participant completed every device condition or how incomplete sequences were handled.
Analysis populations are not described. The record does not state whether the analysis included all randomized participants, only participants with measurements under specified conditions, or another group. It also does not report whether participants were excluded from an analysis or whether any protocol deviations occurred. The trial is marked completed, but completion status does not answer these analysis questions. With no posted analysis or numerical outcome results, neither multiplicity nor missing-data handling can be evaluated from the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Spontaneous Breathing Patients With Tracheostomy | 0 | 12 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Spontaneous Breathing Patients With Tracheostomy | 0 of 12 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Spontaneous Breathing Patients With Tracheostomy | 0 of 12 |
The registry lists a safety group titled “Spontaneous Breathing Patients With Tracheostomy.” For this group, the record reports 12 participants at risk for serious adverse events and 0 affected. It also reports 12 at risk for other adverse events and 0 affected, and deaths of 0. No top serious adverse-event terms are listed.
These are the safety figures recorded in the registry; they do not establish that no adverse events occurred outside the categories or reporting period captured in this entry. The record does not report the observation period, event definitions, collection method, device-specific breakdown, or whether safety surveillance was conducted separately for each crossover condition. It also does not describe how participants were counted for safety reporting across the device configurations.
As a general statistical point, zero reported events in a group is not proof that the underlying risk is zero. The precision of a safety estimate depends on the amount and duration of observation and the event definition, among other factors. Those details are not reported in the registry record. The registry figures should therefore be read as reported counts, not as evidence that any device has no safety risk.
12. What the Result Does, and Does Not, Mean
The registry record defines a randomized crossover investigation of aerosol particle concentrations around spontaneous-breathing patients with tracheostomy using different oxygen-device configurations. It specifies a primary measurement of particles sized 1-3 micrometer at 1 foot from the patient, taken 5 minutes after device use, with results intended to be summarized by median and inter-quartile range. The record also identifies patient comfort as a secondary outcome.
The record does not report numerical primary-outcome results, device-specific medians, inter-quartile ranges, comparison estimates, confidence intervals, or statistical tests. It therefore does not establish which configuration had a higher or lower measured concentration, whether any differences were precise, or whether observed differences were statistically distinguishable. The completed status does not substitute for those results.
The stated motivation is potential transmission risk, but the primary endpoint is a particle concentration in room air. As a general interpretation, an environmental measurement may describe one possible component of exposure without directly measuring infection, transmission, or clinical consequences. The registry does not report transmission outcomes or establish how a measured concentration maps to transmission risk. Thus the endpoint should not be read as a direct count of infections or as proof of a treatment's effect on transmission.
The trial's crossover label suggests a design that can compare conditions within participants, but important features needed to understand that comparison are not reported: condition sequence, washout, repeated-measure handling, and the statistical model. No analysis population or missing-data method is listed. These gaps prevent an independent assessment of the analysis and its uncertainty.
The safety entry reports zero serious adverse events, zero other adverse events, and zero deaths in the listed group, with 12 participants at risk in each adverse-event category. Those registry counts are limited to what is recorded and do not prove the absence of risk. Overall, the registry supports a clear description of the research question and endpoint, but not a conclusion about comparative particle concentrations, transmission, patient comfort, or device safety beyond the listed counts.
13. Why This Trial Matters Statistically
This trial raises a statistical question that is distinct from a usual clinical efficacy comparison: how should particle concentrations measured in a room be compared across device arrangements when the same patient may experience more than one condition? The crossover design could support within-participant comparisons, which may be useful when participants differ in baseline particle generation. In general, that benefit depends on suitable condition ordering, measurement consistency, and an analysis that accounts for repeated observations.
The endpoint also illustrates why the definition of a measurement matters. The registry specifies particle size, distance from the patient, timing after device use, and units. Those details identify the target quantity and make clear that the outcome is an environmental proxy. A particle measurement can be relevant to questions about airborne exposure while remaining different from a direct transmission outcome. Statistical interpretation must keep that distinction explicit.
Summarizing the endpoint with a median and inter-quartile range draws attention to distributional shape and spread. This is useful context for a type of measurement that may be variable, although the registry does not report the observed distributions or analysis. A robust descriptive summary does not itself answer whether devices differ, how large any difference is, or how precisely it is estimated.
The registry record also illustrates the difference between a completed study and an interpretable results record. Enrollment, design labels, endpoint definitions, and safety counts provide information about what was intended and recorded. Without numerical outcome results and analysis details, readers cannot assess the magnitude, precision, or statistical credibility of the primary comparison. That distinction is especially important when an outcome is intended to inform a broader concern such as transmission risk.
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 does not report numerical primary-outcome findings, so the direction, magnitude, and precision of device comparisons cannot be assessed. Although the endpoint is defined by particle size, distance, and time after device use, details of the measurement instrument, sampling duration, and aggregation of readings are not reported in the registry record.
The crossover design is not described in enough detail to evaluate its implementation. Condition order, randomization of sequences, washout, period effects, and possible carryover are not reported. The statistical treatment of within-participant measurements is not reported either. These details are particularly relevant when several device conditions may be assessed in the same participant.
The record lists a high-flow high-humidity oxygen device with tracheostomy adapter as the intervention and gives descriptions of several device configurations. It does not explain the allocation structure or the exact paired contrasts. The enrollment is 12, but the number of usable measurements by condition, participant-level completion, and analysis population are not reported.
The primary outcome is an indirect marker intended to reflect transmission risk, rather than a direct infection or transmission outcome. No validation connecting the recorded particle concentrations to transmission is reported. Patient comfort is listed as a secondary outcome, but its measurement method and results are not reported. The registry also does not report missing-data handling, a multiplicity approach, or a statistical analysis plan. These limitations mean that the available record describes the study question more fully than its findings.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Aerosol Particle Concentrations Among Different Oxygen Devices for Spontaneous Breathing Patients With Tracheostomy — NCT04654754.
- Registry record last updated 2022-12-21; status last verified 2022-11.
- Results first posted 2022-11-22.
- 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.
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18. Record Summary
The registry record describes a completed, randomized, single-masked crossover trial with enrollment of 12. The study concerns aerosol particle concentrations around spontaneous-breathing patients with tracheostomy using different oxygen-device configurations. Its primary endpoint is the median concentration, with inter-quartile range, of particles sized 1-3 micrometer at 1 foot from the patient 5 minutes after device use.
Patient comfort is listed as a secondary outcome, and the record indicates seven outcome measures. It reports zero serious adverse events, zero other adverse events, and zero deaths in the listed safety group. Numerical primary-outcome findings, analysis details, and results for patient comfort are not reported in the registry record. The entry therefore defines the research question and records limited safety counts but does not allow assessment of comparative particle concentrations or their precision.