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 Oxygen Reserve Index: Utility as Early Warning for Desaturation in Morbidly Obese Patients (NCT03021551), a na phase not stated study. The primary outcome is Utility of ORi Providing Added Warning Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03021551 |
| Phase | Phase not stated |
| Condition | Morbid Obesity, Surgery |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 80 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Masimo Corporation |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes obese patients undergoing elective surgical procedures and identifies two BMI ranges for evaluation: 30 < BMI < 40 kg m-2 and 19 < BMI < 25 kg m-2. The title refers to morbidly obese patients, while the outcome description also includes a normal-BMI group. The registry does not provide further detail about the participants in each group or their group sizes.
Intervention
Participants were monitored with a Rainbow sensor, the listed device intervention. The study evaluated the Oxygen Reserve Index (ORi), an index described as scaling measured absorption information from 0.00 to 1.00. The record says that ORi could help clinicians assess normoxic and hyperoxic states.
Comparator
No randomized or parallel control group is identified. Allocation is listed as not applicable, and the study model is single group. The registry record does not report a comparator-based treatment effect or a like-for-like comparison between arms.
Primary question
The stated question is whether a change in ORi provides added warning time before arterial oxygen desaturation during induction of general anesthesia and tracheal intubation. The primary outcome is described as the utility of ORi providing added warning time, measured in seconds. A numerical outcome result is not reported in the registry record.
3. Trial Design
This completed study evaluated the Oxygen Reserve Index during anesthesia induction and tracheal intubation in patients undergoing elective surgery. The registry lists an enrollment of 80 and identifies the Rainbow sensor as the device intervention. The study model is single group; allocation is not applicable, and masking is listed as none. These features describe an evaluation of monitoring in a study group, not a randomized comparison of treatments.
The stated purpose was to assess whether a change in ORi could provide early warning of impending arterial oxygen desaturation. The registry describes participants in two BMI ranges: 30 < BMI < 40 kg m-2 and 19 < BMI < 25 kg m-2. It does not report how many participants belonged to each range, or whether group-specific estimates were planned or produced. The title refers to morbidly obese patients, so the title and the population description do not use identical wording.
The record gives a study start of 2016-09-15, a primary completion date of 2018-07-20, and a completed status. It does not report a randomized allocation method, a control group, or masking procedures. The primary outcome timeframe is listed as 1 year, but the registry does not explain how that timeframe relates to the peri-induction warning-time measurement. The protocol details, including how warning time was operationally defined, are not reported in the registry record.
Four subjects had initial device calibration failure, and clinical care constraints prevented completion of data collection for another subject, according to the primary outcome description. The record does not specify how these cases were handled in an outcome analysis. It lists one outcome measure and no analyses. Consequently, the design and objective can be described, but the registry record does not support a numerical assessment of the primary question.
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
| Stage | Rainbow Sensor |
|---|---|
| STARTED | 80 |
| COMPLETED | 77 |
| NOT COMPLETED | 3 |
Reasons for not completing this period:
| Reason | Rainbow Sensor |
|---|---|
| Equipment Issues | 2 |
| Protocol Violation | 1 |
Analysis population for the primary outcome, as defined in the registry: In 4 subjects, the device failed initial calibration. In another subject, clinical care constraints precluded completion of the data collection.
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 | Rainbow Sensor |
|---|---|---|
| Participants analysed | 77 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 53 |
| Age, Categorical: >=65 years | Participants | 24 |
| Sex: Female, Male: Female | Participants | 51 |
| Sex: Female, Male: Male | Participants | 26 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United States | participants | 77 |
6. Primary Endpoint
The registry lists the primary outcome as Utility of ORi Providing Added Warning Time, measured over 1 year.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | seconds |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled “Utility of ORi Providing Added Warning Time,” with seconds as its unit. It is intended to measure whether a change in the Oxygen Reserve Index gives an early signal before arterial oxygen desaturation during induction of general anesthesia and tracheal intubation. Warning time is clinically interpretable as a time interval: it relates the behavior of a monitoring index to a subsequent event, rather than describing only the index value itself.
The registry explains ORi as a reference that scales measured absorption information between 0.00 and 1.00. It states that an ORi of 0.00 corresponds to PaO2 values of 100 mmHg and below, while an ORi of 1.00 corresponds to PaO2 values of 200 mmHg and above. The stated rationale is that the index may help clinicians assess normoxic and hyperoxic states. These descriptions explain the intended role of the measure; they do not establish its performance in the study participants.
The endpoint description says the evaluation concerns the change in ORi as an early warning of impending arterial oxygen desaturation and names both an obese BMI range and a normal BMI range. However, the registry does not give an observed warning-time value, an estimate of uncertainty, or a group-specific result. The precise event definition, the rule for identifying the warning signal, and the method for calculating the time interval are not reported in the registry record. Without those details and a numerical result, the endpoint’s intended meaning is clear at a broad level, but its measured performance cannot be interpreted quantitatively.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study’s purpose: evaluating whether a change in ORi can provide early warning of arterial oxygen desaturation during anesthesia induction and tracheal intubation. It also identifies the endpoint’s unit as seconds. It does not report a numerical primary outcome result. There is therefore no posted estimate of added warning time to describe, and no confidence interval or other measure of uncertainty for that endpoint.
The record lists one outcome measure and no analyses. This means that the registry information does not give a numerical estimate, a test of a statistical hypothesis, or a comparison between the BMI groups. It also does not report subgroup results, an analysis population, or a stated statistical model. The intended evaluation should not be mistaken for evidence that the outcome was observed in a particular direction or with a particular degree of precision.
The study is listed as single group, with allocation not applicable and no masking. It is not a randomized comparison, and the record does not identify a control arm. Thus, the design described in the registry cannot support a treatment-versus-control interpretation. The study question concerns the timing of an index signal relative to desaturation, not a comparative effect of two assigned treatments.
Enrollment is listed as 80. The outcome description notes that initial calibration failed for four subjects and that clinical care constraints precluded completion of data collection for another subject. The safety record lists 77 participants at risk for the Rainbow Sensor group. These figures describe different registry entries; the record does not explain their relationship or provide a flow accounting that establishes which participants contributed to the primary outcome. They should not be treated as interchangeable analysis denominators.
The absence of a numerical endpoint result is the central interpretive limit. No claim about the size, consistency, or precision of warning time can be made from the registry record. Likewise, the record does not provide enough statistical detail to assess how measurements were handled, how BMI ranges were compared, or how missing observations affected the result. The stated objective is informative about what the investigators sought to evaluate, but it is not itself a reported finding.
9. Statistical Methods Explained
The registry describes a single-group device evaluation, not a randomized comparison. That distinction determines what statistical questions can be answered. In a randomized comparison, an estimate might contrast outcomes between assigned groups. Here, allocation is listed as not applicable, the model is single group, and no control arm is identified. The stated objective is instead to assess whether an ORi change gives warning before arterial oxygen desaturation. The registry record does not report a numerical estimate for that timing question.
What does an endpoint measured in seconds mean?
A time-based endpoint can express how far in advance a signal occurs relative to a defined event. In general, such a measure depends on clear rules for identifying both the signal and the event, as well as the time origin and observation window. The endpoint title refers to added warning time, and its unit is seconds. The specific operational definitions and calculation procedure are not reported in the registry record. Therefore, the unit and broad concept are known, but the exact construction of the outcome cannot be independently assessed from the registry information.
Why does a confidence interval matter?
In general, a confidence interval describes the range of values compatible with an estimate under the assumptions of the analysis. It communicates precision as well as the estimate’s direction and scale. A narrow interval indicates greater statistical precision than a wide interval, while neither width alone nor the interval itself establishes clinical importance. No confidence interval for the primary endpoint is reported in the registry record. As a result, the precision of any warning-time estimate cannot be evaluated.
What can a single-group design establish?
A single-group evaluation can describe observations made under the study conditions and can assess whether a monitoring signal is temporally associated with an event, if suitable outcome data and methods are reported. Without a control group, it does not provide a randomized comparison against another device or monitoring strategy. General statistical interpretation also depends on the measurement process, the definition of the event, and the handling of repeated measurements within participants. Those analytic details are not reported in the registry record, so the extent to which the observations could support broader conclusions cannot be determined.
How should the BMI descriptions be read?
The outcome description names participants in two BMI ranges: 30 < BMI < 40 kg m-2 and 19 < BMI < 25 kg m-2. In general, results from distinct groups can be compared descriptively or analytically, but a comparison requires group sizes, outcome summaries, and a specified method. The registry does not report those details or a group-specific result. The title’s reference to morbid obesity and the broader wording of the outcome description should also be kept distinct rather than treated as a fully documented eligibility definition.
What do the enrollment and safety counts tell us?
Enrollment is listed as 80. Separately, the outcome description records initial calibration failure for four subjects and incomplete data collection for another subject because of clinical care constraints. The safety entry lists 77 participants at risk. In general, enrollment, outcome availability, and safety denominators may differ because they refer to different analysis populations or data collection requirements. The registry does not provide a participant flow or state which denominator was used for the primary outcome. It would therefore be inappropriate to infer the primary analysis population from these counts alone.
The study record also includes planning assumptions for an illustration based on an observed effect, including a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such assumptions describe a planning exercise, not the study’s observed results or observed power. The record does not report a study-specific sample-size justification, and the single-group design described in the registry does not match the equal-allocation illustration. The planning assumptions cannot fill the gap left by the absent primary result or establish that the study had a particular level of power.
Finally, the record lists no analyses. This absence means that the statistical model, any adjustment for repeated observations, uncertainty estimates, missing-data methods, and any planned subgroup procedures are not reported in the registry record. General statistical principles can explain why these details matter, but they cannot substitute for the missing methods or results. The primary endpoint remains a stated measurement objective rather than a quantitatively interpretable finding in the registry information.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and no analyses. It does not report a statistical analysis plan or describe whether multiple hypotheses, time points, thresholds, or subgroups were considered. Multiplicity refers, in general, to the increased chance of at least one false-positive finding when several statistical tests are conducted. Whether that issue arose in this study cannot be determined from the registry record, and no adjustment procedure is reported.
The outcome description includes two BMI ranges, but the record does not state whether these were intended as separate analysis groups, how they were to be compared, or whether any subgroup analysis was planned. There is no group-specific result. The record also does not describe interim analyses or stopping rules; those details are not reported in the registry record.
Missing data are relevant because the primary outcome description notes four initial calibration failures and one case in which clinical care constraints prevented completion of data collection. It does not say whether these participants were excluded from an endpoint analysis, whether partial measurements were retained, or whether any missing-data method was used. The listed enrollment and safety denominators do not by themselves establish the primary endpoint analysis population.
In general, missing observations can affect both the number of participants contributing information and the interpretation of an estimate, depending on why data are absent and how the analysis handles them. Here, the reasons noted are calibration failure and clinical care constraints, but no analysis of their implications is reported. No intention-to-treat population, per-protocol population, or other analysis population is specified in 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 |
|---|---|---|---|
| Rainbow Sensor | 0 | 77 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Rainbow Sensor | 0 of 77 |
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 |
|---|---|
| Rainbow Sensor | 0 of 77 |
The safety entry lists the Rainbow Sensor group, with 77 participants at risk for serious adverse events and 0 participants affected. It also lists 77 at risk for other adverse events and 0 affected, and reports 0 deaths. No top serious adverse-event terms are listed. These are the safety counts recorded for this group.
These figures should be read as registry counts, not as proof that no adverse events of any kind occurred. They indicate that the registry entry reports no affected participants in the listed serious-adverse-event, other-adverse-event, and death categories. The record does not provide event narratives, a detailed event ascertainment method, or an explanation of whether all enrolled participants contributed to the safety denominator.
The safety denominator of 77 is distinct from the listed enrollment of 80. The primary outcome description also mentions four initial calibration failures and one incomplete data collection due to clinical care constraints, but the registry does not reconcile those entries with the safety count. The safety figures do not provide evidence about the primary warning-time endpoint, and they should not be used to infer its result or precision.
12. What the Result Does, and Does Not, Mean
The registry record documents a study intended to evaluate whether changes in the Oxygen Reserve Index provide early warning of arterial oxygen desaturation during induction of general anesthesia and tracheal intubation. It identifies the Rainbow sensor, a single-group design, an endpoint measured in seconds, and the BMI ranges named for evaluation. These details establish the research question and the broad measurement context.
The record does not report the primary endpoint value, a confidence interval, or any analysis. It therefore does not show how much warning time was observed, whether estimates differed between the stated BMI ranges, or how precisely the outcome was measured. The stated objective should not be interpreted as a result. The ORi scale description explains how the index is framed in the registry, but it does not demonstrate how the index performed in these participants.
The design also limits the kind of inference available from the registry description. A single-group evaluation without a reported control arm is not a randomized comparison of monitoring strategies. Even if a numerical timing result were available, interpretation would depend on the endpoint definition, measurement procedures, and analysis methods, several of which are not reported in the registry record.
The enrollment and safety counts provide context but do not resolve the missing endpoint information. The record notes calibration failures and incomplete data collection for clinical care reasons, yet does not explain their effect on the analysis population. The safety entry reports no affected participants in the listed categories, but that information does not answer the primary question about warning time.
Accordingly, the registry supports a description of what the study set out to assess and some aspects of its conduct. It does not support a quantitative conclusion about the amount, reliability, or comparative value of any early warning. Those outcomes and their uncertainty are not reported in the registry record.
13. Why This Trial Matters Statistically
This study raises a useful statistical question about monitoring: whether a changing index provides a measurable interval of warning before a clinically relevant event. Unlike a simple description of index values, a warning-time endpoint connects the signal to the timing of desaturation. In general, that kind of endpoint requires explicit definitions for the signal, the event, and the time interval, as well as a clear account of how observations are summarized.
The record also illustrates why study design and study question need to be read together. The stated objective is about warning performance, while the study is listed as single group with allocation not applicable and no masking. This is not a randomized comparison of monitoring approaches. A reader therefore needs to distinguish assessment of a device signal from evidence based on a controlled treatment contrast.
Population descriptions matter as well. The title refers to morbidly obese patients, while the outcome description identifies both an obese BMI range and a normal BMI range. Without group sizes, separate results, or a stated comparison method, the registry cannot establish how performance was evaluated across those groups. Clear reporting of eligibility, analysis populations, and subgroup procedures would help readers understand the scope of the evidence.
Finally, a well-defined outcome is not enough on its own: an estimate and its precision are necessary for statistical interpretation. The record states the endpoint’s unit but provides no numerical result or analysis. It also notes data collection limitations without specifying how they were handled. These omissions make this study statistically noteworthy as an example of a clearly motivated measurement question for which the registry record does not provide the information needed to judge the observed performance.
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 principal limitation of the registry record is that it does not report a numerical result for the primary endpoint. No estimate of added warning time, uncertainty interval, or analysis result is available. The record lists one outcome measure but no analyses, leaving the statistical approach and observed performance unreported.
The endpoint is described broadly as the utility of ORi providing added warning time, measured in seconds. The exact definition of a qualifying ORi change, the definition of desaturation, and the procedure for calculating warning time are not reported in the registry record. Without these details, reproducibility and the interpretation of the intended time interval are limited.
The title and outcome description differ in how they characterize the population. The title refers to morbidly obese patients, while the outcome description includes 30 < BMI < 40 kg m-2 and 19 < BMI < 25 kg m-2. The record does not report group sizes or a group-specific analysis. Its single-group classification and lack of a listed control arm also mean that a randomized comparison cannot be inferred.
Enrollment is listed as 80, while the safety entry lists 77 at risk. The outcome description notes four calibration failures and one incomplete data collection due to clinical care constraints. The registry does not reconcile these counts, identify the primary analysis population, or state how missing outcome data were handled. It also does not report the study-specific sample-size justification, the analysis plan, or whether interim analyses were conducted. These limitations prevent assessment of endpoint precision, missing-data impact, and the breadth of conclusions supported by the record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Oxygen Reserve Index: Utility as Early Warning for Desaturation in Morbidly Obese Patients — NCT03021551.
- Registry record last updated 2022-04-19; status last verified 2022-03.
- Results first posted 2022-04-19.
- 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
NCT03021551 is a completed, single-group study sponsored by Masimo Corporation. It evaluated the Oxygen Reserve Index as a potential early warning of arterial oxygen desaturation during induction of general anesthesia and tracheal intubation in patients undergoing elective surgery. The Rainbow sensor is listed as the device intervention; allocation is not applicable and masking is listed as none.
Enrollment is listed as 80. The primary outcome is described as added warning time, measured in seconds, and names obese and normal BMI ranges. The record notes four initial calibration failures and one case of incomplete data collection because of clinical care constraints. The safety entry lists 77 participants at risk, 0 affected by serious adverse events, 0 affected by other adverse events, and 0 deaths.
A numerical primary outcome result, statistical analysis, uncertainty estimate, analysis population, and detailed missing-data method are not reported in the registry record. The record therefore describes the study objective and selected conduct and safety details, but not a quantitative finding on warning time.