Oxygen Monitoring of Patients After Surgery on the Hospital General Care Floor: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Oxygen Monitoring of Patients After Surgery on the Hospital General Care Floor (NCT01082575), a registered phase not stated study. The primary outcome is Number of General Care Floor Patients Exhibiting a Saturation Pattern Detection (SPD) Alert..

2. Clinical Question

3. Trial Design

This is an observational study of postoperative patients monitored on a hospital general care floor. Its registered title concerns oxygen saturation monitoring and repetitive reductions in airflow. The brief description frames the study around whether oxygen monitoring may reflect abnormal breathing patterns after major surgery, including patterns that may occur at night while pain medication is being given. That description gives the study's rationale, not a reported finding about how often the pattern occurred.

The registry records an enrollment of 100 and identifies one study arm, Major Surgery, receiving Oxygen Monitoring. It does not describe a randomized allocation or a like-for-like control comparison; allocation is not stated. The listed intervention is a device. Patients wore a finger sensor connected to a Nellcor N600X oximeter, which measured blood oxygen level continuously after surgery. Monitoring was planned for a minimum of two nights and a maximum of five nights; the primary outcome description specifies monitoring for up to 5 days.

The registry lists the study as completed. Its recorded start is 2010-02 and its primary completion is 2010-07. Medtronic - MITG is the sponsor. The primary outcome is the number of patients with a Saturation Pattern Detection alert, with a timeframe of 5 days. The stated primary-outcome population is 93 evaluable patients out of 100 enrolled. The registry record does not report the alert count or explain why the evaluable population differs from the enrolled population.

The record lists 2 outcome measures and 0 analyses. It does not report a statistical analysis plan, a sample-size justification, or details of any interim analyses. Because the study has no stated comparator and is observational, it can describe monitoring observations, but its registered design does not establish a causal contrast between monitoring strategies or treatments.

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.

Before assignment: All enrolled patients were included into the trial. This was an observational study.

Overall Study

Analysis population for the primary outcome, as defined in the registry: 93 evaluable patients out of 100 enrolled.

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 Number of General Care Floor Patients Exhibiting a Saturation Pattern Detection (SPD) Alert., measured over 5 days.

The primary endpoint is the number of general care floor patients exhibiting a Saturation Pattern Detection alert during a 5-day timeframe. The alert is based on a pattern in blood oxygen level that is increasing and decreasing and is associated with periods of no breathing. Each patient wore a finger sensor continuously after surgery for up to 5 days, connected to an oximeter measuring blood oxygen level. The registry describes the outcome in terms of the number of participants, rather than a rate per hour or a measure of alert duration.

Counting patients with an alert is a way to describe how commonly the monitoring system detected the specified pattern in this study population. This type of endpoint can be useful in an observational monitoring study because it records whether the prespecified detection criterion occurred during the monitoring period. It does not by itself establish that a patient had a clinically confirmed episode of stopped breathing: the registry describes the alert as detecting an oxygen pattern associated with periods of no breathing, not as a definitive diagnosis. Nor does a count alone describe how often alerts recurred within a patient, how long a pattern lasted, or whether an alert led to a clinical response.

The registry identifies 93 evaluable patients out of 100 enrolled, but it does not report the number who exhibited an alert. It also does not report the number of alerts, the distribution of monitoring duration, or a statistical estimate of the endpoint. Therefore, the endpoint's observed frequency and precision are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registered primary outcome is a participant count: the number of general care floor patients exhibiting a Saturation Pattern Detection alert. This is a binary outcome at the participant level for the stated monitoring period. In general, a binary outcome distinguishes whether a defined event occurred for each participant; a participant is counted as having the event or not having it. The registry's outcome description does not present a participant-level dataset, an event count, or an estimate of the proportion with an alert. The reported population is 93 evaluable patients out of 100 enrolled, but the alert outcome itself is not reported in the registry record.

What does a count estimate?

A count describes how many participants met the endpoint definition in the analyzed population. It is not the same as a count of all alerts: a participant with repeated alerts could still contribute once to a participant-level endpoint, according to the endpoint wording. The registry does not report recurrent alert counts or clarify additional rules for repeated detections. It also does not report an alert rate adjusted for time under monitoring. Because monitoring could last for different durations within the stated range, interpreting a simple participant count as a time-based rate would require information not reported in the registry record.

Why does endpoint definition matter?

The endpoint depends on the Saturation Pattern Detection alert generated from the oxygen-monitoring signal. The registry describes the signal as an increasing and decreasing pattern in blood oxygen level associated with periods of no breathing. This definition supports interpretation as a device-detected pattern, not as direct confirmation of a breathing event. In general, an endpoint's meaning depends on its operational definition and measurement process. The registry does not report validation details, thresholds beyond the alert description, adjudication procedures, or comparison with a separate reference assessment. Those details are not reported in the registry record.

What can an interval say?

In general, a confidence interval expresses uncertainty around an estimate under a particular statistical model and method. For a binary endpoint, an interval may be used to describe uncertainty around an event frequency. A confidence interval does not make a finding causal, and its interpretation depends on the study design and assumptions. No primary-outcome estimate, confidence interval, standard error, or p-value is reported in the registry record, so there is no reported interval to interpret. Recalculation from summary statistics is not possible from the recorded primary outcome information.

How should over-dispersion be understood?

In general, over-dispersion arises when observed variability in count data is greater than expected under a simple model. It can make standard errors too small if the model does not allow for the extra variability, resulting in overconfident intervals or tests. The registered primary endpoint is a participant count for a binary event, rather than a reported recurrent-event count. The registry does not report a model for counts, repeated observations, or over-dispersion, and does not report analyses that would allow this issue to be assessed. Whether over-dispersion is relevant to any analysis cannot be determined from the registry record.

What do the planning assumptions mean?

The registry-associated sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration considers the effect to detect as a stated fraction of the observed effect. For time-to-event planning, the assumptions describe total events using the Schoenfeld approach; other planning outputs are described as participants per arm. These are planning assumptions, not evidence that the observational study used equal allocation or had two comparable arms. The study record describes no like-for-like control comparison, and its actual allocation is not stated.

Planning sample sizes answer a hypothetical design question under specified assumptions. They are not observed power and do not substitute for the study's result. The registry record does not report the observed effect needed to interpret those planning scenarios, nor does it report the study's own sample-size justification. No planning illustration can establish that the study was adequately powered for its primary endpoint.

What analysis is documented?

The registry lists 0 analyses. It does not report an inferential model, an adjustment strategy, a hypothesis test, or a method for estimating uncertainty. Without those details and without the primary outcome count, the analysis cannot be independently evaluated or reconstructed. The appropriate interpretation is limited to the registered endpoint definition and the information explicitly recorded about the study population and monitoring process.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("General Care Floor")
n      <- c(93)
events <- c(74)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  General Care Floor  93  74  79.6  69.9  87.2  70.3  86.5  70.2  86.5

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures, including the primary Saturation Pattern Detection alert count and a secondary outcome concerning participants with adverse events caused by no breathing. It lists 0 analyses. The record does not describe a multiplicity strategy, such as a hierarchy among outcomes or an adjustment for testing multiple outcomes. It also does not report p-values or other inferential results for either outcome. Accordingly, the effect of any multiplicity considerations cannot be evaluated from the registry record.

The primary endpoint population is described as 93 evaluable patients out of 100 enrolled. The registry does not report why some enrolled participants were not included in the evaluable population, whether endpoint information was incomplete, or how any missing measurements were handled. The reasons for non-evaluability, missing-data assumptions, imputation procedures, and sensitivity analyses are not reported in the registry record. The count of evaluable patients should not be treated as evidence about the reason for missingness.

The record does not explain whether all participants had the same duration of monitoring, beyond the stated minimum of two nights and maximum of five nights and the endpoint timeframe of 5 days. It does not report the number completing each duration or how shorter observation was incorporated into the endpoint analysis. Nor does it state whether alerts were assessed by automated criteria alone or reviewed through an additional process. Such analysis-population and measurement details are not reported in the registry record.

These omissions limit assessment of how the primary endpoint was analyzed and how robust any result might be to missing observations or multiple outcome testing. Since the primary result itself is not reported, there is no basis for describing a multiplicity-adjusted conclusion or comparing complete-case and alternative analyses.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry's adverse-event group is labeled Major Surgery and lists 100 participants at risk. It records 0 serious adverse events and 0 other adverse events in that group. These are the adverse-event figures in the registry record; they should be read as what the record reports, not as proof that no adverse events occurred outside the reporting captured there. The record names a secondary outcome concerning participants with adverse events caused by no breathing, but it does not provide a separate detailed result for that outcome.

The registry does not report the method used to collect or classify adverse events, the observation period used for the safety figures, or whether events were independently reviewed. It does not provide serious adverse-event terms; the listed serious-event terms are empty. The death count is not reported in the registry record. A missing death value should not be interpreted as a recorded zero.

These safety entries do not describe a comparison between monitoring and a control condition. With no comparator described, the figures cannot establish whether monitoring changed the frequency of adverse events. They also do not show whether an alert was associated with a subsequent event, because no participant-level relationship or such analysis is reported.

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

The study's registered question concerns whether continuous postoperative oxygen monitoring detects a Saturation Pattern Detection alert among patients on a general care floor. The registry explains the alert as an oxygen-level pattern associated with periods of no breathing and identifies a primary outcome based on the number of patients exhibiting that alert. It also records 100 enrolled patients and an evaluable population of 93 for the primary outcome.

What the registry does not provide is the observed primary outcome count. Without that result, the prevalence of alerts in the study population cannot be stated. The registry also does not provide an estimate of uncertainty, a comparison group, or an analysis relating alerts to adverse events. As a result, the recorded information does not quantify the alert frequency, establish its precision, or show whether alert detection corresponded to clinically confirmed breathing events.

More generally, an observational monitoring study can describe patterns detected under its monitoring conditions. It cannot, without a suitable comparison and an appropriate analysis, establish that the monitoring procedure caused a change in outcomes. Here, no control group is described and allocation is not stated. The record therefore does not support a treatment-effect interpretation. The alert is described as a signal pattern associated with periods of no breathing, not as a definitive diagnosis or a measure of clinical benefit.

The adverse-event record lists 0 serious and 0 other adverse events for the Major Surgery group, with 100 participants at risk. Those entries do not provide a comparative safety assessment or a separate analysis of the named secondary outcome. The death count is not reported in the registry record. The central statistical message is that the record documents the study's monitoring setup and intended endpoint, while omitting the numerical primary result needed to describe what the monitoring detected.

14. Why This Trial Matters Statistically

This study illustrates an important distinction between a device-generated signal and the clinical event that the signal is intended to reflect. The primary endpoint is an alert based on an oxygen saturation pattern associated with periods of no breathing. The alert count could describe how often patients met the study's detection definition, but it would not automatically establish that every alert represented a confirmed breathing event. Clear separation between a measured signal, an algorithmic alert, and a clinical diagnosis is essential when interpreting monitoring research.

The study also highlights why the analysis population matters. The registry states that 93 evaluable patients came from 100 enrolled patients, but does not explain the difference or report the alert count. Without both the endpoint result and information about evaluability, readers cannot determine the observed frequency or assess whether missing endpoint information could affect interpretation. The absence of a reported uncertainty estimate further prevents judging how precisely the event frequency was estimated.

Its observational design makes the scope of inference important. A monitored group can yield descriptive information about detections, but without a stated comparator it does not provide a like-for-like estimate of what would happen under a different monitoring approach. General statistical interpretation should match that design rather than treating a descriptive endpoint as a causal comparison.

Finally, planning assumptions and study findings answer different questions. A sample-size planning illustration relies on assumptions about allocation, effect size, and statistical method; it is not a result from the enrolled participants and is not observed power. This record documents planning assumptions but does not report a primary outcome analysis. The example therefore reinforces the need to distinguish design calculations from the evidence actually reported for a completed study.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The most consequential limitation of the registry record is that it does not report the primary alert count. The study's central outcome is therefore not quantitatively interpretable from the record, despite the stated endpoint definition and evaluable population. No confidence interval, test result, or other primary analysis is reported, so neither the size nor precision of the observed result can be assessed.

The study is observational and has no described comparator group. Allocation is not stated, and the registry explicitly does not characterize the arms as a like-for-like control comparison. Consequently, the record cannot support a causal comparison between monitoring strategies. It also does not report an independent reference assessment of the alert, so the alert's sensitivity, specificity, or agreement with clinical confirmation cannot be evaluated; those measures are not reported in the registry record.

Monitoring duration could range from a minimum of two nights to a maximum of five nights, while the primary outcome timeframe is 5 days. The registry does not report the distribution of actual monitoring duration, the number of participants with incomplete monitoring, or how observation time affected the endpoint assessment. Reasons for the difference between 100 enrolled and 93 evaluable patients are not reported in the registry record. Missing-data handling, endpoint adjudication, and sensitivity analyses are also not reported.

The record lists a secondary adverse-event outcome but provides no separate outcome analysis, and its adverse-event entries do not establish a relationship between alerts and events. Statistical methods, multiplicity handling, interim analyses, and a study-specific sample-size justification are not reported in the registry record. Taken together, these gaps limit both reconstruction of the analysis and interpretation of the study's intended prevalence question.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Oxygen Monitoring of Patients After Surgery on the Hospital General Care Floor — NCT01082575.
• Registry record last updated 2014-08-07; status last verified 2014-08.
• Results first posted 2012-10-04.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT01082575 is a completed observational study sponsored by Medtronic - MITG, with a recorded start of 2010-02 and primary completion of 2010-07. It enrolled 100 postoperative patients for oxygen monitoring on the general care floor. A finger sensor connected to a Nellcor N600X oximeter measured blood oxygen level continuously after surgery, for a minimum of two nights and a maximum of five nights.

The primary endpoint was the number of patients exhibiting a Saturation Pattern Detection alert during a 5-day timeframe. The record identifies 93 evaluable patients out of 100 enrolled but does not report the observed alert count or an analysis of that endpoint. No comparator is described. The registry lists 2 outcome measures and 0 analyses. Its adverse-event group records 0 serious and 0 other events among 100 participants at risk; the death count is not reported in the registry record.