Prophylactic nCPAP Following Bowel Surgery (Bio-REB File 11-27): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prophylactic nCPAP Following Bowel Surgery (Bio-REB File 11-27) (NCT01316575), a randomized na study. The primary outcome is Alveolar - Arterial Gradient.

2. Clinical Question

The primary endpoint is the alveolar–arterial gradient, reported in torr. It is defined as the difference between the partial pressure of alveolar oxygen and the partial pressure of arterial oxygen. The registry summary describes the investigators’ hypothesis in terms of a higher arterial oxygen partial pressure after nCPAP than after standard low-flow oxygen; the posted primary endpoint is the gradient rather than arterial oxygen pressure alone.

The comparison is between two post-operative respiratory support strategies, applied for the stated one-hour period in the PACU. The primary outcome timeframe is one hour following admission to the PACU. Reintubation, admission to intensive care, and hospital length of stay are listed as secondary outcomes. The clinical question is therefore focused on an early measure of pulmonary gas exchange, with additional outcomes addressing subsequent care and hospital stay.

The record describes a randomized, parallel-group study with no masking. It does not report further details about eligibility criteria, the randomization procedure, or participant characteristics. Those omissions limit how specifically the findings can be applied to patient groups beyond the broad description of elective bowel surgery.

3. Trial Design

NCT01316575, titled Prophylactic nCPAP Following Bowel Surgery (Bio-REB File 11-27), is recorded as a completed randomized, parallel-group trial sponsored by the University of Saskatchewan. Its listed start is 2011-04 and its primary completion is 2012-05. The registry records no masking and gives an enrollment of 40.

Participants were assigned to nCPAP or low-flow oxygen. The nCPAP arm received nasal CPAP at 10cmH20 for one hour in the PACU. The control arm received low-flow oxygen through a simple mask at 8 litres per minute. The main outcome was the alveolar–arterial gradient, measured one hour following admission to the PACU.

For the posted primary outcome, the nCPAP arm has 18 participants and the low-flow oxygen arm has 19. The registry record does not explain why these arm counts differ from the enrollment figure, whether all enrolled participants were randomized, or whether any participants were excluded from the outcome summaries. Reasons for missing or unavailable outcome data are not reported in the registry record.

The endpoint description includes a literature-based sample-size statement: 19 subjects per group were described as required for power >0.9 and alpha <0.05, assuming a normalised difference in A-a gradient between groups of 0.33 and a standard deviation of 0.33. The registry record does not establish whether this statement fully describes the trial’s original design rationale or whether other design considerations were used. Details of the allocation method, planned analysis, interim analyses, and analysis populations are not reported in the registry record.

Three secondary outcomes are named: number of participants requiring reintubation, number requiring admission to ICU, and length of stay in hospital. Numerical arm summaries are included for hospital length of stay. Numerical results for reintubation and ICU admission 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: From the literature, a sample size of 19 subjects per group is required for a power \>0.9 and alpha \<0.05 assuming a normalised difference in A-a gradient between groups of 0.33 and a Standard Deviation (SD) of 0.33

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 Alveolar - Arterial Gradient, measured over 1 hour following admission to PACU.

The primary endpoint is the alveolar–arterial oxygen gradient, expressed in torr and measured one hour following admission to the PACU. It represents the difference between the partial pressure of oxygen in the alveoli and the partial pressure of oxygen in arterial blood. The endpoint is a continuous measure, and the registry reports an arm mean and standard deviation for each treatment group.

As a general statistical concept, a measure of the difference between alveolar and arterial oxygen pressures can describe an aspect of oxygen transfer from the lungs into the blood. It is used in this trial as an early measure of post-operative pulmonary function. The registry’s stated hypothesis refers to a higher arterial oxygen partial pressure with nCPAP, while the selected endpoint is the alveolar–arterial gradient. These measures are related through oxygenation but are not identical; interpretation should stay anchored to the endpoint actually reported.

A lower gradient in one group would indicate a smaller average gap between alveolar and arterial oxygen partial pressures at the recorded assessment time. That interpretation describes the direction of the measure, not a clinical conclusion about the overall value of either treatment. The endpoint is an early, single-timepoint physiological measure; it does not by itself describe later respiratory events, hospital recovery, or patient experience.

The registry reports a mean and standard deviation rather than individual participant values. Consequently, the posted summaries describe group averages and variability, but do not show the distribution of values or how individual participants changed over time.

7. Results Posted in the Registry

• Low Flow Oxygen: mean 134.00 versus 70.60 on control; difference 63.40 (95% CI 28.24 to 98.56), standardized effect d = 1.14; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Length of Stay in Hospital

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Low Flow Oxygen: mean 10.90 versus 10.00 on control; difference 0.90 (95% CI -3.66 to 5.46), standardized effect d = 0.13; z-test p = 0.699.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Low Flow Oxygen and the control. The interval gives the range of effects that remain compatible with the data.

The registry names three secondary outcomes: reintubation, admission to ICU, and hospital length of stay. Numerical arm summaries are included for hospital length of stay, while numerical results for reintubation and ICU admission are not reported in the registry record. The available secondary information is therefore less complete than the primary outcome information.

The posted length-of-stay comparison is compatible with a range of differences in either direction, and its unadjusted result does not provide clear statistical evidence of a group difference. This is a distinct outcome from the early oxygen-gradient measure. A pattern in the primary physiological endpoint does not require the same pattern in length of stay, and a secondary result cannot confirm or overturn the primary result by itself.

Secondary outcomes can help describe whether an early physiological contrast is accompanied by differences in later care or recovery. Their interpretation depends on the endpoint, amount of available information, and analysis plan. In this record, the lack of numerical results for two listed outcomes prevents a complete assessment of the secondary pattern.

Unadjusted secondary results generally carry less weight when several outcomes are examined because the chance of at least one apparently notable finding can increase as more comparisons are considered. As a general statistical principle, multiplicity procedures or a prespecified hierarchy can address this issue, but the registry record does not report whether any such plan was used. The posted secondary comparisons should therefore be regarded as exploratory unless a documented analysis plan establishes otherwise.

The available secondary summaries do not establish a broader effect on clinical outcomes. They offer limited context alongside the primary endpoint, and the registry record does not report a comprehensive set of secondary analyses or a multiplicity adjustment.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Number of Participants Requiring Reintubation
• Number of Participants Requiring Admission to ICU
• Length of Stay in Hospital

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, so the registry reports a mean and standard deviation in each arm. A mean describes the group’s average value. A standard deviation describes how spread out participant values are around that average; it is not the same as the uncertainty in the estimated mean. As a general concept, a large standard deviation indicates greater variation among participants, while the standard error describes the precision of an estimate such as a group mean.

What does the mean difference represent?

The posted comparison defines the difference as the low-flow oxygen mean minus the nCPAP mean. With this ordering, a positive difference means that the low-flow oxygen arm’s average gradient is higher. The reported estimate is 63.4 torr. This contrast is an unadjusted comparison based on the posted group summaries; it does not account for other participant characteristics in a reported model.

As a general statistical concept, a difference in means is useful when the outcome is measured on a numerical scale and the target question concerns average values between groups. Its interpretation depends on the measurement scale and on the trial’s design and data. A mean difference does not show whether every participant in one group had a lower value than every participant in the other group. The standard deviations show that individual values vary within both arms, and the variation is larger in the low-flow oxygen arm.

How should the confidence interval be read?

A confidence interval describes the uncertainty around an estimate under the statistical method used to construct it. The primary comparison’s 95% interval extends from 28.24 to 98.56 torr for low-flow oxygen minus nCPAP. As a general explanation, an interval gives a range of effect sizes reasonably compatible with the observed data and the method’s assumptions. It is not a range containing a stated proportion of individual participant outcomes, and a frequentist confidence interval is not a direct probability statement about where the fixed true effect lies.

The interval’s position relative to zero matters for a mean difference. Zero represents no difference between the group means on this scale. Here, the interval is entirely above zero for the stated subtraction order. This supports the same directional reading as the estimated mean difference. It does not remove uncertainty about the size of the difference or answer whether that size is clinically important.

What does the p-value add?

The unadjusted p-value is p <0.001. In general, a p-value describes how incompatible the observed data, or more extreme data, are with a specified null model, assuming that model and the analysis assumptions are appropriate. It is not the probability that the null hypothesis is true, and it is not the probability that the result occurred by chance in an everyday sense. The registry record does not report a detailed statistical analysis plan, so the p-value should be understood as an unadjusted comparison rather than evidence of a fully documented prespecified analysis.

Confidence intervals and p-values answer related but different questions. The p-value summarizes evidence against a zero-difference null model under the stated comparison. The interval conveys the range of effect sizes consistent with that comparison and its uncertainty. Neither one determines clinical importance by itself. That judgment would require context about the endpoint’s interpretation and the relevance of a difference of this size, which is not established by the statistical summary alone.

Why can variability affect precision?

As a general concept, variability matters because estimates based on a more dispersed outcome tend to be less precise when the sample size is held fixed. Standard deviations describe dispersion in the observed groups. The primary summaries show different degrees of dispersion between arms, so the uncertainty calculation needs to accommodate the observed variability rather than treating every participant as having nearly the same measurement.

Over-dispersion is a term often used when observed variability exceeds what a chosen statistical model expects. In general, ignoring over-dispersion can make uncertainty appear too small and evidence appear stronger than warranted. The registry record does not report an over-dispersion assessment or identify a model for this continuous endpoint. The general concept therefore helps explain why variability and model assumptions matter, but it should not be read as a claim that over-dispersion was found or that a particular correction was used in this trial.

The posted comparison is a simple, unadjusted calculation from the arm summaries, and the registry does not report a separate sponsor analysis. The registry record also does not describe assumptions about distributional shape, handling of outliers, transformations, or covariate adjustment. These details cannot be inferred from the means and standard deviations alone.

What can the analysis establish?

The randomized design is relevant because random allocation is intended, in general, to support a fair comparison between groups. However, the registry does not report the allocation sequence method, concealment procedures, or analysis population. The posted summaries therefore support a comparison of the recorded groups, while the available record does not allow a full assessment of how the trial was implemented or whether all randomized participants were included.

The main statistical reading is limited to the reported mean gradient at the specified timepoint and the unadjusted comparison. The analysis does not, on its own, establish effects on reintubation, ICU admission, length of stay, or later pulmonary function. Those outcomes require their own results and appropriate interpretation. Statistical evidence for one endpoint should not be transferred automatically to outcomes that measure different aspects of care.

11. Confidence Intervals and Precision

The primary mean difference is 63.4 torr, with a 95% confidence interval from 28.24 to 98.56. The interval expresses uncertainty in the estimated difference, using the subtraction order low-flow oxygen minus nCPAP. Values in the interval are positive, so its direction is consistent with a higher average gradient in the low-flow oxygen arm than in the nCPAP arm.

As a general statistical explanation, a confidence interval is constructed by a method that, under repeated use and its assumptions, has a stated long-run coverage property. It is not a statement that there is a 95% probability that the true fixed difference falls inside this particular interval. Nor does it describe the spread of individual participant measurements; the arm standard deviations provide information about that observed spread.

The interval gives more information than the p-value alone because it conveys both direction and a range of plausible effect sizes under the calculation. It does not establish that every value within the range is equally plausible, and it does not set a threshold for clinical importance. The registry record does not report a clinically meaningful difference threshold for this endpoint.

The trial has 18 participants in the nCPAP primary summary and 19 in the low-flow oxygen summary. These arm counts, together with the observed variability, are important context when considering precision. The record does not explain the difference between the enrollment figure and the outcome counts, or describe missing-data handling. The interval therefore characterizes the posted comparison, while its interpretation remains conditional on the analysis and data represented by those summaries.

Precision is outcome-specific. An interval for the alveolar–arterial gradient does not describe the precision of estimates for hospital stay, reintubation, or ICU admission. Each outcome has its own scale, variability, and amount of available information.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed primary effect, not the original enrollment plan. They report participants per arm for 80% power and participants per arm for 90% power. They are not total events: the total-event convention applies to time-to-event outcomes, whereas this continuous outcome is expressed as participants per arm.

The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row uses a stated fraction of the observed effect as the effect to detect. The rows therefore show what the illustrative sample size would be if the target effect were the full observed effect, 75% of the observed effect, or 50% of the observed effect. The assumptions describe this planning illustration; the registry record does not report the full original statistical design assumptions.

The 80% power column represents a planning target under which a study of the indicated size would have an 80% chance of detecting the chosen effect at the stated significance level, if the assumptions used for the calculation hold. The 90% column uses a higher probability target for detecting that effect under those same assumptions. These are prospective planning concepts, not a measure of what happened in this completed trial.

Smaller effects generally require more participants to detect with the same power and significance level. Accordingly, the planning rows for smaller fractions of the observed effect call for larger per-arm sample sizes. This is a consequence of the target effect being harder to distinguish from random variation, not evidence that a larger trial would necessarily reproduce the observed estimate.

These figures are not observed power. They are illustrations calculated from the observed effect and stated assumptions. They should not be treated as the trial’s original justification or as proof that the completed trial had a particular probability of success.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 63.400; pooled standard deviation σ = 55.675.
2. n = 2 × (1.96 + 0.842)² × 55.675² / 63.400² = 12.1, rounded up to 13 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 63.4                      # observed difference in means
sigma <- 55.6747724352268                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1316575)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 13 (80% power), 17 (90% power)
 75% of observed effect: n per arm = 22 (80% power), 29 (90% power)
 50% of observed effect: n per arm = 49 (80% power), 65 (90% power)
power.t.test: 13.1 
Simulated power at n = 13 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The primary outcome is identified, and three secondary outcomes are listed. The registry record does not report a detailed statistical analysis plan describing how the primary and secondary outcomes were prioritized, whether testing was hierarchical, or whether any multiplicity adjustment was planned or applied. This is relevant because examining multiple outcomes can increase the chance of finding at least one apparently unusual result even when there is no underlying effect across the outcomes.

As a general statistical concept, multiplicity refers to the additional false-positive risk that can arise when many hypotheses are tested. A prespecified strategy can control or organize that risk, for example by defining which endpoint is primary or by adjusting inferential thresholds. The record identifies a primary endpoint but does not report a family-wise error strategy, a false-discovery approach, or another method for handling multiple comparisons. No particular method should be assumed.

The registry lists reintubation, ICU admission, and hospital length of stay as secondary outcomes. Numerical summaries are included for length of stay, but numerical results for reintubation and ICU admission are not reported in the registry record. The record also reports zero analyses in its analysis listing and no reported analyses. This means the posted summary statistics should not be mistaken for a fully documented analysis plan or for a complete account of all analyses that may have been undertaken.

Missing-data handling is not reported in the registry record. The primary outcome arm counts are 18 and 19, compared with the listed enrollment of 40, but the record does not state why the counts differ or whether measurements were unavailable. It does not report imputation, complete-case rules, sensitivity analyses, or the reasons for any missing outcomes.

Analysis populations are also not described. The record does not say whether the primary comparison was intention-to-treat, per-protocol, or based on another population. Without these details, the relationship between random assignment and the posted outcome summaries cannot be fully evaluated. These reporting gaps limit assessment of multiplicity, missingness, and analysis choices; they do not establish that any specific problem occurred.

15. 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 5% reporting threshold.

The registry reports serious adverse events affecting 0 of 18 participants at risk in the nCPAP arm and 0 of 19 participants at risk in the low-flow oxygen arm. Other adverse events are also reported as affecting 0 of 18 and 0 of 19 participants, respectively. Deaths are recorded as 0 in both arms, and no serious adverse-event terms are listed.

These figures mean that the registry reports no affected participants for the listed adverse-event categories during the recorded study period. They do not show that the risk of an adverse event is absent. With the arm counts recorded here, uncommon events could remain unobserved, and the registry record does not provide detailed event definitions, collection procedures, or follow-up duration for safety reporting.

Adverse-event counts are separate from the primary oxygen-gradient result. The absence of reported events does not establish the safety of either approach in broader populations or under other conditions. It describes only the events recorded for these trial groups in the registry.

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

The posted primary outcome summaries show a lower average alveolar–arterial gradient in the nCPAP arm than in the low-flow oxygen arm at one hour following admission to the PACU. The unadjusted mean difference is positive when defined as low-flow oxygen minus nCPAP, and its confidence interval is above zero. The reported p-value is p <0.001. Together, these statistics describe a clear group contrast in this early continuous measure in the posted results.

That result does not, on its own, establish that one treatment improves overall recovery or affects outcomes that were not measured at the primary timepoint. The endpoint is a physiological measure, not a direct report of later complications, functional recovery, quality of life, or patient experience. The registry lists some additional outcomes, but the available numerical results do not provide a complete account of all listed secondary outcomes.

The statistical result also does not determine whether the size of the gradient difference is clinically important. The record does not report a threshold for a meaningful difference, and a small p-value is not a measure of treatment benefit or practical importance. The estimate and confidence interval describe the posted comparison, with uncertainty, rather than settling every clinical question about the interventions.

Randomization supports a comparison between assigned groups in principle, but important implementation and analysis details are not reported. The record does not describe allocation procedures, analysis populations, missing-data handling, or a full statistical analysis plan. The arm counts for the primary outcome are smaller than the enrollment figure, and the reason is not reported. These gaps make it difficult to assess the extent to which the posted summaries represent all enrolled participants.

The registry reports no serious or other adverse events affecting participants in either group, and no deaths. Those counts are limited observations from the trial and cannot exclude events that were not observed or support conclusions about other settings. The most defensible interpretation is confined to the reported endpoint, groups, timepoint, and record-level information.

17. Why This Trial Matters Statistically

This trial illustrates the distinction between a biological or physiological endpoint and outcomes that matter at later stages of care. The primary measure captures an early difference in the alveolar–arterial gradient after respiratory support in the PACU. Reintubation, ICU admission, and length of stay address other aspects of post-operative care. A difference in one type of outcome does not guarantee a corresponding difference in another.

It also shows why an effect estimate should be read alongside its uncertainty. The unadjusted mean difference and confidence interval communicate both the direction and plausible range of the primary contrast. The p-value alone would not express the size or precision of that contrast, and none of these statistics determines clinical importance without a relevant contextual threshold.

The posted group summaries allow readers to examine the observed means and their variability, but they do not replace a documented analysis plan. Details such as analysis populations, missing-data methods, and multiplicity procedures matter for judging how robust an inference is, particularly when several outcomes are considered. Those details are not reported in the registry record.

The sample-size illustrations also demonstrate a basic planning principle: detecting smaller effects generally requires more participants than detecting larger effects under the same assumptions. Because those illustrations use the observed effect, they are not evidence of the trial’s original design choices or of the probability that the completed study would find a result.

Overall, the record offers a focused example of how a randomized comparison can produce a strong statistical contrast on an early continuous endpoint while leaving other questions unresolved. It is useful for separating what the numerical result directly describes from what would require further outcomes, analysis details, or evidence beyond this trial.

18. Limitations

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

Several limitations specific to this trial follow from the registry information. The study enrolled 40 participants, while the posted primary summaries include 18 participants in the nCPAP arm and 19 in the low-flow oxygen arm. The record does not explain the difference, report participant flow, or say whether outcome data were unavailable. This prevents a clear assessment of how the analyzed groups relate to enrollment and random assignment.

The trial is recorded as having no masking. The registry does not describe whether outcome measurement was otherwise standardized or whether assessors were unaware of group assignment. Because the primary endpoint is a measured physiological quantity, reporting those procedures would help readers assess possible measurement influences, but the details are not reported in the registry record.

The primary endpoint is measured at one specified early timepoint. The record does not report repeated measurements that would show how the gradient changed over time. The endpoint description concerns pulmonary function, but a single early measurement does not characterize later respiratory status or establish the course of recovery.

The record names three secondary outcomes, but numerical results are included only for hospital length of stay. Numerical results for reintubation and ICU admission are not reported in the registry record. The registry also does not describe the analysis plan, handling of multiple outcomes, missing-data methods, or analysis population. These omissions limit a full appraisal of the posted results.

Finally, the record gives no further participant characteristics or detailed eligibility criteria. This limits assessment of how closely the enrolled group resembles other populations undergoing bowel surgery. These are limitations of what is documented in the registry record; they do not establish that the trial procedures were inadequate.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Prophylactic nCPAP Following Bowel Surgery (Bio-REB File 11-27) — NCT01316575.
• Registry record last updated 2018-06-04; status last verified 2018-05.
• Results first posted 2013-02-27.
• 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.

22. Record Summary

NCT01316575 is a completed randomized, parallel-group, unmasked study sponsored by the University of Saskatchewan. The listed enrollment is 40, with a start of 2011-04 and primary completion of 2012-05.

The trial compared one hour of nCPAP at 10cmH20 in the PACU with low-flow oxygen through a simple mask at 8 litres per minute. Its primary outcome was the alveolar–arterial gradient in torr, measured one hour following admission to the PACU.

The posted primary means are 70.6 for nCPAP and 134.0 for low-flow oxygen. The unadjusted mean difference, low-flow oxygen minus nCPAP, is 63.4, with a 95% confidence interval from 28.24 to 98.56 and p <0.001. The registry lists reintubation, ICU admission, and hospital length of stay as secondary outcomes; numerical summaries are included for length of stay.

Serious and other adverse events are reported for 0 participants in each arm, and deaths are recorded as 0. Further details about missing data, analysis populations, allocation procedures, and multiplicity methods are not reported in the registry record.