Prophylactic Noninvasive Ventilation in vs Postoperative Standard Care in High Risk Patients According to ARISCAT Score: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Prophylactic Noninvasive Ventilation in vs Postoperative Standard Care in High Risk Patients According to ARISCAT Score (NCT03629431), a randomized na study. The primary outcome is Number of Participants With Acute Respiratory Failure Within the First 7 Days Following Surgery (or Until Hospital Discharge if Occurring First).

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group trial comparing prophylactic noninvasive ventilation with postoperative standard care. The registry record labels the study open and reports no masking. The primary-outcome description, however, calls it randomized and single-blind. The record does not explain this difference in descriptions, so the masking status is not fully consistent across the posted information.

The registry lists enrollment as 266. For the primary outcome, the arm-level denominators are 128 participants in the postoperative standard-care arm and 125 in the prophylactic noninvasive ventilation arm. The record does not explain the difference between the enrollment figure and these outcome denominators, or report a participant flow accounting for exclusions, missing outcome data, or departures from assigned treatment.

The study is described as multicenter. Its status is completed, with a start date of 2017-11-03 and a primary completion date of 2019-10-16. The registry record gives the study duration for the primary outcome as 23 months. The phase is listed as NA, which is consistent with the nature of the intervention described as a procedure rather than a drug treatment.

The primary endpoint was the count of participants with acute respiratory failure during the first 7 days after surgery or until hospital discharge if that occurred first. Secondary outcomes named in the record include healthcare-associated infections within 30 days, defined according to CDC criteria, and reintubation within 7 days. Numerical results are available for reintubation, but numerical results for healthcare-associated infections are not reported in the registry record.

The registry does not report the original sample-size justification, the planned analysis methods, the allocation-concealment procedures, or an analysis population definition. These omissions limit assessment of how the study was designed to address its question and how the posted comparisons relate to any prespecified analysis plan.

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:

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 Participants With Acute Respiratory Failure Within the First 7 Days Following Surgery (or Until Hospital Discharge if Occurring First), measured over Up to 7 days post-surgery or until hospital discharge (study duration: 23 months).

The primary endpoint counts participants who experienced acute respiratory failure after surgery. The registry definition is the need for invasive or non-invasive mechanical ventilation within 7 days after surgery, or until hospital discharge if discharge occurred first. It is therefore a binary participant-level outcome: each participant either met the definition during the stated follow-up period or did not.

This endpoint captures a clinically serious postoperative respiratory event and directly reflects the kind of complication the trial aimed to prevent in patients selected as high risk. Counting participants, rather than counting repeated episodes, makes the arm-level outcome a comparison of how many people experienced the event. The registry reports 35 affected participants among 128 in standard care and 30 among 125 in prophylactic noninvasive ventilation.

The record states that all events were validated by an adjudication committee. Adjudication can help apply an outcome definition consistently, although the registry does not describe the committee’s procedures or whether adjudicators were masked to treatment assignment. The primary endpoint’s follow-up ends at the earlier of the stated postoperative period or hospital discharge. The record does not explain how participants discharged before the end of the period were handled beyond this definition.

The endpoint is narrower than the broader concept of postoperative pulmonary complications: it counts acute respiratory failure as defined by mechanical ventilation, not every possible pulmonary complication. The result should therefore be interpreted as a comparison for this specific recorded outcome and follow-up window, rather than as a measure of all respiratory complications after surgery.

7. Results Posted in the Registry

• Prophylactic Non-invasive Ventilation: 24.0% (30/125) versus 27.3% (35/128) on control; risk difference -3.3 percentage points (95% CI -14.1 to 7.4), risk ratio 0.88 (0.58–1.34); unadjusted two-proportion z-test p = 0.543.

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.

Reintubation Rate Within 7 Days

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Prophylactic Non-invasive Ventilation: 7.2% (9/125) versus 6.2% (8/128) on control; risk difference 0.9 percentage points (95% CI -5.2 to 7.1), risk ratio 1.15 (0.46–2.89); unadjusted two-proportion z-test p = 0.763.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Prophylactic Non-invasive Ventilation and the control. The interval gives the range of effects that remain compatible with the data.

The available secondary numerical comparison concerns reintubation within 7 days. Its estimate is uncertain, with a confidence interval that includes no difference and effects in either direction. This overall pattern is consistent with the primary result: neither comparison provides a precise distinction between the two care pathways in the posted data.

Healthcare-associated infection within 30 days is named as a secondary outcome, but numerical results are not reported in the registry record. The overall secondary-outcome picture is therefore incomplete. The available information does not show whether the infection outcome followed the same pattern as the primary endpoint, and no conclusion about its between-arm difference can be drawn from the record.

Secondary endpoints can help describe other outcomes relevant to the research question, but they generally carry less weight than the primary endpoint for confirming a trial’s principal hypothesis. The primary endpoint is the central outcome against which the study question is framed. When multiple secondary outcomes are examined, the chance of finding an apparently notable result by chance can increase unless the analysis plan accounts for multiplicity. The registry does not report such a plan or any adjustment for multiple comparisons.

There are no reported secondary analyses listed in the registry record. The posted reintubation comparison should therefore be treated as an unadjusted descriptive comparison, not as a confirmatory finding. Its uncertainty also means it should not be used to reinforce a definitive interpretation of the primary outcome. Together, the available primary and secondary results show uncertainty rather than a consistent, precise separation between groups; the missing numerical infection result limits any broader synthesis across secondary outcomes.

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

• Number of Participants With Healthcare-Associated Infections Within 30 Days After Surgery (Defined According to CDC Criteria)
• Reintubation Rate Within 7 Days

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary because it records whether each participant experienced acute respiratory failure during the specified follow-up. For this type of outcome, an arm-level event count is considered alongside the number of participants assessed. The posted summary reports 35 events among 128 participants for standard care and 30 among 125 participants for prophylactic noninvasive ventilation. The comparison expresses the difference between the event risks in the two groups.

What the risk difference represents

A risk difference is an absolute contrast between the proportions experiencing the event in the two groups. A negative estimate in this comparison indicates a lower observed event proportion in the prophylactic ventilation arm than in standard care; a positive estimate would indicate a higher observed proportion. The point estimate does not by itself show how precisely that contrast is known. The confidence interval is needed to understand the range of effects reasonably compatible with the observed data under the method used.

The posted risk-difference interval crosses zero, the value corresponding to no absolute difference. It therefore includes the possibility of no difference as well as effects in either direction. This is why the point estimate alone should not be used to make a categorical claim about the comparison.

What the p-value means

The unadjusted p-value for the primary comparison is 0.543. A p-value describes the compatibility of the observed data with a specified null model, assuming the statistical model and its conditions are appropriate. It is not the chance that the null hypothesis is true, the chance that the result occurred randomly, or a measure of the size or clinical importance of an effect. A p-value above a conventional threshold does not prove equivalence or rule out a meaningful effect.

The registry does not report the trial’s prespecified statistical analysis plan, so it is not possible to confirm whether this test was the planned primary analysis, whether any covariate adjustment was intended, or how the investigators planned to address multiple outcomes. The record also lists no reported analyses for the secondary outcomes. The comparisons posted for interpretation are unadjusted and should be read as such.

Why uncertainty matters

A confidence interval reflects statistical uncertainty in an estimate under the method used to construct it. A narrow interval indicates greater precision; a wide interval indicates that the data leave a broader range of effects plausible. Here, the primary interval includes the null value and extends to effects on either side. Thus, the observed difference is not estimated with enough precision in the posted results to exclude either a benefit or a harm direction for the intervention.

Confidence intervals and p-values answer related but different questions. The interval helps show the range and direction of effects compatible with the data, while the p-value summarizes compatibility with a particular null hypothesis. Neither substitutes for considering the study’s design, the endpoint definition, the analysis population, or the completeness of reporting.

General note on binary outcomes

For a binary outcome, the arm-specific event risks depend on both the number of participants with the event and the number assessed. The same event count can imply a different risk when the denominator differs. A risk difference is an absolute measure, whereas a risk ratio or odds ratio is a relative measure. Relative measures can look different from absolute differences, especially when events are uncommon. No single scale gives a complete account of the clinical or statistical meaning of a result, so estimates should be read with their intervals and with the event counts.

The registry also posts relative measures for the primary comparison, but their intervals include the null value of one. For a risk ratio or odds ratio, one represents equal values between groups; an interval spanning one is consistent with no relative difference. These measures do not remove the uncertainty evident in the absolute comparison.

Randomization and analysis

Randomization is intended to create groups that are comparable on average, including on factors that are measured and factors that are not measured. In a particular trial, chance imbalances can still occur. The registry does not report baseline characteristics in the information used for this interpretation, an adjusted model, or details of allocation concealment. It is therefore not possible to assess covariate balance or reproduce a more detailed account of the analysis strategy from the record.

The primary outcome description says events were validated by an adjudication committee, which may support consistent classification. However, the design information labels the study open with no masking, while the endpoint description calls the trial single-blind. The registry does not reconcile these descriptions or state whether the adjudicators were masked. That ambiguity matters when considering the risk of bias in outcome assessment.

These statistical methods describe how to understand the posted estimates; they do not establish whether the treatment should be used in practice. The record’s main inferential limitation is the uncertainty of the effect estimate, alongside incomplete reporting of the original analysis plan and participant accounting.

11. Confidence Intervals and Precision

The primary comparison has an estimated risk difference below zero, but its posted confidence interval crosses zero and extends to both negative and positive values. This indicates that the estimate is imprecise enough to be compatible with no absolute difference and with effects in either direction. The interval does not support a confident conclusion about which care pathway has the lower underlying event risk.

The relative measures convey the same general uncertainty. The posted risk-ratio and odds-ratio intervals include one, the null value for those relative comparisons. Thus, changing from an absolute to a relative scale does not make the result conclusive. A point estimate on any scale should be interpreted together with its interval rather than as a stand-alone answer.

The p-value of 0.543 is consistent with this uncertainty, but it should not be treated as a direct measure of precision or as proof that the groups are the same. Precision concerns the breadth of plausible effects, while a p-value addresses compatibility with a particular null model. The available primary comparison does not tightly constrain the size or direction of the underlying effect.

For the secondary reintubation comparison, the confidence interval also spans the null and effects in both directions. Its uncertainty means the observed difference should not be read as a definitive signal of higher or lower risk. The healthcare-associated infection outcome has no numerical result reported in the registry record, so its precision cannot be assessed from the posted information.

Confidence intervals describe sampling uncertainty under the analysis method; they do not account for every possible source of error. In particular, the registry does not report enough detail to assess missing outcome data, departures from assigned care, or whether the posted analysis follows a prespecified plan. Those limitations are separate from the width of the confidence interval and may affect how much confidence readers place in the comparison.

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 planning figures are illustrations based on the observed effect, not the trial’s original design assumptions. The registry does not report the original sample-size justification. The stated illustration assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For each scenario, the effect to detect is a stated fraction of the observed effect.

The figures are participants per arm, not a total across both arms. The 80% power column describes the number of participants per arm that a hypothetical study would need, under the stated assumptions, to have an 80% chance of detecting the chosen effect if that effect were the true one and the assumptions held. The 90% power column uses a higher target probability of detecting that effect, and therefore calls for more participants per arm than the corresponding 80% target.

Planning for 100% of the observed effect gives 2,678 participants per arm for 80% power and 3,585 participants per arm for 90% power. Planning for 75% of the observed effect gives 4,812 participants per arm for 80% power and 6,442 participants per arm for 90% power. Planning for 50% of the observed effect gives 10,940 participants per arm for 80% power and 14,645 participants per arm for 90% power. Smaller effects need more participants because they are harder to distinguish from random variation.

These calculations are based on the observed effect, which is itself uncertain, and should be treated as planning illustrations rather than a recommendation for a future study. They do not describe the probability that this completed trial detected an effect. This is not observed power.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.273; treatment proportion p₁ = 0.240; average p̄ = 0.257.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6178 = 1.2108.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6173 = 0.5195.
4. n = (1.2108 + 0.5195)² / (-0.0334)² = 2,677.9, rounded up to 2,678 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
p0 <- 0.2734375                          # control proportion
p1 <- 0.24                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(3629431)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 2,678 (80% power), 3,585 (90% power)
 75% of observed effect: n per arm = 4,812 (80% power), 6,442 (90% power)
 50% of observed effect: n per arm = 10,940 (80% power), 14,645 (90% power)
power.prop.test: 2677.9 
Simulated power at n = 2,678 per arm: 0.799 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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 registry lists a primary endpoint and secondary outcomes, but the prespecified statistical analysis plan is not reported in the registry record. It is therefore unknown whether the investigators planned a hierarchy of outcomes, a formal adjustment for multiple comparisons, or a particular approach to interpreting secondary results. When several outcomes are tested, the chance of at least one apparently unusual result arising by chance can increase. Without a reported plan, secondary findings should be interpreted cautiously and should not be treated as independent confirmation of the primary comparison.

The registry names healthcare-associated infections within 30 days and reintubation within 7 days as secondary outcomes. Numerical results are posted for reintubation, but not for healthcare-associated infections. No reported analyses are listed for the secondary outcomes. The missing infection result limits the ability to describe the complete set of secondary findings or evaluate whether all outcomes were reported as intended.

Information about missing data and analysis populations is also limited. The record does not report how many participants had missing primary outcome information, how missing outcomes were handled, or whether the analysis followed an intention-to-treat or per-protocol approach. It does not provide a participant flow accounting that would explain the relationship between the enrollment figure of 266 and the primary-outcome arm denominators of 128 and 125. This difference cannot be interpreted without further reporting.

The registry also does not report whether participants were analyzed according to randomized assignment, whether treatment deviations occurred, or whether any sensitivity analyses were performed. These details matter because the handling of missing outcomes and treatment deviations can influence an estimate, especially when event counts are limited. Their absence does not prove that the analysis was biased, but it prevents readers from assessing those risks from the posted record.

The primary comparison is presented as unadjusted, and no adjusted primary analysis is reported. The record does not say whether adjustment for baseline characteristics was prespecified or considered. These gaps in reporting constrain evaluation of multiplicity, missingness, and analysis populations; they do not alter the arithmetic of the posted counts, but they narrow the conclusions that can be drawn from them.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: bleeding (2.4%), acute renal failure (1.6%), ileus (1.6%), hemodynamic failure (1.6%), mediastinitis (1.6%).

The registry lists serious adverse events for 19 of 128 participants in postoperative standard care and 15 of 125 participants in prophylactic noninvasive ventilation. Deaths are listed for 2 participants in standard care and 3 in prophylactic ventilation. These are counts recorded by arm; the registry information does not establish that the events were caused by the assigned intervention.

The most frequently listed serious-event terms include bleeding at 2.4%, acute renal failure at 1.6%, ileus at 1.6%, hemodynamic failure at 1.6%, mediastinitis at 1.6%, and cardiac arrest at 0.8%. These terms are presented as registry event listings, not as a complete account of every event or an adjusted comparison between the randomized groups.

The record does not report event-level timing, severity detail beyond the serious-event classification, attribution to treatment, or statistical comparisons for safety. The other adverse-event figures list all participants in each arm as affected, but the record does not provide enough detail to interpret the scope or meaning of that category. The counts should therefore be read descriptively and not as evidence of a causal safety difference.

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

The posted results describe a randomized comparison in patients considered at high risk of postoperative pulmonary complications according to the ARISCAT score. The primary endpoint was acute respiratory failure, defined by the need for invasive or non-invasive mechanical ventilation during the specified postoperative period. The observed counts were 35 of 128 participants in standard care and 30 of 125 participants in prophylactic noninvasive ventilation. The estimated difference favored the prophylactic ventilation arm in direction, but the confidence interval includes no difference and effects in either direction.

This result does not establish that prophylactic noninvasive ventilation reduces acute respiratory failure, and it does not establish that the two care pathways have identical outcomes. The uncertainty means the registry data are compatible with a range of possible effects. The unadjusted p-value is not evidence of equivalence, and the point estimate should not be read as a definitive treatment effect.

The finding applies to the recorded endpoint, population, and follow-up definition. It does not directly answer whether the care pathways affect every type of postoperative pulmonary complication, outcomes beyond the follow-up period, or populations not selected according to the stated risk approach. The healthcare-associated infection outcome is named but has no numerical result reported in the registry record, and the available secondary reintubation result is also imprecise.

Interpretation is further limited by missing information about the original analysis plan, the sample-size justification, participant flow, missing data, and analysis populations. The registry’s design label states that the study was open with no masking, while the primary-outcome description calls it single-blind; the record does not resolve this inconsistency. These gaps do not negate the posted data, but they limit assessment of potential bias and of how closely the reported comparisons follow the intended analysis.

The result is best understood as an uncertain estimate rather than a categorical answer about the intervention. It describes what was observed in the recorded trial groups and how imprecisely the difference is estimated. It is not a recommendation for care and does not determine an individual patient’s treatment.

17. Why This Trial Matters Statistically

This trial addresses a statistical challenge that arises when an intervention is proposed for a broad clinical problem but may be most relevant to a subgroup at elevated risk. The registry describes use of a preoperative ARISCAT score to identify patients considered at high risk of postoperative pulmonary complications. The question is therefore not simply whether prophylactic ventilation should be used for all surgical patients, but how the comparison looks in the selected higher-risk population.

For the primary endpoint, the observed event counts differ between groups, but the estimated effect remains imprecise. This illustrates why a randomized comparison should be read through its uncertainty interval as well as its point estimate and p-value. The result does not support a definitive claim of benefit, harm, or equivalence. A nonsignificant p-value alone cannot establish that two care pathways have the same effect.

The trial also highlights the importance of complete registry reporting. The record identifies a primary endpoint, names secondary outcomes, and posts some comparisons, but it does not report the original sample-size rationale, the statistical analysis plan, missing-data handling, or analysis populations. Numerical results for healthcare-associated infection are not reported. These omissions make it harder to assess whether the reported comparisons were prespecified and how complete the outcome picture is.

Finally, the design information is internally inconsistent about masking: the study is labeled open with no masking, while the primary endpoint description calls it single-blind. Because outcome adjudication is mentioned without details about masking, readers cannot fully judge how the event validation was protected from knowledge of treatment assignment. The trial is statistically informative as a record of an uncertain comparison, while also demonstrating how precision, outcome definitions, and transparent reporting shape interpretation.

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 the trial record affect interpretation. First, the primary endpoint’s risk-difference confidence interval includes no difference and extends in both directions. The observed counts therefore do not yield a precise estimate that distinguishes the care pathways. The unadjusted p-value likewise does not establish equivalence.

Second, the registry does not report the original sample-size justification or the assumptions used to plan the trial. The planning illustrations based on the observed effect are not a substitute for the original design rationale. Without that rationale, it is not possible to determine how the planned enrollment related to a prespecified target effect or power.

Third, participant accounting is incomplete in the information available. Enrollment is listed as 266, while the primary outcome uses arm denominators of 128 and 125. The registry does not explain this difference or give a flow of participants through randomization, follow-up, and analysis. Missing outcome data and the chosen analysis population are not reported.

Fourth, numerical results are not reported for the named healthcare-associated infection outcome, and no secondary analyses are listed. This leaves the secondary-outcome record incomplete and prevents a comprehensive account of results across all named outcomes. The analysis plan and any adjustment for multiple comparisons are also not reported.

Finally, the registry describes the trial as open with no masking, but the primary outcome description calls it single-blind. It notes adjudication of events but does not explain whether adjudicators were masked. These reporting gaps prevent a full assessment of outcome-assessment procedures and potential bias. They should be treated as uncertainties in the record, not as proof that a particular bias occurred.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Prophylactic Noninvasive Ventilation in vs Postoperative Standard Care in High Risk Patients According to ARISCAT Score — NCT03629431.
• Registry record last updated 2026-01-27; status last verified 2020-03.
• Results first posted 2026-01-27.
• 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

NCT03629431 is a completed, randomized, parallel-group study comparing prophylactic noninvasive ventilation with postoperative standard care among patients considered at high risk of postoperative pulmonary complications according to preoperative ARISCAT assessment. Enrollment is listed as 266. The primary endpoint was acute respiratory failure within 7 days after surgery or until hospital discharge if earlier, defined by the need for invasive or non-invasive mechanical ventilation.

The primary outcome counts were 35 of 128 participants in standard care and 30 of 125 in prophylactic ventilation. The unadjusted comparison is imprecise, with a confidence interval that includes no difference. Reintubation results are also posted, while numerical healthcare-associated infection results are not reported in the registry record.

The record does not report the original sample-size justification, the statistical analysis plan, missing-data handling, or analysis populations. Its masking descriptions are inconsistent. These limitations leave the observed comparison interpretable as an uncertain estimate, not a definitive distinction between care pathways.