AMBU Bag Manual Ventilation vs. Transport Ventilator Mechanical Ventilation for Transport: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for AMBU Bag Manual Ventilation vs. Transport Ventilator Mechanical Ventilation for Transport (NCT06006208), a randomized na study. The primary outcome is The % Change in Mean Artery Blood Pressure.

2. Clinical Question

The clinical question is about a short-term hemodynamic measurement during transport, not a long-term patient outcome. The trial record also lists oxygenation, carbon dioxide, and visual assessments of left and right ventricular function as secondary outcomes. Their results are not reported in the posted results.

The primary comparison is between groups, while the endpoint itself is a within-person percentage change from the pre-transport value. The reported mean difference contrasts those group-level changes. A positive difference indicates a higher average percentage change in the Hamilton C1 arm than in the AMBU bag arm. It does not, by itself, explain why the groups differed or establish the effect of either approach in other settings.

3. Trial Design

The registry describes NCT06006208 as a completed, randomized, single-masked, parallel-group trial. The intervention comparison is AMBU bag manual ventilation versus Hamilton C1 mechanical ventilation during transport to the ICU after cardiac surgery. The registry lists an enrollment of 78 and a start date of 2023-11-01; primary completion is recorded as 2024-10-09.

The posted primary outcome results give an analyzed group size of 38 for AMBU bag manual ventilation and 39 for Hamilton C1 ventilation. The registry does not explain the difference between its overall enrollment figure and the group counts reported for this outcome. The meaning of single masking, including which people were masked, is not described in the registry record. Further details about the randomization procedure, allocation concealment, and conduct of masking are also not reported in the registry record.

The primary endpoint is the percentage change in mean artery blood pressure before and after transport. Pre-transport hemodynamic values were averaged from the final three readings, taken at 1-min intervals, before switching to the transport monitor. Post-transport readings were recorded immediately after transfer to the ICU monitor. The registry reports the endpoint as a mean with standard deviation for each arm, along with a between-arm mean difference and confidence interval.

The registry lists four secondary outcomes: percentage changes in PaO2/FiO2 and PaCO2, and visual-scale changes in left and right ventricular function. The number of posted outcome measures is five, and the record lists two analyses. Further details of the statistical analysis plan, including analysis populations, are not reported in the registry record. The trial status is completed; completion status alone does not supply details about conduct or completeness of outcome reporting.

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: Patients who needed to be switched the ventilation method from the originally designated method were excluded from the study before assignment to the arms.

Overall Study

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 The % Change in Mean Artery Blood Pressure, measured over Pre-transport hemodynamic values were averaged from the final three readings (taken at 1-min intervals) before switching to the transport monitor, and post-transport readings were recorded immediately after transfer to the ICU monitor..

The primary endpoint is the percentage change in mean artery blood pressure from before to after transport to the ICU. The registry defines the calculation as the post-transport measurement minus the pre-transport measurement, divided by the pre-transport measurement, and multiplied by 100. Thus, positive values represent an increase relative to the pre-transport measurement, while negative values represent a decrease.

Before transport, the baseline value was calculated from the final three hemodynamic readings, taken at 1-min intervals, before switching to the transport monitor. The post-transport reading was recorded immediately after transfer to the ICU monitor. The reported group summaries are means and standard deviations of the percentage change.

As a general statistical and clinical rationale, blood pressure is one aspect of hemodynamic status, so a change during transport can describe how this measurement varied across the transfer period. The registry does not state a specific threshold for a clinically important change or explain why this endpoint was selected over the other measures. This short-term measurement is not the same as a broader assessment of cardiac function, patient recovery, or longer-term outcome. Interpretation also depends on how the percentage change behaves across different starting values; the registry does not report the distribution of baseline measurements.

7. Results Posted in the Registry

• Arm 2: Hamilton C1 Ventilator During Transport to the ICU: mean 13.00 versus -3.73 on control; difference 16.73 (95% CI 9.19 to 24.27), standardized effect d = 0.99; z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean difference represent?

The endpoint is continuous: each participant's result is a percentage change in mean artery blood pressure. The registry reports a mean for each arm, then a mean difference comparing the Hamilton C1 arm with the AMBU bag arm. The reported means are -3.73 and 13.0, and the reported difference is 16.73. This contrast is in percentage-change units, not a ratio of the two group means. It describes the difference between the group averages, not the change for a typical individual or the proportion of participants whose measurement increased.

As a general explanation, a mean is sensitive to the values included in the calculation and can be influenced by unusually high or low observations. The standard deviation describes how dispersed observations are around the mean, but does not give the full distribution. Here, the standard deviations are 18.04 for AMBU bag and 15.61 for Hamilton C1. The registry record does not report individual observations, distribution plots, or checks for unusual values, so the summaries cannot show whether the data were symmetric or affected by influential observations.

How should the confidence interval be understood?

A confidence interval describes statistical uncertainty around an estimated contrast under the method and assumptions used to construct it. The reported interval for the mean difference is 9.187 to 24.27. In repeated use of a procedure with the same coverage properties, intervals constructed in this way would capture the underlying parameter at the stated rate. A particular interval is not a probability statement that the fixed parameter lies within its endpoints. The confidence level and calculation method are not reported in the registry record, so they should not be inferred from the interval alone.

The interval excludes zero, matching the direction of the reported difference. This is consistent with the reported unadjusted p-value of <0.001, although the registry record does not give the test procedure. A p-value is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of a difference. Its interpretation depends on the analysis and assumptions behind the test.

Why does variability matter?

General explanation: greater variation among participant measurements makes a group mean less precise when the group size is unchanged. The standard errors reported for the group means are 2.926 for AMBU bag and 2.5 for Hamilton C1. Standard errors quantify uncertainty in estimated means rather than variation among individual measurements; the standard deviations describe that participant-level spread. These measures answer different questions and should not be used interchangeably.

The comparison also reports a pooled standard deviation of 16.85 and a standardized effect estimate of 0.993. A standardized effect expresses the mean difference in standard-deviation units, making it dimensionless. It can help describe the size of a contrast relative to observed variability, but it does not supply a clinical threshold. The registry record does not report enough detail to determine the exact formula or inferential procedure used for these statistics.

What does over-dispersion mean in general?

Over-dispersion is a general concern when observed variation is greater than a statistical model expects. If a model assumes too little variation, its standard errors may be too small and its intervals too narrow. This endpoint is reported as a continuous measure with means and standard deviations, rather than as a count or binary outcome for which over-dispersion is commonly discussed. The registry does not report a model or a diagnostic assessment, so there is no basis to claim that over-dispersion occurred or that a particular correction was used. More generally, checking whether the model reflects the observed variability is important to valid uncertainty estimates.

What can randomization contribute?

Random allocation is intended, as a general design principle, to make treatment groups comparable on average before intervention, including with respect to measured and unmeasured factors. It does not guarantee balance in a particular trial, and it cannot address bias introduced after allocation by missing outcomes, deviations, or analytic choices. The registry identifies the trial as randomized but does not report the randomization method, allocation concealment, baseline characteristics, or analysis population. Those details are needed to examine how well the design was implemented and how the reported comparison was formed.

The record identifies single masking but does not say who was masked or how masking was maintained. In a general sense, masking can reduce the influence of expectations on care, measurement, or assessment when feasible. The record does not allow an assessment of which potential sources of bias it addressed in this trial.

How should the posted significance result be read?

The reported p-value is unadjusted. It summarizes the compatibility of the data with a specified null model under the analysis used; it is not a measure of the probability that the observed effect is due to chance, and it does not account automatically for multiple outcomes or analyses. The registry lists several outcomes, but it does not report a multiplicity procedure or explain whether the primary comparison was prespecified in a detailed analysis plan. General statistical practice distinguishes a primary endpoint from secondary or exploratory measures, but the record does not provide enough information to judge how testing was organized.

The registry record does not report the test, model, confidence-interval procedure, missing-data method, or assumptions checks. These methods should not be reconstructed from the displayed statistics alone. The numerical summaries are useful for describing the posted comparison, while the missing analysis details limit independent evaluation of the inferential method.

10. Confidence Intervals and Precision

The estimated mean difference comparing Hamilton C1 with AMBU bag was 16.73 percentage points, with a confidence interval from 9.187 to 24.27. The interval conveys uncertainty in the estimated group contrast: values throughout that range are compatible with the data under the method used to construct the interval. The registry record does not identify the confidence level or interval method, so those details are not reported in the registry record.

The interval lies above zero, indicating that the estimated contrast favors a higher average percentage change in the Hamilton C1 arm for this endpoint. The interval's lower and upper limits also show that the estimate is not known with exactness. Precision is not the same as clinical importance; the registry does not state a threshold for a meaningful difference, and the interval cannot establish such a threshold.

The group means and standard deviations provide context for the estimate. The AMBU bag mean was -3.73 with standard deviation 18.04; the Hamilton C1 mean was 13.0 with standard deviation 15.61. The reported standard errors of the means were 2.926 and 2.5, respectively. Standard deviations describe spread across individual measurements, while standard errors describe precision of estimated means. The registry does not provide individual-level data or baseline distributions, so the precision of the summary cannot reveal the range of individual responses or the influence of unusual values.

The confidence interval and p-value address statistical uncertainty under the analysis used. They do not account for uncertainty about missing data, analysis choices, endpoint interpretation, or whether the finding applies beyond this trial. Those issues require information not reported in the registry record.

11. 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 participants per arm, not total event counts. They illustrate the group size that a future two-arm study might require under the stated assumptions and effect scenarios. The calculations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect.

The 80% power column means the planned probability of detecting an effect of the specified size under the calculation assumptions if that effect is present. The 90% power column uses a higher target probability of detection under those same assumptions. These are planning targets, not guarantees for a future study. For the full observed effect, the illustration gives 16 participants per arm for 80% power and 22 participants per arm for 90% power. For planning at 75% of the observed effect, it gives 29 and 38 participants per arm, respectively. For planning at 50% of the observed effect, it gives 64 and 86 participants per arm, respectively.

Smaller effects require more participants to detect at the same power and significance level, because they are harder to distinguish from random variation. These figures are planning illustrations based on the observed effect, not the original trial's design assumptions; the trial's own sample-size justification is not reported in the registry record. This is not observed power. It should not be used to describe the probability that the completed trial detected its result or to judge its success after the fact.

12. 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 = 16.730; pooled standard deviation σ = 16.853.
2. n = 2 × (1.96 + 0.842)² × 16.853² / 16.730² = 15.9, rounded up to 16 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 <- 16.73                      # observed difference in means
sigma <- 16.8526472697912                     # 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(6006208)
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 = 16 (80% power), 22 (90% power)
 75% of observed effect: n per arm = 29 (80% power), 38 (90% power)
 50% of observed effect: n per arm = 64 (80% power), 86 (90% power)
power.t.test: 16.9 
Simulated power at n = 16 per arm: 0.773 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists the primary endpoint and four secondary outcomes. The secondary measures concern percentage changes in PaO2/FiO2 and PaCO2 and visual-scale changes in left and right ventricular function. Results for these secondary outcomes are not reported in the registry record. The record also lists two analyses, but does not describe their purpose or how they relate to the outcomes.

When multiple outcomes or analyses are tested, the chance of at least one apparently notable result can increase. General statistical approaches can address multiplicity by specifying a testing hierarchy or adjusting significance thresholds, but the registry record does not report whether such an approach was planned or used. The primary result is accompanied by an unadjusted p-value; that value does not account for any other tests. It should therefore be interpreted as the reported single-comparison result rather than as evidence that multiplicity was addressed.

The analysis population is not reported in the registry record. It is not stated whether the comparison followed an intention-to-treat principle, included only participants with available outcome measurements, or used another definition. Missing primary endpoint data, reasons for missingness, and any method used to handle missing data are also not reported. These details matter because a comparison based on incomplete outcome data can be affected if the missingness relates to group assignment or to the outcome.

The registry does not report a detailed statistical analysis plan, including the prespecified model, assumptions checks, handling of protocol deviations, or any interim analyses. The absence of these details is not evidence that a particular procedure was or was not used. It means the record does not permit assessment of those choices. The completed status and posted primary outcome summary are not substitutes for a fuller account of analysis and reporting.

14. 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 0% reporting threshold.

The posted serious adverse event figures report zero affected participants in the AMBU bag arm, among 38 at risk, and zero affected participants in the Hamilton C1 arm, among 39 at risk. The death counts are also reported as zero in each arm. Other adverse events are reported as zero affected participants in each arm, with the corresponding at-risk counts of 38 and 39.

These figures describe what was recorded in the registry for the listed groups. They do not establish that no adverse events could occur, nor do they rule out uncommon events or events not captured in the reporting period. The registry record does not report detailed event definitions, severity grading, collection procedures, follow-up duration for safety, or a narrative of events. The absence of reported affected participants should therefore be read as a summary of the posted safety record, not as proof of absence of risk.

Serious and other adverse event counts are safety summaries, distinct from the primary blood-pressure outcome. The available counts do not support conclusions about relative safety beyond the reported observations, particularly without further information about follow-up and event ascertainment.

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

The result shows a difference in the posted group averages for percentage change in mean artery blood pressure during transport. The Hamilton C1 arm had a mean of 13.0, compared with -3.73 in the AMBU bag arm; the reported between-arm mean difference was 16.73 percentage points. The confidence interval, 9.187 to 24.27, describes the estimated contrast's statistical precision under the method used. The unadjusted p-value was <0.001.

This finding is specific to the measured endpoint and timing: pre-transport values based on the final three readings, followed by a measurement immediately after transfer to the ICU monitor. It is not a result about longer-term recovery, survival, or all aspects of cardiac function. It also does not show how each individual participant's blood pressure changed. The group standard deviations indicate variation around the means, and the record does not report individual-level results.

The registry does not report a threshold for clinically important change, so statistical separation cannot by itself establish practical importance. Nor does the comparison identify why the groups differed. Randomization is a relevant design feature, but the record lacks details on its implementation, masking, analysis population, and missing outcome handling that would help assess the strength and scope of causal interpretation.

Four secondary outcomes are listed, but their results are not reported in the registry record. The primary result therefore cannot be used to infer corresponding findings for oxygenation, carbon dioxide, or ventricular-function measures. The safety summary records zero affected participants for serious and other adverse events in each arm, but the record does not supply detailed definitions or follow-up information. Overall, the posted data support a description of the primary group contrast; they do not resolve clinical importance, broader outcomes, or generalizability.

16. Why This Trial Matters Statistically

This trial illustrates how a transport-related clinical question can be framed as a comparison of a continuous physiological measure. The endpoint is a percentage change from a pre-transport value, and the main contrast is between the group means. Reporting both the means and the between-group difference helps distinguish the observed values in each arm from the estimated contrast that addresses the comparative question.

Precision matters as much as the point estimate. The confidence interval gives a range of estimates compatible with the data under the calculation method, while the standard deviations show that participant-level measurements vary around the group averages. A statistically clear contrast is not automatically a clinically important one; a threshold for interpreting the magnitude is not reported in the registry record.

The record also demonstrates why completeness of reporting matters. Randomization is reported, but details of its implementation, masking, analysis populations, missing data, and multiplicity are not. Such information helps readers assess whether the estimate follows from the intended design and how much confidence to place in the analysis. The listed secondary outcomes are relevant to the trial's broader stated comparison, but results for those outcomes are not reported in the registry record.

Finally, sample-size planning based on an observed effect is a planning exercise, not evidence about the completed trial's power. Smaller effects require more participants under comparable assumptions. Separating the observed estimate, its uncertainty, and assumptions for future planning helps prevent statistical significance from being mistaken for certainty or clinical importance.

17. Limitations

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

The registry record gives limited information for evaluating the trial's implementation and analysis. Although it identifies randomization and single masking, it does not describe the randomization method, allocation concealment, who was masked, or how masking was maintained. Eligibility criteria and baseline characteristics are not reported in the registry record, limiting assessment of the participants and their comparability.

The overall enrollment is listed as 78, while the primary outcome groups are reported as 38 and 39. The record does not explain the difference. It also does not report the analysis population, the number of missing primary measurements, reasons for missingness, or methods used to address missing data. These omissions limit interpretation of how the posted group summaries relate to the enrolled participants.

The statistical plan is not described in detail. The test or model used for the primary comparison, confidence-interval method, assumptions checks, and any interim analyses are not reported in the registry record. The unadjusted p-value is available, but the record does not explain how multiple outcomes or analyses were handled. Results for the four listed secondary outcomes are not reported.

The primary measure is taken around transport, with a post-transport measurement immediately after transfer. The registry does not report a clinically important threshold, longer-term outcomes, or details about the distribution of baseline values and individual changes. The safety summaries likewise lack detailed event definitions and follow-up information. These limitations do not negate the posted numerical comparison, but they restrict the conclusions that can be drawn from it.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: AMBU Bag Manual Ventilation vs. Transport Ventilator Mechanical Ventilation for Transport — NCT06006208.
• Registry record last updated 2026-02-03; status last verified 2026-01.
• Results first posted 2025-12-04.
• 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.

21. Record Summary

NCT06006208 is a completed, randomized, single-masked, parallel-group trial comparing AMBU bag manual ventilation with Hamilton C1 mechanical ventilation during transport to the ICU after cardiac surgery. The registry lists enrollment of 78 and primary completion on 2024-10-09.

The primary endpoint is percentage change in mean artery blood pressure from before to immediately after transport. The posted means were -3.73 for AMBU bag and 13.0 for Hamilton C1. The reported mean difference was 16.73, with a confidence interval from 9.187 to 24.27 and an unadjusted p-value of <0.001.

Four secondary outcomes are listed, but their results are not reported in the registry record. Further details about the statistical plan, missing data, and analysis populations are also not reported.