Comparison of Different Ventilator and Vaporizer Technologies to Study Economic and Environmental Implications: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Different Ventilator and Vaporizer Technologies to Study Economic and Environmental Implications (NCT04851314), a randomized na study. The primary outcome is Primary Study Variable: Amount of Gas Vaporized Anesthetic Per Minute Anesthesia.

2. Clinical Question

The question is framed as a comparison of group means in a randomized, parallel-group study. The primary endpoint is the amount of gas vaporized anesthetic per minute, reported in grams/minute for the completed patient population in each ventilator group. The registry describes a minimum of 2 hours of anesthesia as the timeframe for this measure.

The comparison is not a direct estimate of all economic consequences of using either machine. The primary measure concerns anesthetic consumption; the registry record does not report a separate cost endpoint, a cost-effectiveness analysis result, or the monetary value assigned to anesthetic use. The result therefore speaks to the posted consumption measure, not to a complete accounting of costs.

The record also lists time to reach Aldrete > 8 and time to extubation from weaning as secondary outcomes. These outcomes address recovery timing, whereas the primary measure concerns intraoperative anesthetic use. They provide additional clinical context but do not replace the primary question.

3. Trial Design

The registry describes a randomized, parallel-group trial with no masking. Its title concerns comparison of ventilator and vaporizer technologies and its official title describes low-flow anesthesia using the FLOW-i anesthesia machine compared with an established anesthesia delivery unit. The interventions are categorized as devices. The two reported outcome groups are Maquet Flow-i C20 and GE Aisys CS2.

The stated study setting is routine elective general surgery under general anesthesia and standard care, among patients with ASA ratings of 1-2. The primary outcome timeframe is intraoperative, with a minimum of 2 hours of anesthesia. The trial record lists an enrollment of 110. It records a start date of 2018-02-14, a primary completion date of 2019-11-08, and a status of completed.

For the primary outcome, the posted group summaries include 52 participants in the Maquet Flow-i C20 group and 51 in the GE Aisys CS2 group. The registry describes these as completed patient populations for each ventilator type. The posted secondary summaries use 52 participants per group for time to extubation from weaning; for time to reach Aldrete > 8, the reported group sizes are 52 and 51. The record does not explain the differences in outcome-specific group sizes, so their reasons are not reported in the registry record.

The primary measure is reported as a mean with standard deviation. The secondary outcomes are also continuous measures summarized by means and standard deviations. The registry record does not report the trial's original sample-size justification, its prespecified statistical analysis plan, the randomization procedure, allocation concealment, or details of adherence to assigned devices. The record also does not report whether any interim analyses were planned or conducted. These omissions limit what can be concluded about design choices beyond the randomized, parallel, unmasked structure explicitly recorded.

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: Some enrolled subjects were excluded due to unforeseen circumstances in the clinical workflow e.g. a change in anesthetic preference or canceled surgery. Data from these cases could not provide meaningful results for analysis.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Completed patient population for each ventilator type

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.

Population: Completed population only

6. Primary Endpoint

The registry lists the primary outcome as Primary Study Variable: Amount of Gas Vaporized Anesthetic Per Minute Anesthesia, measured over Intraoperative (minimum of 2 hours of anesthesia).

The primary endpoint is the amount of gas vaporized anesthetic per minute of anesthesia, measured in grams/minute. It is intended to quantify anesthetic consumption during the intraoperative period. The registry description places the measure in the completed patient population for each ventilator type and gives a timeframe of intraoperative anesthesia lasting at least 2 hours.

This measure is relevant to the study's stated question because the rationale is to test whether use of a low-volume ventilator in an anesthesia machine reduces anesthetic costs compared with other machines. Consumption can serve as an indicator related to cost, but the endpoint itself is a measure of amount used, not a direct measure of expenditure. The registry record does not report a separate monetary outcome or a formula for translating anesthetic consumption into cost.

The posted summaries report the mean and standard deviation in each group. A mean describes the average observed amount for the group, while a standard deviation describes how dispersed individual measurements are around that mean. Neither summary alone captures every feature of the distribution, such as skewness or unusually high values. The reported comparison of means is therefore best read together with its confidence interval and the group standard deviations.

The primary endpoint focuses on intraoperative anesthetic use. It does not directly measure recovery, patient experience, or all possible environmental effects of the machines. Recovery timing is represented separately by the two secondary endpoints. Other outcomes beyond those listed are not reported in the registry record.

7. Results Posted in the Registry

• GE Aisys CS2: mean 119.30 versus 95.48 on control; difference 23.82 (95% CI 2.12 to 45.52), standardized effect d = 0.42; z-test p = 0.031.

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.

Time to Reach Aldrete > 8

• 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:
  • GE Aisys CS2: mean 89.18 versus 98.13 on control; difference -8.95 (95% CI -29.02 to 11.12), standardized effect d = -0.17; z-test p = 0.382.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between GE Aisys CS2 and the control. The interval gives the range of effects that remain compatible with the data.

Time to Extubation From Weaning

• 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:
  • GE Aisys CS2: mean 10.78 versus 10.37 on control; difference 0.41 (95% CI -2.04 to 2.86), standardized effect d = 0.06; z-test p = 0.743.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between GE Aisys CS2 and the control. The interval gives the range of effects that remain compatible with the data.

The two secondary outcomes concern recovery timing rather than anesthetic consumption. Across them, the posted point estimates are modest relative to their uncertainty, and each confidence interval includes zero. The overall pattern therefore does not show a clear separation in average recovery times in these posted comparisons, while also leaving a range of possible differences compatible with the data.

This pattern is distinct from the primary result, which reports a positive mean difference in anesthetic amount with a confidence interval above zero. The secondary findings do not directly test the primary consumption question, and they should not be combined into a single conclusion about the machines. They address different measures, measured over distinct stated timeframes.

The registry lists the time to reach Aldrete > 8 timeframe as up to 24 hours. The timeframe for time to extubation from weaning is intraoperative, with a minimum of 2 hours of anesthesia. These differences in measurement context matter when relating outcomes: they are not interchangeable measures of one underlying endpoint.

Both secondary comparisons have unadjusted p-values, and the record lists no reported analyses for them. When several outcomes are examined, isolated statistical signals can arise more often than when a single outcome is considered. Without a reported multiplicity strategy or a prespecified hierarchy of outcomes, the secondary results warrant less weight as confirmatory evidence. Their role is best understood as supplementary description rather than proof that the primary result extends to recovery outcomes.

The posted group sizes also differ across outcomes: the Aldrete outcome reports 52 and 51 participants, while the extubation outcome reports 52 in each group. The registry record does not explain why these outcome-specific counts differ, whether any measurements were unavailable, or how missing measurements were handled. That uncertainty further cautions against treating the secondary comparisons as definitive. The overall secondary pattern is informative as context, but it does not resolve the limitations in reporting or alter the fact that the primary and secondary outcomes measure different things.

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

• Time to Reach Aldrete > 8
• Time to Extubation From Weaning

9. Statistical Interpretation

10. Statistical Methods Explained

For a continuous outcome, a mean summarizes the central level of measurements in a group. The primary outcome is reported as a mean amount of anesthetic used per minute, and each group also has a standard deviation. The standard deviation describes the typical spread of observed measurements around the group mean. It is not the same as the uncertainty in the estimated mean: uncertainty in a mean comparison also depends on group size and variability.

What does the mean difference represent?

The primary comparison is reported as a mean difference, with the GE Aisys CS2 group as the comparison against the Maquet Flow-i C20 group. The estimate of 23.82 grams/minute corresponds to subtracting the Maquet group mean from the GE group mean. A positive value therefore indicates a higher observed mean in the GE group on the stated scale. This direction is a matter of how the comparison is defined; it does not by itself indicate clinical or economic importance.

A difference in means focuses on averages. It does not describe how much the individual measurements overlap, nor does it establish that the same difference applies to every operation. The group standard deviations provide context about variability, while the confidence interval provides an estimate of uncertainty around the mean difference.

What does a confidence interval communicate?

A confidence interval gives a range of values that are reasonably compatible with the observed data under the statistical model used. In repeated studies conducted under the same conditions, intervals constructed by the same method would capture the fixed underlying parameter at the stated rate in the long run. A single interval is not a probability statement about the true value after observing the data. It is also not a range containing a specified proportion of individual participant measurements.

For the primary outcome, the interval runs from 2.116 to 45.52 grams/minute. Its positive endpoints indicate that the range of values compatible with this analysis is above zero. The interval's width also matters: it shows that the estimate is not precise to a single value, and that a meaningful range of possible differences remains compatible with the data.

How should the p-value be read?

The primary unadjusted p-value is 0.031. A p-value is calculated under a null hypothesis and a statistical model; it describes how unusual data at least as discrepant as the observed data would be if that null hypothesis and model were correct. It is not the probability that the null hypothesis is true, the chance that the result occurred by chance, or a measure of the size or importance of the difference. It should be read alongside the effect estimate, confidence interval, design, and reporting limitations.

The secondary p-values are also unadjusted. When multiple outcomes are examined, the chance of at least one apparently unusual result can increase if all tests are treated as though they were the only test. A multiplicity adjustment or a prespecified hierarchy can address this issue, but the registry record does not report a multiplicity strategy. Accordingly, the secondary comparisons carry less confirmatory weight than a single prespecified primary analysis would carry in a fully documented analysis plan.

Why does variability matter?

Continuous measurements can vary across participants and procedures. Larger variability makes a group mean less precisely estimated when group size is held constant, because the individual values provide a less concentrated signal about the average. The pooled standard deviation in the posted primary comparison is 56.06, but the registry does not report whether this pooled value was part of the sponsor's original analysis. The posted comparison includes standard errors of 6.835 and 8.713 for the two group means.

General statistical explanation: over-dispersion means that observed variability is greater than a model assumes. If a model underestimates variability, standard errors can be too small and confidence intervals too narrow. That issue is a general consideration, not a claim that over-dispersion occurred in this trial. The registry record does not report a distributional assessment or diagnostics for the continuous outcomes.

What can the posted analysis establish?

The posted summaries support a comparison of observed group means and an unadjusted estimate of uncertainty. The randomized allocation is intended to make groups comparable on average, but interpretation also depends on how randomization was implemented, whether participants were analyzed according to assignment, and how missing outcomes were handled. Those details are not reported in the registry record. No reported formal analyses are listed for the secondary outcomes, and the registry record does not provide a detailed primary analysis method beyond the posted summary statistics.

General statistical explanation: a prespecified analysis plan helps distinguish confirmatory analyses from additional comparisons made after results are known. It also documents choices such as the analysis population, handling of missing measurements, and whether covariates are included. Without those details, the posted mean differences remain interpretable as reported comparisons, but the record offers less basis for assessing whether the analysis choices were fixed in advance.

11. Confidence Intervals and Precision

The primary mean difference is 23.82 grams/minute, with a 95% confidence interval from 2.116 to 45.52. This interval communicates uncertainty about the difference in group means, not the range of individual measurements. It is entirely above zero, while its width shows that the estimate is compatible with a range of positive differences rather than pinpointing one exact amount.

The two group means are 95.48 grams/minute for the Maquet Flow-i C20 and 119.3 grams/minute for the GE Aisys CS2. Their standard deviations are 49.29 and 62.22, respectively. The size of these standard deviations shows why the mean difference should not be interpreted as a uniform difference for each participant or procedure. Individual values can vary substantially within each group, and group summaries do not reveal the full shape of that variation.

Precision is affected by both the amount of variability and the number of observations. The primary summaries report 52 participants for the Maquet Flow-i C20 and 51 for the GE Aisys CS2. The confidence interval incorporates uncertainty in the estimated comparison under the analysis method, but the registry record does not report the complete model specification or diagnostics needed to assess all assumptions.

For the secondary outcomes, the confidence intervals include zero: the time-to-Aldrete comparison ranges from -29.02 to 11.12 minutes, and the time-to-extubation comparison ranges from -2.037 to 2.857 minutes. These intervals allow for differences in either direction under the posted comparisons. They do not establish equivalence or rule out all potentially relevant differences. A conclusion of equivalence would require an appropriate prespecified margin and analysis, which are not reported in the registry record.

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 display is a planning illustration based on the observed effect, rather than the trial's own original design calculation. For these continuous outcomes, the figures are participants per arm, not total events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect targeted in each row is the stated fraction of the observed effect.

The 80% power column gives the number of participants per arm that the illustration estimates would be needed for an 80% chance of detecting the chosen effect under those assumptions, if that effect were the true one and the model assumptions held. The 90% power column uses the same idea with a higher target chance of detection, which generally requires more participants per arm. These are planning quantities, not descriptions of the trial's observed results.

Rows that plan for 75% or 50% of the observed effect assume a smaller difference to detect than the row based on 100% of the observed effect. Smaller effects are harder to distinguish from random variation, so the illustrations require more participants per arm for the same target power. The increase is especially important when planning around a modest effect rather than assuming the comparatively larger observed estimate will recur.

These figures are not observed power. Observed power calculated from a trial's estimated effect adds little information beyond the estimate and its uncertainty. The planning display is more useful for illustrating how sample-size requirements change with the effect targeted, while the confidence intervals from the completed trial are the direct record of the precision achieved.

The registry record does not report the original design assumptions or sample-size justification. These planning illustrations therefore should not be read as evidence that the completed study was designed to achieve the displayed power for its primary or secondary outcomes.

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 = 23.820; pooled standard deviation σ = 56.065.
2. n = 2 × (1.96 + 0.842)² × 56.065² / 23.820² = 87.0, rounded up to 87 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 <- 23.82                      # observed difference in means
sigma <- 56.0649489961473                     # 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(4851314)
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 = 87 (80% power), 117 (90% power)
 75% of observed effect: n per arm = 155 (80% power), 207 (90% power)
 50% of observed effect: n per arm = 348 (80% power), 466 (90% power)
power.t.test: 87.9 
Simulated power at n = 87 per arm: 0.794 (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 registry record does not report a statistical plan describing how multiplicity was handled. This matters because the record lists one primary outcome and two secondary outcomes, and statistical testing across multiple outcomes creates more opportunities for an apparently unusual result than testing one outcome alone. A prespecified primary outcome can help clarify which comparison carries the main confirmatory role, but adjustment or a testing hierarchy may also be relevant when formal conclusions are drawn across outcomes.

The primary p-value is reported as unadjusted, and the secondary p-values are also unadjusted. No adjusted p-values or multiplicity procedure are reported in the registry record. The primary result can still be described as posted, but the reader cannot tell from the record whether the analysis plan designated the primary test as the sole confirmatory test or whether other comparisons were intended to be interpreted jointly.

Missing-data handling is also not reported in the registry record. Outcome group sizes vary: the primary endpoint has 52 and 51 participants, the time-to-Aldrete outcome has 52 and 51, and the extubation outcome has 52 and 52. The record does not explain the differences, identify any missing measurements, or state whether any imputation or other missing-data method was used. It is therefore not possible to assess whether the posted summaries represent all randomized participants, all participants with available measurements, or another analysis set.

The analysis populations are not reported in the registry record. In particular, there is no stated intention-to-treat, per-protocol, or other population definition. The primary endpoint description refers to the completed patient population for each ventilator type, but it does not by itself define how assignment, withdrawals, or incomplete measurements were handled in the analysis.

The registry record also does not report the original statistical analysis plan, the trial's sample-size justification, interim analyses, or prespecified handling of protocol deviations. These missing details do not negate the posted descriptive results, but they limit assessment of whether the analyses were prespecified and how robustly the results address the intended comparison.

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 0% reporting threshold.

The registry reports zero serious adverse events and zero deaths in both machine groups. The serious-event risk groups are reported as 52 for the Maquet Flow-i C20 and 51 for the GE Aisys CS2. For other adverse events, the at-risk groups are also 52 and 51, with zero events reported in each group.

These are counts from the registry's adverse-event fields. They describe what was recorded for the listed categories; they do not demonstrate that no adverse events of any kind occurred, nor do they establish that the two systems have identical safety profiles. The record does not provide event definitions, the method used to collect events, the observation period for adverse-event reporting, or additional detail about how missing safety data were handled.

Zero recorded events in groups of the reported sizes also leave uncertainty about uncommon events. The registry's figures should be read as the posted event counts, not as proof that serious harms are impossible or that the trial can rule out differences in safety. No serious-event terms are listed in the record.

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

The primary result is an estimate of the difference in mean anesthetic amount per minute between the two machine groups in this randomized trial. The posted mean was 95.48 grams/minute for the Maquet Flow-i C20 and 119.3 grams/minute for the GE Aisys CS2. The estimated difference was 23.82 grams/minute, with a 95% confidence interval from 2.116 to 45.52 and an unadjusted p-value of 0.031.

This result does not establish a specific reduction in monetary cost. The study's rationale refers to anesthetic costs, but the primary endpoint is anesthetic amount, and the registry record does not report a monetary cost analysis. It also does not provide a quantified environmental impact outcome. Claims about total cost-effectiveness or environmental benefit would go beyond the posted primary measure.

The result is an average comparison in the studied population and setting. It does not mean that every participant or procedure had lower anesthetic consumption with one machine, because measurements varied within groups. Nor does it establish that the same mean difference would be observed in other surgical settings, patient populations, or machine-use conditions.

The secondary outcomes do not provide clear evidence of a corresponding difference in recovery timing: their confidence intervals include zero, and their tests are unadjusted. This does not establish that the groups are equivalent on recovery measures. The registry record does not report a prespecified equivalence margin or an analysis designed to demonstrate equivalence.

More broadly, a statistical result should be considered alongside the design and reporting. The record documents randomization and parallel groups, but does not provide details of the randomization process, analysis populations, missing-data methods, or original statistical plan. The posted values characterize the reported results; they do not answer every question about implementation, generalizability, cost, safety, or other outcomes.

17. Why This Trial Matters Statistically

This trial is statistically useful because it illustrates how to distinguish a group-average estimate from the uncertainty and variability surrounding it. The primary comparison reports a mean difference and confidence interval, while the group standard deviations show that individual measurements vary within both machine groups. Reading these together is more informative than relying on a p-value alone.

It also highlights the distinction between a measured outcome and the broader rationale for studying it. Anesthetic amount per minute may be relevant to cost, but it is not itself a monetary cost-effectiveness result. Careful interpretation keeps the statistical conclusion tied to the outcome actually recorded rather than extending it to economic or environmental claims that are not reported.

The secondary outcomes provide another useful lesson. Their confidence intervals include zero, but that does not demonstrate equivalence. In addition, unadjusted tests across multiple outcomes carry less confirmatory weight when the multiplicity strategy is not reported. The results can be described without overstating what statistical significance or non-significance establishes.

Finally, the record's omissions demonstrate why complete reporting matters. Details about the original design assumptions, analysis populations, missing data, and prespecified methods help readers judge how closely the posted analysis matches the trial's intended question. Their absence does not make the reported estimates meaningless, but it narrows the conclusions that can be drawn from a registry record alone.

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.

The registry record leaves several trial-specific questions unresolved. Although allocation is recorded as randomized, the method for generating the allocation sequence, concealment before assignment, and implementation details are not reported in the registry record. Masking is listed as none, so participants and study personnel were not described as masked; the record does not specify whether outcome measurement or analysis involved any masking.

The stated primary outcome population is the completed patient population for each ventilator type. The record does not give a fuller analysis-population definition or explain how participants who did not complete the study were handled. Outcome-specific group sizes vary, and reasons for those differences are not reported. No missing-data methods or sensitivity analyses are reported.

The record does not report the sample-size justification used when designing the trial. The planning illustrations based on the observed effect are separate from that original design rationale. The original analysis plan, including any covariate adjustment, distributional checks, interim analyses, and multiplicity strategy, is not reported in the registry record.

The primary outcome is anesthetic amount per minute, not monetary expenditure or a direct environmental measure. The record does not report a complete cost analysis, resource-use accounting, or an environmental endpoint result. The study description also identifies a particular surgery context and a defined ASA range; the registry alone does not establish how results apply outside that context.

Finally, the posted summaries are means and standard deviations for continuous outcomes. The registry record does not provide participant-level distributions or additional descriptive detail that would show skewness, outliers, or other features that could influence interpretation. These limitations qualify the scope of conclusions drawn from the posted data without changing the values reported.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Comparison of Different Ventilator and Vaporizer Technologies to Study Economic and Environmental Implications — NCT04851314.
• Registry record last updated 2021-08-10; status last verified 2021-07.
• Results first posted 2021-08-10.
• 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

NCT04851314 is a completed, randomized, parallel-group, unmasked device trial comparing the Maquet Flow-i C20 with the GE Aisys CS2 during routine elective general surgery under general anesthesia. The registry lists enrollment of 110 and describes the intended population as patients with ASA ratings of 1-2 receiving standard care.

The primary outcome is mean amount of gas vaporized anesthetic per minute, reported in grams/minute. The posted comparison estimates a mean difference of 23.82, with a 95% confidence interval from 2.116 to 45.52 and an unadjusted p-value of 0.031. Two secondary outcomes address recovery timing; their posted confidence intervals include zero.

The record reports zero serious adverse events, zero other adverse events, and zero deaths in the listed groups. It does not report the original sample-size justification, the detailed statistical plan, missing-data methods, or analysis populations. The primary measure concerns anesthetic consumption; cost-effectiveness and environmental results are not reported in the registry record.