A Pilot Study to Assess Effects of Self-Administered Nitrous Oxide (SANO) on Urodynamic Study (UDS) Parameters: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Pilot Study to Assess Effects of Self-Administered Nitrous Oxide (SANO) on Urodynamic Study (UDS) Parameters (NCT05883332), a randomized phase 4 study. The primary outcome is Bladder Capacity.

2. Clinical Question

The clinical rationale in the registry is that urodynamic studies can involve anxiety or discomfort, and that nitrous oxide may affect measurements taken during the procedure. The primary statistical question is therefore about the measurement itself: whether the recorded bladder capacity differs between the runs. The registry also lists outcomes related to pain and anxiety during the study, along with other urodynamic measures.

This is a pilot study, not a report of a large confirmatory trial. The registry does not report a prespecified threshold for an important difference in bladder capacity, nor does it report an inferential comparison for the primary endpoint. The posted summaries can describe the observed distributions, but they cannot by themselves establish whether the run conditions are equivalent or whether any difference would be clinically important.

3. Trial Design

The registry describes a Phase 4, randomized, triple-masked crossover study sponsored by Beth Israel Deaconess Medical Center. It is marked completed, with enrollment of 19. The recorded start date is 2023-01-10 and the primary completion date is 2023-03-02. More detail about eligibility criteria and the intended sample size is not reported in the registry record.

Each participant had two consecutive urodynamic study runs on a single study day. The registry specifies a 2-minute washout between runs and gives an approximate run duration of 15-45 minutes, depending on individual bladder fill rate. Participants were assigned to an oxygen-first or SANO-first sequence. The posted primary results group the runs by condition, with N=19 for each condition.

The arm descriptions state that participants received self-administered nitrous oxide at a range of 25-50% immediately before and during catheter placements, and that a participant-preferred level was determined. The registry summary describes a 20-50% range. The record does not explain this difference in ranges. It also does not describe the masking procedures, the randomization method, or whether any additional sequence or period effects were incorporated into the analysis.

A crossover design allows each participant to experience both conditions, so each participant can serve as their own comparator. That design can be informative when measurements within a participant are related. However, the posted primary results are medians and interquartile ranges for each condition, without a reported paired treatment estimate or analysis. The degree to which the analysis accounted for the within-participant structure is not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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 Bladder Capacity, measured over Measured at max bladder fill during each of two consecutive UDS runs on a single study day. Runs occur back-to-back with a 2-minute washout; each run lasts ~15-45 minutes depending on individual bladder fill rate.

The primary endpoint is bladder capacity, recorded in milliliters as the maximum liquid volume the bladder can hold during a urodynamic study. It is measured at maximum bladder fill during each of the two consecutive runs. In this study, the outcome represents a measurement taken during the procedure rather than a later clinical event.

Bladder capacity is relevant to the stated study question because the registry asks whether SANO affects urodynamic measurements. Comparing capacity across the oxygen and SANO runs can describe whether the recorded volumes appear different under the two conditions. The registry presents this endpoint using a median and interquartile range for each run condition.

In general, the median describes the center of an observed distribution, while the interquartile range describes the middle half of its values. These summaries do not show the paired differences for individual participants. Nor do they provide an interval estimate or significance test for the contrast between conditions. Such inferential results for the primary endpoint are not reported in the registry record.

The posted medians are 363.0 milliliters for the Oxygen UDS Run and 402.0 milliliters for the SANO UDS Run. The corresponding interquartile ranges are 282.0 to 553.0 and 307.0 to 530.0. These are descriptive summaries; they do not establish whether the conditions differ beyond the observed data or whether a difference would matter clinically.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports descriptive summaries for the primary outcome and a comparative result for one secondary outcome. It does not report the statistical analysis plan or an inferential analysis of bladder capacity. The explanations below distinguish the statistical meaning of the posted summaries from analyses that are not documented.

What does a median and interquartile range describe?

The median is a measure of the center of a distribution: half the observed values are at or below it and half are at or above it, subject to ties. The interquartile range runs from the 25th percentile to the 75th percentile and describes the central spread of the observations. For the oxygen run, the posted median is 363.0 milliliters, with an interquartile range from 282.0 to 553.0. For the SANO run, the median is 402.0 milliliters, with an interquartile range from 307.0 to 530.0.

In general, medians and interquartile ranges can be useful when values are skewed or when a few observations are unusually high or low. They are descriptive summaries, not estimates of the uncertainty around a treatment contrast. They also do not show how the two measurements from each participant relate to one another. No primary confidence interval or test result is reported in the registry record.

Why does the crossover structure matter?

In general, crossover data contain repeated measurements within the same participant. Measurements from one participant may be more alike than measurements from different participants. A paired analysis uses the within-participant comparison and can account for that dependence. Treating the two condition groups as independent when they are actually paired can fail to use the design information and can misstate uncertainty.

The study is identified as randomized and crossover, and the posted results identify an oxygen-first and a SANO-first sequence. The record does not describe the exact statistical model, whether it accounted for pairing, or whether it considered sequence, period, or carryover effects. The 2-minute washout is reported as a feature of the procedure; whether that interval was considered adequate for analysis purposes is not reported in the registry record.

How should the detrusor overactivity comparison be read?

Detrusor overactivity is reported as a participant count during each run. The posted counts are 4 of 19 for the Oxygen UDS Run and 6 of 19 for the SANO UDS Run. The registry reports an unadjusted p-value of 0.461 for the comparison. A p-value describes how compatible the observed data are with a specified null model, under the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not measure clinical importance.

The registry also reports an unadjusted risk-difference estimate and interval, as well as relative-risk and odds-ratio estimates and intervals. Those comparative measures are not adjusted for other outcomes or covariates. The record does not describe the statistical method used to account for pairing in this binary outcome, so the analysis should be interpreted as posted rather than assumed to use a particular crossover method.

What do the planning illustrations mean?

The sample-size illustrations are based on the observed detrusor-overactivity effect, not on the study's own design. They assume a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The displayed scenarios plan for 100% of the observed effect, 75% of the observed effect, or 50% of the observed effect.

For planning for 100% of the observed effect, the illustrations give 274 participants per arm for 80% power and 366 participants per arm for 90% power. For 75% of the observed effect, they give 472 participants per arm for 80% power and 631 participants per arm for 90% power. For 50% of the observed effect, they give 1,024 participants per arm for 80% power and 1,370 participants per arm for 90% power. These are planning illustrations, not observed power and not the enrollment target used in this trial. They are not a sample-size calculation for the primary capacity endpoint.

In general, smaller effects require larger samples to distinguish them from random variation at a specified significance level and power. These illustrations depend on the observed effect, which can be unstable in a small pilot. Their assumptions also describe an equal-allocation, two-arm calculation, whereas the trial is reported as a crossover study. The registry does not report a design-specific planning calculation or its assumptions.

What can and cannot be concluded from the posted analyses?

The descriptive primary summaries permit a comparison of the observed medians and ranges, but do not quantify uncertainty in the paired contrast. For the secondary binary outcome, the registry posts counts and unadjusted comparative statistics. A reported p-value does not establish absence of an effect, and a nonsignificant result does not show that conditions are equivalent. In general, confidence intervals convey a range of estimates compatible with the data and the analysis assumptions; no primary confidence interval is reported.

Whether a statistical result is reliable also depends on the analysis population, missing-data handling, and prespecified methods. Those details, along with the protocol's statistical plan, are not reported in the registry record. Accordingly, interpretation should remain close to the quantities actually posted and should not assume undocumented analyses.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a statistical analysis plan describing multiplicity, missing-data handling, or analysis populations. It lists six secondary outcomes and posts an unadjusted comparative result for detrusor overactivity. Whether any outcome was prespecified as a key secondary endpoint, and whether tests were intended to be interpreted jointly or separately, is not reported in the registry record.

Multiplicity matters because testing several outcomes can increase the chance of at least one apparently unusual result even when there is no underlying effect. In general, studies may address this by defining an outcome hierarchy or adjusting significance thresholds, among other approaches. No such procedure is reported for this study. The detrusor-overactivity p-value should therefore be read as unadjusted and exploratory, not as a result corrected for the number of outcomes examined.

The registry does not report whether any participants or measurements were missing, how missing values were handled, or whether all enrolled participants contributed data to each outcome. The posted primary summaries give N=19 for each run condition, and the detrusor-overactivity counts are also reported with 19 participants per condition. These entries do not, by themselves, describe completeness for every endpoint or explain how the analysis treated incomplete paired data.

The record does not specify whether the primary analysis included all randomized participants, only participants who completed both runs, or another analysis population. It also does not report exclusions, protocol deviations, or a method for handling incomplete crossover sequences. These details matter because a paired comparison generally requires measurements under both conditions for a participant. Without the analysis population and missing-data rules, the effect of incomplete records cannot be assessed.

Finally, no primary inferential analysis is posted, and the registry does not describe adjustments for sequence, period, or carryover. These absences limit the ability to judge how the analysis aligned with the randomized crossover design.

11. 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 adverse-event entries report 19 participants at risk in each run condition. For the Oxygen UDS Run, the record lists 0 serious adverse events, 0 other adverse events, and 0 deaths. For the SANO UDS Run, it likewise lists 0 serious adverse events, 0 other adverse events, and 0 deaths. No serious adverse-event terms are listed.

These entries describe what was recorded for the two study conditions in this small completed study. They do not establish that adverse events cannot occur, and they do not precisely characterize uncommon harms. The registry does not provide additional detail about event definitions, surveillance procedures, or the time period covered by the adverse-event entries. Nor does the absence of recorded events resolve the primary question about bladder-capacity measurements.

In general, safety counts should be interpreted in relation to the number of participants observed and the completeness of event collection. Zero recorded events in a limited study is not evidence of zero risk. The figures are a report of the registry's recorded counts, not a guarantee about safety in other settings or populations.

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

The posted results establish that the registry contains descriptive bladder-capacity summaries for 19 participants in each run condition. The median was 363.0 milliliters for the oxygen run and 402.0 milliliters for the SANO run, with interquartile ranges of 282.0 to 553.0 and 307.0 to 530.0, respectively. These values describe observed measurements in this pilot.

They do not establish that SANO changes bladder capacity, nor that it leaves capacity unchanged. The record does not report an inferential primary comparison, a confidence interval for the paired contrast, or a prespecified equivalence margin. A descriptive similarity or difference between condition summaries is not enough to show equivalence, non-inferiority, or a meaningful treatment effect.

The study's stated motivation includes anxiety and discomfort during urodynamic testing, and the registry lists pain and anxiety among secondary outcomes. Numerical results for those outcomes are not reported in the registry record. Therefore, the posted primary capacity summaries do not answer whether participants felt less anxiety or pain, and they do not establish an overall benefit or harm.

The detrusor-overactivity comparison is a secondary, unadjusted result. It should be read cautiously given the limited sample and the absence of reported multiplicity procedures. Results for the other listed secondary outcomes are not reported. The safety entries contain no recorded serious or other adverse events and no deaths in either condition, but the study's size and the absence of additional safety detail limit what can be inferred about risk.

In general, a pilot study can offer preliminary data and inform the planning of later research. It cannot replace a clearly reported primary analysis designed to estimate the treatment contrast with adequate precision. The registry does not report the protocol's statistical plan, intended sample-size justification, or detailed handling of the crossover data. Those omissions prevent a complete assessment of how the study was intended to test its question.

13. Why This Trial Matters Statistically

This trial raises a statistical issue that is central to procedural research: a comfort-related intervention may be evaluated not only by participant experience but also by whether measurements collected during a procedure differ by condition. For this study, bladder capacity is the primary measurement of interest, while anxiety, pain, and other urodynamic features are listed as secondary outcomes.

The randomized crossover design is relevant because each participant underwent both an oxygen run and a SANO run. In general, within-participant comparisons can reduce the influence of stable differences between participants. That advantage depends on using an analysis that respects the pairing and accounts appropriately for the design. The registry does not report the primary paired estimate or describe the statistical model, so the design's potential statistical advantage cannot be evaluated from the posted primary results.

The contrast between descriptive summaries and inferential results is especially important in a pilot. Medians and interquartile ranges give a useful view of observed values, but they do not quantify the precision of the condition contrast. A reader needs an estimate and uncertainty interval for that contrast to judge what effects remain compatible with the data. Such a primary inferential result is not reported in the registry record.

The secondary detrusor-overactivity result illustrates another general challenge: when multiple outcomes are examined, an unadjusted result has to be interpreted in the context of the full outcome set and the analysis plan. The registry provides no multiplicity strategy and does not report numerical results for most listed secondary outcomes. This makes it difficult to distinguish planned confirmatory evidence from exploratory findings.

Finally, the sample-size illustrations are based on an observed secondary effect and stated planning assumptions, rather than a reported design calculation for the primary endpoint. They are useful as illustrations of how assumptions affect planning, but they are not evidence of the trial's power or of its ability to resolve the primary question. Transparent reporting of the paired primary estimate, uncertainty, analysis population, and prespecified methods would be important for interpreting future work on this question.

14. Limitations

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

The most important trial-specific limitation is that the primary outcome is reported descriptively without an inferential comparison. The medians and interquartile ranges do not reveal the paired change for each participant, and the registry does not provide a confidence interval or p-value for the primary contrast. As a result, the precision of the main comparison cannot be assessed from the registry record.

Enrollment was 19, and the study is identified as a pilot. That scale limits the detail available from the observed data, particularly for secondary outcomes and safety counts. The registry does not report a sample-size justification for the primary endpoint or a threshold for a clinically important difference. It is therefore not possible to determine whether the study was intended to assess equivalence, non-inferiority, or another specific hypothesis.

The crossover design also creates analytic questions. The record does not describe how pairing was handled, whether sequence or period effects were assessed, or whether carryover was considered. Although a 2-minute washout is recorded, the analysis plan and its rationale are not reported. The arm descriptions also give a 25-50% nitrous oxide range, while the registry summary gives 20-50%; the record does not explain the difference.

Other limitations are incomplete reporting of analysis populations, missing-data handling, and multiplicity procedures. Numerical results are not reported for most of the listed secondary outcomes, and the posted detrusor-overactivity comparison is unadjusted. The adverse-event entries list no recorded events, but detailed event definitions and collection procedures are not reported. These gaps restrict both the statistical interpretation and the ability to assess generalizability beyond the participants and conditions described.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Pilot Study to Assess Effects of Self-Administered Nitrous Oxide (SANO) on Urodynamic Study (UDS) Parameters — NCT05883332.
• Registry record last updated 2026-03-12; status last verified 2026-03.
• Results first posted 2026-03-12.
• 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.

18. Record Summary

NCT05883332 is a completed, randomized, triple-masked Phase 4 crossover pilot sponsored by Beth Israel Deaconess Medical Center. It enrolled 19 participants with lower urinary tract symptoms. Each participant underwent consecutive oxygen and SANO urodynamic runs on a single study day, with a 2-minute washout.

The primary outcome was maximum bladder capacity. The registry reports condition-specific medians and interquartile ranges but no inferential primary comparison. It reports an unadjusted detrusor-overactivity comparison as a secondary result; numerical results for most other listed secondary outcomes are not reported. No serious or other adverse events or deaths are recorded in either run condition.

Important details—including the primary statistical analysis, missing-data handling, analysis populations, and multiplicity plan—are not reported in the registry record. The posted primary data are descriptive and do not establish whether the conditions differ or are equivalent.