Vacuum-Assisted Dressings (V-AD) in the Management of Open Chest Wounds: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Vacuum-Assisted Dressings (V-AD) in the Management of Open Chest Wounds (NCT02803164), a non-randomized na study. The primary outcome is Duration of Negative Pressure Wound Therapy (NWPT).

2. Clinical Question

The study concerns patients with open chest wounds and asks about the duration of negative pressure wound therapy (NWPT) after treatment with a vacuum-assisted dressing. The registry describes eligible subjects receiving the dressing during surgery. Its stated rationale is that vacuum-assisted dressings might reduce time to wound closure compared with traditional wound care, but the registered primary endpoint is the duration of NWPT, not a reported comparison of time to closure.

The study is registered as a pilot with non-randomized allocation and a single-group model. Although historical controls are described, they do not provide a randomized, concurrent comparison. The registry itself flags that the arms are not a like-for-like control comparison. Consequently, the stated treatment rationale and the registered primary endpoint should not be conflated: the rationale refers to time-to-closure, while the primary endpoint measures the duration of NWPT. Wound closure is listed as a secondary outcome, but no result for it is reported in the registry record.

3. Trial Design

This completed pilot study, NCT02803164, is titled “Vacuum-Assisted Dressings (V-AD) in the Management of Open Chest Wounds.” Mayo Clinic is listed as the sponsor. The recorded phase is NA. Enrollment is 21, and the condition is open chest wounds. The study start date is 2017-02-10 and the primary completion date is 2020-11-03.

The design is classified as non-randomized, unmasked, and single-group. The intervention is a device, described as a wound vacuum-assisted dressing. Eligible subjects were to receive negative pressure wound therapy during surgery. A historical control group was assembled by retrospective review of medical records for patients with open chest wounds managed using traditional treatment techniques. Thus, the record describes a historical comparison while classifying the study model as single-group.

This distinction matters for interpretation. Random assignment is not reported, and the intervention and historical control groups were not enrolled and followed as a concurrent randomized comparison. The registry explicitly warns that the arms are not a like-for-like control comparison. Differences between groups, if reported, could therefore reflect differences in patient characteristics, care practices, or record ascertainment as well as any difference associated with treatment. The registry does not provide details that would allow those possibilities to be assessed.

The primary endpoint is median duration of NWPT in days over a stated 12 month follow up. Wound closure and length of hospital stay are listed as secondary outcomes. The registry identifies three outcome measures, but results for the primary endpoint and secondary outcomes are not reported in the registry record. It also reports zero analyses. A protocol-level sample-size justification, detailed statistical plan, interim analyses, and masking procedures beyond the designation of none are not reported in the registry record.

4. Participant Flow and Accounting

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

Overall Study

Analysis population for the primary outcome, as defined in the registry: Data not collected or analyzed for the Historical Control arm. This arm did not receive the NWPT.

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: 21 completed

6. Primary Endpoint

The registry lists the primary outcome as Duration of Negative Pressure Wound Therapy (NWPT), measured over 12 month follow up.

The primary endpoint is the duration of negative pressure wound therapy, measured as the total number of days a participant received NWPT. The registry specifies that the result is to be summarized by the median and full range, with a timeframe of 12 month follow up. A median describes the middle of the observed values after they are ordered. The full range describes the smallest and largest values, giving a sense of the spread but not showing how values are distributed between those extremes.

Duration is a clinically interpretable measure of how long the wound-vacuum treatment was used. In general, duration outcomes can be useful when the amount of time receiving a treatment is relevant to care or resource use. However, the endpoint should be read as treatment duration, not as time to wound closure. The study rationale mentions time-to-closure, and wound closure is listed as a secondary outcome, but those are distinct measures. The registry does not report a closure result or a primary endpoint value.

The registry says primary endpoint data were not collected or analyzed for the historical control arm because that arm did not receive NWPT. This means the endpoint, as defined, cannot make a direct treatment-duration comparison between the intervention and historical control groups. The record does not report how many intervention participants contributed endpoint data, the median, the full range, or any handling of incomplete observations. Those details are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical interpretation depends on the outcome definition, the comparison design, and the results actually reported. For this study, the registry identifies median duration of NWPT as the primary endpoint, describes a historical control, and records non-randomized allocation. It does not report an endpoint value, comparative estimate, confidence interval, or analysis result. General statistical explanations below describe how such quantities are ordinarily interpreted; they do not describe unreported methods used in this study.

Why use a median and range?

In general, a median is a measure of the center of observed values that is less influenced by unusually high or low observations than a mean. It can be useful for duration data when values are unevenly distributed. A full range gives the observed endpoints of the data, but it does not show whether most observations cluster near the median or are spread throughout the interval. Interpreting a reported median would therefore benefit from information about the number of participants analyzed and the distribution of their durations. Those results are not reported in the registry record.

The endpoint is duration of NWPT, not time to wound closure. General time-to-event methods are designed for outcomes defined by the time until a specified event, and can accommodate observations for which the event has not been observed by the end of follow-up through censoring methods. The registry's statement that the primary endpoint is median duration does not itself establish that a time-to-event analysis was performed. The record does not report a time-to-event estimate, a hazard ratio, or an analysis method for this endpoint. It would be inappropriate to infer one from the outcome's duration wording.

What does a confidence interval communicate?

In general, a confidence interval expresses statistical uncertainty around an estimated quantity under the assumptions of the analysis. A narrower interval indicates greater precision than a wider interval, but interpretation also depends on the outcome, design, and validity of assumptions. A confidence interval does not correct bias from non-random allocation or differences between a prospective intervention group and a retrospective historical group. No confidence interval is reported for the primary endpoint or a comparative outcome in the registry record, so the precision of an effect estimate cannot be assessed.

Why does the comparison design matter?

Randomization, in general, helps make comparison groups similar in expectation with respect to measured and unmeasured baseline factors. Here, allocation is recorded as non-randomized, and the comparator is a historical group assembled by chart review. The registry warns that the arms are not a like-for-like control comparison. If a group difference were reported, it could reflect differences in who entered each group, how care was delivered, or how outcomes were recorded. Statistical adjustment can sometimes address measured differences, but it cannot guarantee removal of unmeasured confounding. The registry does not report an adjustment strategy or a comparative analysis.

The primary endpoint also has an important comparator limitation: historical controls did not receive NWPT, and the record says their primary endpoint data were not collected or analyzed. Therefore, a comparison of NWPT duration across these arms is not available. It is not possible to infer a comparative treatment effect from a measure that is defined as days receiving a treatment and is not collected for the group that did not receive it.

What can planning calculations tell readers?

In general, sample-size planning calculations illustrate how much information might be needed to detect a specified effect under stated assumptions. They depend on assumptions about the effect, variability, significance level, allocation, and statistical model. They are planning illustrations, not observed power and not evidence that the planned effect occurred. The registry's stated illustration assumptions use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. The record says that time-to-event sample-size tables give the total number of events, while other calculations give participants per arm. These are illustrations computed from an observed effect, not the trial's own design justification. The observed effect values and a protocol-level sample-size justification are not reported in the registry record.

Because the record reports zero analyses and supplies no outcome estimates, no recalculated unadjusted estimate can be meaningfully interpreted from the posted registry results. General re-calculations from summary statistics, when available, are not substitutes for the sponsor's own analysis. The registry record does not report a sponsor analysis for comparison. There is also no basis to claim observed power: power is a design concept, while the planning illustrations describe hypothetical assumptions and do not establish the probability that this completed study detected a real effect.

Why can over-dispersion matter?

In general, over-dispersion occurs when outcome variability exceeds what a statistical model assumes. If ignored, standard errors can be too small and uncertainty can be understated. This concept is relevant to count outcomes when their variability is greater than a simple count model expects, but the registry does not report a count-outcome analysis or a model that can be assessed for over-dispersion. It is therefore a general consideration, not a finding about this study.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures: the primary endpoint, wound closure, and length of hospital stay. Listing multiple outcomes raises a general statistical issue called multiplicity: when several hypotheses are tested, the chance of at least one apparently unusual result can increase unless the analysis plan addresses the issue. The record does not report whether any multiplicity adjustment was planned or applied. It also reports zero analyses, so there are no registered p-values or outcome-specific estimates to evaluate.

The registry identifies the primary endpoint as duration of NWPT and gives its timeframe as 12 month follow up. The result itself is not reported. The record says data were not collected or analyzed for the historical control arm because that group did not receive NWPT. Results for wound closure and length of hospital stay are also not reported in the registry record. It is not possible to determine from the registered information whether these outcomes were measured, whether their definitions were specified in greater detail, or whether any analyses were conducted outside the registry record.

Missing-data handling is not reported in the registry record. There is no account of incomplete follow-up, exclusions from outcome analyses, imputation, censoring, or sensitivity analyses. These omissions matter because incomplete outcome information can affect both the estimate and its uncertainty, especially if missingness differs across groups or relates to outcome status. This is a general concern, not a claim that missing data occurred in this study.

Analysis populations are also not described in detail. The record does not report which enrolled participants were included in each outcome analysis or how participants with unavailable measurements were handled. The enrollment is 21, but enrollment alone does not establish the number analyzed for any endpoint. Without analysis-population details, outcome definitions, and results, readers cannot assess how completely the reported outcomes represent the enrolled participants. No protocol-specific multiplicity or missing-data method should be inferred from the registry record.

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 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: sepsis (63.6%), reintubation (18.2%), hemothorax (10.0%), major cardiac event (9.1%), air embolism (9.1%).

The registry lists serious adverse events for the intervention group with 10 at risk and 2 affected, and for the historical control group with 11 at risk and 11 affected. Other adverse events are listed for 10 at risk and 2 affected in the intervention group, and 11 at risk and 8 affected in the historical control group. Deaths are listed as 2 in the intervention group and 1 in the historical control group. These are descriptive registry counts; they are not, by themselves, a causal comparison.

The serious adverse event terms include Sepsis at 63.6%, Reintubation at 18.2%, Hemothorax at 10.0%, Major cardiac event at 9.1%, Air Embolism at 9.1%, and Acute Respiratory Distress Syndrome at 9.1%. The registry record does not report the calculation details for these percentages, including their precise denominator or whether participants could contribute more than one event. They should therefore be read as the listed term-specific percentages rather than converted into event counts or compared as rates.

General safety interpretation requires attention to how events were defined, collected, and followed, as well as participants' time at risk. Those details and adjusted comparisons are not reported in the registry record. The intervention and historical control groups were not randomized and are explicitly described as not like-for-like. Differences in the counts cannot establish that the dressing caused, prevented, or changed the frequency of adverse events. The death counts also do not establish a treatment effect or explain the circumstances of the deaths.

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

The registry record documents a completed pilot study of vacuum-assisted dressings for open chest wounds, with enrollment of 21, and describes an intervention alongside a retrospective historical control group. It identifies duration of NWPT as the primary endpoint and lists wound closure and length of hospital stay as secondary outcomes. These details clarify what the study was intended to examine, but the record does not provide the outcome values needed to judge what the study observed.

In particular, the primary endpoint result is not reported. The historical control group did not receive NWPT, and the registry says its primary endpoint data were not collected or analyzed. The record also gives no result for wound closure or length of hospital stay, and reports zero analyses. There is no reported effect estimate, confidence interval, p-value, or comparative model result. Thus, the posted registry record does not show whether treatment duration or wound closure differed between groups, nor how precisely any difference was estimated.

The study rationale describes an expected reduction in time-to-closure, but a stated expectation is not a result. Time-to-closure and duration of NWPT are different outcomes, and the registry names wound closure as secondary rather than primary. No conclusion about either outcome can be drawn from the absence of a reported result. Lack of a posted estimate is not evidence that the intervention had no effect, just as the rationale is not evidence that it had an effect.

The design limits interpretation of any group comparison that might be available elsewhere. Allocation was non-randomized, the comparator was historical, and the record cautions that the arms are not a like-for-like comparison. Those features leave potential for confounding and differences in outcome ascertainment. The registry does not report analytic methods that could quantify or address these concerns.

The safety counts provide a descriptive record of adverse events and deaths but do not establish causation. Taken together, the registered information describes the study structure and safety entries, while leaving efficacy outcomes and statistical uncertainty unreported. It cannot support a treatment recommendation or a conclusion about comparative benefit or harm.

13. Why This Trial Matters Statistically

This study is statistically notable because its motivating comparison and its registered primary endpoint are not the same question. The rationale refers to time-to-closure, while the primary endpoint is duration of NWPT. Wound closure is listed as a secondary outcome. Keeping those outcomes distinct is essential: the amount of time a treatment is received is not interchangeable with the time until a wound closes.

The historical control creates another important interpretive issue. The comparator was assembled retrospectively from medical records, while eligible intervention subjects were to receive NWPT during surgery. The study was non-randomized, and the registry explicitly warns that the arms are not a like-for-like comparison. This makes the design useful to discuss as a pilot, but it also means that a simple group contrast would not automatically isolate a treatment effect. Patient selection, clinical practices, and documentation could differ between groups; the record does not report how these possibilities were handled.

The primary endpoint is also not available for the historical controls because they did not receive NWPT. This is a structural limitation of comparing treatment duration across groups with different treatment exposure, rather than simply a missing value that can be filled by statistical adjustment. The registry does not report the intervention group's median or full range either, so even a descriptive account of NWPT duration is unavailable from the posted results.

Finally, this record illustrates why completed status and enrollment do not guarantee that outcome estimates are available in a registry entry. It identifies outcomes and adverse event counts, but reports zero analyses and no efficacy estimates. Readers can distinguish the study's question, design, and reported safety entries from the evidence needed to estimate an effect. The resulting uncertainty is not a statistical finding of no effect; it reflects the limited outcome information reported in the registry record.

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.

Several limitations specific to this study follow directly from its registered design and reporting. It is a pilot study with non-randomized allocation, no masking, and a single-group model, while also describing a retrospective historical control. The registry explicitly notes that the arms are not a like-for-like control comparison. Without randomized allocation or reported adjustment methods, any group difference would be vulnerable to confounding and differences in patient selection or care.

The primary endpoint has no reported result. The registry defines it as median duration of NWPT in days, with full range and a 12 month follow up, but does not report the intervention group's median, range, or number analyzed. The historical control did not receive NWPT, and the registry says primary endpoint data were not collected or analyzed for that group. Therefore, the primary endpoint does not furnish a direct comparison across the described groups.

The stated rationale concerns time-to-closure, yet time-to-closure is not the primary endpoint. Wound closure is listed as a secondary outcome, as is length of hospital stay, but neither result is reported in the registry record. The record reports zero analyses, and detailed outcome definitions, analysis populations, missing-data methods, and comparative statistical methods are not reported.

Enrollment is 21, but the registry does not report the number analyzed for each outcome. A protocol-level sample-size justification is not reported, and the planning illustrations are explicitly not the trial's own design justification. The record also does not report details needed to evaluate safety-event ascertainment or the term-specific percentage denominators. These reporting limitations prevent an assessment of efficacy estimates, precision, completeness of follow-up, or the comparability of adverse event counts.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Vacuum-Assisted Dressings (V-AD) in the Management of Open Chest Wounds — NCT02803164.
• Registry record last updated 2021-09-29; status last verified 2021-09.
• Results first posted 2021-09-29.
• 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

NCT02803164 is a completed pilot study sponsored by Mayo Clinic, titled “Vacuum-Assisted Dressings (V-AD) in the Management of Open Chest Wounds.” It enrolled 21 participants with open chest wounds. The study is classified as non-randomized, unmasked, and single-group. The intervention was a wound vacuum-assisted dressing, with negative pressure wound therapy during surgery. A retrospective historical control group received traditional wound-care techniques.

The primary endpoint was median duration of NWPT in days over a stated 12 month follow up, reported as median and full range. The registry says primary endpoint data were not collected or analyzed for the historical control group. Wound closure and length of hospital stay are listed as secondary outcomes. The record reports zero analyses and does not report outcome estimates or comparative efficacy results.

Serious adverse event counts, other adverse event counts, deaths, and selected serious-event terms are listed. The registry cautions that the intervention and historical control groups are not a like-for-like comparison. Accordingly, the record describes study design and selected safety entries, but does not provide the results needed to estimate comparative efficacy or precision.