Hypothesis / aims of study
Air-charged urodynamic catheters measure pressures in the bladder, urethra, and abdomen via a microvolume of trapped air within a small inflatable balloon. Unlike water-filled systems, this technology is capable of simultaneously reducing pressure artefacts while speeding up the setup [1]. Recently, a novel air-charged catheter was developed and put into preliminary clinical use. T-DOC® NXT air-charged catheters have been redesigned to improve pressure offset, along with the introduction of a patent-protected charge mechanism to enable a streamlined workflow. The aim of this study is to evaluate the clinical safety and efficacy of T-DOC® NXT air-charged catheters, while also exploring usability advancements in tracing quality and clinical workflow as well as patient satisfaction. We hypothesize that the novel catheter’s performance is considered clinically adequate if safety and subjective efficacy success rates exceed 75 percent.
Study design, materials and methods
A 20-patient pre-market, single-arm, single-center human clinical study was conducted from July to October 2018. The study recruited adult patients with a clinical indication for urodynamic testing. An institutional review board approved the study and patients’ informed consent were obtained prior to performing urodynamic testing. Study objectives were to qualify the safety, effectiveness, usability, and patient satisfaction using subjective data collection of the investigator, clinician, and patients. Further, adverse event data was collected to report on safety of the product and procedure.
For each patient, the investigator evaluated the T-DOC® NXT catheters based on a yes-no questionnaire, which was used in a one-sided binomial test to evaluate the subjective experience of safety and efficacy. To assess usability, the clinician (user) evaluated the catheter on two parameters; quality of the pressure tracing and efficiency of the workflow. In addition, each patient reported their level of discomfort and were asked if they were willing to repeat the procedure if medically necessary.
Both usability parameters were graded on a 5-point rating scale. The first parameter, tracing quality, compared the T-DOC® NXT catheters to previous air-charged catheters based on the smoothness and stability of the pressure tracing, the quality of vesical and abdominal pressure subtraction, and the sensitivity of artefact detection. The second parameter, workflow efficiency, was comparatively rated at several steps in the workflow. The instructions for use (IFU) workflow step was ranked non-comparatively according to the user’s level of difficulty following the instructions, ranging from difficult to easy. Lastly, patient discomfort was evaluated using a numerical pain rating scale (NPRS) during four stages of the procedure; catheter insertion, bladder filling, catheter removal, and urethral pressure profilometry (UPP) measurements (where applicable). The NPRS ranged from 0 (no pain) to 10 (worst pain), and 5-point comparative rating scales ranged from 1 (worse than) to 5 (better than). All scores are reported as the mean.
Results
A total of 20 adult female (n = 17) and male (n = 3) patients (aged 34 to 84 years) successfully completed the study. All procedures were performed using T-DOC® NXT single and dual sensor bladder and abdominal air-charged catheters. For twelve non-consecutive days, a trained clinician performed cystometry on all patients (n = 20) and UPP on a subset of patients (n = 5).
In all 20 questionnaires, the investigator deemed the T-DOC® NXT catheters as safe and effective, and the binomial test revealed that both success rates exceeded 75 percent (p = 0.003). Both usability parameters averaged to 3.0 or higher overall. All tracing quality ratings were above 3.0 but less than 4.0 (Figure 1). Tracing smoothness scored the lowest during UPP (3.4) and the highest during bladder filling (3.8). Both pressure subtraction quality and artefact detection sensitivity received high ratings (3.8). Workflow efficiency also rated favorably, with overall impact to workflow scoring 4.0 (Figure 2). Catheter removal and securing to the patient received the lowest ratings (3.0 and 3.1 respectively), and test setup and zeroing received the highest (4.3). We observed a normalization of ratings at 3.0 or 4.0 after five days except for setup and cleanup time, whose ratings fluctuated between 3.0 and 4.0 throughout the study. Time savings for setup and cleanup equated to 1-2 minutes per day. Readability of the IFU scored 5.0 for eleven of the twelve days; day three received a rating of 3.0. All patients rated their perceived pain at or below the midpoint of 5.0 during each stage in the procedure, with a mean rating of 0.9 for all stages. Combined bladder and rectal catheter insertion had the highest pain rating (1.3), while catheter removal had the lowest (0.6). Insertion and removal in the rectum had considerably lower ratings than in the bladder. When patients were asked if they would undergo the procedure again, 85 percent agreed yes. No adverse events were reported.
Interpretation of results
An overall usability rating between 3.0 and 4.0 indicates that the T-DOC® NXT catheters were at least as easy to use as previous air-charged catheters. All aspects of pressure tracing quality were considered equivalent. The learning curve for use was short, as most workflow steps leveled out at a rating of 3.0 or 4.0 before the half-way point of the study. Historically, the methods for air-charged catheters were challenging because of the complicated quality checks required for pressure offset. Conversely, the IFU for the T-DOC® NXT catheters were perceived as easy to read and understand, suggesting that the new charge mechanism simplified the workflow. Patient satisfaction was demonstrated by the moderately low pain ratings and high percentage of patients willing to repeat the test.