Assessment of Intra-Abdominal Pressure with a Novel Continuous Bladder Pressure Monitor-A Clinical Validation Study

Abstract

Introduction: Intra-abdominal hypertension and the resulting abdominal compartment syndrome are serious complications of severely ill patients. Diagnosis requires an intra-abdominal pressure (IAP) measurement, which is currently cumbersome and underused. We aimed to test the accuracy of a novel continuous IAP monitor.

Methods: Adults having laparoscopic surgery and requiring urinary catheter intra-operatively were recruited to this single-arm validation study. IAP measurements using the novel monitor and a gold-standard foley manometer were compared. After anesthesia induction, a pneumoperitoneum was induced through a laparoscopic insufflator, and five randomly pre-defined pressures (between 5 and 25 mmHg) were achieved and simultaneously measured via both methods in each participant. Measurements were compared using Bland-Altman analysis.

Results: In total, 29 participants completed the study and provided 144 distinct pairs of pressure measurements that were analyzed. A positive correlation between the two methods was found (R² = 0.93). There was good agreement between the methods, with a mean bias (95% CI) of -0.4 (-0.6, -0.1) mmHg and a standard deviation of 1.3 mmHg, which was statistically significant but of no clinical importance. The limits of agreement (where 95% of the differences are expected to fall) were -2.9 and 2.2 mmHg. The proportional error was statistically insignificant (p = 0.85), suggesting a constant agreement between the methods across the range of values tested. The percentage error was 10.7%.

Conclusions: Continuous IAP measurements using the novel monitor performed well in the clinical setup of controlled intra-abdominal hypertension across the evaluated range of pressures. Further studies should expand the range to more pathological values.

Keywords: abdominal compartment syndrome; foley manometer; intra-abdominal hypertension; intra-abdominal pressure monitoring.

Figure 1

Study system design (not to scale). A—Insufflator—allows setting a pre-defined abdominal pressure during the study. B—Study device control unit—mounted on a pole or bed-rail. Can be placed anywhere near the bed or move with the patient. C—Tube from CO₂ insufflator to the surgical port. D—Classic fluid column manometer measures intra-vesical pressure via a Foley catheter. E—Surgical port into the peritoneal cavity. F—Mid-axillary line (reference level). G—Urinary bladder. H—Urine collection bag. I—Study device disposable measurement unit, located between the Foley catheter and urine bag, and transmitting pressures to the controller.

Figure 2

Study flow-chart.

Figure 3

Scatter-plot of acceptance between the two measurement methods.

Figure 4

Bland–Altman analysis. The Y-axis shows the difference between measurements made by the study device minus those of the foley manometer, and the X-axis presents the means of measurements via both methods. The red line represents the mean bias (-0.4 mmHg), and green lines represent the upper and lower limits of agreement (2.2 and -2.9 mmHg, respectively).