Introduction: Intra-abdominal pressure (IAP) has been recognized as an important vital sign in critically ill patients. Due to the high prevalence and incidence of intra-abdominal hypertension in surgical (trauma, burns, cardiac) and medical (sepsis, liver cirrhosis, acute kidney injury) patients, continuous IAP (CIAP) monitoring has been proposed. This research was aimed at validating a new CIAP monitoring device, the TraumaGuard from Sentinel Medical Technologies, against the gold standard (height of a water column) in an in vitro setting and performing a comparative analysis among different CIAP measurement technologies (including two intra-gastric and two intra-bladder measurement devices). A technical and clinical guideline addressing the strengths and weaknesses of each device is provided as well. Methods: Five different CIAP measurement devices (two intra-gastric and three intra-vesical), including the former CiMON, Spiegelberg, Serenno, TraumaGuard, and Accuryn, were validated against the gold standard water column pressure in a bench-top abdominal phantom. The impacts of body temperature and bladder fill volume (for the intra-vesical methods) were evaluated for each system. Subsequently, 48 h of continuous monitoring (n = 2880) on top of intermittent IAP (n = 300) readings were captured for each device. Using Pearson's and Lin's correlations, concordance, and Bland and Altman analyses, the accuracy, precision, percentage error, correlation and concordance coefficients, bias, and limits of agreement were calculated for all the different devices. We also performed error grid analysis on the CIAP measurements to provide an overview of the involved risk level due to wrong IAP measurements and calculated the area under the curve and time above a certain IAP threshold. Lastly, the robustness of each system in tracking the dynamic variations of the raw IAP signal due to respirations and heartbeats was evaluated as well. Results: The TraumaGuard was the only technology able to measure the IAP with an empty artificial bladder. No important temperature dependency was observed for the investigated devices except for the Spiegelberg, which displayed higher IAP values when the temperature was increased, but this could be adjusted through recalibration. All the studied devices showed excellent ability for IAP monitoring, although the intra-vesical IAP measurements seem more reliable. In general, the TraumaGuard, Accuryn, and Serenno showed better accuracy compared to intra-gastric measurement devices. On average, biases of +0.71, +0.93, +0.29, +0.25, and -0.06 mm Hg were observed for the CiMON, Spiegelberg, Serenno, TraumaGuard, and Accuryn, respectively. All of the equipment showed percentage errors smaller than 25%. Regarding the correlation and concordance coefficients, the Serenno and TraumaGuard showed the best results (R2 = 0.98, p = 0.001, concordance coefficient of 99.5%). Error grid analysis based on the Abdominal Compartment Society guidelines showed a very low associated risk level of inappropriate treatment strategies due to erroneous IAP measurements. Regarding the dynamic tracings of the raw IAP signal, all the systems can track respiratory variations and derived parameters; however, the CiMON was slightly superior compared to the other technologies. Conclusions: According to the research guidelines of the Abdominal Compartment Society (WSACS), this in vitro study shows that the TraumaGuard can be used interchangeably with the gold standard for measuring continuous IAP, even in an empty artificial bladder. Confirmation studies with the TraumaGuard in animals and humans are warranted to further validate these findings.
Keywords: bladder fill volume; error grid analysis; intra-abdominal pressure; intra-gastric pressure; intra-vesical pressure; temperature dependency.