An Automated Hardware-in-Loop Testbed for Evaluating Hemorrhagic Shock Resuscitation Controllers

Abstract

Hemorrhage remains a leading cause of death, with early goal-directed fluid resuscitation being a pillar of mortality prevention. While closed-loop resuscitation can potentially benefit this effort, development of these systems is resource-intensive, making it a challenge to compare infusion controllers and respective hardware within a range of physiologically relevant hemorrhage scenarios. Here, we present a hardware-in-loop automated testbed for resuscitation controllers (HATRC) that provides a simple yet robust methodology to evaluate controllers. HATRC is a flow-loop benchtop system comprised of multiple PhysioVessels which mimic pressure-volume responsiveness for different resuscitation infusates. Subject variability and infusate switching were integrated for more complex testing. Further, HATRC can modulate fluidic resistance to mimic arterial resistance changes after vasopressor administration. Finally, all outflow rates are computer-controlled, with rules to dictate hemorrhage, clotting, and urine rates. Using HATRC, we evaluated a decision-table controller at two sampling rates with different hemorrhage scenarios. HATRC allows quantification of twelve performance metrics for each controller configuration and scenario, producing heterogeneous results and highlighting the need for controller evaluation with multiple hemorrhage scenarios. In conclusion, HATRC can be used to evaluate closed-loop controllers through user-defined hemorrhage scenarios while rating their performance. Extensive controller troubleshooting using HATRC can accelerate product development and subsequent translation.

Hardware-in-Loop Comparison of Physiological Closed-Loop Controllers for the Autonomous Management of Hypotension

“…Logic was modified to a target pressure of 65 mmHg and each step in the logic was proportional to the max flow rate (Q Max ) for HATRC infusion—500 mL/min—and target pressure (P Target ). From previous work, the logic was found to be incapable of reaching the target in severe hemorrhage scenarios [ 21 ], so it was adjusted as highlighted in Table 1 for the aggressive and conservative DT tuning. Due to the nature of DT logic, it was not as objectively tuned as the other three controller types.…”

“…To physiologically imitate volume responsiveness of swine during various hemorrhaging scenarios, a Hardware-in-loop Automated Testbed for Resuscitation Controllers (HATRC) was utilized [ 21 , 24 ]. The HATRC consisted of a closed loop system, circulating water via a peristaltic pump at 145 mL/min and monitored through a pressure transducer (ICU Medical, San Clemente, CA, USA).…”

“…A series of metrics was used to assess the performance of each PCLC in handling the four test scenarios. Some of these were as described by Varvel [ 29 ], Mirinejad [ 30 ], Marques [ 22 ], and the International Electrotechnical Commission [ 31 ], others are modifications of those same metrics, and another set we introduced in a previous work [ 21 , 24 ]. For aggregate metrics, unitless or percentage-based metrics were preferred, so normalization methods are detailed below when they were required.…”

“…The goal for this effort was to determine, as objectively as possible, which of the many possible controllers demonstrate the best performance, making it favorable for further development. Towards this, we use the HATRC test platform we previously developed for hardware-in-loop testing of controllers through a range of hemorrhage scenarios [ 21 ]. We propose a series of aggregate metrics tuned to different controller performance features for inter-controller comparisons across various testing scenarios.…”

Adaptive closed‐loop resuscitation controllers for hemorrhagic shock resuscitation

“…Accordingly, we have designed a new set of controllers that are more robust to diverse patient presentations in various hemorrhagic shock scenarios as embodied in our Hardware-in-Loop Automated Testbed for Resuscitation Controllers (HATRC) system. 6 These new adaptive resuscitation controllers (ARCs) dynamically adjust their performance to the patient's responsiveness to fluid infusion during resuscitation. In this article, we first optimize the performance of the ARCs, then compare their execution against that of our previously developed dual-input fuzzy-logic controller, itself the best performer of a series of traditional control systems.…”