Robust predictive control for respiratory CO2 gas removal in closed-loop mechanical ventilation: an in-silico study

In this study a physiological closed-loop system for arterial CO2 partial pressure control was designed and comprehensively tested using a set of models of the respiratory CO2 gas exchange. The underlying preclinical data were collected from 12 pigs in presence of severe changes in hemodynamic and pulmonary condition. A minimally complex nonlinear state space model of CO2 gas exchange was identified post hoc in different lung conditions. The control variable was measured noninvasively using the endtidal CO2 partial pressure. For the simulation study the output signal of the controller was defined as the alveolar minute volume set value of an underlying adaptive lung protective ventilation mode. A linearisation of the two-compartment CO2 gas exchange model was used for the design of a model predictive controller (MPC). It was augmented by a tube based controller suppressing prediction errors due to model uncertainties. The controller was subject to comparative testing in interaction with each of the CO2 gas exchange models previously identified on the preclinical study data. The performance was evaluated for the system response towards the following five tests in comparison to a PID controller: recruitment maneuver, PEEP titration maneuver, stepwise change in the CO2 production, breath-hold maneuver and a step in the reference signal. A root mean square error of 2.69 mmHg between arterial CO2 partial pressure and the reference signal was achieved throughout the trial. The reference-variable response of the model predictive controller was superior regarding overshoot and settling time

Development of a Novel Low-cost Lung Function Simulator

In order to test medical devices, industry increasingly uses simulators closely reassembling the behaviour of physiological systems. In the context of respiratory therapy, most available simulators are designed based on a ventilated volume. This highly adjustable volume allowing for fast dynamical changes often leads to very costintensive test devices, particularly when incorporating realistic spontaneous breathing. Therefore, in this article we introduce a novel concept for a low-cost lung simulator, capable of mimicking the ventilation behaviour of the human lung at the Y-piece of a mechanical ventilator. The proposed design does not require any enclosed spaces to hold inhaled air nor expensive precise linear actuators adjusting its volume. Instead, the setup is designed based on the design of a mechanical ventilator, connecting the system with one port to the ventilator and then dividing the hose into two independent branches. Each branch has an integrated radial fan and a proportional valve, controlling the inspiratory and expiratory flow, individually. The mass flow and pressure are measured at the systems inlet port, representing the condition at patient airway. In contrast to existing setups, the proposed design is not limited by the physical properties of a volume such as fixed maximum size, allowing the simulation of various types of patients and conditions. Numerical simulations to evaluate this system design showed the ability to generate a realistic spontaneous breathing pattern. With a first experimental setup it was possible to prove the feasibility of this approach, by generating common flow curves during spontaneous breathing. Building on this design, the approach could eventually lead to a more accessible method for testing

Towards Dual-Use Training Simulator in Interventional Neuroradiology

Cerebral aneurysms are common lesions in the general population and are increasingly treated by endovascular procedures. Training of these methods not only improves the learning period of physicians but also increases patient safety. However, the use of traditional medical training methods such as training in living animal models is decreasing due to high costs and ethical issues, so computer simulations and 3D-printed phantoms are being used instead. A more realistic simulation requires pulsatile blood flow that can be customized and has body temperature. Current simulators that use 3D-printed phantoms are mainly used under X-Ray in an angiography intervention room, therefore a dual-use simulator that is easy to transport and can be used also without X-Ray is desirable. Either it could be used traditionally in an angiography intervention room or externally in any regular room with an image simulation according to rotational angiography. In this work, a prototype for blood flow simulation is presented as a first step towards such simulator and its application is demonstrated through different investigations. The fluid system is capable of simulating a given blood flow profile and the heating system can generate an accurate body temperature. The case can be easily integrated into a modular phantom system and is convenient to transport, although the weight could be further reduced

Robust predictive control for respiratory CO2 gas removal in closed-loop mechanical ventilation: An in-silico study

In this study a physiological closed-loop system for arterial CO2 partial pressure control was designed and comprehensively tested using a set of models of the respiratory CO2 gas exchange. The underlying preclinical data were collected from 12 pigs in presence of severe changes in hemodynamic and pulmonary condition. A minimally complex nonlinear state space model of CO2 gas exchange was identified post hoc in different lung conditions. The control variable was measured noninvasively using the endtidal CO2 partial pressure. For the simulation study the output signal of the controller was defined as the alveolar minute volume set value of an underlying adaptive lung protective ventilation mode. A linearisation of the two-compartment CO2 gas exchange model was used for the design of a model predictive controller (MPC). It was augmented by a tube based controller suppressing prediction errors due to model uncertainties. The controller was subject to comparative testing in interaction with each of the CO2 gas exchange models previously identified on the preclinical study data. The performance was evaluated for the system response towards the following five tests in comparison to a PID controller: recruitment maneuver, PEEP titration maneuver, stepwise change in the CO2 production, breath-hold maneuver and a step in the reference signal. A root mean square error of 2.69 mmHg between arterial CO2 partial pressure and the reference signal was achieved throughout the trial. The reference-variable response of the model predictive controller was superior regarding overshoot and settling time

The HEV Ventilator: at the interface between particle physics and biomedical engineering.

A high-quality, low-cost ventilator, dubbed HEV, has been developed by the particle physics community working together with biomedical engineers and physicians around the world. The HEV design is suitable for use both in and out of hospital intensive care units, provides a variety of modes and is capable of supporting spontaneous breathing and supplying oxygen-enriched air. An external air supply can be combined with the unit for use in situations where compressed air is not readily available. HEV supports remote training and post market surveillance via a Web interface and data logging to complement standard touch screen operation, making it suitable for a wide range of geographical deployment. The HEV design places emphasis on the ventilation performance, especially the quality and accuracy of the pressure curves, reactivity of the trigger, measurement of delivered volume and control of oxygen mixing, delivering a global performance which will be applicable to ventilator needs beyond the COVID-19 pandemic. This article describes the conceptual design and presents the prototype units together with a performance evaluation