From Benchtop to Beside: Patient-specific Outcomes Explained by Invitro Experiment

Study: Recent analyses show that females have higher early postoperative (PO) mortality and right ventricular failure (RVF) than males after left ventricular assist device (LVAD) implantation; and that this association is partially mediated by smaller LV size in females. Benchtop experiments allow us to investigate patient-specific (PS) characteristics in a reproducible way given the fact that the PS anatomy and physiology is mimicked accurately. With multiple heart models of varying LV size, we can directly study the individual effects of titrating the LVAD speed and the resulting bi-ventricular volumes, shedding light on the interplay between LV and RV as well as resulting inter-ventricular septum (IVS) positions, which may cause the different outcomes pertaining to sex. Methods: In vitro, we studied the impact of the heart size to IVS position using two smaller and two larger sized PS silicone heart phantoms derived from clinical CT images (Fig. 1A). With ultrasound crystals that were integrated on a placeholder inflow cannula, the IVS position was measured during LV and RV volume changes (dV) mimicking varying ventricular loading states (Fig. 1B). Figure 1 A Two small (blue) and two large PS heart phantoms (orange) on B benchtop. C Median septum curvature results. LVEDD/LVV/RVV: LV enddiastolic diameter/LV and RV volume. Results: Going from small to large dV, at zero curvature, the septum starts to shift towards the left; for smaller hearts at dV = -40 mL and for larger hearts at dV = -50 mL (Fig. 1C). This result indicates that smaller hearts are more prone to an IVS shift to the left than larger hearts. We conclude that smaller LV size may therefore mediate increased early PO LVAD mortality and RVF observed in females compared to males. Novel 3D silicone printing technology enables us to study accurate, PS heart models across a heterogeneous patient population. PS relationships can be studied simultaneously to clinical assessments and support the decision-making prior to LVAD implantation

Systematic Design, Control and Parametric Testing of an Automated Resuscitator Bag Mechanical Ventilator

The COVID-19 crisis has revealed and exacerbated a shortage of mechanical ventilators in hospitals around the world, regardless of their government’s resources. Where some countries can respond to the situation by ordering more high-end ventilators, the price is often too high for low- and middle-income countries (LMICs) and securing them can be difficult. The goal of this work is to design, prototype, and test a low-cost ventilator, called ETH breathe, based on the automated compression of a resuscitator bag. A holistic and systematic design approach is taken to create a compact and adaptable device that can safely meet the current requirements. This is achieved by using 72% standard parts out of 33 (72%) and prioritizing compactness in the mechanical design. The control system is developed to provide both continuous mandatory ventilation (CMV) and spontaneous breathing support or assist control (AC), which significantly extends the potential use cases beyond patient sedation. The prototype is tested for accuracy, modularity, and oxygen response using a full physiological artificial lung. The results show for the first time in literature that the design operates within the defined requirements, based on emergency government regulations, and can be used with different sizes of resuscitator bags and different positions of the flow sensor. This provides a sound basis for further development of a low-cost, portable mechanical ventilator for potential use in LMICs.ISSN:1050-0472ISSN:1528-900