 Thank you for the introduction Thank you to the profusion conference for inviting me to this. I Will be quick okay, so I Will be presenting Our work in the idea lab, which is our MCL mock circulatory loop used in conjunction with a Vascular model to create a training environment for cardiac surgeons Real quick, I'm gonna give a little introduction background to some of the buzzwords in this really long title Like doctor Brady before me. I'm also probably gonna mansplain a little bit, but I would like everyone to be in the loop And so mock circulatory loops are mechanical representations of the cardiovascular system And they strive to be physiologically and anatomically correct in order to test cardiac assist devices Prior to animal studies So modern MCL technologies are able to recreate sophisticated Pulsatile flow And simulate various heart conditions including rest exercise mild severe heart failure and recreate Autoregulatory mechanisms such as the barrel receptor response and the Frank Starling mechanism So we're exploring the idea of using our in seal technology that we're developing to create an improved training environment for cardiac surgeons and we're doing this by Having our mock circulatory loop pump fluids through a 3d printed silicone vascular structure There is So the vessels of the structure were reconstructed from human MRI and CT data and it uses varying vessel geometries and Thicknesses to or in stiffnesses to recreate flow conditions in a wide variety of major blood vessels So in our lab, we actually have two mock circulatory loops on the left we have our Functioning pneumatic mock circulatory loop that uses compressed air to create pulse tile flow and on the right We have our linear motor driven mock circulatory loop, which is what this presentation is about. This is what's connected to the vascular structure and Right now this MCL recreates or it simulates the left ventricle left atrium and Systemic flow so it's more of a mock left heart at the moment and we've connected this to the vascular structure And we actually have both MCLs in the back on display if anyone is interested So The last little bit. This is probably going to be the most mansplaining But in order to address how the mock circulatory loop is elastance controlled as it said in the title um I first i'm going to just elaborate real quick on the frank on frank starling's law of the heart the heart I'm so sorry That's the stage fright Um according to frank and starling the greater the stretching of the cardiac muscle the greater the force of contraction uh When the heart contracts and so this leads to This also leads to you could also say when volume of preload into the ventricle increases Uh pressures being generated by the force of contraction are also increased And this is important because contractility relates these volumes and pressures and contractility as a function of time Is what we call our elastance function And this elastance function on the right ultimately controls our MCL And what this function is is it's basically two two really long polynomial equations, uh that are put together to create what we have up there and um And uh So the time element on the x-axis it ranges from zero to one Um, which is the time of a heartbeat at 60 beats per minute And this allows us to determine what the pressure volume relationship should be at any given moment during the heartbeat I'd also like to mention briefly the uh motivation for uh developing this mock circulatory or this system, but um but It improves upon existing, uh, we want to improve upon existing in vitro training training environments for cardiovascular surgeons It improves upon existing in vivo models Which is usually animals or cadavers which have logistical ethical and functional limitations and current and also improves on current in vitro models where the generated pulsatile flow is Generally not as sophisticated as modern mcl flows And so now I will discuss the actual mcl so the mcl consists of acrylic chambers that represent the left atrium and the left ventricle And mechanical heart valves for clinical use are used to simulate the aortic and mitral valves in their respective locations Uh, syringes are attached to the rigid chambers to add some compliance and a linear motor driven piston Is what creates pulsatile flow in the system? Okay so There was originally a little video of the mock circulatory that isn't there right now So if you would like to see it pump them, it's back there, but On the left is a little block diagram Uh of fluid flow in the system Uh, so following the left ventricle and aortic valve is our vascular structure And following that a clamp stimulates or simulates systemic vascular resistance and following that a compliance chamber simulates systemic vascular compliance Not as interesting I'll briefly go over the the engineering that went into the electrical and control side of the project But lab view controls the system using an n i data acquisition device disposable pressure sensors measure pressure in the aorta and left ventricle and displacement sensors Help us determine the volume of fluid that's inside of each ventricle and motor drivers receive instructions from our controller and then send a signal to the linear motors to control them So control of the mcl is actually really interesting. So as I mentioned, we do use lab view And within lab view, we're using the elastance function that I mentioned earlier to create a theoretical pressure volume loop And on this graph that is the dotted line And the solid line is our experimental pressure volume loop that is attempting to follow the theoretical pressure volume loop And so Based on the time between zero and one second There is a certain value for contractility that the mock circulatory loop should be at and because Contractility relates pressure and volume. We're able to create this theoretical pressure volume loop and rp ad controller attempts to follow And it follows decently. Well, actually So These are the results of our mcl Alone which the results are very promising the pv loop is The the pressure range is good It reaches the uppers and the lowers and the ordered pressure is approximately 120 over 80 and aside from some noise When pressure starts descending, it's really solid and the frank starling curve. We actually were able to obtain which uh, we were able to obtain this frank starling curve by slowly adjusting preload of A fluid preload into the left ventricle as we ran continuous pressure volume loops and As you can see as preload increase so did pariac output, which is promising There should also be so there's also we also have some results of when the mock circulatory loop was connected to the vascular structure So the pressure ranges the uppers and lowers of aortic and left ventricular pressure are physiologically accurate And the pid controller actually the controller follow allows the pressure volume pressure volume to follow the theoretical loop very well except for during Iso volumetric relaxation. So when pressure is supposed to drop smoothly, it doesn't quite drop as smoothly as it should And along with that the flow is a little bit low during each contraction Um Not as not as much volume should be displaced out of out of the left ventricles as there is So a little bit of tweaking to the mechanical structure and the controller is still needed in order to perfect it So As for some just just some discussion the mcl in conjunction with the vascular model shows promise as a training platform for vascular surgeons By using mcl technology certain auto regulatory responses and physiological conditions can be simulated to provide a More sophisticated flow environment in these training environments than existing platforms Additionally, there are limitations to the mcl as I mentioned flow Is rather low when the mcl is connected to the vascular structure And this is because the vascular structure essentially acts as a giant compliance chamber and so normally the This causes high pressures to dissipate rather quickly. And so and so the left ventricle in order can't reach target pressures So in order to counteract this we have pretty high resistance Following the vascular training model and this high resistance allows us to reach target pressures But it has a direct effect on the flow. So flow is low probably around and As for future work So we would like to improve the PID controller in order to allow for better Pressure volume loop tracking We would also like to implement personalized elastance functions. So This is in the linear motor driven mcl specifically on its own We So I mentioned we derived the elastance function from The pneumatic mock circulatory loop and basically what this means is we said that that mock circulatory loop is an individual and it has a heart and it has its own unique heart function and we took it the pressure volume relationship inside of the mock circulatory loop and we Could find values of contractility Which we could then turn into the elastance function and then we inserted this elastance This elastance function into the linear motor driven mock circulatory loop and so in doing this we are recreating the heart that is the pneumatic mock circulatory loop and so if we were able to Derives an elastance function from an individual by using their own heart function data We could simulate their own heart when testing cardiac assist devices elvads and This is a one of the long-term goals of our Of our mock circulatory loop project. Additionally, we also hope to build a four chamber system The goal is always the goal with the mock circulatory loops is to create an environment that's Exactly physiologically and anatomically correct because in theory if you can test a cardiac assist device against a perfectly functioning mock circulatory mock circulatory loop you should be able to say that it will work in depth permanently or in a in in a human and although that's a bit of a reach They can at least reduce the amount of animal trials being put on the money spent on animal trials and the uh animals lives being used to test Test the devices so the goal is ultimately to create a mock circulatory loop And yeah, that's that's our that's my presentation