Linear Hemodynamics




This begins a section on linear hemodynamics, the meat and potatoes of a great deal of both clinical and physical hemodynamics. This deals with concepts that are in everyday clinical cardiology practice, like vascular resistance, but also goes into the physical basis of hemodynamics and illustrates many of the dynamical principles that aren't necessarily included in your cardiology text. In particular, I believe concepts like impedance can be difficult for clinicians to get a handle on and I hope the explanations will be helpful.  

I've put together a rather extensive Active Figure to illustrate concepts in this section. It's a model of a compliant tube which, believe it or not, is plenty complicated enough to be getting started with.  Yes, I DO understand that the circulation is significantly more complicated than this.  I think you'll find that the simple straight tube is a good place to learn the basics The model does allow for multiple compliant tubes in series with each other to demonstrate principles of impedance mismatch and wave reflection.    Somewhere high on my To Do list is another active figure demonstrating more of these same concepts in branching networks.

The software isn't complete and is being posted still with quite a few bugs that I know of.  The way things are going, I'll be dead before I get any of these webpages "finished", so I decided I'd better start posting ready or not. I'll be changing the software without notice as it's modified and improved so you should download a fresh copy if you want to make sure you're using a current version.  For the 2-3 of you that actually download and try the software, feel free to send me your suggestions or gripes. Many of the figures and videos shown in the section were created using the software and the intention is for you to change model parameters and fiddle with the controls so that you can see how it affects model behavior.

DOWNLOAD the Linear Hemodynamics software which is an executable file.  (Software and Scenerio Files subject to change at any time and without provocation.  Download the files afresh if it's not working for you.) Your computer will warn you that I am NOT a trusted source which is certainly true.  The software comes up with a default model and settings that start when you double-click the executable file (LinearHemodynamics.exe), but will also load  "Scenario" files – model and display presets that set the system up quickly to demonstrate particular aspects of hemodynamics.  Individual scenario files can be downloaded as you follow through the webpages to set the software up for the topic at hand.  None of the software on this website is designed to be malicious - I apologize in advance if the software causes EITHER of you any problems.


 When you first activate the Linear Hemodynamics active figure, it starts out with a default model and all of the display screens (images) activated. The software has the potential to display too much information at one time and attempting to show it all at once also slows down the computations and displays. You're going to want to Minimize screens that you are not observing at the moment which also decreases the amount of computing and drawing that your computer has to do.  in the following snapshot of my desktop, software has been activated and then the convenient "Arrange" button has been clicked.  This sets all of the display screens at a convenient size ( 800 x 600 ) and tiles the screens.  The "Application Control" screen remains on top and has a variable degree of opacity ( set using "Form Opacity" slider in the upper left of the screen).  This allows you to actually watch the display right through the control form if that works best for you.



This is a full-size image of the Application Control screen with the "SCENARIOS" Tab activated.  Once you have set the software EXACTLY the way you want it ( model parameters, screen size, specific screens visible, etc. etc. ) you can save everything about the setup as a Scenario so that you'll be able to set up the system the exact same way without having to push a lot of buttons.  As suggested below, you can give the scenario a title and also include whatever text you like to save with the scenario. Obviously you're going to push the "SAVE" button to save the scenario for later retrieval and the "LOAD" button to cause the software to set everything the way you had it before.

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