5 The Contraption: A Low‐Cost Participatory Hemodynamic Simulator

A hemodynamic simulator assembled from readily‐available, inexpensive components can be used to demonstrate complex, clinically pertinent physiologic concepts in a hands‐on experiential setting. Our simulator is composed of clear plastic tubing, squeeze bulbs, Heimlich valves, simple plastic connectors, balloons, IV tubing, plastic storage containers, a low‐pressure gauge, and a child's water wheel. After a short introduction, student participants reproduce cardiac and systemic vascular function in a coordinated simulation. Normal functional physiology is demonstrated, followed by scripted changes in physiologic conditions. At least four students are simultaneously involved in managing the simulation, including squeezing the bulbs in simulating heart chamber contraction, modifying afterload, preload, and heart rate, and assessing output parameters such as blood pressure, cerebral blood flow, and cardiac output. Using this model, we are able to demonstrate and teach the following concepts: preload, afterload, hypertensive consequences, effects of dysrhythmias, valve disorders, preload criticality with disorders such as tamponade and right ventricular MI, gradual nature of change in physiology, normal compensation despite serious malfunction, relationship of blood pressure with cardiac output, shock state despite normal BP, neurogenic shock, septic shock, hypovolemic shock, cardiogenic shock, cardiac work, maximum blood pressure, vasopressor physiology, diastolic dysfunction coupled with decreased preload or atrial dysfunction, and CHF treatment options. Trainee feedback has been overwhelmingly positive. Trainees at all levels of training, including EMTs and senior EM residents, have grasped complex hemodynamic physiology concepts intuitively after participating with this trainer.