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To the Editor:—
At our institution, we use the Human Patient Simulator (HPS), model D, developed by Medical Education Technology, Inc. (METI, Sarasota, FL). Although this model is a high-fidelity simulator, one of its disadvantages is that there is not a module to simulate and train the procedure of arterial cannulation. The arterial pulses are created by means of pneumatic bladders that can be palpated, but vessel cannulation is not possible. Another disadvantage of the HPS pulses is that although the rate of the pulses correlates with that of the programmed simulation, the intensity is invariable, so hemodynamic changes are not reflected in changes in pulse intensity.
We have developed a device that, when attached to the Trauma Disaster Casualty Kit (TDCK) of the HPS, allows the trainee to palpate the radial and femoral pulses as well as cannulate the simulated vessels using commercially available cannulation devices. The TDCK is an adjunct to the HPS that is used for trauma training. This kit simulates arterial or venous hemorrhage using simulated blood when adjunctive devices that mimic lacerated body parts are attached to the HPS. Because the TDCK communicates with the HPS, the programmed cardiac rate of the HPS correlates with that of the TDCK arterial pulses. Our device is easily constructed with readily available commercial tubing and intravenous stopcocks (fig. 1). It is comprised of inflow channels that separate the “blood flow” to either the radial or the femoral sites, as well as other anatomical sites the operator chooses, and outflow channels that drain the fluid. Resistance in the system can be varied by limiting outflow with the stopcocks. Increased flow is regulated by increasing the flow into the system using the METI TDCK software. When our device is attached to the TDCK and placed within the HPS, palpable radial and femoral pulses are created by the flow of simulated blood through our device (fig. 2). When the “vessels” are cannulated, a pulsatile flash is observed that correlates with the pulse of the HPS. A transducer can then be attached, and a simulated waveform generated by the simulator software is then displayed on the monitor. In addition, when the hemodynamics of the “patient” change (e.g. , increased cardiac output, vasoconstriction), by regulating the flow into the “vessels” or controlling the resistance to outflow, the intensity of the pulse can be varied to match that of the situation. We believe that this device further increases the fidelity of any training scenario involving arterial cannulation and adds another procedure that can be taught using a simulator. Moreover, because we can change the intensity of the pulses, this device can be used to teach inexperienced clinicians the importance of evaluating the arterial pulses as a qualitative clinical sign and to demonstrate basic clinical cardiovascular physiology. For example, we can demonstrate the changes in pulse intensity with changes in cardiac output or systemic resistance by having students palpate the pulse when either flow or outflow resistance are varied.
For those institutions that have an HPS, we believe this device is a very useful adjunct to anesthesiology training. Trainees can learn to perform an arterial cannulation within the context of a simulated clinical situation in real time in a nonthreatening learning environment. Although our device is designed to work with the METI HPS/TDCK, it can also be easily adapted to any other configuration (e.g. , artificial limb, HPS without a TDCK) to produce a low-cost arterial cannulation simulator (albeit without the benefit of a synchronized pulse) when attached to either a powered or a manual pumping device. Detailed assembly instructions, illustrations, and a video on how to construct this device can be found on the Anesthesiology Web site.
* Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee. firstname.lastname@example.org