have resorted to a simulated software-âbased patient vital signs monitor that ... is inadequate for some simulations, particularly for tasks that are monitoring ...
VITALSBRIDGE FOR SIMMAN 3G: INTERFACING A VITAL SIGNS MONITOR WITH A LOW COTST, HIGH FIDELITY PATIENT SIMULATOR Presenting Author: Soeren Hoehne, Dipl.-‐Ing.1 Co-‐Authors: Noah Syroid, M.S.1, Joseph Orr, Ph.D.2, Jim Azukas3, Dwayne Westenskow, Ph.D.1 1Dept. of Anesthesiology, University of Utah, Salt Lake City, UT; 2Dynasthetics Inc, Salt Lake City, UT, 3Laerdal Medical, Wappingers Falls, NY
Introduction: High fidelity patient simulation has and continues to have a prominent role in anesthesia training. The first patient simulators were primarily intended for anesthesia and critical care audiences. They produced highly realistic and accurate physiologic signals on a real patient vital signs monitor, but were quite expensive. As simulation audiences broadened and demanded cost-‐conscious solutions, many high fidelity patient simulators have resorted to a simulated software-‐based patient vital signs monitor that displays numerical values and waveforms on a laptop computer. This solution has less fidelity and is inadequate for some simulations, particularly for tasks that are monitoring intensive. We have designed and implemented the VitalsBridge. Its hardware and software translates the physiologic information from a patient simulator (SimMan 3G, Laerdal Inc., Norway) into signals that are compatible with traditional patient vital signs monitors such as the Philips monitor shown in the figure below. Methods and Results: The VitalsBridge consists of hardware and software that presents the vital signs from the Laerdal SimMan3G on a traditional vital signs monitor. It is capable of simulating multiple physiologic monitoring devices, including: pulse oximetry, capnography, impedance respiration, non-‐invasive blood pressure, invasive blood VitalsBridge pressures, and temperatures. Invasive blood pressure waveforms and temperature trends are created by the VitalsBridge. Pulse oximetry is simulated by placing a cable and small circuit board with infrared and red LEDs under the manikin’s skin, at the tip of the index finger, where a SpO2 probe may be placed over the fingertip. Non-‐invasive blood pressure is simulated by sending pneumatic pulses to a small bladder that resides inside of the blood pressure cuff or under the manikin’s arm skin. For capnography, CO2 and air are mixed together and is drawn to the capnometer. Software was written in C# (Visual Studio 2010, Microsoft Inc., Redmond WA) to interface with the Laerdal operating system, which sends the simulated vital signs from the SimMan 3G’s to the microcontroller in the VitalsBridge. Communication between the VitalsBridge and the SimMan 3G occurs using Wi-‐Fi or Ethernet.
Five VitalsBridge units were tested for accuracy. The simulated variables generated by the VitalsBridge were measured using a vital signs monitor (Philips MP30, including a capnography module). The table below shows the average difference between the value of the variable sent to the VitalsBridge (by the Laerdal simulator) and the value of the variable generated by the VitalsBridge (as measured by the Philips monitor). The second column lists the standard deviation of these differences.
Parameter SpO2 (%) ABP Systolic (mm Hg) ABP Diastolic (mm Hg) NIBP Systolic (mm Hg) PAP Systolic (mm Hg) PAP Diastolic (mm Hg) CVP (mm Hg) Resp. rate (breaths/minute) EtCO2 (mm Hg) Temperature 1 (⁰F) Temperature 2 (⁰F)
Average error 0.88 1.67 1.85 2.30 0.58 0.57 0.00 0.00 0.63 -‐0.04
Std dev error 0.11 1.82 1.01 2.25 0.85 0.51 0.00 0.00 0.72 0.10
-‐0.08
0.15
Discussion: The ability to present vital signs from the SimMan 3G on a traditional vital signs monitor will provide enhanced realism and learning opportunities, particularly during anesthesia and critical care simulations where patient monitoring plays a significant role.
