1. Digitally-Bypassed Transducers: Interfacing Digital Mockups to Real-Time Medical Equipment Scott Sirowy*, Tony Givargis and Frank Vahid* This work was supported in part by the National Science Foundation *Department of Computer Science and Engineering University of California, Riverside {ssirowy,vahid}@cs.ucr.edu Center for Embedded Computer Systems University of California, Irvine givargis@ics.uci.edu

2. Introduction: Medical Device SW Development Matlab, MML, VisSim, etc Lung Ventilator PC Simulation Simulate medical device and physiological system completely in software Supports rapid software changes, faster than real-time execution, and avoids potential safety concerns

3. Introduction: Medical Device SW Development Physical Mockups Later in development, migrate simulated physiological models to physical models Used when medical device software is running on actual hardware Potential inability to adapt to new features

4. Introduction: Medical Device SW Development Digital Mockups Combines the benefits of faster than real-time execution of simulation with advantages of developing software on real device Potentially cheaper than physical mockups too Matlab, MML, VisSim, etc Lung Ventilator PC Simulation Physical Mockups (Flexibility, speed, no real hardware) (Real Hardware, more realistic, costly, some scenarios difficult to model )

5. Introduction: Medical Device SW Development PC Simulation Supports rapid software changes, faster than real-time execution, and avoids potential safety concerns Physical Mockups Used when medical device software is running on actual hardware Potential inability to adapt to new features Digital Mockups Combines the benefits of faster than real-time execution of simulation with advantages of developing software on real device Potentially cheaper than physical mockups too

6. Introduction: Medical Device SW Development Physical Mockups Ventilator Physical Lungs Mockup SW Core Physical Tube Transducers Pressure and Volume Sensors

7. Introduction: Medical Device SW Development Digital Mockups Ventilator Digital Lungs Mockup SW Core Left Unconnected Digital Interface

8. Digital Mockups Digitally-Bypassed Transducers Medical Device Digital Mockup SW Core Output 1 Input 1 (Digital) Sensed Input … Input n Output n Sensed Input (Digital) Control/Synchronization Channel Input 1 … Physical Value Input n Output 1 = Digitally-bypassed Transducer Output n Digital Bypass

9. Digital Mockups Digitally-Bypassed Transducers Transducer Digital input Sensed Value Bypass Transducer (to medical device) Digital output Input Digitally-Bypassed Transducer Output Digitally-Bypassed Transducer Transducer Digital output Physical Value Digital input (from medical device) Simple and inexpensive hardware additions enable bypassing the transducer inputs and outputs, and enable working completely in the digital domain

10. Digital Mockups Medical Device-Digital Mockup Synchronization Rate Synchronization: Dedicated Control/Synchronization Channel used to exchange connectivity information, sampling rates, and mockup execution speeds Step 1: On initial connection, digital connectivity handshake Step 2: Medical device sends required sampling rate Step 3: Medical device and Digital Mockup agree on execution speed (real time, 2X faster, etc) Step 4: Begin Execution Medical Device Digital Mockup Step 1 Step 2 Step 3 Step 4 All communication done on the bi-directional control/synchronization channel

11. Medical Software Development with Digitally-Bypassed Transducers Ventilator SW Core Ventilator SW Core Ventilator SW Core Digital Lungs Mockup 1)All Digitally-Bypassed Transducers 2) Combined Digital and Transducers 3)Full Interaction with Physical System Tube Physical Interface

12. Digitally-Bypassed Transducers Early Prototype Medical Device (Pacemaker) Digital Mockup of a Heart Control/Synchronization Channel Digital Inputs/Outputs Open leads for real physical analog connections Transducers

13. Medical Software Development Prototype Results Heart Digital Mockup and Pacemaker Implemented both pacemaker model and digital model using a number of off-the- shelf microcontrollers Digital Mockup based off a simple physical heart model Able to test pacemaker in real-time, and faster and slower than real time

14. Medical Software Development Prototype Results Lung Digital Mockup and Ventilator Lung Mockup Ventilator based off of models from the NSR Physiome Projects Plan on augmenting a real ventilator with digitally-bypassed transducers in the near future

15. Conclusions With a small amount of hardware and software additions, we introduced the digitally-bypassed transducer Digitally-bypassed transducers enable interfacing to digital mockups, enable medical software development at faster than real-time execution while still developing software on the real medical device