Digitally-Bypassed Transducers: Interfacing Digital Mockups to Real-

Time Medical EquipmentScott 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 SystemsUniversity of California, Irvine

givargis@ics.uci.edu

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

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

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 )

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

Introduction: Medical Device SW DevelopmentPhysical Mockups

Ventilator Physical Lungs Mockup

SW Core

Physical Tube

TransducersPressure and Volume Sensors

Introduction: Medical Device SW DevelopmentDigital Mockups

Ventilator Digital Lungs Mockup

SW Core

Left Unconnected

Digital Interface

Digital MockupsDigitally-Bypassed Transducers

Medical Device Digital Mockup

SW Core

Output 1Input 1

(Digital)SensedInput …

Input n Output n

SensedInput

(Digital)

(Digital)

(Digital)

Control/Synchronization Channel

Input 1

…

Physical Value

Physical ValueInput n

Output 1

= Digitally-bypassed Transducer

Output n

Digital Bypass

Digital MockupsDigitally-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

Digital MockupsMedical 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

Medical Software Development with Digitally-Bypassed Transducers

Ventilator

SW Core

Ventilator

SW Core

Ventilator

SW Core

Digital Lungs Mockup

Digital Lungs Mockup

1) All Digitally-Bypassed Transducers

2) Combined Digital and Transducers

3) Full Interaction withPhysical System

TubePhysical Interface

Digitally-Bypassed TransducersEarly Prototype

Medical Device (Pacemaker)

Digital Mockup of a Heart

Control/Synchronization Channel

Digital Inputs/Outputs

Open leads for real physical analog connections

Transducers

Medical Software DevelopmentPrototype 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

Medical Software DevelopmentPrototype 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

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