Sensor Networks for Medical Care

Authors: Victor Shnayder, Borrong Chen, Konrad Lorincz, Thaddeus R. F. Fulford Jones, Matt Welsh

Presenter: Velin Dimitrov

Introduction

• Why do we need WSNs in medicine Continuously monitor patients long

term Emergency/Disaster Scenario

• “Active Triage Tag”

Immediate life-critical notifications Augment/replace existing wired

telemetry systems Improve overall care of patients

Motivation

• Real time continuous patient monitoring In-Hospital setting

• Home Monitoring – Elderly/Chronic Continuous data Long term care/trend analysis

• Collection of clinical data

Adapted from Matt Welsh’s presentation on CodeBlue at UCSD

Medical Applications

• Stationary nodes with low data rates to central station

• Improvements High Data Rates Reliable communications Multiple receivers

• In-network aggregation cannot be used

Current Implementations

• Wireless medical monitors EKG Pulse Oximeters Fetal Heart Rate Maternal Uterine

• “Cut the cord” implementations• Bluetooth, WMTS, Wi-Fi• Systems do not scale well

Current Implementations

Develop tiny, wearable, wireless sensors for medical care and disaster response

• Scalable, robust wireless communication protocols

• Integrate real-time sensor data into medical care

• Explore a range of clinical applications

Adapted from Matt Welsh’s presentation on CodeBlue at UCSD

CodeBlue Goals

• Sensor modules compatible with Mica2, MicaZ, and Telos mote designs

• Pulse Oximeter• Two lead electrocardiogram (EKG)• Motion analysis sensor• SFF Telos design for wearable use• telosb_datasheet_rev 20111109 (1).

pdf

CodeBlue – Hardware

• Device Discovery• Publish/Subscribe multi-• hop routing• Query interface – simplicity• RF-based localization

Low power Bluetooth and 802.15.4 (WPAN)

CodeBlue - Software

• Wearable Sensor Platform “…large batter packs and protruding

antennas are suboptimal for medical use.”

Small, Lightweight, Wearable sensors

• Reliable Communications Data Availability How much packet loss is acceptable? Sample rates vary 1Hz to 10’s kHz

Requirements

• Multiple Receivers Multicast capabilities

• Device Mobility Multi-hop routing Device Discovery

• Security Health Insurance Portability and

Accountability Act

Requirements

• A review of the implementation of the HIPAA Privacy Rule by the U.S. Government Accountability Office found that health care providers were "uncertain about their legal privacy responsibilities and often responded with an overly guarded approach to disclosing information...than necessary to ensure compliance with the Privacy rule".

Wilson J (2006). "Health Insurance Portability and Accountability Act Privacy rule causes ongoing concerns among clinicians and researchers". Ann Intern Med

HIPAA

• Disaster Response Research Funded US National Library of

Medicine SMART AID-N WiiSARD

• Centralized systems Reliability and Scalability Concerns

Related Work

Wireless Medical Sensors

• Mature technology (1970s)• Measures heart rate and SpO2• Catch hypoxemia before visible

symptoms• Array of Infrared LEDs• Array of IR detectors

650nm and 805nm

• BCI Medical Micro-Power Pulse Oximeter

Pulse Oximeter

• Two different types• Standard EKG

30 sec of data from 12-15 probes Diagnose wide range of cardiac

arrythmias

• Continuous EKG 2-3 probes Diagnose intermittent problems

EKG

• Single pair of electrodes• INA321 CMOS instrumentation

amplifier• 94dB CMRR• Gain of 5• TinyOS samples at 120Hz

Mote-Based EKG

• Parkinson's Disease and Stroke• Wired systems with many wires

carried in a waist harness• Sensors are placed on limbs of

interest• Accelerometers• Gyroscopes• EMG

Motion Capture Systems

• Wireless• 3 Axis Acc – STMicroelectronics• 1 Axis Gyro – Analog Devices• 1 EMG unit – Motion Lab Systems• One mote is placed on each

segment of interest

Mercury Motion Analysis Board

• Mica2Dot No 802.15.4

• Pluto TI MSP430 ChipCon CC2420 radio 120 mAh Li-Ion battery Mini USB

Pluto Mote

CodeBlue Software Architecture

• Sensors publish data to relevant channel

• Requirements Requested data rates/local filters to

limit bandwidth Multi-hop routing Mobility of senders/receivers in

calculation of routing paths

Publish/Subscribe Routing Layer

• Adaptive Demand-Driven Multicast Routing

interface PubSub {command result_t publish(uint16_t chan);command result_t subscribe(uint16_t chan);command result_t leave(uint16_t chan);command result_t send(uint16_t channel,

uint8_t length, TOS_Msg* msg);event result_t sendDone(TOS_MsgPtr msg,

result_t success);event TOS_MsgPtr receive(TOS_MsgPtr m,

uint16_t channel, uint16_t srcAddr);}

ADMR

• Implemented by forwarders• Rebroadcasts messages to a given

channel with duplicate suppression• Route discovery

Node table indexed by Publisher ID Each entry has path cost and previous

hop to the publisher Path costs are updated continuously

Multi-Hop/Multicasting

• PDR – path delivery ratio• CC2420 radio provide Link Quality

Information (LQI)• LQI mapped to Link Delivery Ratio

(LDR)• Summed for the path making PDR• Link Cost is 1-PDR or Path Loss

Ratio• PDR is held and updated in the

header of the ADMR messages

Calculating Path Cost

• Very simple• Periodically all nodes broadcast

metadata Node ID Sensor types

• Receivers subscribe to the broadcast channel

Discovery Protocol

• CBQ query are supplied by the GUI• Instructs CB to publish data to a

specific channel that meets query conditions

• S – Node IDs• Tau – Sensor Type• Rho – Sampling Rate• Chan – Channel to publish to• C – Total Number of Samples

Query Interface

• ADMR and CBQ are separate• Simplifies CBQ protocol• Inefficiencies arise that ADMR and

CBQ both flood the network with broadcast requests

• CBQ may not be sufficient in all situations but is for most

Inefficiencies

• Generic interface for sensors• getData()• dataReady()

Sensor Interface

RF Based Location Tracking

RF Based Location Tracking

MoteTrack, Konrad Lorincz, Harvard University

User Interface

Evaluation

Scalability - Location

Scalability – 1 Reciever

Scalability – 3 Receivers

Fairness

Packet Jitter

Mobility

Multiple Transmit Packets

• Sharing bandwidth across sensors Data priority

• Security Private Key encryption Public Key protocol

• Integration outside of a hospital setting

Future Work

Progress

• From 2009• http://www.ted.com/talks/eric_topol

_the_wireless_future_of_medicine.html

• 2:45 minutes

Questions/Comments/Discussion

• What characteristic make this a CPS?

• What potential challenges exist in the successful real-world implementation of CodeBlue?

• How does the boom in smartphones and ubiquitous computing help CodeBlue or does it make it obsolete?

• Is current encryption technology adequate to secure the system?

Questions