medical device trends

8/12/2019 Medical Device Trends

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White PaperTrends in Medical Device DesignNew Regulations and Technologies Will Shape

Future Devices

ABSTRACT

y Lawrence RicciWith the number of older persons projected to double from the year to 2000 to 2030 to 71.5million, technology is advancing to meet the need for new medical devices to providebetter, more cost effective, healthcare. Often, these medical device developments requireapplication of technology originally developed for PDAs and cell phones. This electronicstechnology is fundamentally different from the electronics used in the last generation ofmedical devices. To meet these challenges, new design and engineering techniques withpartnerships spanning the supply chain are emerging.

Doctors Reaching Out

Soon, medical monitoring andtreatment equipment will shrink foruse in the home, even to wearable orimplanted form factors.Communications media unknown, evenundreamt of, a decade ago will linkthem to medical practitioners aroundthe globe and vast databaseschronicling best care strategies.Battery - and even bio power willbecome the norm. Yet these

technologies must be employed withinthe properly conservative requirementsfor medical devices. This paper willoutline some of the forces and concernsthat will govern the development ofsuch equipment.

Applied Data Systems

10260 Old Columbia Road

Columbia, Maryland 21046Phone 301-490-4007 Fax 301-490-4582


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New Regulations And Technologies Will Shape Future Devices

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IntroductionThe new challenges of medical devicedesign include proscriptive complianceto regulations, extended productlifecycles, reduced product developmenttime, and of course, product safety. Thechallenge is to meet these goals and stillachieve modern communication, devicereliability, and sometimes batterypower/power management.

These new designs, once achieved, willnot only improve the devices withinclinics and medical centers, but willfacilitate the transition of monitoringand therapeutic devices into thepatients home.

Communications: Now

Fundamental to FunctionTen years ago, medical monitoring wastypically done on individual devices,without interconnection. If data was

linked, it was through written notes ona clipboard. Now, to reduce costs and toimprove access to data, most devices inthe hospital or home - whetherdiagnostic or therapeutic - must benetworked to reduce errors andfacilitate faster data exchange.

This need to network medical devicesoccurs at the same time as rapidadvances in digital radio technologyexpands the playing field of what is

possible, and the rapidly maturing FCCguidelines put regulations in place tocontrol the safety of the technology.

Previously, in addition to wiredEthernet, in-hospital devices have usedelectromagnetic spectrum shared with,but not protected from, local Land

Mobile Radio and TV stationsi. Since1997, with the FCC assigning more

bandwidth for HDTV, some devices inhospitals have been reset to usechannels still left unoccupiedii.However, this is only a small change inthe landscape, affecting mostly legacydevices and their one-to-onereplacements.

The most popular new communicationstechnology is 802.11 and its variants.Here is where the interface betweenFDA regulations, FCC regulations, and

FIPS regulations (Federal InformationProtection and Security) collide with thereality of fast-moving, high-techconsumer hardware, and software.

Keeping abreast with these issues, theFood and Drug Administration hasrecently published a Draft Guidanceforcomment, where the evolution of thevarious 21 CFR device design guidelinesis being discussediii.

WiFi Will Be KingThe 802.11 (a,b,g) specifications,published by the IEEE, define only themost basic level of compatibility.Workable interoperability typicallydemands additional conformance to theWiFi Alliance specifications and to asuite of Extensible AuthenticationProtocols (EAP) and other features,sometimes identified as the CiscoCompatible Extensionsiv(CCX), now at

Revision 4. Then, additionally, there isa host of application extensions neededto make it practical and simple to dothings like logon securely and transferfrom one access point to another.

Figure 1 is included to indicate themechanics of how just a portion of the


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EAP (Extended Access Protocol) of aWiFi net might be managed. This figure

is a extreme simplification; in practice,multiple 802.11 devices adhering todifferent access protocols will contendfor the in the same airspace andspectrum. All of these, includinginvited and uninvited guests with PDAsin their pocket, need to be administered.

Diligent third party testing andapplication focused implementationtends to mask all this complexity fromthe consumer/user. The designer of a

laptop knows that it is typicallyoperated from a desk, so its connectionto an access point should be sticky.The designer of a PDA knows that it willbe used by a moving user, and needs tofrequently reconnect from one AP toanother (slippery). For a medical

device, the engineer needs to designthese properties in, and for some

devices, properties like stickiness aremandated by regulation. Getting thisdesign right is not as simple as selectingthe right CF card. The problem is thestandards change so fast, that the comchip selected in January may be EOL bythe fall, and approval cycles may takeup much of the time in-between.Careful coordination between design,and supply chain management areneeded to effectively apply technologies

like 802.11 in medical devices.

MedRadio is Coming, MICS isstill here

Many other forms of communication arealso being used or being planned formedical devices. All of them are

Client device AP RADIUSserverProtocol : 802.1X Protocol: RADIUS

EAP: Request identi ty

EAP: Identity response* RADIUS: Request/Identity

Blocks portfor data traffic

Blocks portfor data traffic

authenticationserver

authenticationserver

authenticatorauthenticator

* Specif ic to EAP type

Mutual authentication*: Server authenticates c lient; client authenticates server

Derivation of pairwisemaster key (PMK)

RADIUS: Accept w ith PMK

EAP: Success

Derivation of pairwisemaster key (PMK)

Figure 1- Secure WiFi Access, Courtesy of Summit Data Communication


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regulated and protected by the FCC,and all of them require certain design

and testing standards. Most critical, ofcourse, are the recently proposed FCCstandards for Medical DeviceRadiocommunication Service orMedRadiov. This term refers toexpanded bandwidth for implanted andbody-worn medical radio communicationdevices. The older rules for MedicalImplant Communications Standards(MICS) are still largely in place,including the rules for low frequency,

inductively coupled sensors.The promise of MedRadio is great.Patients can wear various vital signmonitors, and even therapeutic deviceslike insulin pumps, yet still havereasonable mobility within the facilityor even at home. It is hoped that asmore wearable and implantable devicesare developed, more of the chronic careprocess can be moved out of the hospitaland costly nursing home to lower cost

assisted-living and at-home care.These networks require additionaltesting for susceptibility, for emission,and for certain protocol behaviors, suchas checking for a frequency before usingit. We have found this testing welladvised as the clock frequency ofmodern PDA/cellphone components is inthe range of MedRadio, and thefrequency of the low-frequencyinductively coupled MICS devices is inthe range of the switched mode powersupplies that power this class of device.The specs for susceptibility andemissivity can be tight, and designfeatures may have to be adjusted tomeet them.

Not Too Far Away-Metro Area

HealthHealth care professionals can be hard tofind in the rural areas of the UnitedStates. As an experiment, the FederalCommunications Commission (FCC)established in September 2006via pilotprogram that will assist in thedevelopment and deployment of region-wide broadband networks dedicated tothe provision of healthcare services.

Figure 2: Some day soon, devices like this,located in homes, will perform much monitoring

now done by vesting nurse services

This is an exciting development. Socalled 3G and 4G network technologieslike Intel WiMax exist now and providebroad band speed and easy connectionacross wide areas. Some of these pre-WiMax networks have already beendeployed over multi-county areas forspecific functions like homelandsecurity.

The use of such a metro area LAN willsolve the last mile problem forconnection to the house, and in fact,could solve the last yard problem forconnection to the device. Many of thetarget households for such health caredevices are not broad band equipped


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now and would probably benefit from adevice as easy to connect to the network

as a cell phone. The challenge will beengineering these devices.

Notably, forward thinking devicemanufacturers are looking at broadbandcapability as a way to reach out andteleconference with patients. Thisbroadband capability would provide thehealth care professional with anoverview of how the patient is doing, hisposture and general demeanor, andperhaps a suitable view of wounds,

bandage applications and so forth. Atthe same time, the patient will have, tosome degree, psychologicalreinforcement that comes from thebedside manner of the health careprovider.

These functional requirements put aserious burden on the design of thehealth care device. Not only must itestablish a network connection like aleading edge cell phone, but it must do it

within the power budget and designconstraints of various medical deviceregulations. Finally, its design must beconsistent with the documentation andtest standards for medical devices.

HIPPA will be a FactorCurrently HIPAA regulationsvii(HealthInsurance Portability and

Accountability Act of 1996) mandateconfidential transfer of patient

information. To date, properapplications of commercial WiFiprotocols have satisfied this need, but itis possible that prevailing rules maysoon mandate moving past the IEEE802.11i and 802.11x security package(an overlay to 802.11a,b or g) . The

logical step would be to move to theNIST-maintained FIPS-140 Rev 2 which

defines a series of strong encryption,identification and authenticationtechniques. Sometimes, this basket oftechnologies is referred to as SuiteBviii. These techniques are, in general,network-independent and couldessentially span WiFi and other nets aswell.

At such time as the Suite B becomesthe expectation, medical device designwill be taken to the edge of the envelope

of available silicon technology. Thevarious crypto protocols and keyexchange protocols are much morecomputation intensive than those usedtoday; special purpose chips may beneeded and these need to be integratedwith the operating systems Crypto API.If the teleconference data is alsomandated to have enhancedcryptographic security, the compute loadmight be heavy indeed.

These technologies are all available,have been proven in DoD systems, aredeclassified for civilian use, royalty-freeor reasonably priced (depending on end-use), and are now ready for applicationas part of any serious OEM devicedevelopment. Development and productcosts are inside the envelope typicallyestablished for medical devices, soperhaps the move to more secure datahandling will be made by an OEMlooking for first mover/regulatoryadvantage.


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ReliabilityFrom the designers point of view, itseems that the Hippocratic pledge to dono harm is ninety percent of medicaldevice design. The other 10% isdocumenting compliance to the 90%.Safety of the device typically focuses onpower supply design, software designand overall FMEA considerations(Failure Mode and Effects Analysis)

Power supply safety is, for the most

part, regulated by IEC 60601-1. Designto this spec is, among other things, agood assurance that high or unsafevoltage will never reach the patient.IEC 60601 also stipulates proper deviceperformance in the face of powerinterruptions and surge wave

interference. The standards for RFI

emission and immunity are likewiseinside this and related IEC regulations.The net effect of these regulations is tosignificantly increase the size and costof the power supply elements in thedevice. Cost and size of the device isreduced if less power is consumed, soapplication of power-thrifty RISCprocessors is a good way to keep devicesize and cost in line.

Figure 3- This is part of an actual FMEA study done for a mobile, embedded computer to monitor

implanted devices


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Software reliability is also an area ofconcern. The regulations specify rules

for the software in Class I, II and IIIdevices, with Class III the most critical,life sustaining service, and subject toextensive PMA (Pre Market Approval)process. Regulations for topic areevolving quickly, the FDA publishesactivity reportsix. Device design mayencompass split functions, with certainmore critical tasks done by 100%hardware subsystems, others done bylow level assembly coded

microcontrollers and finally some higherlevel functions like operator interfaceand network communications managedby a fully-functioning Off the Shelfoperating system like Microsoft

Windows CE or Linux. Use of such OTSsoftware is possible for most medical

devices provided hazards are mitigatedby an FDA regulated process as shown,in part, in Figure 3. While designdetails might change, the important facthere is that once approved, changes tosoftware are generally not allowed, andif allowed must be carefullydocumented. Since the RISC CPUsunder consideration for many of theseprograms change very often, thismandates a special controlled Bill of

Materials and excellent supplierrelationships.

Finally, reliability is not just a MTBFcalculation. The specific performance ofthe device must be analyzed for eachconceivable failure, and ranked byprobability and consequence of thatfailure. This FMEA (Failure Mode andEffects Analysis) analysis is, in itself, aregulated processxdetailing the failuremode, its causes, its effects, the

frequency of occurrence, the severity ofoccurrence and the actions to mitigatethe effects. This analysis can beperformed on individual components oron the medical devices embeddedcomputer as a unitized subsystem.Then, this analysis becomes an elementof the FMEA for the full device. Finally,an FMEA process is adopted for theentire health-management process inthe facility. Figure 3 is a section of thesummary report for an actual Single

Board, PDA style computer used in aMedical application.

The design must be documented andany change to the Bill of Material maybe a regulatory event. This can makeuse of COTS devices difficult as theyoften change as component suppliers

Figure 4- Process for Hazard Mitigation,

Off-The-Shelf Software Use in Medical

Devices, September 9, 1999 Seehttp://www.fda.gov/cdrh/ode/guidance/585.html


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shift prices and otherwise EOL items.The medical device OEM sill must

maintain a Device Master RecordDMR in accordance with regulation.xi

Sensor Integration and

Signal AnalysisMedical device design often is centeredon the integration of some novel sensorand application of its data. Ultimately,this will require measurement of avoltage and often it will require this be

done at high frequency, to enablespectrum analysis. While theserequirements are common with almostany measurement device, the design ofthis sensor electronics within thegeneral electrical requirements formedical devices can demand specializedtechniques.

To get this done in a small devicesuggests a considered design where thesensor electronics and computer

electronics are balanced carefully.Modern cell phone and PDA deviceshave excellent signal analysis capabilityin the form of in-built DSPs and DSP-like general CPU instructions. Thesefeatures, developed by silicon suppliersat great cost to supporttelecommunications functions, can beapplied to solve signal analysis andsignal processing for medical sensors.But, of course, this must be done withinthe regulations for medical devices.

For example, very high resolution A/Dconverters may be needed to resolve thetiny signals at EKG electrodes fromthepotentially high common mode voltageexclusion mandated by patient isolation.

Getting to Core Value

As exciting as the new size, power andcommunication options are for medicaldevices, they are all, essentially,commodity specifications. The real corevalue of a medical device is its sensorsand their proper application withinestablished guidelines.

Figure 5: A computer board like this might cost

10,000 development man-hours. Yet, it

provides only 'commodity' specs and is far from

the value proposition of medical device

This is not to diminish the difficulty inmeeting various communication andpower supply design specs. It can bevery difficult and require experiencedengineers, test facilities and so forth.

Any one of these can take man-monthsto engineer and to test to compliance.

But in the end - all of these specs, like802.11, IEC 60601-1, 21 CFR 820compliance, etc - are simple

commodities, in the most part tested fortheir commodity nature by third partylabs. This dichotomy between the corevalue of a medical device and the effortrequired to commoditize elements of itsdesign is causing companies to


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reconsider their engineering anddevelopment models.

In the past, the controls required formedical devices meant that mostcompanies kept engineering, design, andproduction in house. Now, with thedemand for more of this low power andcommunication oriented commodityfeatures, the same firms are looking atdesign/build models with sharedresponsibility. While not completelyoutsourcing or private labeling thedevices, the companies are seeking

business models where the commodityportion of the device can be releasedturn key to a supplier who can engineerto the specifications and manage thesupply chain.

SummaryMedical device design is advancing ontwo fronts. Proprietary technology likebetter sensors, measurements, andanalytical techniques are moving to

market. Emerging commodityspecifications for connectability andportability allow these devices to betterintegrate with a broader healthcarenetwork. Getting the best devices tomarket will require new partnershipsand development of new supply chains.

iFederal Communications Commission, 47 CFR

Part 15, part 90iiFederal Communications Commission, ET Docket

No. 95-177, Released: October 20. 1997iiiDRAFT GUIDANCE, FDA, Health and Human

Services, issued on: January 3, 2007, contactDonald M. Witters Jr. at 301-827-4955, ([email protected].)ivCisco Website (Jan 10,2007),

http://www.cisco.com/web/partners/pr46/pr147/partners_pgm_concept_home.htmlvFCC Amendment of Parts 2 and 95 of the

Commission's Rules to Establish a Medical ImplantCommunications Service in the 402-405 MHz BandWT Docket No. 99-66viNEWS Federal Communications Commission.

Seehttp://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-267605A1.pdfvii

Federal Register, 45 CFR Parts 160 and 164,December 28, 2000 as amended: May 31, 2002,

August 14, 2002, February 20, 2003, and April 17,2003viii

See NSA Fact Sheet,http://www.nsa.gov/ia/industry/crypto_suite_b.cfm, ,Jan 10, 2007ixTelemedicine Related Activities, Center for

Devices and Radiological Health, Food and DrugAdministration 11 July 1996xInternational Standards Organization, ISO

13485:2003, published in July 2003. Standardbased on the ISO 9001:2000xiCode of Federal Regulations, 21CFR820.181,

Volume 8, Revised April 1, 2006

Copyright , Applied Data Systems, Inc, 2006.All Rights Reserved. This document may not be used for

commercial gain without permission of Applied DataSystems, Inc. Any trademarks used within are the property

of their respective owners. This document containstechnical descriptions that may not be representative of

Applied Data Systems product or services

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