Chapter 21: Product Chapter 21: Product IssuesIssues

Design of Biomedical Devices and SystemsDesign of Biomedical Devices and SystemsBy:By:

Paul H. KingPaul H. KingRichard C. FriesRichard C. Fries

Product Safety & Legal IssuesProduct Safety & Legal Issues

Risk AssessmentRisk Assessment What failure could cause harm to the patient What failure could cause harm to the patient

or user?or user? What misuse of the device could cause harm?What misuse of the device could cause harm?

Liability AssessmentLiability Assessment Have all possible failure modes been explored Have all possible failure modes been explored

and designed out?and designed out? Have all possible misuse situations been Have all possible misuse situations been

addressed?addressed?

SafetySafety

Freedom from accidents or lossesFreedom from accidents or losses A function of the situation in which it is A function of the situation in which it is

measuredmeasured Drinking water & kidney failureDrinking water & kidney failure

A measure of the degree of freedom from A measure of the degree of freedom from risk in any environmentrisk in any environment

SafetySafety

Accident – unwanted or unexpected Accident – unwanted or unexpected release of energy (old definition, see release of energy (old definition, see history of gunpowder, TNT manufacture, history of gunpowder, TNT manufacture, etc.)etc.)

Mishap – unplanned event or series of Mishap – unplanned event or series of events that result in death, injury, events that result in death, injury, occupational illness, damage to or loss of occupational illness, damage to or loss of equipment or property, or environmental equipment or property, or environmental harmharm

MishapMishap

Multiple factors that flow in series until the Multiple factors that flow in series until the system is out of control and a loss is system is out of control and a loss is producedproduced Anticipation of simpler problems needed!Anticipation of simpler problems needed! Opportunities for interruption –study!Opportunities for interruption –study!

How Do Engineers Deal With How Do Engineers Deal With Safety Problems?Safety Problems?

Operational or Industrial SafetyOperational or Industrial Safety Examination during operational lifeExamination during operational life Correcting unacceptable hazardsCorrecting unacceptable hazards

Goal: design an acceptable safety level Goal: design an acceptable safety level into the system before actual production or into the system before actual production or operationoperation

Examine Accidents

Determine Causes

Correct

Safety and ReliabilitySafety and Reliability

Safety – only concerns itself with failures Safety – only concerns itself with failures that introduce hazardsthat introduce hazards

Reliability – probability of failure of a Reliability – probability of failure of a device to meet its requirements device to meet its requirements

Safe SystemSafe System One in which damage to persons or property doesn’t One in which damage to persons or property doesn’t

happen often or, when it does, the damage is minorhappen often or, when it does, the damage is minor Small damage potentialSmall damage potential

Able to occur more oftenAble to occur more often Still considered SafeStill considered Safe

Large damage potentialLarge damage potential Chance for mishap smallChance for mishap small

System that fails all the time can still be safeSystem that fails all the time can still be safe System can be up and running all the time and System can be up and running all the time and

consistently put people at riskconsistently put people at risk Reliable system, but not SafeReliable system, but not Safe

Example: PacemakerExample: Pacemaker

Pacemaker that paces at 110 beats per Pacemaker that paces at 110 beats per minute continuously no matter what is very minute continuously no matter what is very RELIABLERELIABLE

If patient is in cardiac failure, high pacing If patient is in cardiac failure, high pacing rate is medically inappropriate. UNSAFErate is medically inappropriate. UNSAFE

Reliable but Unsafe deviceReliable but Unsafe device

MTTF & MTBFMTTF & MTBF

Mathematical laws of probability used to Mathematical laws of probability used to estimate reliabilityestimate reliability

Published values for reliability measures:Published values for reliability measures: Mean Time To FailureMean Time To Failure Mean Time Between FailureMean Time Between Failure

Legal Aspects of SafetyLegal Aspects of Safety

3 Most Common Theories of Liability:3 Most Common Theories of Liability: NegligenceNegligence Strict liabilityStrict liability Breach of warrantyBreach of warranty

NegligenceNegligence

One should pay for injuries that he causes when One should pay for injuries that he causes when acting below the standard of care of a acting below the standard of care of a reasonable, prudent person participating in the reasonable, prudent person participating in the activity of the action in questionactivity of the action in question

People have the right to be protected from People have the right to be protected from unreasonable risks of harmunreasonable risks of harm

A manufacturer that does not exercise A manufacturer that does not exercise reasonable care or fails to meet a reasonable reasonable care or fails to meet a reasonable standard of care in the manufacture, handling, or standard of care in the manufacture, handling, or distribution of a product may be liable for any distribution of a product may be liable for any damages caused.damages caused.

Strict LiabilityStrict Liability

Focus on productFocus on product One who sells any product in a defective One who sells any product in a defective

condition unreasonably dangerous to the user or condition unreasonably dangerous to the user or consumer or to his property is subject to liability consumer or to his property is subject to liability for physical harm thereby caused to the ultimate for physical harm thereby caused to the ultimate user or consumer or to his property if the seller user or consumer or to his property if the seller is engaged in the business of selling such a is engaged in the business of selling such a product, and it is expected to and does reach product, and it is expected to and does reach the user or consumer without substantial change the user or consumer without substantial change to the condition in which it is sold.to the condition in which it is sold.

Risk/benefit analysisRisk/benefit analysis

Breach of WarrantyBreach of Warranty

3 Types3 Types Breach of implied warranty of merchantabilityBreach of implied warranty of merchantability Breach of the implied warranty of fitness for a Breach of the implied warranty of fitness for a

particular purposeparticular purpose Breach of an express warrantyBreach of an express warranty

System SafetySystem Safety

Fail-safe – designed to fail into a safe and Fail-safe – designed to fail into a safe and harmless stateharmless state

Enter safe states by terminating or Enter safe states by terminating or preventing hazardous conditions (lockouts preventing hazardous conditions (lockouts or shutdown systems)or shutdown systems)

Should be able to work despite failure of Should be able to work despite failure of other functionsother functions

Hardware SafetyHardware Safety

Techniques for reducing failure of Techniques for reducing failure of component:component: Component deratingComponent derating Safety marginSafety margin Load protectionLoad protection

Software SafetySoftware Safety

Safety is a concern when used to control Safety is a concern when used to control potentially unsafe systemspotentially unsafe systems

Safety needs to be considered in the Safety needs to be considered in the design of software packages, especially design of software packages, especially when considering the “crash” of a systemwhen considering the “crash” of a system

Software failures are a major source of Software failures are a major source of recalls…recalls…

Verification & Validation of SafetyVerification & Validation of Safety

Proof of Safety –fault cannot occure or if a Proof of Safety –fault cannot occure or if a fault occurs it is not unsafe…fault occurs it is not unsafe…

Verification – capture the semantics of the Verification – capture the semantics of the hardware, software code, and the system hardware, software code, and the system behaviorbehavior

Fault-tree analysisFault-tree analysis

Effective Safety ProgramEffective Safety Program

Implementation of internal hazard analysis Implementation of internal hazard analysis procedures, a firm grasp of regulatory and procedures, a firm grasp of regulatory and other standards, and an awareness of the other standards, and an awareness of the current industry practice regarding safety current industry practice regarding safety controlscontrols

Figure 21-1 Safety Analysis ChecklistFigure 21-1 Safety Analysis Checklist

Accident Reconstruction & Accident Reconstruction & ForensicsForensics

Biomedical Engineers may be used to Biomedical Engineers may be used to analyze accidentsanalyze accidents

Analysis of Medical Device accidentsAnalysis of Medical Device accidents Discussion on biomechanics and accident Discussion on biomechanics and accident

investigationinvestigation

Medical Device AccidentsMedical Device Accidents

Process for a medical device accident Process for a medical device accident investigation: accident/contact/data investigation: accident/contact/data collection(MAUDE, DHF, collection(MAUDE, DHF, other)/hypothesis/report/court or settleother)/hypothesis/report/court or settle

Examples follow:Examples follow:

Medical Cases:Medical Cases:

Enteral feeding tube complicationEnteral feeding tube complication Pressure limited respiration systemPressure limited respiration system IM Nail accidentIM Nail accident Penile implantPenile implant Blood oxygenatorBlood oxygenator Failure to monitorFailure to monitor Failure to perform (car/ventilator/child)Failure to perform (car/ventilator/child)

Biomechanics & Traffic Accident Biomechanics & Traffic Accident InvestigationsInvestigations

Data CollectionData Collection National Highway Transportation Safety National Highway Transportation Safety

Administration (NHTSA) Administration (NHTSA) Injury EstimationInjury Estimation

Abbreviated Injury Scale (AIS)Abbreviated Injury Scale (AIS) Impact AnalysesImpact Analyses

Accident report, crush patterns, etc to estimate Accident report, crush patterns, etc to estimate probable outcomeprobable outcome

Generally collaborate with OrthopedicsGenerally collaborate with Orthopedics……

Safety or lawsuit!Safety or lawsuit!