Chapter 20: Product Issues

1
Chapter 20 Product Issues

• Design of Biomedical Devices and Systems
• By
• Paul H. King
• Richard C. Fries

2
Product Safety Legal Issues

• Risk Assessment
• What failure could cause harm to the patient or
  user?
• What misuse of the device could cause harm?
• Liability Assessment
• Have all possible failure modes been explored and
  designed out?
• Have all possible misuse situations been
  addressed?

3
Safety

• Freedom from accidents or losses
• A function of the situation in which it is
  measured
• Drinking water kidney failure
• A measure of the degree of freedom from risk in
  any environment

4
Safety

• Accident unwanted or unexpected release of
  energy
• Mishap unplanned event or series of events that
  result in death, injury, occupational illness,
  damage to or loss of equipment or property, or
  environmental harm

5
Mishap

• Multiple factors that flow in series until the
  system is out of control and a loss is produced
• Anticipation simpler problems
• Opportunities for interruption

6
How Do Engineers Deal With Safety Problems?

• Operational or Industrial Safety
• Examination during operational life
• Correcting unacceptable hazards
• Goal design an acceptable safety level into the
  system before actual production or operation

7
Safety and Reliability

• Safety only concerns itself with failures that
  introduce hazards
• Reliability probability of failure of a device
  to meet its requirements

8
Safe System

• One in which damage to persons or property
  doesnt happen often or, when it does, the damage
  is minor
• Small damage potential
• Able to occur more often
• Still considered Safe
• Large damage potential
• Chance for mishap small
• System that fails all the time can still be safe
• System can be up and running all the time and
  consistently put people at risk
• Reliable system, but not Safe

9
Example Pacemaker

• Pacemaker that paces at 110 beats per minute
  continuously no matter what is very RELIABLE
• If patient is in cardiac failure, high pacing
  rate is medically inappropriate. UNSAFE
• Reliable but Unsafe device

10
MTTF MTBF

• Mathematical laws of probability used to estimate
  reliability
• Published values for reliability measures
• Mean Time To Failure
• Mean Time Between Failure

11
Legal Aspects of Safety

• 3 Most Common Theories of Liability
• Negligence
• Strict liability
• Breach of warranty

12
Negligence

• One should pay for injuries that he causes when
  acting below the standard of care of a
  reasonable, prudent person participating in the
  activity of the action in question
• People have the right to be protected from
  unreasonable risks of harm
• A manufacturer that does not exercise reasonable
  care or fails to meet a reasonable standard of
  care in the manufacture, handling, or
  distribution of a product may be liable for any
  damages caused.

13
Strict Liability

• Focus on product
• One who sells any product in a defective
  condition unreasonably dangerous to the user or
  consumer or to his property is subject to
  liability for physical harm thereby caused to the
  ultimate user or consumer or to his property if
  the seller is engaged in the business of selling
  such a product, and it is expected to and does
  reach the user or consumer without substantial
  change to the condition in which it is sold.
• Risk/benefit analysis

14
Breach of Warranty

• 3 Types
• Breach of implied warranty of merchantability
• Breach of the implied warranty of fitness for a
  particular purpose
• Breach of an express warranty

15
System Safety

• Fail-safe designed to fail into a safe and
  harmless state
• Enter safe states by terminating or preventing
  hazardous conditions (lockouts or shutdown
  systems)
• Should be able to work despite failure of other
  functions

16
Hardware Safety

• Techniques for reducing failure of component
• Component derating
• Safety margin
• Load protection

17
Software Safety

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

18
Verification Validation of Safety

• Proof of Safety
• Verification capture the semantics of the
  hardware, software code, and the system behavior
• Fault-tree analysis

19
Effective Safety Program

• Implementation of internal hazard analysis
  procedures, a firm grasp of regulatory and other
  standards, and an awareness of the current
  industry practice regarding safety controls
• Figure 20-1 Safety Analysis Checklist

20
Accident Reconstruction Forensics

• Biomedical Engineers may be used to analyze
  accidents
• Analysis of Medical Device accidents
• Discussion on biomechanics and accident
  investigation

21
Medical Device Accidents

• Process for a medical device accident
  investigation
• p. 456
• Case Pressure Limited Pump

22
Biomechanics Traffic Accident Investigations

• Data Collection
• National Highway Transportation Safety
  Administration (NHTSA)
• Injury Estimation
• Abbreviated Injury Scale (AIS)
• Impact Analyses
• Accident report, crush patterns, etc to estimate
  probable outcome