Device Safety

Question 1

What are the 2 components of risk?

Answer 1

Probability (likelihood) & Consequence (severity)

Question 2

What are the 4 categories of risk severity?

Answer 2

Minor (recoverable)
Major (slow recovery/permanent)
Critical (immediate/prolonged treatment)
Fatal (death)

Question 3

How are hardware failures characterised?

Answer 3

Systematic (poor features) & Random (wear and tear/overuse)

Question 4

What values are measured in the evaluation of new devices?

Answer 4

Accuracy
Precision
Resolution
Reproducibility

Question 5

Accuracy

Answer 5

“Accuracy = Aiming for bullseye”
A measurement that is as close to the true value as possible
Example true BP of someone is 130/80 but the monitor reads 115/70, it is not accurate

Question 6

Precision

Answer 6

“Precision = measurements are Packed together closely into clusters”
If BP is taken 3 times and reads 127/80, 128/80, 129/80 then it is precise because they are all so closely similar.
Can be both precise and inaccurate, the true value might actually be 140/90

Question 7

Resolution

Answer 7

“Resolution = Reveals the Ridiculously smallest differences”
The smallest possible difference that can be detected, revealing the amount of decimals in the difference between two values
Example if a machine is set to resolution of 0.1, it can detect a change from 50kg to 50.1kg, but it cannot detect a change from 50kg to 50.01kg as this is even smaller than the smallest number it is set to detect

Question 8

Reproducibility

Answer 8

“Reproducibility = Repeatable measurements in different environments”
The ability to obtain consistent results no matter the environment/conditions.
Example two labs with two different testers test the same sample and get the same results, it is reproducible

Question 9

What 2 factors determine the quality of a medical device?

Answer 9

Sensitivity & Specificity

Question 10

Sensitivity

Answer 10

Sensitivity = confirming, identifying true positives, can also end up with false positives
Example testing for an infectious disease to identify those with it, can also diagnose healthy people with it who do not

Question 11

Specificity

Answer 11

Specificity = screening, identifying true negatives, can also end up with false negatives
Example screening for breast cancer - ruling out everyone who does not have it, but can miss those who do

Question 12

For what reason should you seek high sensitivity?

Answer 12

To screen for disease

Question 13

For what reason should you seek high specificity?

Answer 13

To confirm a disease

Question 14

What is the main reason for electrical incidents to occur?

Answer 14

Wear and tear of power cables

Question 15

What are the physiological effects of a current passing through the body to the ground?

Answer 15

Muscle cramps
Respiratory arrest
V-Fib
Physical burns and tissue damage

Question 16

Severity of electric shock injury is dependent on what?

Answer 16

The amount of current and duration of shock
Pathway of the current (heart?)
AC or DC
If the current causes cramps you may be unable to detach from the live source

Question 17

What can reduce the naturally high resistance of the body?

Answer 17

Wet (conducting gel)
Broken skin
IV catheters

Question 18

Macroshock

Answer 18

Macroshock is a large current passing through the body via skin contact. Has minimal flow through the heart and low risk of V-Fib - flows through larger areas of the body and external tissues.
Occurs at higher ranges (mA)
Example touching live wire or faulty electrical equipment with bare hands.
Protection with grounding measures and insulated equipment

Question 19

Microshock

Answer 19

Small electrical current flowing through the body with a direct conductive path to the heart with high risk V-Fib.
Occurs at lower ranges (µA)
Example faulty medical equipment delivering stray current through implanted devices.
Protection with equipment maintenance and testing