Instrumentation CA1 Flashcards
Transducer +3 clinical examples
Anything that converts one electrical source to another electrical source
Electrodes
Piezoelectric crystal
Spirometer
Filters
Mitigate any unwanted frequencies
Amplifiers
Electric bio signals are very small, so amplifiers increase the signal but is also used for filtration
Signal digitisation
electric bio signals are analogue and will need to be converted into digital form using an analogue to digital converter
When assessing the usefullness of a device, what two peramiters do we take into account
Specificity and Sensitivity
In what cases to we want a high specificity and in what cases do we want a high sensitivity
Want high sensitivity when screening for a disease
High specificity when confirming a disease
When assessing the quality of the medical devices the performance if determine by what 4 values
accuracy, resolution, precision, reproducibility
ROC curve
- what does it plot
- where on the graph would a device be deemed an acceptable classifier
ROC curve asseses the ability of the binary classifier. Plots sensitivity vs specificity
Anything above the positive slanted line is acceptable
What are the 4 rules in classifying non-invasive devices
- either do not touch the patient or contact only intact skin (I)
- intended for channelling or storing blood, body liquids, cells or tissues, liquids or gases for the purpose of eventual infusion into the body (I)
- unless using with blood/body fluids (II1)
- unless connected to a active device class IIa or higher (IIa)
- unless bloodbags
- modifying the biological or chemical composition of human tissues, or cells, blood, other body liquids, or other liquids intended for implantation or administration into the body (IIb)
- unless only filtration, centrifugation or exchange of gas or heart (IIa)
- consisting of a substance intended to be used in vitro in direct contact with human cells (embryo) (III)
- In contact with injured skin or mucous membrane (or invasive device) (IIa)
- unless as a mechanical barrier, compression or absorption (I)
- unless intended for wounds which breach dermis and heal only by secondary intent (IIb)
Qualities of class 1 device
mostly non-sterile and non-invasive
e.g blood pressure machine, stethoscope, reusable surgical instruments
qualities of class IIa devices
short term, non-invasive devices intended for channelling or storing blood, body liquids for eventual administration into the body
If they are principally intended to manage the microenvironment of the cell
e.g ultrasound, diagnostic software
Qualities of class IIb devices
long term, intended to be used principally for injuring the skkin which can breach the dermis
e.g equipment used for intraoperative monitoring, ionizing radiation
intended to administer medicinal product by means of a delivery system
qualities of class 3 device
critical for patients life
e.g pacemaker, stent
What is not the responsibility of the regulatory bodies in medical device standardisation
designing specific safety tests that medical devices must pass
What are the two independent testing agencies
ISO and IEC
What are the 4 levels of risk severity
- Minor - recoverable
- Major - very slow to recover or permanent
- Critical - immediate or prolonged treatment
- Fatal - may result in death
What two components is risk made up of
Probability and consequence
What is requirement for hardware failures
A medical device must be safe in the case of a single fault
2 independent failures should not harm the patient
Therefore equipment must be designed so that the combination of the first and second failures cannot cause a hazard
What are the two primary principles behind software verification
- describe the exact function the software is supposed to perform
- device a very specific test to verify that the software works s designed
Resolution
The smallest differential value that can be measured
An electric shock of 80-600uA is likely to cause what to happen in a body
Ventricular Fibrillation
What is the difference in the travel path between macro and micro electric shocks
Macro - only a small amount of the current flows through the heart
Micro - introduced directly into the body via a high conducting avenue with a direct conduction path to the heart
What two parameters depend how bad an electric shock is
skin resistance and spatial distribution
How do you protect someone after having a macro shock
isolate patient from any grounded surface and all current sources.