Syllabus: PC_BK_05
This page covers terms like accuracy and precision, drift, hysteresis and calibration and has some videos on how you can explain this succinctly during a physics viva.
Definitions
Accuracy: The ability of a measurement device to match the actual value of the quantity being measured.
Precision: The reproducibility of repeated measurements and a measure of their likely spread.
In the analogy of firing arrows at a target, the accuracy would represent how close the arrow was to the bullseye, whereas the precision would be a measure of how tightly packed together a cluster of arrows were once they had all been fired.
Drift: A fixed deviation from the true value at all points in the measured range.
Hysteresis: The phenomenon by which a measurement varies from the input value by different degrees depending on whether the input variable is increasing or decreasing in magnitude at that moment in time.
Non-linearity: The absence of a true linear relationship between the input value and the measured value.
What does this have to do with anaesthetics?
Accuracy and precision
Best examples for zeroing – arterial line. Removes a fixed drift and improves measuring system.
Good examples for calibration
Galvanic fuel cell: as these systems utilise a two-point calibration (gas containing zero oxygen, and one containing a fixed concentration), calibration drift occurs when protein and lipid deposits build up on the membrane or bubbles form in the electrolyte solution. To prevent this, a combination of regular electrode cleaning and quality control is necessary.
Blood sugar meter: There are two solutions of known glucose concentration, which give a high and low point for calibration.
Further reading:
The Anaesthetic Room 