Describe the essential components of an ECG monitor (60% marks).

Outline the methods employed to reduce artefact (40% marks). 

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College Answer

Monitoring and monitors are essential to Intensive Care practice, and is the reason why it is 
included in the syllabus. Unfortunately candidates have performed poorly in this question, as they 
have in previous measurement and monitoring questions. Future candidates need to be aware 
that such questions WILL get asked again. 

For a good answer it was expected that mention would be made of what an ECG monitors does 
(ie detects and amplifies the small electrical changes on the skin that are caused when the heart 
muscle depolarizes), how (ie use of 2 or more electrodes, typically being made of silver or silver 
chloride), the type of leads (ie unipolar and bipolar, and a description of the latter), the way the 
signal is handled (isolation, amplification, gain, filtering) and displayed. Methods to reduce 
artefact and improve signal:noise ratio, should have included skin conductive measures, 
minimising external interference (filters, earthing), common mode signal artefact rejection, high 
input impedance amplification and mention of diagnostic and monitoring modes.

Recommended sources: Davis and Kenny pgs 160-178, also Sykes & Vickers Principles in 
measurement and monitoring in Anaesthesia and Intensive Care, Chps 4, 5, 6, 23.