Defib Technology Flashcards
What are the two types of biphasic waveform?
Truncated exponential and rectilinear
Compare the flow of current in monophasic and biphasic waveforms
Current flows in one direction from one electrode to the other. The heart is momentarily stopped allowing sinus rhythm to be restored.
In biphasic the current then flows back through the heart in the reverse direction
What is the advantage of biphasic defib technology
It uses lower energy meaning less damage to the myocardium and less post shock arrhythmias
Newer models will analyse impedence and alter shock accordingly
What are the current issues with defibrillation
Can’t shock yourself
Hands of to rhythm analyse and shock = no flow time
Myocardium is damaged
Describe 3 future ideas to improve defibrillation technology
Fibrillation waveform analysis - tailored shocking only when likely to be successful to decrease pointless shocks that cause no flow time and myocardial damage
Pause free analysis - software to prevent ECG artefact caused by CPR
Double sequential fibrillation - used in refractory VF. The first shock reduces threshold for depolarisation and the second works better. Also overcomes impedance and air in lungs
Name some future defibrillation strategies
Fibrillation waveform analysis
Pause free analysis
Double sequential defibrillation
What is the 3 phase model of cardiac arrest
Electrical (0-4 mins)
Circulatory (4-10 mins)
Metabolic (>10 mins)
What is happening in the electrical phase of cardiac arrest
Unorganised electrical activity. The cells are functioning they’re just out of sync
What is happening in the circulatory phase of cardiac arrest
Cells are ischaemic
Will defibrillation work in the circulatory phase of cardiac arrest?
Only likely to after a period of CPR to restore O2 and remove metabolites.
CPR increases the amplitude and frequency of the VF waveform so there is increased change of ROSC
