AED and Airway Obstruction
Why defibrillation matters β β β
Unit 2's simplified adult sequence has a step that is easy to skim past: get an AED, and use it as soon as possible. The deck is explicit about why β early electrical defibrillation is essential to improve the survival chances of patients with cardiac arrest.
The reason is what actually causes the arrest. Sudden cardiac arrest in most adults is caused by ventricular fibrillation or pulseless ventricular tachycardia β and those are the indications for defibrillation.
This is the point worth understanding rather than memorising. In ventricular fibrillation the heart has not stopped β it is contracting chaotically, every region firing independently, so no coordinated beat occurs and no blood moves.
Chest compressions can push blood around mechanically, which keeps the brain alive. But compressions cannot make a fibrillating heart beat properly again. Only a shock can.
So CPR is the holding action and the AED is the cure β which is exactly why the sequence says start CPR and send someone for an AED simultaneously, rather than one after the other.
- What causes most adult sudden cardiac arrests? → Ventricular fibrillation or pulseless ventricular tachycardia
- What are the indications for defibrillation? → Those same two rhythms
- Why is CPR not enough on its own? → It circulates blood but cannot restore an organised rhythm β only a shock can
How an AED works β β
- The defibrillator sends an electrical current through the heart in an instant.
- This stops all electrical activity in the heart.
- The sinus node then first emits a regular impulse and regains control of the entire heartbeat.
Note the logic: the shock does not 'restart' the heart. It silences everything, so that the fastest natural pacemaker β the sinus node β is the first to fire and can retake control.
The film image of a shock making a flat-line heart leap back into rhythm is exactly backwards. The heart in VF is doing too much, not too little β thousands of independent electrical wavefronts with no coordination.
The shock depolarises the entire myocardium at once, so every cell is refractory simultaneously and all the chaotic circuits are extinguished together. For a moment there is silence. Then the sinus node, being the fastest intrinsic pacemaker, fires first β and because nothing else is competing, its impulse spreads normally.
You are not adding rhythm; you are removing chaos and letting the normal pacemaker win.
- What does the shock do to the heart's electrical activity? → Stops all of it, momentarily
- What happens next? → The sinus node fires first and regains control of the heartbeat
- Is defibrillation a jump-start? → No β it is a reset that silences chaotic activity so the normal pacemaker can resume
Operating an AED β β β
- Turn on the power.
- Follow the voice prompts.
- Attach the electrodes as shown.
- Tell people not to touch the victim.
- The AED analyses the heart rhythm and decides whether defibrillation is required.
- If a shock is required: wait for the AED to charge, make sure no one is touching the patient, then press the button to defibrillate.
- Continue CPR immediately. The AED automatically re-analyses the rhythm 2 minutes later.
- If no shock is required: follow the voice prompt and continue operation.
After defibrillation, CPR is continued for 2 minutes before the AED analyses again.
| Electrode | Placement |
|---|---|
| One pad | Right edge of the sternum, below the clavicle |
| The other | Lateral to the left nipple β the fifth intercostal space, behind the left anterior axillary line |
The deck stresses that electrode placement is related to the defibrillation effect β this is not a detail that can be approximated. The two pads must sit on opposite sides of the heart so the current passes through the myocardium rather than across the chest wall.
Notice that the instruction to keep everyone clear is given at two separate points β once before analysis and once before the shock. They are there for different reasons.
Before analysis, any movement or contact adds electrical noise and can make the AED misread the rhythm β either missing a shockable rhythm or advising a shock wrongly.
Before the shock, the reason is obvious: anyone in contact becomes part of the circuit.
And the step after the shock is just as important β resume CPR immediately rather than waiting to see whether it worked. A heart that has just been defibrillated pumps poorly for some time, and every second without compressions is lost perfusion.
- Where do the two electrodes go? → Right sternal edge below the clavicle; lateral to the left nipple at the 5th intercostal space behind the anterior axillary line
- What must you do before analysis and before the shock? → Ensure nobody is touching the patient
- What do you do immediately after the shock? → Continue CPR
- How soon does the AED re-analyse? → After 2 minutes
Airway foreign body obstruction β β
| Who | Typical circumstances |
|---|---|
| Babies | Eating grapes or jelly; playing with coins, toys or pen caps |
| Adults | Swallowing large, unchewed food; after drinking |
| Elderly | Loose dentures and dysphagia |
The presenting sign is the βVβ sign β the universal choking gesture, both hands to the throat. The first-aid procedure begins with a question: βAre you stuck?β If the patient nods, give immediate rescue and simultaneously call for help and emergency services.
The question is diagnostic precisely because of how they respond. Someone who can speak, cough or shout has a partial obstruction β air is still moving, and coughing is more effective than anything you can do, which is why the deck says encourage loud coughing.
Someone who can only nod has a complete obstruction and needs intervention now. The nod is the sign that they cannot move air β and that changes what you do next.
| Situation | Method |
|---|---|
| Self-rescue β incomplete obstruction | Abdominal shock method β hit the abdomen against the back of a chair |
| Mutual rescue | Encourage loud coughing; then the back percussion method and abdominal impact |
- What is the 'V' sign? → The choking gesture β both hands to the throat
- What question do you ask first? → βAre you stuck?β β and the nod signals complete obstruction
- What do you do for a patient who can still cough? → Encourage loud coughing β it is more effective than intervention
- Name the two rescue techniques. → Back percussion and abdominal impact
Revision
| Question | Answer |
|---|---|
| Commonest arrest rhythm? | Ventricular fibrillation or pulseless VT |
| What does the shock do? | Stops all electrical activity so the sinus node can retake control |
| Electrode positions? | Right sternal edge below clavicle Β· lateral to left nipple, 5th ICS behind anterior axillary line |
| Twice-repeated safety rule? | Nobody touches the patient β before analysis and before the shock |
| Immediately after the shock? | Resume CPR |
| AED re-analysis interval? | 2 minutes |
| Choking sign? | The βVβ sign |
| Patient can cough? | Encourage loud coughing β do not intervene |
| Rescue techniques? | Back percussion Β· abdominal impact |
- Why is early defibrillation essential? → Most adult arrests are VF or pulseless VT, and only a shock restores organised rhythm
- Give the AED sequence. → Power on β follow prompts β attach electrodes β clear everyone β analyse β charge β clear again β shock β resume CPR β re-analyse at 2 min
- Why must nobody touch during analysis? → Movement adds noise and the AED may misread the rhythm
- What is the first-aid question in choking, and why? → βAre you stuck?β β the response distinguishes partial from complete obstruction