Assuming it hasn't been opened and screwed with (which should hopefully be apparent from tamper-evident case construction), it should have a fairly comprehensive self-test built in. There's a pretty in-depth tear-down of one on youtube[1] that describes some of the test aspects.
Assuming it does pass, it's probably better than none at all, although in the worst case the person trying to use it is wasting time with it when they could be giving you CPR.
Definitely a tough call.
If you have an AED, then you're not 'wasting time' getting it set up.
CPR won't restart the heart. An AED _might_. If the person has been down for several minutes, then a few rounds of CPR is a good thing, but if it's less that 2-3 minutes, go right to the AED, don't bother with compressions.
Except you cannot know if the patient is flat-lined or has arrhythmia. The AED performs an ECG and delivers a shock only if appropriate; if you have one available, you should always use it (which does not exclude CPR in the meantime).
Hence the 'might'. An AED may be able to restart a heart in ventricular fibrillation or ventricular tachycardia (I suppose we can quibble over what 'restart' means).
CPR alone never restarts a heart (ok... not 'never', but it's uncommon enough (in adults) that it's not worth fighting over).
In most cases you are correct, an exception is a lightning strike. Random Google coughed up this result "CPR usually has a success rate of 10% or less. In cases of lightning injury, CPR can have success rates of up to 90%. As such, normal rules of triage do not apply. If you find someone without a pulse or respirations after a lightning strike, begin CPR immediately." [1]
[1]http://www.wildernessutah.com/learn/lightning.html
Do you have a source on this? We're talking about a healthy but traumatized heart, right? And are we talking about totally stopped, arrhythmia, or either?
We're talking about a heart that has been sent into either a pulse less ventricular tachycardia, or ventricular fibrillation, due to the timing of the electric shock (generally during the S-T interval).
By 'stopped' I mean 'stopped being effective'. If the heart has truly stopped (asystole), then by all means, pump on the chest.
Clarification is great, but what I really want is a source saying that an AED can help a healthy heart but CPR can't. I've heard somewhat similar things but I've seen little hard data and none of it was related to healthy hearts.
It's simply a matter of what each thing is designed to do.
If a heart has stopped completely (asystole or 'flatline'), then an AED is useless. You can try CPR and epinephrine, and in the best case scenario, you might get the heart into a condition where you can use the defibrillator.
A defibrillator is useful when the heart is beating in a chaotic fashion (or _way_ too fast). The electrical shock it delivers completely stops the heart, in the hopes that the heart's internal pacemaker can take over again.
CPR can't 'reset' the heart, all it can do it help slow down the dying process until you can get a defibrillator in use. Without the defibrillator, the heart will progress into a state where even the defibrillator won't be useful.
Here's the basic protocol:
1) If it's a child, do two minutes of CPR before using the AED (the most common cause of cardiac arrest in kids is respiratory arrest, so ventilating them is sometime all they need)
2) If it's an adult, and they've been down for more than a few minutes, do 2 minutes of CPR to 'prime' the heart to make it more 'shockable'
3) If it's an adult, and you just witnessed the arrest, use the AED straight away. Their heart is likely still oxygenated enough to restart easily. If they're not breathing, be sure to fix that...
I think by "restart", he meant the useful shorthand of "restore a useful rhythm, restart the heart as a pump instead of a tasty snack", and only in the case where the heart was in ventricular fibrillation or tachycardia. AEDs won't turn a "dead" heart into anything but slightly-cooked meat.
(I think you can use them in full manual mode with open chest and electrodes to treat a few more weird rhythms, along with cardiac massage (open-chest or regular CPR), but probably not happening on a paramedic call-out, more likely in a hospital setting. Normally you use CPR + drugs and then try the AED again. I'm not really sure of the details of the limits of dealing with asystole in a hospital setting, but I suspect in an OR they have some extra options vs. other places.)
I wonder if the next step would be being able to deliver drugs (atropine?) in a more targeted way (maybe tiny doses highly localized and recurring? I'm not sure exactly how it works) along with electrical or manual stimulation.
I guess another option might be a rapid way to put someone on heart/lung bypass, either in the field or at least in the ER, rather than only in the OR. Or rapid chilling, or both. I suppose if we either had long-term useful artificial hearts, or a more efficient/effective organ transplant regime, this might be more of an issue.
Atropine is mostly deprecated in cardiac arrest scenarios nowadays. It's still in-protocol for brady PEAs, but that's about it.
Rapid cooling is becoming very widespread in post-ROSC situations (we're spec'ing a chiller box for saline in our next rigs for that very reason), but if they're still dead, cooling them isn't likely to do much for them.
It would be really interesting to see cooling applied to dive medicine (I dive, and a friend of mine is a Canadian Forces MD who did a hyperbaric/dive med fellowship at Duke, so I read some papers on this stuff more than I would otherwise). Also seems like it could be really useful for flight medicine/extended distance transport post ROSC/etc.
