Anatomy/Physiology and Health Care for Writers

CPR

Short for cardiovascular pulmonary resuscitation, CPR is a very practical skill to have and can be life saving depending on how quickly it's started. The order of events is referred to as the "chain of survival" and this differs slightly if an adult collapses v a child. If you see an adult down or see one go down it is most likely due to a heart attack whereas for a child it is more likely to be a breathing related issue.

The very first step for either is to assess the scene. It doesn't help others if you or your character are entering into undo danger- at least without assessing the risks of doing so.

Steps from there

Adult:

1- Try and wake the person. In classes we're told to shake the person's shoulder while trying to verbally get a response (ex sir can you hear me?). From there you take no more than 10 seconds to see if they're breathing (chest rising/falling) and check their carotid (neck) pulse. You only start CPR if there's no breathing and no pulse.

2- Call emergency services. A downed adult will definitely need further work up than just CPR that the emergency personal will take from there.

3- Start chest compressions. These need to be about 2in (5cm) in depth. The compressions are deep enough to get through the rib cage to the heart. It is not uncommon for the individual to have broken ribs/sternum afterward from the aggressive necessity that is CPR. The rate is 100-120 beats per minute (commonly "Staying Alive" by the BeeGees has been used to perform CPR on beat to in training). Locking elbows and kneeling over the person is the best way to use your weight and gravity to help. 

Chest compressions are done in five sets of 30. After the five 30s the person doing the compressions can either do 2 rescue breaths (which, while good, aren't exactly required if you're a lay person who doesn't want to get that up close and personal with a stranger) or if there's 2 people present who are trained in CPR this is when they trade spots. This is done until EMS arrives, an AED arrives, the person regains a pulse/consciousness, or in a non modern day scenario whoever is in charge after doing CPR for an extended period of time determines the person is not coming back.

(Child refers to before puberty rather than just "8")

4- AED stands for automated external defibrillator. These machines are amazing and early use can exponentially increase a person's chance of being resuscitated. They're fairly foolproof because most give verbal instructions once they're turned on. 2 pads are placed on the person's abdomen and the AED will say stop compressions. It will then analyze the person's heart rhythm. If they have a shockable rhythm it will say shock advised, stand clear. After the shock the AED will say resume compressions. If the person doesn't have a shockable rhythm the AED will say shock not advised, continue with compressions. The AED will continue to evaluate the heart every few minutes. Continue with the AED and compressions until EMS arrives or the person regains a pulse/consciousness.

The purpose of an AED isn't to start the heart beating, but to reset an abnormal rhythm this is why NO ONE else can be touching the person when a shock is given- the jolt will 'restart' even a regularly beating heart which can inadvertently kill the person trying to help.

For children the process is almost the same, however after confirming the child has no pulse or respirations you start compressions for a couple cycles before calling emergency services because children more likely collapse from a respiratory emergency than cardiac and since their bodies aren't as mature as adults they aren't able to go without oxygen as long as an adult's physiology allows.

Side note: For all intensive purposes a person who needs CPR is "dead" at least for a period of time. Because of that it's not uncommon for a person's muscles to relax and for them to release "fluids" while having CPR done to them.