CPR is used whenever someone’s heart stops beating or they stop breathing, regardless of what caused it. That covers a wide range of emergencies, from cardiac arrest and drowning to drug overdoses and electrical injuries. The common thread is that blood is no longer circulating oxygen to the brain, and without intervention, irreversible brain damage begins within four to five minutes.
Sudden Cardiac Arrest
This is the most recognized reason to perform CPR. Sudden cardiac arrest happens when an electrical malfunction causes the heart to beat erratically or stop entirely. The person collapses, loses consciousness, and has no pulse. It strikes without much warning and is fatal without immediate action.
Cardiac arrest is not the same as a heart attack, though the two are often confused. A heart attack is a circulation problem: a blocked artery cuts off blood flow to part of the heart muscle. The person is usually conscious and in pain. A heart attack can trigger cardiac arrest, but many heart attack patients never go into arrest. CPR becomes necessary only when the heart actually stops pumping, meaning the person is unresponsive and pulseless.
A large study tracking nearly 195,000 witnessed cardiac arrests found that starting CPR within the first minute nearly doubled the odds of survival compared to not performing CPR at all. Even starting at eight to nine minutes still improved survival. Beyond ten minutes, that benefit disappeared. Every second counts, and bystander CPR is the single most important factor in whether someone makes it to the hospital alive.
Drowning
When someone drowns, water blocks the airway and prevents oxygen from reaching the lungs. The heart continues to beat for a short time, but without oxygen it eventually stops. Respiratory arrest, the cessation of breathing, is actually the most common pathway to cardiac arrest across all emergencies, and drowning is a textbook example.
For drowning victims, rescue breaths are especially important because the core problem is oxygen deprivation. Standard CPR with both chest compressions and breaths is ideal here. If the person is pulled from the water, is unresponsive, and isn’t breathing normally, CPR should begin immediately.
Choking That Leads to Unconsciousness
Choking typically calls for abdominal thrusts (the Heimlich maneuver) while the person is still conscious. But if a choking victim loses consciousness and collapses, the approach shifts to CPR. Chest compressions can help dislodge the object while also keeping blood moving. The Mayo Clinic recommends starting standard CPR with chest compressions and rescue breaths if a choking person becomes unresponsive.
Before beginning compressions, check the mouth for a visible object you can sweep out. If you can’t see one, don’t waste time fishing around. Start compressions.
Drug Overdose
Opioid overdoses kill by shutting down the drive to breathe. Drugs like fentanyl, heroin, and prescription painkillers suppress the brain’s respiratory center, and breathing slows to dangerous levels or stops entirely. If breathing stops long enough, the heart follows. Death from opioid overdose results from cardiac arrest caused by progressive respiratory failure.
Because the fundamental problem is a lack of oxygen rather than a heart rhythm issue, rescue breathing is particularly valuable in overdose situations. Naloxone (Narcan) reverses the effects of opioids and should be given if available, but CPR should not wait for it. If someone is unresponsive and not breathing after a suspected overdose, start CPR. Current guidelines recommend beginning airway support and assisted breathing before administering naloxone when the person is still breathing weakly, and full CPR if they’ve gone into cardiac arrest.
Electrical Shock and Lightning Strikes
Contact with high-voltage power lines, faulty wiring, or lightning can send electrical current through the body and disrupt the heart’s rhythm, causing it to stop. These victims often go into cardiac arrest from the direct effects of the current on heart muscle.
One encouraging detail: because most electrical injury victims are relatively young and don’t have underlying heart disease, their chances of successful resuscitation may actually be better than average, even when their initial heart rhythm looks grim. Prompt CPR and defibrillation give these patients a real shot at survival. The key precaution is making sure the electrical source is no longer active before you touch the person.
Severe Allergic Reactions
Anaphylaxis, a severe allergic reaction to foods, insect stings, or medications, can cause the airway to swell shut and blood pressure to plummet. In the worst cases, the heart stops. Epinephrine (an EpiPen) is the primary treatment, but if the person becomes unresponsive and pulseless before epinephrine is available or after it fails to reverse the reaction, CPR is necessary to maintain circulation until paramedics arrive.
Suffocation and Smoke Inhalation
Any situation that cuts off oxygen can lead to cardiac arrest. Suffocation from a plastic bag, a collapsed structure, or carbon monoxide exposure in a fire all follow the same pattern: oxygen deprivation leads to respiratory arrest, which leads to the heart stopping. Smoke inhalation is especially dangerous because toxic gases like carbon monoxide bind to red blood cells and prevent them from carrying oxygen, even if the person is still technically breathing.
If someone is pulled from a smoke-filled building or found in an enclosed space and is unresponsive with no normal breathing, CPR should begin immediately after moving them to a safe area with clean air.
Hypothermia
Extreme cold slows the body’s metabolism and can cause the heart to beat irregularly, then stop. Hypothermia victims sometimes appear dead, with very slow or undetectable pulses and shallow breathing. CPR is still appropriate if you cannot detect a pulse after checking for up to ten seconds. Cold actually has a protective effect on the brain, so hypothermia victims have been successfully resuscitated even after prolonged cardiac arrest. The medical saying is “they’re not dead until they’re warm and dead.”
How to Recognize When CPR Is Needed
Across all these emergencies, the signs that trigger CPR are the same: the person is unresponsive and not breathing normally. That second criterion trips people up, because about 60% of cardiac arrest victims display agonal breathing, gasping, snoring, or labored breaths that bystanders often mistake for real breathing. Agonal breaths are not effective breathing. They’re a reflex, and they mean the person needs CPR. If someone is unconscious and their breathing sounds like irregular gasps, snoring, or gurgling, treat it as cardiac arrest.
The current guidelines call for chest compressions at a rate of 100 to 120 per minute, pushed to a depth of at least 5 centimeters (about 2 inches) for adults. Push hard, push fast, and don’t stop until paramedics take over or an automated defibrillator is ready to use.
When CPR Should Not Be Started
There are a few situations where CPR is not appropriate. If there are obvious signs that death occurred some time ago, such as rigor mortis (stiffness of the body), skin discoloration from blood pooling, or injuries clearly incompatible with life, CPR will not help. CPR should also not be performed if doing so would put the rescuer in serious danger, such as in an active fire, a collapsing structure, or near a live electrical source that hasn’t been disconnected. A valid do-not-resuscitate order also means CPR should not be initiated, as the person has made a legal decision about their care in advance.