Cardiac respiratory arrest, more commonly called cardiopulmonary arrest, is the simultaneous failure of both the heart and lungs. The heart stops pumping blood, breathing ceases, and without immediate intervention, death follows within minutes. It’s distinct from a heart attack (where blood flow to part of the heart is blocked but the heart may still beat) and from respiratory failure alone (where breathing falters but the heart initially keeps going). In cardiopulmonary arrest, both systems have shut down.
How Cardiac and Respiratory Arrest Are Connected
Cardiac arrest and respiratory arrest are technically separate events, but one inevitably triggers the other if left untreated. About 50% to 60% of cardiopulmonary arrests start with a cardiac cause, meaning the heart fails first. The second most common origin is respiratory failure, accounting for roughly 15% to 40% of cases.
When breathing stops first, oxygen levels in the blood plummet. If breathing isn’t restored quickly, the heart loses the oxygen it needs to maintain its electrical rhythm, and cardiac arrest follows within minutes. The reverse also happens: when the heart suddenly stops, blood no longer delivers oxygen to the brain and lungs, and breathing ceases almost immediately. Either way, the endpoint is the same. Both systems fail, and the body’s organs begin to sustain irreversible damage. Brain cells are especially vulnerable, with permanent injury beginning as early as four to six minutes after collapse.
What It Looks Like
Cardiopulmonary arrest is unmistakable. The person suddenly collapses, has no pulse, stops breathing, and loses consciousness. There is no gradual buildup of symptoms once arrest occurs. Some people experience a few seconds of gasping breaths called agonal gasps, which can look like labored, irregular gulping. These are not true breathing and should not be mistaken for a sign that the person is okay.
In some cases, warning signs appear in the minutes or hours before arrest. Chest pain, shortness of breath, dizziness, or a racing heartbeat can precede a cardiac event. But many arrests happen with no warning at all, particularly those caused by an abnormal heart rhythm.
Common Causes
The triggers for cardiopulmonary arrest fall into two broad categories. Cardiac causes include heart attacks, dangerous heart rhythms, and structural heart disease. Respiratory causes include choking, drowning, severe asthma attacks, drug overdoses that suppress breathing, and allergic reactions that close off the airway.
Emergency medicine organizes the reversible causes into a checklist sometimes called the H’s and T’s:
- Hypovolemia: severe blood or fluid loss
- Hypoxia: dangerously low oxygen
- Acidosis: a harmful shift in the blood’s pH balance
- Electrolyte imbalances: too much or too little potassium, for example
- Low blood sugar
- Hypothermia: dangerously low body temperature
- Toxins or poisoning
- Fluid or air compressing the heart: conditions where pressure around the heart prevents it from filling
- Blood clots: in the heart’s own arteries or in the lungs
- Trauma: severe physical injury
Identifying and treating the underlying cause is the only way to give someone a real chance at recovery. CPR buys time, but the arrest won’t resolve until the trigger is addressed.
Why Children Are Different
In adults, a sudden heart rhythm problem is the most common starting point. In children, the pattern is reversed. Pediatric arrests most commonly begin with progressive respiratory failure or shock rather than a primary heart problem. In one large study of in-hospital pediatric arrests, respiratory decompensation was the leading cause in about 41% of cases, and low blood pressure or shock accounted for roughly 46%. More than half of children who experienced arrest were already on a ventilator due to breathing problems.
This distinction matters because the treatment approach differs. For children, restoring adequate breathing and oxygen delivery is often the most critical early intervention, whereas adults more frequently need their heart rhythm corrected first.
Survival Rates and What Improves Them
Survival after out-of-hospital cardiopulmonary arrest remains low. The median rate of survival to hospital discharge in the United States is 10.4%, a number that has barely changed in three decades. For children between ages 1 and 18, the figure is slightly higher at about 15.9%.
Bystander action makes a measurable difference. When someone receives CPR from a bystander before paramedics arrive, survival to hospital discharge rises to 13.0%, compared with 7.6% when no bystander CPR is given. Using an automated external defibrillator (AED) within the first five minutes pushes outcomes even further. Research modeling universal early AED use projects that it could more than double the rate of favorable brain recovery. The estimated number needed to treat is about 24, meaning that for every 24 witnessed arrests where a bystander applies an AED within five minutes, one additional person walks away with a good neurological outcome.
The math behind these numbers is straightforward: the brain starts suffering irreversible damage within four to six minutes. Every minute without blood flow or oxygen narrows the window for meaningful recovery.
What Happens After Resuscitation
Getting someone’s heart restarted is only the beginning. Survivors face a condition known as post-cardiac arrest syndrome, which involves four overlapping challenges. First, the brain sustains injury from the period without oxygen. This can range from mild confusion and memory problems to severe, lasting neurological damage. Second, the heart itself is often weakened and may pump poorly for hours to days after being restarted. Third, the entire body mounts an inflammatory response similar to what happens in severe infections, as organs react to having been starved of blood and then suddenly reperfused. Fourth, whatever caused the arrest in the first place, whether a blocked artery, an overdose, or a lung problem, still needs to be treated.
Recovery timelines vary enormously depending on how long the arrest lasted and how quickly effective CPR began. Some people recover fully within days. Others face weeks or months of rehabilitation, and some sustain permanent brain injury. The strongest predictor of a good outcome is the time between collapse and the start of circulation, either through CPR or return of the heart’s own rhythm. This is why rapid bystander response carries so much weight in the survival data.