Differences Between Respiratory Arrest and Cardiac Arrest

In the medical world, the term arrest is used often to describe a condition where something that should be happening has stopped.

Though respiratory arrest and cardiac arrest mean specific things, the terms can be confusing for patients or laypeople. The difference between them is the presence of a pulse.

During respiratory (also known as pulmonary) arrest, breathing stops. During cardiac arrest, blood flow stops. Technically, cardiac arrest means that the heart has stopped beating, but it's really assessed by the fact that blood flow is no longer detectable, even if the heart might still be trying to beat.

Without treatment, respiratory arrest will lead to cardiac arrest, and cardiac arrest will quickly cause respiratory arrest. When the two occur together—when the person's heart has stopped and they're not breathing—it's typically just called cardiac arrest.

How to Tell the Difference

In both respiratory arrest and cardiac arrest, the patient will be unconscious and not be breathing. However, respiratory arrest patients still have a beating heart that is pushing blood around the body. Cardiac arrest patients do not.

Without fancy equipment, the only way to tell if the blood has stopped flowing is to feel for a pulse. The way to feel that beating heart is through the blood pulsing through the arteries. It's not a perfect procedure and there is a possibility of getting it wrong, even if you're a trained healthcare provider.

Both respiratory arrest and cardiac arrest are treated with cardiopulmonary resuscitation (CPR). If you encounter a person whose heart has stopped or isn't breathing, you should do the same thing: Call 911 and push on the chest.

Respiratory Arrest Leads to Cardiac Arrest

These two conditions are absolutely linked. Respiratory arrest will always lead to cardiac arrest if nothing is done to treat it. When a patient has respiratory arrest, two things happen:

1. Carbon dioxide is not removed properly from the bloodstream, leading to a buildup of carbonic acid. The excess acid can cause problems in the brain and in the heart.
2. Eventually (much slower than the buildup of carbon dioxide), oxygen levels in the bloodstream will diminish. The lack of oxygen will also lead to problems in the brain and heart.

Without treatment, respiratory arrest always leads to cardiac arrest. Sometimes, however, it can take several minutes.

Cardiac Arrest Always Includes Respiratory Arrest

Cardiac arrest means the heart is no longer moving blood through the body. It might be beating or not, but either way, there isn't any blood pulsing around. Without blood, the brain cannot survive. A constant supply of fresh blood is required to keep the brain alive and functioning properly.

When blood supply stops, the brain shuts down, including its respiratory center. So, when the heart stops, so does breathing, usually within a minute or less. A person may have irregular, "gasping" breaths (called agonal breathing) before they stop breathing completely.