Tag Archives: ABC vs. CAB

What’s the Deal with CPR ABCs?

The “ABCs” of CPR have always referred to “airway, breathing, and circulation” or, to be more specific:

  • A: Open the airway and make sure it is clear
  • B: Check for breathing; if necessary, give 2 breaths
  • C: Check for signs of circulation (pulse); make sure there is no severe bleeding; give chest compressions in the absence of a pulse or other signs of life

In 2010, when CPR and first aid guidelines were last reviewed, these ABCs were in certain cases modified in an effort to increase the speed and effectiveness of CPR and related care. Understanding the new ABCs of CPR is key to understanding techniques like compression-only CPR and important priorities that make all the difference when seconds count.


The most significant change by far enacted by the Emergency Cardiac Care (ECC) Committee of the American Heart Association consists of rearranging the ABCs of CPR to CAB for patients of sudden cardiac arrest (SCA). CAB means (upon determining you have an unresponsive patient who suddenly collapsed):

  • C: Determine that there is no severe bleeding and begin 30 chest compressions immediately; if you are reluctant to give ventilations or do not have training in that skill, continue to give compressions to the patient until EMS personnel arrive
  • A: If you decide to give breaths, open the airway and make sure it is clear
  • B: Give 2 breaths followed by 30 more compressions

Why CAB Works

This change is designed to get compressions started as quickly as possible for victims that have oxygenated blood. Think about it. The patient was breathing until the moment of collapse. The heart stopped due to an electrical problem, not a lack of oxygen. Giving compressions immediately starts some oxygen-rich blood moving through the body, delivering oxygen to the brain and other vital organs. Taking time to give breaths delays the care this patient really needs.

According to the Sudden Cardiac Arrest Association, SCA is a leading cause of death in the United States, claiming more than 325,000 lives each year. During a sudden cardiac arrest, heart function ceases – abruptly and without warning. When this occurs, the heart is no longer able to pump blood to the rest of the body, and, in some 95 percent of victims, death occurs.

Why Compression-Only CPR Works

CAB is also explains why compression-only CPR works. Since the patient has oxygen in his/her system, performing compression immediately is a more critical care step. A recent study published in the New England Journal of Medicine showed no significant difference between the survival outcomes of patients given compression-only CPR and standard CPR. Compression-only CPR is easier to teach and to perform, especially by bystanders without protective devices learning CPR over the phone.

(For a hilarious American Heart Association public safety announcement starring Ken Jeong, go here.)

So, What About ABC?

Despite the ease and effectiveness of CAB and compression-only CPR for victims of SCA, the ABCs of CPR should still be followed for patients who are hypoxic (without oxygen). This includes the majority of infants and children and cases of respiratory problems that lead to cardiac arrest due to oxygen depletion.

Take a drowning victim for example. This begins as suffocation in water, but the heart usually keeps beating until the oxygen in the blood is used up. Then cardiac arrest occurs. This patient needs ventilations first and then compressions (standard ABC CPR). Giving compression first, or compressions only, to this patient may not be effective due to lack of oxygen in the bloodstream.

What About the “D”?

The “D” stands for defibrillation, administered using an automated external defibrillator (AED). Both patients may benefit from AED administration, which converts disorganized electrical activity in the heart to a normal rhythm. In other words, you can add a D to either ABC or CAB for a more comprehensive solution.

Come to think about it, “E” is for emergency medical services (EMS), which should already have been called (as soon as you know the patient is unconscious). So, now you have a complete chain of survival in both cases:

  • ABCDE for hypoxic patients and children
  • CABDE for adults who suddenly collapse (SCA) or children with known heart conditions