The current guidelines for Cardiopulmonary Resuscitation (CPR) use the mnemonic CAB (Compressions, Airway, Breathing) to guide rescuers. This sequence represents a fundamental shift from the previous ABC protocol. The primary goal of this updated order is to minimize delay in starting chest compressions, ensuring the most critical life-saving step is performed first. This change reflects a greater understanding of what is required to sustain life in the initial minutes following a cardiac arrest.
What Compressions Means
The “C” in the CAB sequence stands for Compressions, which are rhythmic, forceful pushes on the center of the chest. Compressions are the first and most emphasized step in adult CPR because they mechanically circulate blood when the heart has stopped. The brain and heart need a continuous supply of oxygenated blood to prevent rapid cell death. When an adult collapses from sudden cardiac arrest, there is often enough residual oxygen in the bloodstream for a few minutes. Compressions move this existing oxygenated blood to the vital organs immediately, utilizing this limited supply until professional medical help arrives.
Proper Technique for Chest Compressions
Effective chest compressions require a specific technique focused on depth, rate, and recoil to generate adequate blood flow. The heel of one hand should be placed in the center of the chest, on the lower half of the breastbone, with the other hand placed on top. The rescuer should position their shoulders directly over their hands, keeping their elbows straight and using their body weight to press down.
For an adult, compressions must be delivered to a depth of at least 2 inches, but not exceeding 2.4 inches. The rate of compressions requires a rhythm of 100 to 120 pushes per minute. Equally important is allowing the chest to fully recoil after each compression, which permits the heart to refill with blood. Interruptions to compressions should be minimized, ideally to less than 10 seconds, as pauses reduce the blood pressure needed to sustain the brain and heart.
Completing the Sequence: Airway and Breathing
Following the initial set of 30 compressions, the rescuer proceeds to “A” for Airway and “B” for Breathing. The airway is opened using a head-tilt, chin-lift maneuver, which involves gently tilting the head back and lifting the chin. This action moves the tongue away from the back of the throat, preventing obstruction. After opening the airway, “B” involves giving two rescue breaths, each lasting about one second, while watching for the chest to visibly rise.
For lay rescuers who are untrained or uncomfortable giving rescue breaths, Hands-Only CPR is recommended, focusing solely on continuous chest compressions. This approach ensures that compressions, the most significant life-saving intervention, are not delayed. The complete sequence for trained rescuers involves alternating 30 compressions with two breaths, continuing until emergency medical services arrive or the person begins to move.