Basic Life Support (BLS) is the foundation of emergency care for individuals experiencing cardiac arrest, respiratory failure, or airway obstruction. For adults, the current protocol emphasizes immediate chest compressions, following the sequence known as Circulation, Airway, Breathing (C-A-B). This systematic approach maintains oxygen flow to the brain and other organs until advanced medical help arrives, minimizing delays in restoring blood flow.
Scene Safety and Emergency Activation
The first action upon encountering an unresponsive adult is to verify the safety of the surrounding environment for both the victim and the rescuer. Hazards like traffic, fire, or live wires must be addressed or avoided before approaching the individual. Once the scene is safe, the rescuer should tap the victim’s shoulder and shout loudly, “Are you okay?” to check for responsiveness.
If the person does not respond, a bystander must be instructed to activate the emergency medical services (EMS) system by calling the local emergency number, such as 911. Simultaneously, the rescuer must look for breathing and check for a pulse for no more than 10 seconds. The pulse is typically checked at the carotid artery in the neck, while observing the chest for signs of normal breathing or only gasping.
If the adult is unresponsive, not breathing, or only exhibiting agonal gasps, and no pulse is felt within the 10-second window, cardiac arrest is presumed. The rescuer must immediately begin chest compressions, as this is the most time-sensitive intervention. If a second rescuer is present, they should be sent to retrieve an Automated External Defibrillator (AED).
High-Quality Chest Compressions
Effective chest compressions are the most important component of high-quality BLS, as they manually circulate oxygenated blood to the heart and brain. To perform this technique correctly, the victim must be lying on their back on a firm, flat surface. The rescuer should kneel beside the victim, placing the heel of one hand on the center of the chest, specifically on the lower half of the sternum.
The second hand is placed directly on top of the first, with fingers interlocked or held up to ensure pressure is not applied to the ribs. The rescuer must keep their arms straight and position their shoulders directly over their hands, using their upper body weight to deliver the force. Compressions must be delivered at a rate of 100 to 120 compressions per minute.
The required depth for each compression is at least 2 inches (5 centimeters) but should not exceed 2.4 inches (6 centimeters). After each compression, it is crucial to allow the chest to fully return to its normal position, known as full chest recoil. Leaning on the chest prevents the heart from refilling with blood, which reduces the procedure’s effectiveness.
The goal is to minimize interruptions in compressions, as blood flow stops completely when compressions are paused. High-quality CPR is sustained by continuing this rapid, deep, and fully recoiled compression technique until the AED is ready or emergency medical personnel take over.
Airway Management and Rescue Breathing
Following 30 high-quality chest compressions, the rescuer provides rescue breaths to deliver oxygen to the lungs. This begins by opening the victim’s airway using the Head-Tilt/Chin-Lift maneuver, which involves placing one hand on the forehead and gently tilting the head back while lifting the chin with the fingers of the other hand.
This simple maneuver moves the tongue away from the back of the throat, which is the most common cause of airway obstruction in an unresponsive person. If a neck or spinal injury is suspected, a modified Jaw-Thrust maneuver should be used instead to open the airway without tilting the head. Once the airway is open, the rescuer pinches the victim’s nose closed and creates a tight seal over the mouth, ideally using a barrier device.
Two rescue breaths are delivered, with each breath lasting approximately 1 second, and the rescuer must watch for the chest to visibly rise. If the chest does not rise with the first breath, the rescuer should quickly reposition the head with the Head-Tilt/Chin-Lift and attempt the second breath. The standardized cycle for a single rescuer without an advanced airway is 30 compressions followed by 2 breaths, which is repeated continuously.
The Role of the Automated External Defibrillator
The Automated External Defibrillator (AED) is an essential device in the chain of survival, delivering an electrical shock to correct chaotic heart rhythms. The AED should be retrieved and applied to the victim’s bare chest as soon as it is available. The device uses adhesive electrode pads, which are placed according to the diagrams found on the pads or the AED unit itself.
In adults, one pad is typically placed on the upper right side of the chest, above the nipple, and the second pad is placed on the lower left side, below the armpit. Once the pads are connected to the AED unit, the rescuer must follow the device’s voice prompts. The AED will analyze the victim’s heart rhythm to determine if a shockable rhythm is present.
If the AED advises a shock, the rescuer must ensure no one is touching the victim before pressing the shock button. Immediately after the shock is delivered, or if the AED advises “no shock,” the rescuer must instantly resume high-quality chest compressions. Minimizing the pause in compressions is paramount for a positive outcome.