Basic Life Support An Overview

After an initial evaluation for response to voice or tactile stimulation, observation for respiratory movements and skin color, and simultaneous palpation of major arteries for the presence of a pulse, the determination that a life-threatening incident is in progress should immediately prompt a call to EMS (911).

After confirming the cardiac arrest, the goal of BLS is to establish perfusion as quickly as possible using CPR or the concept of cardiocerebral resuscitation (see later). The “ABC” algorithm of BLS (airway-breathing-compression) has been changed to “CAB” (compression-airway-breathing), based on the recognition that compression alone is the primary maneuver because the patient is better perfused by minimizing interruptions between compressions and can be harmed by excessive ventilation.

A precordial thump may be attempted by a trained rescuer as part of an initial response, although its added benefit is questionable. The technique involves one or two blows delivered firmly to the junction of the middle and lower thirds of the sternum from a height of 8 to 10 inches. It should not be used in an unmonitored patient with a perceptible rapid tachycardia or without complete loss of consciousness because of concern about converting organized electrical activity into VF.

Prompt initiation of CPR, which can be performed by professional and paraprofessional personnel, by emergency medical technicians, and by trained laypersons, is the key element for successful resuscitation. The delay between diagnosis and starting CPR should be minimal. If only one witness is present, the only activity that should precede BLS is telephone contact (911) of EMS. The untrained lay bystander can be prompted on how to perform CPR by the EMS telecommunicator.9

Clearing the airway includes tilting the head backward and lifting the chin, in addition to exploring the airway for foreign bodies—including dentures—and removing them. The Heimlich maneuver should be performed if there is reason to suspect a foreign body lodged in the oropharynx, as suggested by severe respiratory stridor rather than by slow agonal respirations or apnea. When the person at the scene has insufficient physical strength to perform the maneuver, mechanical dislodgment of a foreign body can sometimes be achieved by abdominal thrusts with the unconscious patient in a supine position. If there is suspicion that respiratory arrest precipitated the cardiac arrest, particularly in the presence of a mechanical airway obstruction, a second precordial thump should be delivered after the airway has been cleared.

With the head properly positioned and the oropharynx clear, mouth-to-mouth respiration can be initiated. With the exception of Heimlich maneuvers, however, mechanical ventilation strategies are now reserved for EMS responders and medical professionals, rather than bystanders. Devices for establishing ventilation include plastic oropharyngeal airways, esophageal obturators for establishing ventilation, a masked Ambu bag, and endotracheal tubes. Intubation is the preferred procedure, but time should not be sacrificed, even in the in-hospital setting, while awaiting an endotracheal tube or a person trained to insert it. Temporary support with Ambu bag ventilation is the usual method in the hospital until endotracheal intubation can be accomplished. When ventilatory support is provided by EMS responders in the out-of-hospital setting, the lungs should be inflated twice in succession after every 30 chest compressions.