Lesson 3 of 10
In Progress

Basic Life Support (BLS)

Jimmy September 14, 2021

Basic Life Support (BLS) is the basic, fundamental skills set used for emergency care.

  • BLS provides the basic level of care in cardiopulmonary arrest.
  • BLS can be provided at a quickly or more slowly acquired level of patient response or illness. This is dependent on the skill of the provider and availability of equipment and training to provide a specific benefit.
  • BLS is a level of care used to treat people with life-threatening illnesses until advanced life support can be provided by trained healthcare professionals.
  • The knowledge gained from BLS is required for qualified providers to continue their education in ALS/advanced care level providers, prevent injury to the provider, and provide the best possible outcome for the patient.

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  • After confirming that there is no pulse at the carotid, chest compressions should be started as soon as possible.
  • The aim is to push hard and fast enough to move blood through the body.
    With 100 to 120 compressions per minute, the rescuer should be aiming for a depth of at least 5cm or 2 inches. It is not recommended that rescuers perform more than two minutes of continuous CPR because high levels of fatigue will reduce the effectiveness of chest compressions.
  • For a successful resuscitation, chest compressions of high quality are necessary. A chest compression increases intrathoracic pressure by compressing the heart directly. 
  • When not provided with chest compressions, the patient’s time without a pulse is extended.
    • The patient’s chances of regaining a pulse diminish with each passing moment without chest compressions.

Historically, chest compressions have been interrupted during CPR quite often, and the “hands-off” period accounts for a significant amount of the total resuscitation time.

  • High-quality cardiopulmonary resuscitation
    • Chest compressions are associated with increased survival to hospital discharge
    • Do not interrupt for vascular access, drug delivery, or advanced airway placement
  • Blood Flow Models During CPR
    • Cardiac pump model
      • The heart is squeezed between the sternum and the spine in the cardiac pump model. During systole, compressions of the chest mimic atrioventricular valve closure making sure unidirectional, antegrade flow takes place. Within the relaxation phase (diastole), the heart pressure decreases, the valves open, and blood comes to the heart from the lungs and vena cava.
    • Thoracic pump model
      • The heart is considered a passive conduit in the thoriac pump model. A chest compression increases pressure uniformly throughout the thorax. One-way valves in the great veins prevent retrograde flow and stiff-walled arteries promote forward blood flow in the arterial system.  When performed properly, chest recoil during CPR serves two purposes: (1) it improves the quality of chest compressions by increasing the volume of blood in the heart, and (2) it increases coronary blood flow due to the negative intrathoracic pressures

Airway & Breathing

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  • There has been an emphasis to change initial BLS from ABCs to CABs to promote more efficient chest compression and less emphasis on establishing an airway.
  • If the rescuer is not trained in BLS, they should only apply chest compressions to adults experiencing cardiac arrest outside of the hospital until trained personnel arrive.
  • For trained BLS providers provide ventilation 1 breath every 6-8 seconds (10 breaths per minute

During resuscitation, excessive ventilations can worsen hemodynamics by increasing intrathoracic pressure and reducing cardiac output. As a consequence, excessive ventilations should be avoided.


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Immediately place the AED leads on the victim.

If the rhythm is shockable, deliver one shock. Then resume CPR for 2 minutes or until the AED prompts you to make another rhythm check; otherwise, resume CPR immediately.

Delays in the application of defibrillation are clearly deleterious; research shows that survival rates drop sharply after an eight-minute delay, and drop even more over time. Every second matters when it comes to saving patients with cardiac arrest caused by ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT).

Defibrillate the patient according to the manufacturer’s instructions. If it’s a monophasic defibrillator, set the machine to deliver 150 J; if it’s a biphasic defibrillator, set the dosage at 200 J.

  • Associated with increase in survival  with a number need to treat of ~4