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Essential Guide to Basic Life Support

May 2, 2025

Basic Life Support (BLS)

Learning Outcomes

  • Describe the components of BLS.
  • Define cardiopulmonary resuscitation (CPR).
  • List steps for performing BLS.
  • Describe how to help a person choking during BLS.

Key Components

  • BLS includes CPR and defibrillation using automated external defibrillators (AED) when available.
  • Keys to survival from sudden cardiac arrest (SCA):
    • Recognition and treatment.
    • Immediate initiation of excellent CPR.
    • Early defibrillation.

Cardiopulmonary Resuscitation (CPR)

  • Emergency first-aid procedure to maintain respiration and blood circulation when breathing and heartbeats stop.
  • Restores the flow of oxygenated blood to the brain and organs during SCA.

Chain of Survival

  • Three basic vital functions: Breathing, Circulation, Consciousness.

Thoracic Pump Theory

  • Chest compression increases intrathoracic pressure to propel blood out of the thorax.
  • Equal time for compression and decompression.
  • Pressure should be completely released.
  • Hands should remain in contact with the chest.

Oxygen Content

  • Atmospheric air: 21% O2.
  • Alveoli: 14.5% O2.
  • Expired air: 16–18% O2.
  • Chest compressions provide about 30% of normal perfusion to brain and heart.

Timing

  • Irreversible cerebral damage can occur 3-5 minutes after circulation failure.
  • The chance of successful CPR (ROSC) decreases by 10% with each minute following SCA.

Conducting BLS

  • Based on guidelines by:
    • International Liaison Committee on Resuscitation.
    • American Heart Association.
    • European Resuscitation Council.

Performance of Chest Compressions

  • Most important element of CPR.
  • CPR-ECC Guidelines: "Push hard and fast on the center of the chest."
  • Optimal rescuer and patient position: firm surface, rescuer's chest above hands.
  • Goals for excellent chest compressions:
    • 100 to 120 compressions per minute.
    • Compress at least 5 cm (2 inches) but no more than 6 cm (2.5 inches).
    • Allow full recoil of chest wall.
    • Change every 2 minutes if possible, minimize interruptions.
    • 30:2 ratio of compression to ventilation.

Ventilation

  • Open airway using head tilt, chin lift, jaw thrust.
  • Check for normal breathing (not agonal gasps).
  • Perform ventilations in hospital with a bag/mask.
  • Ventilation supersedes compressions over time.
  • Give two ventilations after every 30 compressions.
  • Avoid excessive ventilation, 6 to 8 breaths per minute are adequate.

Defibrillation

  • Non-synchronized delivery of a shock during the cardiac cycle.
  • Use AED or normal defibrillator.
  • Assess cardiac rhythm and perform defibrillation quickly when indicated.
  • BLS involves a single shock followed by chest compressions.

CPR Complications

  • Possible injuries: rib and sternal fractures, cardiac and pulmonary contusions, pneumo- and hemothorax, intra-abdominal trauma.
  • Risk of withholding treatment exceeds the risk of complications.

Choking

  • Occurs when a foreign object lodges in airway.
  • Common signs: inability to talk, difficulty or noisy breathing, blue skin/lips/nails, loss of consciousness.
  • Provide first aid quickly to prevent oxygen cut-off to the brain.

Choking First Aid

  • Five back blows:
    • Stand to the side and behind the person.
    • Bend person over at the waist, deliver five blows between shoulder blades.
  • Five abdominal thrusts (Heimlich maneuver):
    • Stand behind person, arms around waist, fist above navel, perform upward thrusts.
  • Alternate between five blows and five thrusts until blockage is dislodged.