Basic Life Support, CPR Guidelines, Defibrillation & Disaster Triage

Cardiopulmonary arrest and mass casualty disasters demand rapid clinical assessment, flawless psychomotor execution, and prioritized intervention. According to the American Heart Association (AHA) and International Liaison Committee on Resuscitation (ILCOR) guidelines, survival from sudden cardiac arrest relies upon the robust implementation of the Chain of Survival: immediate recognition and activation of emergency response, early high-quality Cardiopulmonary Resuscitation (CPR), rapid defibrillation, advanced resuscitation, and post-cardiac arrest care. In acute crises, healthcare providers must execute standardized algorithms instinctively without hesitation.

1. The C-A-B Sequence Paradigm Shift

Historically, CPR followed the classic A-B-C (Airway, Breathing, Chest Compressions) sequence. The AHA permanently overturned this sequence to C-A-B (Chest Compressions, Airway, Breathing) for adults, children, and infants (with the sole exception of newly born neonates, whose arrests are primarily asphyxial):

• Physiological Rationale: In sudden adult cardiac arrest (frequently arising from ventricular fibrillation), the blood remains well-oxygenated at the moment of arrest, but systemic circulation ceases instantly. The traditional A-B-C sequence introduced critical delays of 30 to 40 seconds while rescuers positioned the victim, cleared the mouth, and delivered rescue breaths. Transitioning to C-A-B initiates chest compressions immediately, generating immediate coronary perfusion pressure (CPP) and cerebral blood flow to preserve vital organ viability.

Systematic Basic Life Support Sequence

1. Step 1: Ensure Scene Safety: Verify that the surrounding physical environment is entirely safe for both rescuers and the victim (check for electrical hazards, fire, traffic, toxic fumes).
2. Step 2: Check Responsiveness: Tap the victim's shoulders firmly and shout loudly: "Are you okay?"
3. Step 3: Activate Emergency Response & Retrieve Equipment: If unresponsive, shout for nearby assistance, immediately activate the hospital emergency code (e.g., "Code Blue") or dial emergency medical services (108/112 in India), and dispatch someone to retrieve the Automated External Defibrillator (AED) and emergency crash cart.
4. Step 4: Simultaneous Assessment of Breathing and Pulse (5 to 10 Seconds):
   • Look for normal breathing: check whether the chest is rising normally or if the patient exhibits abnormal agonal gasps (agonal gasps are reflex, spasmodic gasps that are not normal breathing and represent a sign of cardiac arrest).
   • Simultaneously palpate for a central pulse for a minimum of 5 seconds, but no more than 10 seconds:
     • Adults & Children (1 year to puberty): Palpate the carotid artery in the groove between the trachea and sternocleidomastoid muscle (or femoral artery in children).
     • Infants (<1 year): Palpate the brachial artery on the medial aspect of the upper arm midway between the elbow and shoulder.
5. Step 5: Immediate Action Based on Findings:
   • Pulse present, normal breathing: Place in recovery position and monitor.
   • Pulse present, respiratory arrest (no normal breathing): Provide rescue breaths without compressions:
     • Adult: 1 breath every 6 seconds (10 breaths/min).
     • Child/Infant: 1 breath every 2 to 3 seconds (20–30 breaths/min).
     • Recheck pulse every 2 minutes; if pulse falls below 60 bpm in an infant/child with signs of poor perfusion, initiate CPR.
   • No definitive pulse and no normal breathing (or only agonal gasps): START CPR IMMEDIATELY (C-A-B).

2. High-Quality CPR: Essential Metrics & Performance Criteria

High-quality CPR is the critical biological determinant of Return of Spontaneous Circulation (ROSC). Rescuers must maintain uncompromising adherence to five clinical standards:

1. Compression Rate: 100 to 120 compressions per minute across all age categories (adults, children, and infants). Rates below 100/min compromise perfusion pressure, while rates above 120/min shorten diastolic filling time, reducing stroke volume.
2. Adequate Compression Depth:
   • Adults: Compress to a depth of at least 2 inches (5 cm), but not exceeding 2.4 inches (6 cm). Compressing deeper than 6 cm significantly escalates rib fractures, sternal flail, and internal organ laceration.
   • Children (1 year to puberty): Compress at least one-third the anterior-posterior (AP) diameter of the chest, roughly 2 inches (5 cm).
   • Infants (<1 year): Compress at least one-third the AP diameter of the chest, roughly 1.5 inches (4 cm).
3. Allow Complete Chest Recoil: Allow the chest to re-expand completely after each compression. Leaning on the chest between compressions prevents negative intrathoracic pressure generation, which impairs cardiac venous return, drastically reducing coronary perfusion pressure.
4. Minimize Interruptions in Compressions: Keep all pauses (for ventilation, pulse checks, rhythm analysis, or pad application) strictly under 10 seconds. The goal is a Chest Compression Fraction (CCF) of at least 60%, with optimal clinical performance targeting >80%.
5. Avoid Excessive Ventilation: Each rescue breath must be delivered over 1 second using just sufficient tidal volume (~500–600 mL in adults) to produce visible chest rise. Hyperventilation causes elevated intrathoracic pressure, impeding venous return to the right heart, diminishing cardiac output, and causing gastric distension with pulmonary aspiration.

3. Compression-to-Ventilation Ratios & Techniques Across the Lifespan

Advanced Airway Ventilation in CPR

When an advanced airway is secured (e.g., endotracheal tube, Laryngeal Mask Airway - LMA, or i-gel):

• Chest compressions become continuous without pauses for ventilation at a rate of 100 to 120 compressions per minute.
• Rescuers deliver 1 breath every 6 seconds (10 breaths per minute) asynchronously with compressions.
• Compressing providers must switch roles every 2 minutes (or after every 5 cycles of 30:2) to avoid compressor fatigue and undetected degradation in compression depth.

4. Defibrillation & Management of Cardiac Arrest Rhythms

Cardiac arrest rhythms are partitioned electrophysiologically into Shockable and Non-Shockable categories.

Shockable Rhythms

1. Ventricular Fibrillation (VF): Chaotic, disorganized electrical activity without discernible P waves, QRS complexes, or T waves; myocardium quivers without cardiac output.
2. Pulseless Ventricular Tachycardia (pVT): Rapid, wide, bizarre QRS complexes (>100–200 bpm) originating from ventricular ectopic foci without an associated palpable pulse.

• Management:
  • Deliver an immediate unsynchronized defibrillation shock:
    • Biphasic Defibrillator: 120 to 200 Joules (or manufacturer recommendation; if unknown, use maximum available energy).
    • Monophasic Defibrillator: 360 Joules.
  • CRITICAL RULE: Immediately resume chest compressions for 2 minutes (5 cycles) following shock delivery. Never pause to check rhythm or pulse immediately post-shock, because the stunned heart cannot generate an effective cardiac output even if an organized rhythm is restored.
  • Administer Epinephrine 1 mg IV/IO every 3 to 5 minutes after the second shock, and Amiodarone 300 mg IV/IO bolus after the third shock (repeat 150 mg for subsequent refractory VF/pVT) or Lidocaine (1–1.5 mg/kg initial dose).

Non-Shockable Rhythms

1. Asystole: Complete absence of electrical and mechanical cardiac activity ("flatline"). Confirm in two orthogonal ECG leads to rule out fine VF, disconnected leads, or operator gain error.
2. Pulseless Electrical Activity (PEA): Presence of an organized or semi-organized electrical rhythm on the cardiac monitor without a detectable palpable pulse.

• Management:
  • DO NOT DEFIBRILLATE. Electrical shocks provide zero benefit and worsen myocardial recovery.
  • Provide continuous high-quality CPR.
  • Administer Epinephrine 1 mg IV/IO immediately and repeat every 3 to 5 minutes.
  • Rapidly identify and treat the underlying reversible etiology: The 5 H's and 5 T's.

Reversible Causes: The 5 H's and 5 T's

5. Disaster Triage Systems & The START Algorithm

In routine emergency department practice, triage identifies the sickest patient to receive immediate maximum care. However, in Mass Casualty Incidents (MCIs)—where casualty numbers overwhelm available medical resources and personnel—the fundamental triage philosophy shifts:

"The greatest good for the greatest number of casualties with the most efficient use of available resources."

The START Triage System

The Simple Triage and Rapid Treatment (START) system evaluates adult casualties in 60 seconds or less per patient based on four sequential physiological assessments: Ability to walk, Respiration, Perfusion, and Mental Status (RPM).

Step-by-Step START Algorithm Workflow

1. Step 1: Verbal Directive (Walking Wounded): The triage officer arrives and calls out loudly: "Anyone who can hear my voice and can walk, move to the designated green area now." All patients capable of ambulation are immediately triaged as Green (Minor / Walking Wounded / Priority 3). This clears the scene of lightly injured victims.
2. Step 2: Respiration Assessment (in remaining non-ambulatory casualties):
   • If spontaneous respiration is absent: Manually position the airway (head-tilt chin-lift or jaw-thrust). If breathing resumes, tag Red (Immediate). If the patient remains apneic after opening the airway, tag Black (Deceased / Expectant). In disaster triage, do NOT perform CPR.
   • If breathing is spontaneous: Count respiratory rate:
     • If rate is >30 breaths/min, tag Red (Immediate).
     • If rate is <30 breaths/min, proceed immediately to evaluate Perfusion.
3. Step 3: Perfusion Assessment (RPM - P):
   • Check radial pulse or Capillary Refill Time (CRT):
     • If radial pulse is absent or CRT > 2 seconds, tag Red (Immediate); control any life-threatening external arterial hemorrhage using direct pressure or tourniquet.
     • If radial pulse is present and CRT ≤ 2 seconds, proceed immediately to evaluate Mental Status.
4. Step 4: Mental Status Assessment (RPM - M):
   • Assess ability to follow simple commands (e.g., "Squeeze my hand" or "Touch your nose"):
     • If unable to follow simple commands (unconscious, confused, or altered sensorium), tag Red (Immediate).
     • If able to follow simple commands, tag Yellow (Delayed / Serious / Priority 2).

6. Disaster Triage Tagging Matrix