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PE24.{1,21} | Cardiorespiratory Arrest — SDL Guide

Learning Objectives

• Describe the aetio-pathogenesis and clinical recognition of cardiorespiratory arrest in children
• Explain the anatomical and physiological basis of paediatric basic life support (BLS)
• Demonstrate the correct sequence, compression technique, compression-to-ventilation ratio, and depth of paediatric BLS
• Distinguish shockable (VF/pVT) from non-shockable (asystole/PEA) rhythms and describe rhythm-directed advanced life support
• Outline the principles of post-resuscitation care after return of spontaneous circulation (ROSC)
• Perform BLS on a paediatric manikin using the correct PALS C-A-B sequence

INSTRUCTIONS

Cardiorespiratory arrest in a child is among the most time-critical emergencies in clinical medicine. Unlike adults, where cardiac arrest is most often primary (arrhythmic), paediatric arrests are predominantly secondary to progressive respiratory failure or shock — making early recognition and airway management pivotal. A final-year student who witnesses a paediatric arrest must be able to initiate BLS immediately, perform effective chest compressions, provide mask ventilation, and call for help in a structured manner. This module equips you with the knowledge and simulated skill to respond to cardiorespiratory arrest in a child or infant.

References

• Ghai Essential Pediatrics, 9th ed., Ch. 27 — Paediatric Emergencies (textbook)
• Nelson Textbook of Pediatrics, 21st ed., Ch. 78 — Resuscitation and Stabilisation (textbook)
• AHA PALS Guidelines 2020 — Paediatric Basic and Advanced Life Support (guideline)

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Version 2.0 | NMC CBUC 2024

Clinical Indication: Recognising Cardiorespiratory Arrest in a Child

Cardiorespiratory arrest is defined as the cessation of effective respiratory effort and effective cardiac output, resulting in absent delivery of oxygenated blood to vital organs. In the clinical setting, arrest is recognised by the triad of unresponsiveness (no response to voice or touch), absence of normal breathing (apnoea or only agonal gasps), and absence of a palpable central pulse for ≥10 seconds. Unlike adults, where sudden cardiac arrest most often reflects a primary arrhythmic event (typically ventricular fibrillation), paediatric arrests are predominantly secondary — occurring as the end-point of progressive respiratory failure or circulatory shock. This is why the peri-arrest state (impending arrest) is often detectable and therefore preventable with prompt intervention.

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Aetiologically, the commonest precursors to paediatric cardiorespiratory arrest include: severe respiratory conditions (pneumonia, bronchiolitis, croup, asthma, foreign-body aspiration), circulatory shock (septic, hypovolaemic, cardiogenic), near-drowning, trauma, severe metabolic derangements (hypoglycaemia, electrolyte disturbances), and toxin ingestion. Respiratory arrest precedes cardiac arrest in most paediatric cases by several minutes, during which the child is hypoxic but the heart is still perfusing — this is the critical window for intervention. Primary ventricular fibrillation and primary cardiac arrest are less common in children but do occur in congenital heart disease and commotio cordis (chest trauma).

Clinical recognition is structured around a rapid primary assessment:
• Responsiveness: tap shoulders firmly and call the child's name
• Breathing: look, listen, and feel for ≤10 seconds — note agonal breathing (occasional, gasping, irregular) is NOT effective breathing
• Pulse check: brachial artery in infants (<1 year), carotid or femoral in children; check for ≤10 seconds; if absent or heart rate <60/min with signs of poor perfusion in an infant, initiate CPR
• Colour and tone: mottled, cyanosed, or ashen skin with generalised hypotonia are ominous signs

Anatomy and Physiology Relevant to Paediatric Resuscitation

The paediatric airway differs from the adult airway in several critical ways that directly shape resuscitation technique. In infants, the occiput is proportionally large, causing passive neck flexion when the child is supine — this naturally obstructs the airway and requires a 'sniffing' or neutral position to open it (not hyperextension as in adults). The tongue is proportionally larger relative to the oral cavity, making it the most common cause of upper airway obstruction in an unconscious child. The larynx is located more anteriorly and superiorly (at C3-4 in infants vs C4-5 in adults) and the epiglottis is floppy and omega-shaped, both of which increase the difficulty of direct laryngoscopy. The subglottis is the narrowest part of the airway in children (vs the glottis in adults) and is functionally 'funnel-shaped', which is why even a small amount of mucosal oedema (croup, post-extubation) causes dramatic obstruction.

The physiological rationale for the airway-first approach in children is rooted in their higher metabolic rate and oxygen consumption per kilogram body weight. Children consume approximately 6–8 mL O₂/kg/min compared to 3–4 mL/kg/min in adults, meaning their oxygen reserves deplete far faster during apnoea. The functional residual capacity is proportionally lower, and the closing capacity may exceed FRC during tidal breathing in infants — leading to early airway closure and V/Q mismatch. This physiology explains why a child can progress from respiratory distress to respiratory failure to cardiac arrest within minutes, and why restoration of oxygenation and ventilation (not just cardiac rhythm) is the cornerstone of paediatric resuscitation.

Cardiac physiology relevant to CPR: the myocardium is relatively non-compliant in infants, and cardiac output is primarily rate-dependent (stroke volume is less variable). Effective chest compressions must restore adequate coronary and cerebral perfusion pressure — determined by compression depth, rate, and minimising interruptions. The thorax in children is more compliant and elastic than in adults, enabling effective compressions with a single hand or even two fingers in infants, but requiring one-third anteroposterior (AP) depth to generate sufficient intrathoracic pressure.

BLS for Children: Technique and Sequence

Paediatric basic life support (BLS) follows the C-A-B sequence (Compressions → Airway → Breathing) rather than the traditional A-B-C, because cardiac output and coronary perfusion must be established promptly in arrested patients. The sequence is as follows:

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Step 1 — Ensure safety and check responsiveness. Tap the child's shoulders and call aloud; tap the foot of an infant. If no response, shout for help and activate the emergency response system (in hospital: call code).

Step 2 — Simultaneously check pulse and breathing (≤10 seconds). In infants: brachial or femoral pulse. In children: carotid or femoral pulse. If absent pulse (or HR <60/min with poor perfusion) and no normal breathing, begin CPR immediately.

Step 3 — Compressions. Position the child supine on a firm surface.
• Infants (<1 year): 2-finger technique (middle and ring fingers over the centre of the chest, just below the nipple line) for a single rescuer; 2-thumb-encircling technique for two rescuers (thumbs over mid-sternum, hands encircle the chest — preferred as it generates higher peak aortic pressure).
• Children (1 year to puberty): heel of one or two hands over the lower half of the sternum (two-hand technique preferred for larger children).
• Depth: compress to one-third the anteroposterior (AP) chest diameter — approximately 4 cm in infants and approximately 5 cm in children. Do not exceed 6 cm.
• Rate: 100–120 compressions per minute for all ages.
• Recoil: allow full chest recoil after each compression; do not lean on the chest.
• Interruptions: minimise to <10 seconds; high-quality uninterrupted CPR is the most important determinant of outcome.

Step 4 — Airway. Open the airway using head-tilt chin-lift (no cervical spine injury) or jaw-thrust (suspected cervical injury). In infants, use a neutral/sniffing position; in children, use slight extension.

Step 5 — Breathing. Deliver two rescue breaths (1 second each, visible chest rise). In infants: mouth-to-mouth-and-nose. In children: mouth-to-mouth with nose pinched. In a healthcare setting, use a bag-valve-mask (BVM) with supplemental oxygen.

Compression-to-ventilation ratio:
• Single rescuer (infant or child): 30:2
• Two rescuers (infant or child): 15:2
• Exception: Once an advanced airway (endotracheal tube, LMA) is in place, give continuous compressions at 100–120/min with asynchronous ventilation at 10 breaths/min — do NOT pause compressions for each breath.

AED use: attach as soon as available; use paediatric pads/key (for children <8 years or <25 kg) if available to reduce energy delivery; if only adult pads available, proceed with them. Defibrillation is ONLY for shockable rhythms — do not shock asystole or PEA.