A nurse is performing cardiopulmonary resuscitation (CPR) on a 6-month-old infant who is unresponsive and not breathing. What is the most appropriate compression-to-ventilation ratio for this infant?

The question asks for the most appropriate compression-to-ventilation (C:V) ratio during single-rescuer cardiopulmonary resuscitation (CPR) for a 6-month-old infant. The correct answer is 30:2. This ratio is a critical component of high-quality CPR and is designed to simplify training, improve skill retention, and maximize perfusion pressure during a pediatric cardiac arrest, which is most often triggered by a respiratory, not a primary cardiac, event.

The 2025 Korean Guidelines for Cardiopulmonary Resuscitation and the 2025 American Heart Association (AHA) Guidelines provide a unified, evidence-based framework for pediatric resuscitation ^[1][3]. A fundamental shift in the 2025 guidelines is the recommendation for a universal C:V ratio of 30:2 for single rescuers across all pediatric age groups (infants, children, and adolescents), aligning pediatric basic life support (BLS) more closely with adult protocols ^[3]. This replaces older, age-specific ratios like 15:2 for two-rescuer infant CPR or 3:1 for newly born infants. The rationale is grounded in the pathophysiology of pediatric arrest and practical considerations of resuscitation science.

Pediatric cardiac arrest differs fundamentally from adult arrest. In infants and children, the primary cause is overwhelmingly progressive respiratory failure or shock (asphyxial arrest), not a sudden primary cardiac event ^[1][3]. This means that while chest compressions are vital to circulate oxygenated blood, effective ventilation to deliver oxygen and remove carbon dioxide is equally crucial. The 30:2 ratio for a single rescuer balances these two priorities. It provides a long enough cycle of compressions to build coronary perfusion pressure, which is necessary for the return of spontaneous circulation, while ensuring that ventilations are delivered frequently enough to address the underlying hypoxemia and hypercapnia ^[3].

A recent randomized crossover simulation study compared CPR performance metrics using 15:2 and 10:2 ratios in an infant model ^[2]. While this specific study did not test the 30:2 ratio, it highlights the ongoing scientific inquiry into the optimal C:V ratio. The study's focus on chest compression quality metrics, such as depth and rate, underscores a key principle: the best ratio is one that minimizes interruptions in compressions while still allowing for effective ventilation. The 30:2 ratio achieves this by reducing the frequency of pauses for breaths compared to a 15:2 ratio, thereby increasing the chest compression fraction (the proportion of time during a cardiac arrest that compressions are performed). A higher chest compression fraction is strongly associated with better outcomes ^[3].

It is important to distinguish this single-rescuer recommendation from other scenarios to avoid confusion. The 15:2 ratio (Option 1) remains the recommended C:V ratio for two-rescuer CPR for infants and children ^[3][4]. When two trained rescuers are present, the rescuer performing ventilations can deliver breaths more efficiently, allowing for a shorter compression cycle and a different ratio that prioritizes ventilation slightly more. The 3:1 ratio (Option 4) is specific to newly born infants in the delivery room where the arrest is purely asphyxial in origin. For a 6-month-old infant in any other setting, the single-rescuer BLS protocol with a 30:2 ratio is the evidence-based standard ^[1][3].