Poor survivability following infant cardiac arrest has been attributed to poor quality chest compressions. Current infant CPR manikins, used to teach and revise chest compression technique, appear to limit maximum compression depths (CDmax) to 40 mm. This study evaluates the effect of a more "physiological" CDmax on chest compression quality and assesses whether proposed injury risk thresholds are exceeded by thoracic over-compression. A commercially available infant CPR manikin was instrumented to record chest compressions and modified to enable compression depths of 40 mm (original; CDmax40) and 56 mm (the internal thoracic depth of a three-month-old male infant; CDmax56). Forty certified European Paediatric Life Support instructors performed two-thumb (TT) and two-finger (TF) chest compressions at both CDmax settings in a randomised crossover sequence. Chest compression performance was compared to recommended targets and compression depths were compared to a proposed thoracic over-compression threshold. Compressions achieved greater depths across both techniques using the CDmax56, with 44% of TT and 34% of TF chest compressions achieving the recommended targets. Compressions achieved depths that exceeded the proposed intra-thoracic injury threshold. The modified manikin (CDmax56) improved duty cycle compliance; however, the chest compression rate was consistently too high. Overall, the quality of chest compressions remained poor in comparison with internationally recommended guidelines. This data indicates that the use of a modified manikin (CDmax56) as a training aid may encourage resuscitators to habitually perform deeper chest compressions, whilst avoiding thoracic over-compression and thereby improving current CPR quality. Future work will evaluate resuscitator performance within a more realistic, simulated CPR environment.
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