Objective: Current CPR depth guidelines of approximately 50mm or at least one-third the anterior-posterior diameter (APD) for paediatric sudden cardiac arrest (SCA) are based on limited evidence compared to adult guidelines. Previous research indicated that 50mm is excessive in a paediatric porcine model, causing traumatic injury including atrial rupture. As highlighted in the recent ILCOR Consensus Statement, there are no recommendations for guiding paediatric CPR depth using physiological parameters. American Heart Association adult guidelines recommend increasing CPR quality if end-tidal carbon dioxide (EtCO2) is less than 10mmHg. The study objective is to assess depth and APD proportion required to achieve EtCO2 of approximately 15mmHg.
Methods: Twelve piglets (11.5–25.0kg) had chest diameter recorded and VF induced. CPR was applied for five two-minute episodes at a rate of 110 compressions per minute. Compressions were administered to achieve a targeted EtCO2 of approximately 15mmHg. The piglets were defibrillated and post-mortem examinations were conducted. Depth was recorded using a Philips MRx with Q-CPR technology. Physiological parameters, were recorded using a Datex Ohmeda S/5 monitor.
Findings: A median(IQR) EtCO2 of 17mmHg (15,19) was observed, which required a median(IQR) compression depth of 24mm (20.64,26.18). This equated to a median(IQR) APD proportion of 15% (13.6,16.4). The median(IQR) systolic blood pressure was 55mmHg (47,69). All animals achieved first shock success, and 11 achieved return of spontaneous circulation (ROSC). Rib fractures occurred in 9 piglets. 
Conclusions: CPR administered at approximately half guideline depth and APD proportion, yielded EtCO2 at least 50% greater than the adult guideline indicator to improve CPR quality. Combined with the high proportion of ROSC, this study indicates that lower than guideline CPR depth and ADP proportion may be sufficient for paediatric patients. As 75% of animals suffered rib fractures at 24mm, increasing CPR depth to 50mm may cause additional damage, with little potential benefit.

7 - The Use of End-Tidal Carbon Dioxide to Evaluate CPR Depth Requirement in a Porcine Model of Paediatric Sudden Cardiac Arrest: Are Current Depth Guidelines Excessive?