Optimal chest compression depth during CPR is 4.56cm which is at variance with the current guidelines of 5.0-6.0cm. A change in guidelines is only worthwhile if healthcare professionals can accurately judge a subtle reduction in chest compression depth during CPR by a relatively small amount.

Chest compression depth and rate during cardiopulmonary resuscitation (CPR) are important predictors of return of spontaneous circulation and survival following cardiac arrest. Stiell et al (2014) found optimal survival at a compression depth of 4.56cm, which is at variance with the current guidelines of 5.0-6.0cm. A change in guidelines is only likely to improve survival rates if healthcare professionals can accurately implement these subtle depth modifications into the basic life support (BLS) algorithm. This study aims to determine if healthcare professionals can accurately judge compression depth without real-time feedback.

Inclusion Criteria:

• NHS professionals (staff or students), who have successfully completed a hospital-accredited basic life support (BLS) course, including a practical CPR component.

Exclusion Criteria:

• Pregnancy, significant medical illness or injury that would impair delivery of chest compressions

Available on request

Participants and researchers are blinded to the actual depth achieved during each CPR run.