In this retrospective study, the investigators seek to investigate the incidence of pneumothorax following possible risk factors, and elucidate its association with outcomes.

This is a retrospective analysis of routine data, collected by a single Emergency Medical System (EMS). Adult patients (≥18 years) hospitalised after Out-of-Hospital Cardiac Arrest (OHCA) who received chest compressions and underwent chest imaging within 12 hours after hospital admission were included.

Variables and outcomes ascertained are built up of the core elements of the latest version of the Utstein Resuscitation Registry Template for OHCA. This includes sex, age, aetiology of arrest, response times of the first emergency medical service team and emergency physician, witnessed cardiac arrest, bystander CPR/AED, arrest location, first monitored rhythm, defibrillation time, drugs given, reperfusion attempted and target temperature management. Additional variables studied were pre-existing health status represented by the Pre Emergency Status Assessment (PESA), history of lung disease, no-flow-time (time from collapse until initiation of CPR), use of a mechanical chest compression device and prehospital CPR duration.

The primary outcome is incidence of pneumothorax, secondary outcomes are survival to hospital discharge and favourable neurological condition at hospital discharge defined by a cerebral performance category (CPC) of 1 or 2.

Inclusion Criteria:

• Hospitalized after out of hospital cardiac arrest
• Chest compressions received
• Chest imaging within the first 12 hours of admission

Exclusion Criteria:

• Traumatic cardiac arrest
• Chest trauma/surgery/pneumothorax one month prior to cardiac arrest

Mid-Size European city + surrounding areas