A helicopter-based emergency service (HEMS), commonly known as an air ambulance, deploys helicopters crewed by highly trained paramedics and doctors to provide advanced pre-hospital care and rapid transport of seriously ill or injured patients to hospital.
HEMS serves two main functions. In primary responses, the helicopter is dispatched to the scene of an emergency, such as a serious trauma, major illness, or out-of-hospital cardiac arrest, to deliver advanced medical interventions before hospital arrival. These include anaesthesia, surgical airways, blood transfusion, and advanced life support. A helicopter can reach remote or hard-to-access locations and bypass road traffic that would delay ground ambulances. In secondary transfers, critically ill patients are transported between hospitals more rapidly than ground transport allows, for example from a local emergency department to a specialist cardiac, neurosurgical, or paediatric centre.
In the UK, HEMS services are operated by NHS ambulance trusts and independent air ambulance charities. Crew members typically have advanced skills in pre-hospital anaesthesia, resuscitation, and critical care procedures. For out-of-hospital cardiac arrest, HEMS teams can work alongside ground ambulance crews, and some services are trained to initiate extracorporeal cardiopulmonary resuscitation (eCPR) for refractory cardiac arrest.
The presence of a HEMS team can significantly influence outcomes for cardiac arrest patients in remote locations or when prolonged resuscitation is required. Families who see an air ambulance respond to a cardiac arrest should understand that it represents the highest level of pre-hospital medical care available in the UK.
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