Each year around 30,000 people in the United Kingdom suffer out of hospital cardiac arrests and less than one in twelve of those returns home alive. Early high quality Cardio-Pulmonary Resuscitation (CPR – ventilation and chest compressions) is critical to survival. However maintaining high quality chest compressions during resuscitation is difficult for crews of emergency vehicles, especially if they are on their own, because of fatigue and the need to perform other actions. Chest compression is particularly difficult in moving vehicles.

A number of mechanical devices, suitable for out of hospital use, have been developed over the years to improve the quality of chest compressions and therefore attempt to improve patient outcomes. Some NHS organisations decided to purchase devices to use although there is limited evidence of their effectiveness. To equip all emergency vehicles in the NHS would cost tens of millions of pounds plus costs for on-going training and maintenance. This prompted the UK Joint Royal College Ambulance Liaison Committee to advise against the purchase of further mechanical chest compression devices until further research had been carried out.

The aim of this trial was to compare the effects of the mechanical chest compressions (LUCAS-2) device versus standard manual chest compressions (crew using their hands) on survival.

LUCAS-2 is a machine that fits around the patient’s chest and performs chest compressions. The potential advantage of LUCAS-2 is that it can provide compressions of a standard depth at a constant rate of 100 per minute for a long time without tiring, it can work in places where it would be difficult to do manual compression, and it enables paramedics to treat the patient in other ways, or attend to other patients.

The LUCAS-2 device has been CE marked by the regulatory authorities, which means that it has been approved to meet European health and safety requirements. However, we do not yet know whether using LUCAS-2 is better than manual chest compression during out of hospital cardiac arrest.

The University of Warwick’s Clinical Trials Unit initiated the trial in collaboration with the Universities of Coventry, Leeds and Surrey and the Welsh and West Midlands Ambulance Services. It is funded by the National Institute of Health Research Health Technology Assessment Programme.

The trial was conducted in partnership with West Midlands, North East, South Central and the Welsh NHS Ambulance Services.

The PARAMEDIC trial was reviewed and approved by Coventry Research Ethics Committee.

All research studies run in the NHS are conducted in accordance with the Research Governance Framework and relevant legislation. The Health Research Authority provides robust, ethical review of proposed research via independent Research Ethics Committees (RECs) who scrutinise applications and put the rights, safety, dignity and wellbeing of research participants at the centre of their decision-making.

NHS Research Ethics Committees consist of 12 members, a third of whom are lay persons (i.e. they are not researchers or healthcare professionals).

They safeguard the rights, safety, dignity and wellbeing of research participants, independently of research sponsors. They review applications and give an opinion about the proposed participant involvement and whether the research is ethical. RECs are entirely independent of research sponsors (that is, the organisations which are responsible for the management and conduct of the research), funders and investigators.

Patients in cardiac arrest in the out-of-hospital environment who were attended by an emergency ambulance vehicle were involved in the trial. Patients who were known, or believed to be under 18 years of age, those known or apparently pregnant and cases where the cardiac arrest was the result of trauma were not included.

Patients were recruited into the study between April 2010 and June 2013. A total of 4,471 patients were enrolled of which 1,652 were in the group where emergency vehicles carried the LUCAS-2 device. A total of 985 patients were treated with the device.

The main result of the trial was that there was no difference in the number of people alive one month after their cardiac arrest (approximately 6 out of 100 were alive in both groups). The trial provides reassurance that the high quality treatments delivered by NHS Ambulance Paramedics are not improved by using a mechanical chest compression device.