Title: A feasibility study of the use of a mechanical chest compression device for in-hospital cardiac arrest
Funder: Department of Health and Social Care

Abstract: Background: Each year, 35,000 patients have a cardiac arrest in UK hospitals. Only 18% of these survive to leave hospital. Survival is dependent on the delivery of high-quality chest compressions, but delivery of high-quality chest compressions is often unachievable in the hospital setting. Mechanical chest compression devices have been developed which consistently deliver high-quality chest compressions. Observational studies in animals and humans report an association between the use of mechanical chest compression devices and improvements in cardiac arrest blood flow and survival. However, three recent large pre-hospital randomised controlled trials of mechanical chest compression devices found no evidence of benefit. Key differences limit the generalisibility of these data from the pre-hospital to the in-hospital cardiac arrest setting. Indeed, these differences make it likely that mechanical chest compression devices will improve survival in the hospital setting. A key reason for this is that chest compressions in the hospital setting are usually delivered with the patient on a compressible bed mattress that makes it extremely difficult to achieve the recommended chest compression depth, as during chest compressions the mattress is compressed as well as the patient's chest. There are few data on the use of chest compression devices in hospital. We are aware of one randomised controlled trial published in the last twenty years. This small study with 150 participants found that devices improved survival (hospital survival odds ratio 2.81, 95% CI 1.26 to 6.24). A Cochrane systematic review and the International Liaison Committee on Resuscitation have highlighted the urgent need for further research. There is a need for a randomised controlled trial comparing mechanical CPR with manual CPR in the adult in-hospital cardiac arrest population. A survey of 224 UK clinicians provides evidence of clinical equipoise; most respondents (79%) supported the need for a trial. Such a trial would require over 3500 participants and be challenging to deliver. We propose to first undertake a feasibility study to establish whether such a trial is deliverable. Aims: To assess the feasibility of undertaking a definitive trial to compare mechanical and manual chest compression delivery in the hospital setting. Plan of investigation: Work Package 1. I will undertake an evaluation manikin study to test a training programme to ensure that the device can be used effectively during the feasibility study.Work Package 2. A randomised controlled trial in two large NHS hospitals to assess feasibility of recruitment, i.e. proportion of eligible patients recruited. This work package may also enable me to identify whether or not an effectiveness trial might show a clinically important difference between treatments. 330 adult cardiac arrest patients in a non-shockable rhythm will be randomised to either mechanical chest compressions or manual chest compressions. We will measure CPR quality and patient outcome. Survivors will be followed-up to seek retrospective consent. This work package will provide important information about whether a definitive study is feasible. Work Package Three. Tape-recorded semi-structured interviews will be conducted with approximately 30 clinicians. I will purposively sample clinicians involved in the study, who have either randomised or been unable to randomise a patient in to the study. I will explore participant's experiences of enrolling patients in the study. This will enable the identification of actual and potential barriers to study recruitment, that can be addressed both in this study and a subsequent definitive study. Potential benefits to patients and the NHS: The vast majority of patients who have an in-hospital cardiac arrest will die. Improving chest compression delivery through the use of mechanical devices may be a clinically and cost-effective way to improve patient outcome.

Lay abstract: Every year, 35,000 patients have a cardiac arrest in UK hospitals. However, less than one in five patients survives to leave hospital. A cardiac arrest occurs when the heart suddenly stops pumping blood. When someone has a cardiac arrest, immediate treatment is essential. Chest compressions are a key part of this treatment. This involves pressing down on the patient's breastbone at about 100 times per minute to a depth of 5-6cm. The effectiveness of chest compressions is extremely important and affects how likely someone is to survive. However, high-quality chest compressions are difficult to perform and the performance of doctors and nurses often does not reach the standard required. Mechanical chest compression machines can be used to deliver chest compressions instead of a human. These devices deliver a high standard of chest compressions. Researchers have done a series of large studies, where patients who had a cardiac arrest outside of hospital were allocated by chance to receive either mechanical chest compressions or chest compressions delivered by a person. These studies found that using these machines did not improve survival, when compared with a human delivering chest compressions. There are a number of reasons to explain these findings. One possible explanation is that because ambulance paramedics do not treat cardiac arrest patients very often, they may not have used the chest compression machine as well as people who have more experience of using the machine. There are important differences between cardiac arrests that happen inside and outside of hospitals. We think it is likely that these differences will mean that mechanical chest compression machines may improve survival following in-hospital cardiac arrest. We want to test this idea in a large trial in which patients who have a cardiac arrest in hospital will receive chest compressions delivered by either a mechanical device or a human. The treatment that patients receive will be decided by chance. Only by undertaking this large trial will we know for sure whether chest compressions delivered by a machine are better than those delivered by a human. A large trial will be expensive and may face quite a few practical challenges, so we plan to undertake a small study first to make sure that the large trial is practically possible. The aim of this first study is to assess whether or not the large trial can be done. We will do this by undertaking three packages of work: i) test our training package to ensure that mechanical chest compression devices can be used effectively by doctors and nurses involved in the study, ii) undertake a small version of the larger trial; and iii) interview doctors and nurses to explore practical changes that affect how well we can deliver the study. This study will take place in two NHS hospitals. After developing and testing the study training programme, we will implement it at study hospitals. We will then start the small version of the larger trial. Patients who have a cardiac arrest receive either chest compressions delivered by either a human or the chest compression machine. The treatment will be decided by chance. Over a two-year period, 330 patients will be enrolled. There will be some people who are unable to take part, including patients that are pregnant and patients who need an electric shock (defibrillation) to restart their heart.All patients will receive chest compressions as well as all other necessary treatments. For this first study, we are mainly interested in how many patients actually take part. We will also collect information about patient's hospital stay. If we are able to conduct a large study, we will look at the effect of mechanical chest compression devices on patient survival. We will interview staff about any difficulties they have had with their involvement with the study. We will do this by undertaking approximately 30 tape-recorded interviews. Results of these interviews will help us identify any problems we may face in the large trial. We will share information about this work through a number of ways. For health professionals, we will publish the results in journals and present them at conferences. For members of the public, we will publicise the results through hospital newsletters and websites. We will also present the results at a public meeting, where attendees will have the chance to learn how to perform chest compressions.

Research activity codes: 6.3 MEDICAL DEVICES
Health categories: CARDIOVASCULAR