Reducing peri-shock pauses in out-of-hospital cardiac arrest increases odds of survival
Following publication of the 2010 American Heart Association-International Liaison Committee on Resuscitation (AHA-ILCOR) guidelines, there has been an increased focus on the characteristic components of cardiopulmonary resuscitation (CPR) including length of peri-shock pause, chest compression fraction (CCF), chest compression depth, chest compression rate and chest compression recoil.
This study set out to examine the association between the length of the peri-shock pause and survival from shockable out-of-hospital cardiac arrest (OHCA) using data from patients enrolled in a randomised control trial known as the Resuscitation Outcomes Consortium Prehospital Resuscitation Impedance Valve and Early versus Delayed Analysis (ROC PRIMED).
Peri-shock pause is the sum total of both pre- and post-shock pauses. Preshock pause is the time between cessation of chest compressions and the shock being delivered, and postshock pause is the time between shock delivery and resumption of chest compressions.
For this study, 2 006 patients (from a total of 15 794 in ROC PRIMED) met the inclusion criteria: adults aged 18 years or older, who had sustained a non-traumatic OHCA and had an initial presenting rhythm of ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT) for which CPR process data for at least one shock was obtainable.
The primary outcome was survival to hospital discharge and the secondary outcome involved assessment of neurological function using a Modified Rankin Score.
During analysis the shock pause length (seconds) was examined categorically, <10, 10–20, ≥20 for pre-shock pauses, <5, 5-10, ≥10 for post-shock pauses and <20, 20–40, ≥40 for peri-shock pauses.
Comparison of CPR components demonstrated no significant difference for CCF, compression rate or depth between survivors and non-survivors. For shock pause duration, however, pre-shock pause was 18% shorter (14 seconds versus 17 seconds) for survivors compared to non-survivors; 17% shorter for both postshock pauses (5s vs. 6s) and peri-shock pauses (20 seconds versus 24 seconds) for survivors compared to non-survivors. Pre-, post- and peri-shock pause durations were significantly different (p<0.001) between survivors and non-survivors.
Odds ratios were calculated to examine the relationship between pre-, post-, and peri-shock pause duration and survival to hospital discharge. Shorter pre- and peri-shock pauses were significantly associated (p<0.001) with survival to hospital discharge. Specifically, patients experiencing a pre-shock pause of <10 seconds had a higher odds of survival to hospital discharge (OR: 1.52, 95%: 1.09, 2.11) when compared to episodes with a median pre-shock pause of ≥20 seconds. For perishock pause duration, a peri-shock pause of <20 seconds produced a higher odds of survival to hospital discharge (OR; 1.82, 95%: 1.17, 2.85) when compared to peri-shock pause duration of ≥40 seconds. Interestingly, post-shock pause was not significantly associated with survival to hospital discharge.
When looking at the relationship between shock pause duration and a positive neurologically intact survival (MRS ≤3), lower pre- and peri-shock pause duration were significantly associated (p<0.001) with positive neurological outcome. The odds of neurologically intact survival were significantly higher with a pre-shock pause <10 seconds (OR: 1.49, 95%: 10.05, 2.13) compared to ≥20 seconds; similarly with the peri-shock pause, the odds of neurologically intact survival were significantly higher if the pause was <20 seconds (OR: 1.99, 95%: 1.21, 3.29) when compared to duration ≥40 seconds.
Limitations to the study are that the data are taken retrospectively from other research and are observational. Further investigation would be needed to determine whether the effects of peri-shock pause duration is of a causal relationship. The authors also note that the study is undertaken in a region with a heavily monitored EMS system, with overall rapid response times and high CPR quality, therefore they caution against generalisation to other EMS systems which may not have similar characteristics.
The results of this research reinforce the importance of minimising ‘time off the chest’ during CPR attempts, especially during the pre-shock phase supporting the practice of performing chest compressions during the charging phase when using an AED, or using defibrillators in manual mode to reduce pre-shock pause length. Although further research is required, these findings indicate that shortening the peri-shock pause (especially pre-shock) could possibly improve the odds of patients surviving to hospital discharge with favourable neurological outcomes after out-of-hospital cardiac arrest.
Patient safety: can we learn from the aviation industry?
Patient safety is a key priority in UK healthcare provision and is an issue that must be considered by healthcare professionals during every encounter with their patients.
In healthcare contexts, recognition of human factors (HF) includes exploration of people and culture (staff delivering care) and their relationship with a variety of systems and processes (organisational and clinical) within which the care is being delivered. In relation to serious adverse incidents, rather than looking to attribute blame to specific individuals for error, the HF approach seeks to understand the fallibility of human performance within complex organisations and socio-technical systems.
The aviation industry has developed this approach over many years with considerable success, and recently healthcare organisations in the UK have begun to examine HF training in a variety of settings including the emergency department (ED).
This paper reports on a qualitative study which set out to determine whether aviation-based HF trainingis acceptable and useful to healthcare professionals. This involved employing experts in HF from aviation to train 20 senior clinicians (physicians, surgeons, nurses and theatre practitioners) to act as an interprofessional faculty for HF training. Once trained, this faculty group delivered a six day HF programme to 19 professional staff (six males; 13 females) from ED and theatres. The paper outlines the course content in detail which included knowledge of HF; effective teamworking and communication; analysis of serious incidents; and management of change, amongst other topics.
Data collection methods comprised two focus groups with 12 members of the faculty during the initial training course; plus, three months after the programme had finished, researchers conducted 10 semi-structured individual interviews with faculty members and 11 interviews with participants from the first course. All events were recorded, transcribed and analysed thematically.
Five key themes emerged: evaluation of the programme; ‘tried to do it’; social context; barriers to implementation; is HF work a professional or managerial activity?
Overall participants evaluated the programme positively and viewed HF from an aviation approach to be acceptable and useful. The researchers note that its success could be attributed to the clinical focus in the programme and the fact that it was delivered by clinicians rather than ‘management’.
Everyone reported trying to put what they had learned in to practice although there appeared to be differences in social context between theatres and ED, with ED staff reporting a loss of momentum since completion of the course.
In addition, several barriers to implementation were identified which were embedded in organisational structures and culture. There was some reluctance for people to change ways of working especially if these changes were perceived to involve extra work. Participants suggested that some of the barriers may have been overcome had they continued to meet as a support group after the initial course; that ‘management’ needs to provide more active support to enable changes to be implemented; and all staff should receive HF training so that everyone understands the approach.
There was no consensus as to whether HF work was a professional or a managerial activity and, on occasion, participants found it difficult to separate the two. Some participants were clear that certain issues in HF were the responsibility of ‘management’ and not clinicians, which the authors suggest could be an obstacle to future development of HF in healthcare.
‘Ambulance services could provide excellent environments in which to develop this area of research’
This is an interesting study which has provided valuable insight into this area of clinical work. However, the study has some limitations in relation to the small numbers involved in the evaluation, the limited number of clinical speciality groups that were included and, further to this, that it was carried out in just one Trust.
The authors identify that this was service evaluation rather than research and, clearly, there is a need for additional research on the potential usefulness and relevance of aviation-based HF training in healthcare environments before widespread adoption is considered.
Ambulance services could provide excellent environments in which to develop this area of research, especially given the increasing demand on the workforce, the continually expanding scope of paramedic practice, the challenging and dynamic settings within which patients are managed, and the complex organisational culture(s), systems and processes that exist in each ambulance Trust.