Clinical paperThe analysis of efficacy for AutoPulse™ system in flying helicopter☆
Introduction
The survival rate of patients suffering from cardiopulmonary arrest (CPA) is related to 5 links of the “chain of survival” concept: early access, early CPR, early defibrillation, early advanced life support, and integrated post-cardiac arrest care.1, 2, 3 Previous studies have shown that the survival of out-of-hospital cardiac arrest is more closely associated with prehospital factors such as early CPR and early defibrillation than with in-hospital factors.4, 5, 6 Therefore, prehospital emergency care is an important factor in survival. To enable earlier commencement of treatment, helicopters and other aircraft are used in order to carry doctors to the sites of emergency in many countries. The helicopter emergency medical service (HEMS) was introduced in Japan in 2001, and it was referred to as “Doctor Heli” in Japan in order to emphasize that the doctors move rapidly to patients by a helicopter to provide medical device. By March 2011, 26 helicopters had been deployed in 22 prefectures across Japan.
Our hospital is responsible for the eastern region of Shizuoka Prefecture, including the Izu Peninsula (Fig. 1). This region, approximately 4090 km2 in area with a population of approximately 2 million, is mountainous with only a few hospitals. In order to reduce hospital transport times using ambulances, HEMS was initiated in 2004 with Juntendo University Shizuoka Hospital serving as the base hospital. The journey from the southern tip of the peninsula to the Critical Care Medical Center of our hospital takes a 2 h by ambulance, but only 15 min by helicopter. Currently, most CPA patients are carried using this HEMS.
In cases of CPA, continuous manual CPR must be administered during the transport of patients by helicopter.7 However, this raises several difficulties in terms of effective chest compression. Because the limited space are available in helicopters for medical devices and medical staff, incorrect compression rates or depths and frequent interruptions may occurred during transporting CPA patients by helicopter.8, 9, 10, 11 Therefore, it is difficult to administer continuous and effective CPR inside a helicopter.12, 13 Incorrect chest compression results in poor return of spontaneous circulation (ROSC), and any interruption to chest compression generated blood flow is detrimental.14, 15, 16, 17 To overcome these problems, we introduced the AutoPulse™ system (ZOLL Circulation, Sunnyvale, CA), which is automated mechanical CPR devices.
According to the American Heart Association (AHA) Guidelines 2010, AutoPulse™ CPR is classified into Class IIb of the Evidence Levels.1 Some studies have found improved hemodynamics and ROSC with the use of AutoPulse™ on CPA patients,18, 19, 20, 21 while others showed a negative neurological outcome.22 This means that there is insufficient evidence regarding the efficacy of automated chest compression devices. To our knowledge, there are no previous studies analyzing CPR supplemented with an automated chest compression device on CPA patients in helicopters. Therefore, we conducted a retrospective study to establish the efficacy of AutoPulse™ CPR on CPA patients compared with that of manual CPR only during helicopter transport.
Section snippets
Patients’ characteristics
A total of 205 CPA-related patients between April 2004 and March 2011 were enrolled in the study. Between April 2004 and June 2008, there were 93 CPA-related patients. Among these, we excluded cases involving hopeless resuscitation, transportation by ambulance, and spontaneous circulation return before arrival at the scene. The hopeless resuscitation defined the presence of obvious evidence that clearly indicates irreversible death such as rigor mortis or dependent livido according to Utstein
Patients’ characteristics
The characteristics of 92 patients (manual CPR group, N = 43; AutoPulse™ group, N = 49) are summarized in Table 1. There were no significant differences between the 2 groups. The median age was 65 years in the manual CPR group, and 71 years in the AutoPulse™ group. In the manual CPR group, the etiology of CPA was cardiac in 16 cases and non-cardiac in 27 cases. Among 27 patients with non-cardiac CPA, 7 cases involved an endogenous etiology, and 20 involved an exogenous etiology (14 cases of trauma
Discussion
The results of the present study demonstrate that use of the AutoPulse™ system in flying helicopters was effective in CPA patients. In fact, the number of patients achieved ROSC was significantly increased after introduction of the AutoPulse™ system.
Our region of Japan is mountainous, and the provision of emergency medical facilities was not sufficient. HEMS is provided in cases of CPA. However, it has always been very difficult to continue effective CPR in flying helicopters. Because
Conclusions
In conclusion, our results demonstrated that the use of AutoPulse™ in flying helicopters was significantly effective among CPA patients: the use of automated chest compression devices such as AutoPulse™ inside helicopters appears to ROSC and survival. However, further studies including larger or prospective randomized studies are required to clarify the efficacy of the AutoPulse™ system.
Conflict of interest
The authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.
Acknowledgement
We are grateful to the emergency doctors of Juntendo University Shizuoka Hospital and the staff of the emergency medical system (Central Helicopter Service Inc., Aichi, Japan).
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2013.01.014.