Automated External Defibrillator Delivery By Drones

Graphical Abstract: What will OHCA management look like in the near future? Warning symptoms will prompt early ECG, that the patient will be able to perform and transmit to EMS using connected devices. If the risk of OHCA is deemed high based on the ECG and simple clinical data, pre-emptive measures will be undertaken (near-term prevention). In the case of OHCA, bystanders will be alerted using lay responders' smartphone apps to start early CPR, with directions towards the closest AED when available, and/or information regarding the arrival of an AED-equipped drone. An EMS ambulance will be sent to the site for advanced life support, and survivors will be transferred to hospital, where investigations will be undertaken to identify OHCA aetiology. In addition to personalized medicine, secondary prevention measures will be undertaken according to the cause of the OHCA and risk profile of the patient, using new defibrillation technologies.

The incidence of ventricular fibrillation and survival probability drops rapidly during the first minutes following out-of-hospital cardiac arrest (OHCA). Early defibrillation is therefore crucial for increasing OHCA survival rate, and has led to remarkable survival rates, reaching up to 90% in specific settings where it was optimally used.^[1] However, early defibrillation is jeopardized by the sudden nature of OHCAs, as a time delay is required to send Emergency Medical Services (EMS) equipped with a defibrillator to the OHCA site. The general strategy to reduce the interval from collapse to defibrillation until now has been to widely deploy automatic external defibrillators (AEDs) through public access defibrillation (PAD) programmes, and allow their public use by all-comer laypersons.^[2–4] However, despite those efforts, only a minority of OHCAs receive early defibrillation, even when multiple bystanders are on site, mainly due to suboptimal AED deployment, difficulties in localizing the AEDs in an emergency setting, and their limited accessibility in some cases. Indeed, the general population is not always aware of where and how to find the nearest AED.^[5] In addition, as demonstrated by a study carried out in Copenhagen, in half of OHCA cases occurring during non-working hours, such as the evening, night-time, and weekends, AEDs were inaccessible, despite being within walking distance from the OHCA site.^[6] Selection of the best AED placement, their visibility, and their accessibility to the witnesses remain unsolved issues, limiting the efficiency of AED deployment strategies.

Given all these obstacles to PAD programmes, a new concept has emerged, offering an alternative for AED access, where the AED is brought to the bystander once an OHCA has occurred.^[7,8] In the current issue of the European Heart Journal, Schierbeck et al. assess a novel method for delivering the AEDs to patients with a suspected OHCA, using drones.^[9] Although some data were available from simulated scenarios,^[10–13] this represents the first prospective, feasibility, clinical study where AED-equipped drones placed within controlled airspace in Sweden were fully integrated as a part of the medical system and dispatched in parallel with the ambulance to real-life cases of OHCA. The primary outcome measure was the proportion of successful accurate AED deliveries when drones were dispatched and took off for suspected OHCA. AED drone take off was initiated in 12 (23%) of the 53 suspected OHCAs within administrative areas during the study period. The median distance to OHCA location was 3 km, and AEDs were delivered at a median of 9 m from the victim. Overall, the median time benefit of all cases was 00:49 min, but in cases where AED drones arrived before EMS (around two-thirds of cases), the median time gain was 01:52 min. No AEDs were damaged, and no adverse events occurred during the real-life flights.

The concept of bringing the AED to the OHCA site seems appealing given the low rate of AED use before EMS arrival obtained with the current strategy of systematic deployment of AEDs. Several strategies have been tested so far, such as the use of AED-equipped police cars, with studies showing an actual reduction in time to defibrillation and an increase in survival rate.^[14,15] The current study offers another alternative using AED-equipped drones. Despite its small sample size, this study provides a proof of concept, confirming the feasibility of adding AED delivery by drones to the OHCA resuscitation arsenal. However, it also shows the importance of further improvement in the functionality of drones, careful selection of OHCA cases in which a drone should be used, and educating bystanders regarding AED use.

The need to improve the functionality of drones is highlighted by the low proportion (<50%) of suspected OHCAs where a drone was eventually sent. Indeed, drones were only available during the day, in areas where the airspace was open, and under appropriate climatic conditions with dry weather and no wind. If a more systematic use of drones in OHCA is to be considered, their performance has to be improved in order to limit the circumstances in which they cannot take off, especially poor weather conditions and darkness, which were the main reasons for refraining from sending the drone. Potential adjustment in the legislations might be needed to support this potentially life-saving strategy, aiming to reduce as much as possible the presence of no-fly zones prohibiting the use of drones.

Another important measure to consider is the careful selection of OHCA cases for which this new strategy should be applied, according to the time gain that can be expected with the use of drones. In the current study, the time benefit obtained with drones in absolute value was low, even though an almost 20% reduction in call to AED delivery delay was achieved, probably due to short trip distances and durations. In comparison, the simulated Stockholm experience led to a median time from dispatch to arrival of the drone of 5 min vs. 22 min for EMS.^[12] In order to draw the best benefit from this new strategy, the dispatcher should probably estimate the predicted delay for EMS arrival at the OHCA site, taking into account the traffic and the weather conditions, in addition to the road configuration. When the estimated delay for EMS arrival is relatively long, sending an AED by a drone could of particular benefit.

Besides increasing the time gain, we also need to work on educating bystanders regarding AED use, to improve the efficiency of this strategy. Of note, in this study, the AED was not used in any of the cases before EMS arrival, despite the earlier delivery of the AED to the OHCA site. When the AED is delivered by a drone, the paramedics are not on board, and efforts should be made to avoid losing precious time before starting AED use by untrained bystanders. Several options can be considered. Dispatchers are now trained to give instructions for bystanders to start CPR while awaiting EMS arrival. We can envisage that the dispatchers also provide explanations regarding AED use to the available bystanders while awaiting the drone's arrival. Another option would be to combine the use of drones with lay responders' smartphone apps in order to increase the chances of having a trained responder at the site of an OHCA when the AED arrives. Accordingly, when sending a drone to an OHCA site, an alert can also be sent through smartphone apps of lay responders to inform them of the OHCA occurrence and the AED arrival.

Increasing OHCA survival rates have been a challenge for decades and, despite the spectacular rates obtained in optimal settings where trained bystanders and an AED are available at the time of OHCA occurrence, we need to acknowledge that real-life statistics remain disappointing in most cities. Advances in technologies, such as the introduction of AED-equipped drones to the field of resuscitation, might offer the opportunity to overcome several barriers to optimal resuscitation, despite only addressing one link in the chain of survival. The overall management of OHCA, which should now further include the timely detection of subjects with warning symptoms at high risk of developing ventricular fibrillation, will definitively change over the next decades (Graphical Abstract). The future of OHCA will depend on the extent to which scientists, politicians, and the community are willing to invest in the field.