Transport and delivery of defibrillators to victims of cardiac arrest
Cardiac arrest outside hospital is common and in Europe the annual incidence is reported to be between 67 and 170 per 100,000 inhabitants. Resuscitation is attempted or continued by EMS personnel in about 50–60% of cases and discharge rates from hospital are very low (an average of 8%). Many initiatives have attempted to improve survival [
8] and improving the rate of bystander CPR and the use of automated external defibrillators (AEDs) have been identified as crucial to improving survival. Bystander CPR and early defibrillation doubles the chance of survival and reduces morbidity associated with cardiac arrest [
9]. Although there are many public access defibrillator programmes in place to facilitate earlier access to defibrillators, many OHCAs occur in places where defibrillators are not immediately accessible, and novel methods of enabling faster access to defibrillators are required [
10].
Studies across Europe have demonstrated the feasibility of UAV transport of defibrillators directly to the patient. In rural areas it has been suggested that UAVs can deliver defibrillators prior to the arrival of land crews in 93% of cases [
11] and that delivery of a defibrillator using UAVs can often be quicker than a pedestrian can locate and retrieve a community defibrillator [
12]. Although particularly relevant for rural areas, mathematical modelling in both North America and Europe has shown that UAVs also have the potential to reduce time from OHCA to defibrillation in urban areas [
13‐
15]. Modelling in the Toronto region estimated time savings to be around six minutes in urban areas and ten minutes in rural areas using approximately 100 UAVs in the region for defibrillator delivery [
13]. In Sweden detailed modelling has been reported to calculate the number of AED– UAVs that would be required to deliver an eight minute response to different proportions of the population [
16]. Much of the work reported on defibrillator delivery has been theoretical but in 2021 Schierbeck et al. reported a case of an individual who underwent successful defibrillation with a UAV delivered defibrillator in Sweden just prior to the arrival of a land emergency ambulance team [
17].
Prompt delivery of a defibrillator by UAV to a patient in the pre-hospital environment appears to be a realistic and safe option. Delivery may even be possible at night [
18]. However, there may be additional work required in educating the public in the effective use of UAV delivered automated defibrillators for OHCA. In a simulation study Rosamond et al. demonstrated that despite a UAV being delivered prior to the arrival of land crews a significant proportion of participants had some difficulties with AED use. [
19]. Clear instruction, possibly by telephone dispatchers [
20] and training and information campaigns via media and social media may be required to familiarise the public with delivered defibrillators [
21‐
23]. Some initiatives have examined the possibility of delivery to the location of a mobile telephone to ensure an accurate delivery location and also delivering to community first responders to ensure that an effective user is immediately available to operate the defibrillator [
24].
Although strong evidence for feasibility is available, many emergency medical service (EMS) systems still need to develop robust and safe dispatch models within aviation regulatory rules as well as ensuring that the AEDs are effectively utilised after successful delivery. The published work on UAV defibrillator delivery has resulted in the European Resuscitation Council and the International Liaison Committee on Resuscitation to comment in their 2021 guidelines [
25], on the potential benefits and future work required for practical implementation of this intervention.
Transport and delivery of medical supplies
UAVs have the potential to play a role in delivery of time-sensitive medical supplies, including blood products and emergency medications. The exact role and potential benefits of this type of initiative depend very much on the operating environment– the delivery of an emergency medication in an urban medical emergency is very different to the delivery of medical supplies or blood in a remote or difficult access location.
Blood products have become an integral component of early resuscitation in major haemorrhage, both in hospital and in the pre-hospital environment. Both military and civilian studies have demonstrated reduced mortality after early transfusion of blood products in major trauma [
26].
Transport of blood products requires careful quality control to ensure that the products are safe for transfusion after delivery. This includes prevention of the adverse effects of temperature variation and prevention of haemolysis when compared to standard land transport [
27,
28]. Errors in transport and storage of blood products carries a significant risk for patient safety [
29]. Pilot studies have indicated that using UAVs to transport blood products (packed red cells, platelets and frozen plasma) is safe and feasible, with little adverse impact on the products during transport. UAV delivery of blood products has been utilised successfully in both Rwanda and Ghana for many years with a significant reduction in delivery times when compared to standard land transport [
30,
31]. Rwanda is particularly suitable for a blood delivery programme because it is a small densely populated country with a poor road infrastructure and a majority of the population living in rural areas. When over 12,000 UAV blood deliveries were evaluated in Rwanda between 2017 and 2019 the mean delivery time was reduced by 79 min to 49.6 min. Significant reductions in blood wastage were also reported [
32]. This study also reported internal data by the UAV provider which suggested that of more than 100,000 units of blood delivered over three years less than 1% were damaged during delivery.
The treatment of trauma victims in remote and inaccessible places is a key aspect of military medicine. Delivery of blood to medics treating military casualties has been considered for a number of years and a recent review has summarized current capability [
33]. Various military simulations, some involving delivery of real blood products, have indicated that UAV delivery is not only practical but also maintains the quality of blood products delivered [
34,
35].
The administration of medication in time critical conditions can be life saving. This may be particularly effective where medications can be administered by non-medical personnel. Examples include epinephrine for anaphylaxis, anticonvulsants for prolonged seizures and naloxone for opiate overdose. UAVs offer the potential to reduce time to access lifesaving medications and computer modelling has shown the potential for a significant reduction in time to delivery of these medications compared to standard land crew delivery [
33‐
35].
Although not strictly emergency medicine related but demonstrating logistical feasibility, UAVs have also been shown to be effective in transporting chemotherapeutic agents which typically have a short shelf-life, to rural and remote areas, providing access to these medications in areas where it was previously logistically challenging [
36]. In common with blood, there are quality control factors to consider when transporting and administering medications. These may include stable storage temperature and vibration during the transportation process and safe use of potentially harmful or controlled drugs. In terms of safe administration, a feasibility study performed in the US has demonstrated that bystanders were able to successfully carry out instructions given by the emergency call handlers to retrieve UAV-delivered intranasal naloxone and administer this safely to the patients whilst awaiting arrival of land emergency medical teams [
37]. Although further studies are required to confirm the safety of administration of medication in this manner, this does support the real possibility of layperson administration of life-saving medication delivered by UAVs. Other useful medications delivered in specific time critical conditions (e.g. bronchodilators for asthma or snake antivenom in inaccessible sites) may also justify future investigation.
The challenges of the introduction of medical UAV delivery systems need to take into account many factors before implementation and are very specific to regional demand and conditions. An example of the scope of factors that need to be considered is demonstrated in a concepts paper published in 2019 [
38] which examined potential medical UAV uses in Madagascar, Malawi and Senegal. The challenges were extensive and included the provision of robust and simple UAVs to be used in difficult climatic conditions with a limited communications infrastructure and challenging aviation regulatory legislation. The paper provides recommendations on key areas which need to be addressed in setting up a UAV service including regulatory, feasibility studies, acceptability by the target population and how to monitor and evaluate the implementation. These recommendations are targeted at service providers, governments, UAV providers and potential funders.
UAV Transport of patients
Evacuation of combat casualties to medical care in a timely manner has long been a key objective of military medicine and continues to influence modern military policy [
39]. The use of UAVs to evacuate patients from a non-permissive environment has been extensively discussed in recent years [
40]. Challenges include the provision of UAVs with the capacity to carry a heavy load and the possibility of a casualty having to fly without medical supervision. Larger UAVs with the capacity to carry heavy loads, are currently available, particularly for military applications although they are expensive. Prototype UAVs with the capacity to carry two adults in a military environment have been reported for several years [
41]. A recent study has also confirmed that many military casualties do not require critical interventions during evacuation and might therefore be suitable for unsupervised UAV evacuation [
42]. Although intervention may not be possible during evacuation remote monitoring devices are available and receiving centres could have real-time physiological observations and be able to observe a patient’s condition prior to arrival. There have been recent reports of remotely operated military helicopters completing simulated casualty evacuations without incident [
43] and it seems likely that pilotless aircraft will soon be part of military medical practice. Although casualty evacuation by UAV has been mostly theoretical and developmental there are now reports of real casualties being evacuated by UAV in the Ukraine conflict [
44]. Military requirements have often driven progress in civilian trauma medicine and these developments may be significant in understanding and developing UAV potential in civilian evacuation pre-hospital practice.