Ambulance dispatch algorithms should function as clinical prediction tools, identifying those patients that require advanced life support, and differentiation from those who require less urgent care. Using clinical prediction rules and some oversight by trained staff, can algorithms be standardized enough to provide intelligent dispatch systems for HEMS teams?

The Golden Hour is often mentioned in emergency medicine. Seconds count when it comes to emergency dispatch, it can literally mean the difference between life and death, and affect long term patient outcomes.  Computer Aided Dispatch systems (CAD) are usually the sieve whereby the caller is taken through a scripted interrogation process.

Clinician review is also sometimes part of the process, and when this is the case, it usually results in enhanced accuracy in dispatching the correct level of prehospital care. But as this element is dependent on the individual dispatcher and nature of the emergency call it renders it unclear how much or an influence it has in dispatch accuracy. 

Clinician review is also sometimes part of the process, and when this is the case, it usually results in enhanced accuracy in dispatching the correct level of prehospital care.

Only human
Hampshire and Isle of Wight Air Ambulance (HIOWAA) Paramedic John Gamblin shared the service’s experience of the human element in action when triaging a call.

“Here paramedics often rotate support through the dispatch desk, and it's our job when we're dispatching the aircraft to interrogate and get early identification. So, a lot of our work comes from an ambulance crew, present at the scene, recognizing that this person really, really sick, and then they call us in for that support.

Alternatively, to avoid being delayed, sometimes we're on the desk spotting the job as it's happening live, and we can send the helicopter out concurrently with the ground ambulance response. So, the real success is when you have both working together, completely collaboratively. HEMS don't have the monopoly on sick patients, but we are able to add some meaningful interventions that will hopefully deliver care closer to the point of injury and stabilize the patient before getting them to hospital.

Can delivery of prehospital care be remodeled by major trauma networking (MTN) such as seen in the West Midlands? It would seem from a cancellation and over-triage point of view, yes it can, with the West Midlands MTN seeing a more accurate tasking of HEMS assets where the call involved a significant injury, along with a reduction in mission cancellations being observed over a period of six months since implementation of the network (McQueen, Crombie & Perkins 2014).

Gamblin counters that over triage is tolerated withing the Hampshire and Isle of Wight Air Ambulance service. “We tolerate a degree of over triage because we'd rather be going out five times a day and maybe only finding the two really sick patients. The other three it might be that they got better, and they may be not quite as bad as first thought. That's great news for us, but if we were too stringent with our criteria, and later hear that someone turned up the hospital really in a bit of a poor state, where we could have been on scene helping them, stabilizing them and shortening their overall journey into rehabilitation, which is what the work that we do is proven to do, it shortens that patient pathway, then over triage and earlier specialist intervention is preferable.”

SAR approach
Dominic Golden JRCC Commander (Aviation) of the Maritime & Coastguard Agency also demonstrated how the human element is key in delivering care, and necessary when considering search and rescue protocols. “The rule of thumb for us is: is the task achievable and is it appropriate. Outside the scope of your question is the achievable piece - this is usually driven by weather considerations, but occasionally issues of crew fatigue or aircraft serviceability (although I can look at dispatching a helicopter from the adjoining region to overcome these).
Appropriate is the threshold used in the informed decision-making here.

There is no doubt that the majority of requests received here are achievable by use of search and rescue helicopters (SAR-H), but with such a limited resource, the danger is of tasking SAR-H to an incident that could be completed just as efficiently by use of a ‘land’ ambulance, police search dogs, et cetera.

"Ultimately, the Aeronautical Rescue Coordination Centre (ARCC) needs to be satisfied that there exists a Risk to Life or Limb that justifies tasking a SAR-H and that the resolution of that incident could not just as efficiently be resolved by other means available. Even when there is an obvious time saving, that time-to-critical care factor must really demonstrate that without use of SAR-H the increased risk to the casualty outweighs using another asset.”

Multiple decisions
With SAR missions, a consideration that must be factored in in which method of assistance is the best dependent on other factors outside of the patient trauma such as injury and risk to the attending emergency team.

Golden continued, “I can think of examples where I would deem use of SAR-H as appropriate in the transportation of other emergency services (e.g. Mountain Rescue) as a means of mitigating against risk to other emergency services.

Ultimately, it is the optimal provision of assistance to the casualty is our driving factor. Various protocols exist that make is explicitly clear that it is ‘better to do something rather than nothing’ or ‘giving benefit of doubt’ to drive our decision making process.”

With the majority of SAR helicopter tasking being in direct support to the ambulance service, there will always be incidences where the unique capability of the SAR-H will be needed. Whether that be to ability to extract a casualty, to dealing with adverse weather conditions whereby it is deemed SAR provide the better or only solution.

He added, “we also undertake a significant number of inter-facility medical transfers, where the time factor is considered critical, or the volume of space (for equipment/additional medical staff) that SAR-Helicopters provide makes us the optimum solution.”

He added “We also undertake a significant number of inter-facility medical transfers, where the time factor is considered critical, or the volume of space (for equipment/additional medical staff) that SAR-Helicopters provide makes us the optimum solution.”

With the current resource issue impacting on many regional ambulance services, there is a danger that some stakeholders see using SAR-H as a viable alternative.

“Despite fairly well defined protocols established between us and the ambulance services - reviewed regularly, there are always requests that test those boundaries. These can be reviewed as subsequent meetings between the UK Coast Guard and the appropriate ambulance authority, where examples of either good and bad practice can be reviewed and discussed,” said Golden. 

With SAR missions, a consideration that must be factored in in which method of assistance is the best dependent on other factors outside of the patient trauma such as injury and risk to the attending emergency team

The future of dispatch
It is clear the human element, particularly in multidisciplinary calls such as SAR is not going anywhere fast, but what would SAR like to see from dispatch criteria going forward?  “In my honest opinion a combined, state funded (aerial policing/HEMS/coastguard) helicopter service with a central JRCC (Joint Rescue Coordination Centre) is the way forward. I understand other European countries already do this, such as Norway. Whilst the assets themselves would remain located across the country in their current locations, the Operational Control (OPCON) would pass to this JRCC who would not just entertain requests from the numerous stakeholders (other emergency services) but also would reduce some of the occasional duplication of effort whilst delivering a truly coordinated, timely and more efficient response. I suspect that at higher management levels there might be a nervousness or perception of ‘losing’ control of their assets, but corporate identity/branding on assets could be easily maintained, against the potential other sticking point of funding, and whose budgets (equally shared or some other agreed division) this would come from,” concludes Golden.

It is clear that algorithms have their place and that they do aid the tasking of HEMS assets where significant injury is involved, helping produce an overall reduction in missed cancellations. The human element, however, cannot be ignored and until a more detailed study of patient outcomes in correlation with algorithm use is undertaken, HEMS dispatch will continue to be based on both the knowledge of the human dispatch team and the individual algorithms used. 

References
McQueen C, Crombie N, Perkins GD, et al Impact of introducing a major trauma network on a regional helicopter emergency medicine service in the UK Emergency Medicine Journal 2014;31:844-850