Monthly Archives: August 2011

Measured Response to Response Measures

In conversations lately I have been hearing more diverging opinions on measuring EMS response ranging all the way from it being a definitive criteria to saying  it shouldn’t be considered at all. A recorded example of such a discussion is a recent blogtalkradio episode by “EMS Office Hours”.  While certainly appearing to be diametrically opposing opinions on the surface, I believe that there is more in common between these positions than actual difference.  Everyone agrees that responder safety is paramount and also that speeding ambulances endanger not only the medics, but the public as well.  However, to assume that the “observer effect” of simply measuring the response time is a casual factor in promoting unsafe practice is not always justified.

To clarify the commonality, it is worthwhile to first discuss the measurement itself.  When does the clock measuring response performance actually start and when does it stop?  The answer likely depends on your perspective.  As a patient in cardiac or pulmonary distress, rescuer performance is rightfully measured from symptomatic onset to relief.  For a dispatcher, it can be from the point of answering the call for service to the paramedic greeting the patient.  For the responding agency, it can be from the initial dispatch time to the time of “wheels on the curb” at the scene.

In reality, it doesn’t matter what you choose measure, the point is ultimately how efficiently can service safely be rendered to achieve a positive clinical outcome.  Opponents to time response measures will say that the focus is brought to the wrong objective.  That only considering the arrival time leads to the foolish notion that arriving within a compliant time when the patient ends up dying is somehow better than being late while the patient ultimately survives.  But carrying the discussion to that ultimate extreme of logic is not beneficial to the underlying argument.  There is little disagreement that many EMS calls do not require excessive speed, but the outcome of certain calls clearly depend on early treatment and the difference between those cases is not necessarily clear at the time of dispatch.  So arriving in a short time after being dispatched can aid in achieving a positive outcome clinically.

What everyone wants to avoid is the danger of excessive speed in arriving to calls without any delay in beginning treatment for the patient.  The answer is in pre-positioning vehicles closer to the call before it is received.  That leads back to my last post on forecasting calls for dynamic system status management.  With proper forecasting and posting of ambulances, you can assure the fast, safe arrival of resources to begin treatment.  So again, no matter how you measure it, the positive relief of ailment is the outcome we all look to achieve.  To compare efficiency you need some objective measure of performance.  The responsive initiation of treatment leading to a healthy outcome is such a measure but is just not the only factor to be used in describing performance.

Let me know how you see it.

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Dynamic System Status Management

System Status Management (SSM) is the fluid deployment of ambulances based on the hour-of-the-day and day-of-the-week in order to match supply, defined as Unit Hours of Utilization (UHU), with expected demand, expressed as calls for service, in the attempt to provide faster response by locating ambulances at “posts” nearer their next calls.  While the practice is still not unanimously embraced by all services, it has a sound foundation both in the research literature dating back to the 1980’s as well as in practice today.  Experience has shown that ambulance response times can be dramatically decreased using this type of dynamic deployment, but it is also recognized that it is possible to reduce performance when these techniques are not applied properly.  The direction of the results of a system implementation are typically influenced by the system design, competence of the managers creating the plan, and commitment of the workforce in implementing it.  Therefore the best practice is a simple and straightforward implementation that will show positive results quickly.  This methodology ensures a positive return on investment along with garnering the necessary buy-in from staff to make the project a success.

In his article, “System Status Management – The Fact is, It’s Everywhere“,  published in the Journal of EMS (JEMS) magazine back in 1989, Jack Stout explained the concept of SSM and tried to dispel certain myths.  Based on foreseen Geographic Information System (GIS) technology and even general computing capabilities of that time, it was quite logical to assume in his Myth #2 that “no matter how thoroughly the response zone concept is fine-tuned in practice, it cannot be made to cope effectively with the dynamic realties of the EMS environment.”  But systems implemented today around the US are capable of calculating dynamic response zones in a small fraction of a second while even being based on time-aware historic driving patterns making a truly dynamic system status management process a reality.  A practical and proven example of a dynamically functioning system status management application is the Mobile Area Vehicle Routing and Location Information System, or simply MARVLIS.

The following Slideshare presentation does an excellent job of telling the story of why and how the system works:


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