IJE Advance Access originally published online on March 31, 2005
International Journal of Epidemiology 2005 34(2):431-432; doi:10.1093/ije/dyi018
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Commentary |
Commentary: Modern day ‘flying ambulances’ for coronary care: a tale of two cities
University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. E-mail: wayne_rosamond{at}mail.cscc.unc.edu
Although mobile medical care dates back to the horse-drawn wagons used in battlefields across Europe in the 12th century, creation of the modern ambulance is often credited to Dominique-Jean Larrey in 1792.1 Larrey, Napoleon's private surgeon, designed horse-drawn carts called ‘flying ambulances’ to carry surgeons and medical supplies into the field of battle. The idea of using mobile units for treating civilians grew from the visionary work of Peter Shepherd, who, with the St. Johns Ambulance Association of London, helped establish Britain's first ambulance transport service in 1872.2 Pre-hospital emergency care designed specifically for acute coronary events marks its history with the pioneering work of Pantridge and colleagues in the 1960's in Belfast with their work demonstrating that correction of ventricular fibrillation outside the hospital was possible.3,4 These early versions of hospital based mobile coronary care units (MCCUs) had only a small number of interventions to offer acute coronary patients compared with today's mobile units.5 Careful and critical evaluation of today's ‘flying ambulances’ is of utmost importance if further advancements in rapid medical care for coronary events are to be achieved. The outstanding paper by Moore and colleagues in this issue of the Journal makes several key contributions to the understanding of the role of MCCUs in the chain of survival from acute coronary events.6
First, Moore and colleagues took a much-needed community-based perspective by using MONICA surveillance registries in a quasi-experimentation mode. In doing so, the authors took full advantage of MONICA surveillance data to evaluate a natural experiment. The conceptual straightforwardness of the task of comparing coronary events in environments with (Belfast) and without (Glasgow) MCCU contrasts sharply with the methodological challenges and complexities faced by Moore and colleagues. Population based rates of coronary events and case fatalities are the final measures of the effect of public health programs or treatment interventions. By utilizing these ultimate indicators of success the authors demonstrate the complexity and dynamic nature of the methodological issue facing investigators trying to evaluate interventions as they actually are implemented at the community level. One of the main methodological challenges was obtaining valid data on the timing of events. Interpreting the impact of MCCUs places great emphasis on accurate measurement of the timing of event onset and arrival of medical care. Symptom onset time is notoriously difficult to collect and even harder to validate. Furthermore, the finding that the care pathway delay interval was over one and a half hours longer for Glasgow events than for Belfast events appears to be due, in part, to the differential way this variable was defined in the two cities. Constrained by the MONICA definition of medical presence after symptom onset as attendance of personnel specially trained to treat cardiac arrest, Moore and colleagues defined the care pathway interval as the time between event onset and MCCU attendance in Belfast and as the time between onset and ward admission in Glasgow. Hence, although Glasgow paramedics do have some cardiac equipment and training, their presence is not included in this definition of medical presence, potentially inflating the interval duration in Glasgow. Nevertheless, the data as a whole support Moore and colleagues' conclusion that the delay to coronary care is the critical difference between Glasgow and Belfast.
Other methodological challenges Moore and colleagues address are the uncertainty of individual level disease severity as well as community level differences. Moore and colleagues acknowledge that these factors may affect both the probability of receiving pre-hospital care as well as of surviving until its arrival. Methodological limitations prevented a more in-depth investigation of the potential confounding effect of severity on the finding that among those who survived up to admission to the hospital, the case fatality differed little between those attended by a MCCU and those not attended by a MCCU. Although Moore and colleagues conclude that this does not suggest a large survival benefit associated with pre-hospital MCCU care, it is possible that MCCUs do confer an increased probability of survival that is masked by confounding by severity and case mix.
Another chief contribution of the current study is that it provides a model for which other community-based surveillance studies can be of value to researchers and policy makers alike. Existing studies can follow the lead of Moore and colleagues by carefully considering the limits of the data when interpreting natural experiments. Furthermore, ongoing studies should strive to re-invent themselves to explore new and better ways to obtain the type of community and individual level data required to more accurately address the impact of intervention such as that of MCCUs.
A third contribution of the article by Moore and colleagues is the research questions it raises. We are surprised that case fatality among those Belfast events with pre-hospital MCCU care was 45%. One can only guess what the case fatality would have been in Belfast had MCCUs not been available. This counter-factual question is important considering 30% of coronary events registered in Belfast were attended by mobile teams compared with 4% of registered events in Glasgow. What are the barriers to increased use of emergency medical services in these communities? What elements of rapid out-of-hospital medical care are the most critical for improved survival? Can elements of a ‘treat in the field’ vs a ‘load and go’ approach that may have the biggest positive impact be identified and maximized? Answers to these questions may identify specific approaches to improving the impact of MCCUs.
Although mobile medical care systems grew out of wartime necessity, their current role in the battle for survival after acute coronary syndrome is of everyday importance. We submit that the continued high rates of out-of-hospital coronary heart mortality in many countries constitute a contemporary necessity calling for improvements in both prevention and rapid access to appropriate acute care throughout the community. What are the most effective and efficient models for the current day coronary ‘flying ambulance’? Continued evaluation of and advancements in community level surveillance studies like those presented by Moore and colleagues may hold the answers.
 |
References |
|---|
 Top References |
|---|
1 Travers B, Freiman F (eds). Medical Discoveries: Medical Breakthroughs and the People Who Developed Them. Volume 1. New York: Gale Publishers, 1997, pp. 12–14.
2 Pearn J. The earliest days of first aid. BMJ 1994; 309:1718–20.
3 Pantridge JF. Philosophy of prehospital coronary care. Topics Emergency Med 1980; 4:1–8.
4 Pantridge JF, Geddes JS: A mobile intensive-care unit in the management of myocardial infarction. Lancet 1967; ii:271.
5 Sternbach G. History and emergency medicine. J Emerg Med 1986; 4:171–72.[Medline]
6 Moore W, Kee F, Evans AE, McCrum-Garder EE, Morrison C, Tunstall-Pedoe H. Pre-hospital coronary care and coronary fatality in the Belfast and Glasgow MONICA populations. Int J Epidemiol 2005;34:422–30.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||