Tucson, AZ - A study of emergency medical service (EMS) responders has shown that during resuscitation efforts for out-of-hospital cardiac arrest, less than 50% of the time on scene is spent providing circulatory support through chest compressions [1]. The lack of hemodynamic support during the critical circulatory phase of cardiac arrest is a possible contributing factor to the poor long-term outcome of these subjects, say investigators.

"The first few minutes of EMS therapy are probably the most important for successful resuscitation," write lead investigator Dr Terence Valenzuela (University of Arizona College of Medicine, Tucson) and colleagues in a report published online August 22, 2005 in Circulation. "Because almost all EMS resuscitation therapy will begin in the circulatory phase, simply because of the elapsed time from notification to arrival and treatment, providing circulation must be deemed the crucial early step. In the out-of-hospital scenario, chest compressions should occupy the majority of the first few minutes of EMS therapy."

Speaking with heartwire, Dr Karl Kern (University of Arizona College of Medicine), second author on the paper, said that survival after nontraumatic out-of-hospital cardiac arrest has been relatively flat for the past decade, despite advances in resuscitation, including automated external defibrillators (AEDs). Numerous studies have also highlighted the fact that many professional providers are failing to accomplish the resuscitation tasks outlined in the guidelines, with some findings showing that chest compressions are delivered just over half the time.

Because of this lack of improvement in cardiac-arrest survival, the Arizona researchers conducted a retrospective review of the Tucson Fire Department cardiac-arrest resuscitation efforts during a 12-month period between November 2001 and November 2002. The fire department provides emergency services for the city and works mainly in pairs to provide multirescuer cardiopulmonary resuscitation (CPR). The department provides regular training about the EMS aspects of their responsibilities, including quarterly education and skill refreshment and a mandatory skills session every six months.

During the 12-month period, the AED-equipped EMS first responders treated 61 adult out-of-hospital cardiac-arrest patients. Reviews of the procedure were performed according to the code arrest record and verified with the use of the AED continuous-waveform data to determine when chest compressions were and were not performed. The median time interval from the 911 call to arrival at the patient's side was six minutes and 27 seconds, with an additional 54 seconds required until the first delivery of a shock for the patient in ventricular fibrillation (VF).

During the resuscitation effort, chest compressions were performed during 43% of the time spent on scene. The compressions were typically not started when EMS providers initially arrived at the patient and were frequently interrupted for other tasks. During the first five minutes of the resuscitation effort, chest compressions were performed only 40% of the time.

"The Tucson Fire department is fabulous, and the firefighters are some of the best in the world," said Kern. "But for whatever reason, mostly because of the guidelines we gave to them—put a tube down their throat, put an IV in their arm, check the rhythm, reassess the patient—a lot of things get in the way. When we really measure how much time they spend at the patient's side, really pushing on the chest, it is only 43% of the time. We can't kid ourselves. We're generally not doing what we think we're doing, and less than half of the time are we really providing blood-flow support."

Kern pointed out that the current 2000 guidelines for CPR and emergency cardiovascular care emphasize the importance of rapid defibrillation because most survivors of out-of-hospital cardiac arrest are those with VF. While defibrillation is important, he noted that the current era of AED-equipped EMS responders might result in significant periods during the resuscitation effort when no chest compressions are performed. Although the newer devices are quicker, with less delay between shock delivery and when EMS providers can touch the patient, these interruptions still hinder blood-perfusion efforts, he said.

Kern told heartwire that they also measured the amount of time responders are "off the chest" during these emergencies. He said most EMS responders are likely not aware of the amount of time that has elapsed when compression stops.

"If you were to ask a paramedic or even a doctor, they'll tell you only a couple of seconds," said Kern. "But the average time off the chest was a minute, and they were off for as long as three minutes before they started pushing again. In the same vein, when they are pushing, they're only pushing for about 55 seconds before they stop. So we're just not cognizant in the throes of these emergencies how often we stop the compression, how long it takes us to get back to them, or even how long we're pushing for."

A new method currently being tested in Tucson is called cardiocerebral resuscitation. With this method, 200 compressions are delivered even before the exact rhythm of cardiac arrest is determined, and only after this is a rhythm analysis conducted. If the patient is in VF, a single shock is delivered, followed again by 200 chest compressions.

"Most of the new devices will eliminate the VF, but they don't bring the subject back to a beating heart," said Kern. "What really helps the heart recover and is needed is blood flow."