Speeding ambulances might do more harm than good to patients receiving cardiopulmonary resuscitation (CPR), Korean doctors suggest.
Using a computerized mannequin called Resusci Anne, the researchers monitored how well EMTs performed as the ambulance — lights flashing, sirens squealing — picked up speed.
Both depth and rate of chest compressions increased, but what made the researchers worry was that EMTs tended to spend less time doing CPR at high velocities.
The exact reasons for the added hands-off time are unclear. What is clear, however, is that during this time, no blood gets pumped into the body of a patient in cardiac arrest, starving the brain and other organs of vital oxygen.
At 37 miles per hour and faster, the extra "no-flow" time amounted to only a few seconds, compared to going 19 miles per hour or slower. But the ambulance was driving on a straight expressway with no traffic lights, said Dr. Tae Nyoung Chung, an emergency physician at Yonsei University College of Medicine in Seoul, Korea, who led the study.
In real life, sharp turns, stops and bumpy roads would likely exaggerate the effects, he told Reuters Health in an e-mail.
Based on the findings, published in the journal Resuscitation, "there may be a threshold speed between 30 km/hour and 60 km/hour which doesn't increase the portion of hands-off interval while maintaining the speed of ambulance," he said. "This speed level can be suggested as a speed limit for the ambulance transport with ongoing CPR."
Dr. Dana Edelson, associate chair of the CPR Committee at the University of Chicago, urged caution before slowing down ambulances. While she said continuous CPR is paramount to survival, she noted that the effects found in the current study were "pretty small."
"The downside of slowing down your ambulance is that it takes longer to get to the hospital," she said. "We need to be looking for other ways to increase CPR quality."
One way to increase that quality, recommended by the American Heart Association, is for emergency personnel to attempt resuscitation where it happened, instead of rushing the victim off to the hospital.
"Trying to do CPR in the back of an ambulance is not terribly effective," said emergency physician Dr. Michael Sayre, a spokesman for the association.
Still, experts say it is common practice both in Korea and the US. Some patients go into cardiac arrest during transport, for instance, and others might not respond to CPR initially.
While a few emergency services do moderate ambulance speed when the EMT is doing chest compressions in the back, there are currently no official guidelines, said Jerry Johnston, a paramedic and the immediate past president of the National Association of Emergency Medical Technicians.
Mechanical devices that deliver chest compressions dependably already exist, but the price — between $10,000 and $15,000 per ambulance — is prohibitive, said Johnston.
"Right now the overarching recommendation is that the person driving the ambulance needs to be really cognizant about making the ride smooth so that quality CPR can be performed," he said.