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Emergency treatments delivered in ambulances that offer “Advanced Life Support” for cardiac arrest may be linked to more death, comas and brain damage than those providing “Basic Life Support.”

That’s according to a study published Monday in JAMA Internal Medicine, which suggests that high-tech equipment and sophisticated treatment techniques may distract from what’s most important during cardiac arrest — transporting a critically ill patient to the hospital quickly.

“They’re taking a lot of time in the field to perform interventions that don’t seem to be as effective in that environment,” said Prachi Sanghavi, lead author of the study and a PhD student in Harvard University’s Program in Health Policy. Those interventions include the use of advanced defibrillators to shock the heart, the administration of IV drugs, and perhaps most risky in the field, intubation — the insertion of a plastic tube in the airway to help with breathing.

“Of course, these are treatments we know are good in the emergency room, but they’ve been pushed into the field without really being tested,” she said. “And the field is a much different environment.”

Adding to the danger is the fact that many paramedics in “advanced” units are trained in these procedures but rarely have a chance to perform or practice them in high-pressure situations, often leading to more delays, Sanghavi said.

Basic Life Support (BLS) ambulances stick to simpler techniques, like chest compressions, basic defibrillation and hand-pumped ventilation bags to assist with breathing. More emphasis is placed on getting the patient to the hospital as soon as possible.

For decades, ALS has been the standard method for transporting patients to the hospital after an emergency. But little scientific evidence supported the “advanced” practices over BLS. And while studies in other countries called into question the effectiveness of these high-risk procedures in the field, the topic hasn’t received much attention in the United States.

Survival rates for cardiac arrest patients are extremely low regardless of the ambulance type. In fact, roughly 90 percent of the 380,000 patients who experience cardiac arrest outside of a hospital each year don’t survive to hospital discharge.

But in this study, researchers found that 90 days after hospitalization, patients treated in BLS ambulances were 50 percent more likely to survive than their counterparts treated with ALS. The basic version was also “associated with better neurological functioning among hospitalized patients, with fewer incidents of coma, vegetative state or brain trauma.”

The researchers collected Medicare data for ambulance services provided to patients in non-rural areas between 2006 and 2011. They then compared neurological outcomes and survival rates for the two types of care, using statistical methods to balance for differences between the groups, including age and other factors that could influence the type of ambulance used and chance of survival.

“Our study shows that we clearly need a shift in the way we respond to cardiac arrest in this country,” Sanghavi said.

But not everyone’s so convinced. Judith R. Lave, a professor of health economics at the University of Pittsburgh, called the study “interesting”, but far from definitive.

“They’ve done as much as they possibly can with the existing data,” she said. “But I’m not sure that I’m convinced they have solved all of the selection biases.”

For instance, some hospitals might send a BLS ambulance if the patient is close to the emergency room or relatively stable. That would mean the comparison is not truly equal and other factors besides the type of ambulatory care may have been at play.

“There’s no way you can really control for this,” Lave said. “I would say that it should be taken as more of an indication that there may be some very significant problems here.”

The Harvard team agrees that more research is needed. Joseph Newhouse, co-author of the study and director of the Division of Health Policy Research and Education, said it’s “a little bit premature to talk about any implications for programs like Medicare.

“But I think that if these results were found to be similar for other kinds of diseases, then we could start to have a conversation about whether Medicare should be more proactive in trying to make some changes in the way it reimburses hospitals,” he said.

Which is among the reasons the group’s next project will be to investigate how ambulatory care impacts patients facing other emergencies, including stroke, respiratory failure and trauma.