In a study of residential high-rise buildings, people who suffered cardiac arrest had a better chance of survival if they lived on lower floors, and survival odds decreased as floor number increased.

"We thought there might be something here because once somebody collapses into cardiac arrest, their chance of survival decreases really quickly," said lead author Ian Drennan, a paramedic with York Region Paramedic Services and a researcher with Li Ka Shing Knowledge Institute at St. Michael's Hospital in Toronto.

"If you find them in a shockable heart rhythm then most of the time you can reset the heart and get a pulse back. If you wait too long, the chance of finding that rhythm deteriorates," he said.

With other time-sensitive conditions, like heart attack or stroke, minutes count, but with cardiac arrest a difference of just a few seconds can determine survival, Drennan told Reuters Health by phone.

The researchers studied 7,842 people who had cardiac arrest in private residences and were treated by first responders after a 911 call. Less than four percent of people survived to be discharged from the hospital.

Of the 5,998 people who lived below the third floor of their buildings, 4.2 percent survived, compared to 2.6 percent of those living above the third floor. Less than one percent of those living above the 16th floor survived, and none of the 30 patients who lived above the 25th floor survived, the researchers reported in CMAJ.

Regardless of floor, an automated external defibrillator (AED) device, which can shock the heart back to pumping regularly in some cases, was rarely used.

The time it takes for a first responder arriving at the building to reach the patient having a cardiac arrest increases when the patient lives on a higher floor, the researchers found.

On average, it took responders about six minutes from the time of the 911 call to arrive at the building. But it took them an average of three minutes between arriving at the building and first contact with the patient for those lived on the first or second floor, compared to an average of almost five minutes for those who lived on or above the third floor.

"A cardiac arrest is a condition when the heart actually stops beating," said Dr. Robert A. Silverman of Long Island Jewish Medical Center, who was not part of the Canadian study. "The body can only go for a short period of time without the heart pumping blood; therefore it is essential that CPR (chest compressions) and other medical assistance be given as quickly as possible."

Medics need to go through one or more outer doors and possibly encounter an intercom system, navigate the lobby, locate the elevators - which may take time to arrive or stop at other floors before the patient's floor - then locate the correct apartment, all of which delay care, Silverman told Reuters Health by email.

Buildings and residents can help expedite the process by having an emergency response plan, being sure the responders can get in the building immediately and can access the elevators immediately, Drennan said.

"Having some kind of response plan will minimize avoidable delays," he said.

It also helps to have people in the building trained in CPR and in using AEDs, and having the devices available in the lobby, on certain floors or even in the elevators, he said.

For bystanders who witness a cardiac arrest, in which the patient has no pulse, "the best thing to do is call 911 and do what you can, follow CPR guidelines, get an AED," he said.

Although most high-rise residents shouldn't be concerned about these findings, and don't need to move based on them, people who are very sick may want to consider floor number when they move, Drennan said.

He added, "It's the same thing as if you're trying to move out to the country, you think if I get into trouble, is this the best spot for me?"

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