New Delhi, Jan. 18: Returning from the brink of death may be easier from the lower floors of high-rise buildings.

A study in Canada has found that the higher people live, the lower their chances of survival after cardiac arrests.

The researchers say the extra time taken by emergency teams to reach patients on higher floors may help explain the lower survival rates.

A study by doctors in a New York hospital nine years ago had indicated that each additional stop of an elevator can add up to 54 seconds of extra time.

The researchers have also underscored the need to train the public in cardiopulmonary resuscitation (CPR) to revive patients.

Emergency medicine specialists say the findings may be relevant to Indian cities where high-rise apartments and emergency ambulance networks have proliferated over the past decade but where most members of the public are untrained in CPR.

How fast emergency paramedic units reach patients is key to survival rates after cardiac arrests. But several past studies have established that CPR and the use of devices called automatic external defibrillators to bring back a normal heart rhythm too can improve survival rates.

"People should initiate CPR while emergency services are en route to the patient's side," Ian Drennan, a researcher at St Michael's Hospital in Toronto and the lead author of the study, told The Telegraph.

"Bystander CPR can more than double survival after out-of-hospital cardiac arrest."

Coronary artery disease and heart attacks are among the commonest triggers of cardiac arrest, a condition in which the cardiac electrical rhythm is disrupted and the heart stops beating. Excessive bleeding after trauma, drowning, a clot in a lung's main artery are among the other causes.

When a patient collapses from cardiac arrest, the heart's condition quickly deteriorates from what doctors call a "shockable rhythm" to a "non-shockable rhythm".

High-quality CPR and defibrillation are critical, with about a 10 per cent decrease in survival with each one-minute delay in defibrillation.

Drennan and his colleagues analysed the outcomes of 7,842 patients who had suffered cardiac arrest on different floors of high-rise buildings and found survival rates dropping with higher floors. (See chart)

The findings were published today in the Canadian Medical Association Journal.

The time emergency units take to reach a site after receiving a telephone alert depends on the road and traffic conditions and the density of ambulances in a city. A manager with an emergency medical services group in India said it takes ambulances in major cities an average 12 to 15 minutes to reach the site.

"We provide pre-arrival instructions to the callers so that critical actions can be taken before professional help arrives," said Subodh Satyawadi, an executive with the Emergency Management Research Institute, which operates the world's largest emergency response network with about 10,000 ambulances across 10 states.

"Given the growing burden of cardiovascular diseases in the country, there is a need to encourage public access to automatic external defibrillators."

Doctors say the public can be easily trained to deliver high-quality CPR and use defibrillators.

"It is relatively easy to operate defibrillators, but the current levels of awareness among the public even about how to administer CPR are dismal," said Rajesh Pande, an executive council member of the Indian Society of Critical Care Medicine.

"We need a massive campaign. Ideally it should start at the high-school level."

Survival after cardiac arrest has increased over time although, Drennan says, it is still low.

"Patients who survived tended to be younger, their cardiac arrest was more often witnessed by bystanders, and the bystanders were more likely to perform CPR (on them)," said Drennan, who is himself a professional paramedic. "Survivors also had shorter times for first responders to reach the patient."

"Roughly 10 per cent of people who have suffered a cardiac arrest will survive (with help from) highly sophisticated emergency medical services," Drennan said.

"While the delay before attempted resuscitation determines survival, other conditions such as age and heart rhythm also influence the outcome."

P. Kottayil Asokan, a consultant cardiologist at the Fatima Hospital, Calicut, and president-elect of the Indian College of Cardiology, said: "Training ordinary people to give CPR and defibrillation becomes important in our cities because of delays caused by road traffic."

The All India Institute of Medical Sciences, New Delhi, has been conducting a "bystander care" programme, training volunteers from the public in CPR and operating defibrillators.

"We've already trained about 5,000 people. The health ministry wants to expand this to other cities," said Sanjeev Bhoi, additional professor of emergency medicine and trauma at AIIMS.

"We need to train more people and we need more defibrillators in public places and in high-rise buildings."