Coughing vigorously until an ambulance arrives could save the lives of people suffering from a stroke, said researchers.
Tadeusz Petelenz and colleagues at the Silesian Medical School in Katowice, Poland, studied 115 people who had previously fainted or come close to losing consciousness because of various heart problems, reported health portal Country Roads.
They were taught how to recognise the symptoms - sudden dizziness and weakness, shortness of breath, sudden sweating and blurred vision - and then taught the proper coughing technique.
The patients used the cough in 365 instances where they thought they were about to faint. The symptoms disappeared in 292 cases and medical attention was required in only 73 cases, it said.
"Since the onset of the loss of consciousness is very rapid, people usually don't have enough time to call for help," said Petelenz. "However, if victims could maintain consciousness until circulation is restored or help arrives their chances of survival would greatly increase."
Currently, only one in 10 victims of cardiac arrest survive without serious brain damage. Petelenz said high-risk patients should be taught how to cough effectively, starting with a single cough every one to two seconds in bouts of five coughs.
Petelenz's idea is not entirely new. Doctors sometimes ask heart disease patients undergoing angiograms to cough rhythmically and forcefully to get their circulation going.
Leo Bossaert, a professor at the University Hospital in Antwerp, Belgium, said coughing probably would not be harmful, but it is far too early to recommend people to try it at home.