Simple actions like sniffing and gasping for air can prevent the most common form of fainting, researchers have found.
"Recurrent syncope (fainting) has serious effects on quality of life," said Marta Bavolarova, a cardiologist at Louis Pasteur University Hospital in Slovak Republic.
"Patients are often injured when they fall, which reduces their mobility and ability to look after themselves. Depression is common in these patients," Bavolarova said.
The study focused on the most common type of fainting, called vasovagal syncope, which can be caused by prolonged standing or standing up quickly.
It leads to drops in blood pressure and heart rate, and a brief loss of consciousness.
Vasovagal syncope is an abnormality in the reflex actions controlled by the autonomic nervous system (ANS). The sympathetic and parasympathetic nervous systems together create the ANS.
They have opposite effects on the cardiovascular system - sympathetic actions increase heart rate and blood pressure while parasympathetic actions lower them.
Researchers studied whether sniffing and gasping could prevent fainting by interrupting the falls in blood pressure and heart rate.
The study included two women aged 56 and 62 years with a history of vasovagal syncope. The head up tilt test was performed on each patient.
For the test, patients lie on a table which is rapidly tilted to a 60 degree angle to mimic standing up. The table has built in monitors for measuring blood pressure and heart rate (using ECG).
At the moment blood pressure began to drop, patients were asked to sniff or gasp twice with their mouths closed and then breathe out. The researchers found that blood pressure and heart rate did not drop and syncope was avoided.
"Our test, which is like standing up quickly, previously led to falls in blood pressure and heart rate and subsequent syncope in these patients," Bavolarova said.
"But strong and forced inhalation by sniffing or gasping seemed to prevent these drops and they did not faint," she said.
"We believe that sniffing and gasping have a strong sympathetic effect that inhibits the abnormal parasympathetic activity in these patients. This stops fainting at the highest level," said Bavolarova.
"Patients with recurrent fainting are advised to avoid standing up quickly and standing for long periods of time," she said.
"Those who have prodromal symptoms like weakness, sweating or visual disturbances are advised to do counterpressure manoeuvres like leg crossing and hand grips to increase their heart rate and blood pressure," she said.
"We now also tell patients that they can sniff or gasp to prevent themselves from fainting," she said.
