There are a number of reasons why a person might hyperventilate and those can generally be divided into two camps: psychological and physiological conditions. As a symptom of more serious ailments it can result from renal (kidney) failure, pulmonary oedema (fluid in the lungs), drug overdose, a fever and, more frequently, asthma. The most common causes of hyperventilation, however, are psychological – a result of a stressful situation or a panic attack.
Contrary to popular belief, the effect of this kind of breathing isn’t to increase oxygen intake, but to lower the volume of carbon dioxide in the blood by exhaling more than the amount produced by the body. When carbon dioxide levels are too low, blood vessels in the brain constrict causing lightheadedness and – in extreme cases – fainting. This can only serve to increase a person’s anxiety and exacerbate the hyperventilation.
The well-known treatment of breathing into a paper bag (neither advised nor taught) was invented by a US army medic in 1951. Although this method – known as rebreathing – often works, today’s medical experts say it is dangerous and should be avoided.