Source
Causes
Sudden and unexpected breathlessness is most likely to be caused by one of the following health conditions. Click on the links below for more information about these conditions.
A problem with your lungs or airways
Sudden breathlessness could be an asthma attack. This means your airways have narrowed and you'll produce more sticky mucus (phlegm), which causes you to wheeze and cough.
You'll feel breathless because it's difficult to move air in and out of your airways.
A heart problem
It's possible to have a "silent" heart attack without experiencing all the obvious symptoms, such as chest pain and overwhelming anxiety.In this case, shortness of breath may be the only warning sign you're having a heart attack. If you or your GP think this is the case, they'll give you aspirin and admit you to hospital straight away.
Heart failure can also cause breathing difficulties. This life-threatening condition means your heart is having trouble pumping enough blood around your body, usually because the heart muscle has become too weak or stiff to work properly. It leads to a build-up of water inside the lungs, which makes breathing more difficult.
Panic attack or anxiety
A panic attack or anxiety can cause you to take rapid or deep breaths, known as hyperventilating. Concentrating on slow breathing or breathing through a paper bag should bring your breathing back to normal.
Treatment
Treatment will depend on the likely cause of your breathlessness. You will be strongly encouraged to stop smoking if you are a smoker. It will also help if you lose weight if you are overweight.You will probably be referred to a heart specialist (a cardiologist) or to a lung (respiratory) specialist, for further tests, depending on the most likely underlying cause. Most cases will be managed by your GP but you may be referred for further investigation and treatment at a hospital.
