Causes of sudden shortness of breath

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 phlegm (sticky mucus), which causes you to wheeze and cough. You'll feel breathless because it's difficult to move air in and out of your airways.

Your GP may advise you to use a spacer device with your asthma inhaler. This delivers more medicine to your lungs, helping to relieve your breathlessness.

Pneumonia (lung inflammation) may also cause shortness of breath and a cough. It's usually caused by an infection, so you'll need to take antibiotics.

If you have COPD, it's likely your breathlessness is a sign this condition has suddenly got worse.

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  aheart 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.

A combination of lifestyle changes and medicines or surgery will help the heart pump better and relieve your breathlessness.

Breathlessness could also relate to a problem with your heart rate or rhythm, such as atrial fibrillation (an irregular and fast heart rate) or supraventricular tachycardia (regular and fast heart rate).

Panic attack or anxiety

A panic attack or generalised anxiety disorder 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.

More unusual causes

These include:

• a severe allergic reaction (anaphylaxis)
• pneumothorax partial collapse of your lung caused by a small tear in the lung surface, which allows air to become trapped in the space around your lungs
• pulmonary embolism a blockage in one of the blood vessels in the lung
• idiopathic pulmonary fibrosis a rare and poorly understood lung condition that causes scarring of the lungs
• pleural effusion acollection of fluid next to the lung
• diabetic ketoacidosis acomplication of diabetes where acids build up in your blood and urine

Causes of long-term breathlessness

Long-term breathlessness is usually caused by:

• obesity or being unfit
• poorly controlled asthma
• chronic obstructive pulmonary disease (COPD) permanent damage to the lungs usually caused by years of smoking
• anaemia alow level of oxygen in the blood caused by a lack of red blood cells or haemoglobin (the part of red blood cells that carries oxygen)
• heart failure when 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
• aproblem with your heart rate or rhythm, such as atrial fibrillation (an irregular and fast heart rate) or supraventricular tachycardia (regular and fast heart rate)

More unusual causes of long-term breathlessness are:

• bronchiectasis a lung condition where the airways are abnormally widened and you have a persistent phlegmy cough
• pulmonary embolism are current blockage in a blood vessel in the lung
• partial collapse of your lung caused by lung cancer
• pleural effusion a collection of fluid next to the lung
• narrowing of the main heart valve, restricting blood flow to the rest of the body
• frequent panic attacks, which can cause you to hyperventilate (take rapid or deep breaths)