In most cases, it happens as a result of severe heart problems.
Pulmonary oedema develops over time in the presence of heart failure or can appear suddenly (acute pulmonary oedema).
If this happens suddenly it is a medical emergency and needs immediate treatment.
Our lungs are made up of numerous small air sacs called alveoli. These air sacs fill with each breath, taking in oxygen and releasing carbon dioxide. If the alveoli are filled with fluid instead of air, oxygen cannot be absorbed into the blood stream.
Veins carry blood back to your heart. This blood is low in oxygen as it has travelled around your body. It returns to the right side of your heart where the right ventricle then pumps the blood into your lungs.
The blood absorbs oxygen in your lungs and then returns to the left side of your heart. If the left side of your heart is damaged or overworked leading to heart failure, it may be unable to pump enough of the blood it receives out around the body, and back pressure into the lungs follows. This back pressure forces the fluid into the alveoli sacs. This is called cardiogenic pulmonary oedema and is usually the result of coronary artery disease, cardiomyopathy, heart valve problems, uncontrolled and untreated high blood pressure.
Pulmonary oedema can also be caused by non-cardiac conditions but the mechanism is somewhat different. These include acute respiratory distress syndrome, high altitudes, nervous system diseases, adverse drug reactions, pulmonary embolism, viral infections, chest trauma, and exposure to toxins.
Reducing your risk factors for heart disease will help prevent subsequent heart failure. Lifestyle changes can also help you manage your symptoms and reduce your discomfort.
Avoiding excess alcohol consumption
It is important that you recognise the early signs of fluid retention which are responsible for many of your symptoms, so that prompt treatment can begin.
Pulmonary oedema is initially diagnosed on the basis of your symptoms and a physical examination. Prompt treatment is needed so your doctor will ask about your past medical history which may increase your risk, particularly if you have cardiovascular disease or lung problems. Initial tests will include ECG, chest xray, blood tests, and a measure of your blood oxygen level.
Acute pulmonary oedema is a medical emergency and urgent treatment is required. It can sometimes be fatal. Prompt treatment for pulmonary oedema and treatment for the underlying cause improves the outcome.
Initial treatment is with oxygen therapy, intravenous medications to reduce the fluid build-up and possibly drugs to improve the pumping ability of the heart when a heart problem is the underlying cause.