18th February 2025

Overview of pulmonary oedema

Pulmonary oedema is the accumulation of excess fluid in the lung’s interstitial and/or alveolar spaces, occurring when fluid is filtered into the lungs faster than it can be removed. This fluid reduces the surface area available for gas exchange, leading to hypoxaemia and acute respiratory failure. 

Cardiogenic pulmonary oedema occurs when the left heart is unable to pump effectively, resulting in raised left cardiac filling pressures and back pressure in the lungs manifesting as pulmonary oedema. The most common cause of this is acute decompensated heart failure which will be the focus of this section.