Pulmonary eema (American English), or oedema (British English), is swelling and/or fluid accumulation in the lungs. It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the heart to remove fluid from the lung circulation ("cardiogenic pulmonary edema") or a direct injury to the lung parenchyma ("noncardiogenic pulmonary edema"). Treatment depends on the cause, but focuses on maximizing respiratory function and removing the cause.