This occurs as a result of left ventricular failure. There is an abrupt increase in the venous and capillary pressure in the blood vessels supplying the lungs, followed by flooding of fluid into the interstitial spaces and alveoli. The commonest cause of acute pulmonary oedema is myocardial infarction, which reduces the ability of the left ventricular myocardial muscle to handle the incoming blood. Pulmonary oedema may result from other causes of left ventricular failure such as hypertension or valvular disease of the mitral and aortic valves. The initial symptoms are cough with breathlessness and, occasionally, with wheezing (once called ‘cardiac asthma’). The patient becomes extremely short of breath and in a severe attack becomes pale, sweating, cyanosed and gasping obviously for breath. Frequently frothy sputum is produced which may be blood-stained. Treatment is with diuretics and measures to deal with the myocardial infarction or other underlying cause.