Pulmonary edema (American English), or oedema

(British English; both words from the Greek οἴδημα), is fluid accumulation in the air spaces and parenchyma of the lungs.[1] It leads to impaired gas exchange and may cause respiratory failure. It is due to either failure of the left ventricle of the heart to adequately remove blood from the pulmonary circulation (“cardiogenic pulmonary edema”), or an injury to the lung parenchyma or vasculature of the lung (“noncardiogenic pulmonary edema”).[2] Treatment is focused on three aspects: firstly improving respiratory function, secondly, treating the underlying cause, and thirdly avoiding further damage to the lung. Pulmonary edema, especially in the acute setting, can lead to respiratory distress, cardiac arrest due to hypoxia, and death.

1Symptoms and signs

The overwhelming symptom of pulmonary edema is di culty breathing, but may also include coughing up blood (classically seen as pink, frothy sputum), excessive sweating, anxiety, and pale skin. Shortness of breath can manifest as orthopnea (inability to lie down flat due to breathlessness) and/or paroxysmal nocturnal dyspnea (episodes of severe sudden breathlessness at night). These are common presenting symptoms of chronic pulmonary edema due to left ventricular development of pulmonary edema may be associated with symptoms and signs of “fluid overload”, this is a non specific term to describe the manifestations of left ventricular failure on the rest of the body and includes peripheral edema (swelling of the legs, in general, of the “pitting” variety, wherein the skin is slow to return to normal when pressed upon), raised jugular venous pressure and hepatomegaly, where the liver is enlarged and may be tender or even pulsatile. Other signs include end-inspiratory crackles (sounds heard at the end of a deep breath) on auscultation and the presence of a third heart sound.[2]

Pulmonary edema on CT-scan (coronal MPR)

caused by increased left ventricular pressure pulmonary edema may form when mean pulmonary pressure rises from the normal of 15 mmHg[3] to above 25 mmHg.[4] Broadly, the causes of pulmonary edema can be divided into cardiogenic and non-cardiogenic. By convention cardiogenic refers to left ventricular causes.

2.1 Cardiogenic

Left ventricular failure may be due to a heart attack leading to arrhythmias (tachycardia/fast heartbeat or bradycardia/slow heartbeat) and fluid overload, e.g., from kidney failure or intravenous therapy which may cause dilatation and failure of the left ventricle or may cause pulmonary edema in the absence of heart failure.

2Causes

Pulmonary edema is an accumulation of fluid within the parenchyma and air spaces of the lungs. Classically it is cardiogenic (left ventricular) but fluid may also accumulate due to damage to the lung. This damage may be direct injury or injury mediated by high pressures within the pulmonary circulation. When directly or indirectly

2.2 Non-cardiogenic

Hypertensive crisis. The cause of pulmonary edema in the presence of a hypertensive crisis is probably due to a combination of increased pressures in the right ventricle and pulmonary circulation and also increased systemic vascular resistance and left ventricle contractility increasing the hydrostatic pressure within the pulmonary capillaries leading to extravasation of fluid and edema.