Pulmonary edema overview

# Overview
Pulmonary edema is fluid accumulation in the lungs. This fluid accumulation leads to impaired gas exchange and hypoxia.

# Historical Perspective
Pulmonary edema was first described as a result of heart failure by Andreas Nerlich. In 1891 the first case of high altitude pulmonary edema was reported. In 1908, W. T. Shanahan noted acute pulmonary edema as an adverse effect of epileptic seizures.

# Classification
Pulmonary edema can be classified on the basis of etiology into 2 subtypes, including cardiogenic pulmonary edema (left ventricular failure, myocardial infarction, left ventricle hypertrophy cardiomyopathy) and, noncardiogenic pulmonary edema (acute respiratory distress syndrome, pneumonia, pulmonary embolism, chest trauma).

# Pathophysiology
Pulmonary edema is due to either failure of the heart to remove fluid from the lung circulation ("cardiogenic pulmonary edema"), or due to a direct injury to the lung parenchyma or increased permeability or leakiness of the capillaries ("noncardiogenic pulmonary edema").

# Causes
Common causes of cardiogenic pulmonary edema are cardiomyopathy, congestive heart failure, coronary heart disease, aortic regurgitation, aortic stenosis. Common causes of noncardiogenic pulmonary edema are acute respiratory distress syndrome, high altitude pulmonary edema, pulmonary embolism.

# Differentiating Pulmonary edema from Other Diseases
Pulmonary edema should be distinguished from other conditions that cause dyspnea, orthopnea, cough.

# Epidemiology and Demographics
The prevalence of pulmonary edema was estimated to be 75000-83000 cases per 100,000 individuals among heart failure patients with reduced ejection fraction. Pulmonary edema commonly affects individuals older than 65 years of age. Males are more commonly affected by pulmonary edema than woman.

# Risk Factors
The risk factors in pulmonary edema refer to the risk factors for the underlying disease that cause pulmonary edema. Risk factors of cardinogenic pulmonary edema include high blood pressure, hyperlipidemia, atherosclerosis, diabetes mellitus, obesity. And risk factors for noncardiogenic pulmonary edema include sepsis, aspiration, pneumonia.

# Screening
There is insufficient evidence to recommend routine screening for pulmonary edema.

# Natural History, Complications and Prognosis
Some patients may need to use a breathing machine for a long time, which may lead to damage to lung tissue.Kidney failure and damage to other major organs may occur if blood and oxygen flow are not restored promptly. If not treated, this condition can be fatal. If left untreated, acute pulmonary edema can lead to coma and even death, generally due to its main complication of hypoxia.

# Diagnosis
Pulmonary artery catheterization is the gold standard test for the diagnosis of pulmonary edema. Elevated pulmonary-artery pressure indicates cardiogenic pulmonary edema or pulmonary edema due to volume overload.

# History and Symptoms
The history of a patient with pulmonary edema varies according to the underlying cause. The most common symptom of pulmonary edema is shortness of breath (dyspnea). Depending on the cause, it may occur acutely or have a gradual onset. When pulmonary edema is due to an acute myocardial infarction chest pain is common symptom.

# Physical Examination
Patients with pulmonary edema usually appear agitated. Physical examination of patients with pulmonary edema is usually remarkable for dyspnea, tachypnea. The presence of abnormal cardiac examination on physical examination is diagnostic of cardiogenic pulmonary edema. Patients with noncardiogenic pulmonary edema may have warm extremities, whereas patients with cardiogenic pulmonary edema may have cool extremities.

# Laboratory Findings

## Chest X Ray
The diagnosis is confirmed on X-ray of the lungs, which shows increased fluid in the alveolar walls. Kerley B lines, increased vascular filling, pleural effusions, upper lobe diversion (increased blood flow to the higher parts of the lung) may be indicative of cardiogenic pulmonary edema, while patchy alveolar infiltrates with air bronchograms are more indicative of noncardiogenic edema

## Electrocardiography
Although there is no diagnostic criteria of pulmonary edema on the EKG, there may be signs of the underlying cardiogenic cause of pulmonary edema.

## CT
Thoracic CT scan may be helpful in the diagnosis of pulmonary edema. Findings on CT scan diagnostic of hydrostatic pulmonary edema include cardiomegaly, vascular engorgment, pleural effusions.

## MRI
There are no MRI findings associated with pulmonary edema.

## Echocardiography
Echocardiography is useful in confirming a cardiac or no-cardiac cause of pulmonary edema. Echocardiography may identify the presence and severity of valvular causes of pulmonary edema. Echocardiography is helpful in diagnosis of ischemia or myocardial infarction, cardiomyopathy as an underlying cause of pulmonary edema. Echocardiography is less sensitive in identifying diastolic dysfunction. Thus, a normal echocardiogram may not rule out cardiogenic pulmonary edema.

## Other imaging findings
There are no additional imaging findings associated with pulmonary edema.

## Other diagnostic findings
Pulmonary artery catheterization is the gold standard test for the diagnosis of pulmonary edema. Elevated pulmonary-artery pressure indicates cardiogenic pulmonary edema or pulmonary edema due to volume overload.

# Treatment

## Medical Therapy
Pulmonary edema classified into cardiogenic and non-cardiogenic pulmonary edema, each requires different management and has a different prognosis. The main goal of a treatment are alleviate symptoms and improving hemodynamics. The initial management of patients is following the ABCs of resuscitation, that is, airway, breathing, and circulation. Medical treatment of cardiogenic pulmonary edema focuses on preload reduction, afterload reduction and inotropic support.

## Surgery
The mainstay of treatment for pulmonary edema is medical therapy. Surgery is usually reserved for patients who experienced cardiogenic shock following acute cardiogenic pulmonary edema.

## Primary Prevention
Effective measures for the primary prevention of cardiogenic pulmonary edema include maintaining a healthy lifestyle, avoid tobacco, treat dyslipidemia, low salt diet, controlling hypertension, avoid cardiotoxic agents, controling diabetes. Effective measures for the primary prevention of high-altitude pulmonary edema include, encourage healthy lifestyle and exercise, gradual ascent, preacclimization, avoiding alcohol ingestion, high carbohydrate in diet, adequate hydration, vigorous exertion during the first few days at high altitude, oxygen enrichment.

## Secondary Prevention
The major complications of cardiogenic pulmonary edema are respiratory failure and sudden cardiac death secondary to cardiac arrhythmia. Prompt diagnosis and treatment are effective for secondary prevention in cardiogenic pulmonary edema.