OVERVIEW

What is pulmonary edema?

Pulmonary edema refers to a condition where fluid leaks from the pulmonary blood vessels into the lung interstitium or alveoli, causing symptoms such as coughing and difficulty breathing^[1]. It is characterized by sudden onset and critical severity^[2].

Based on the underlying cause, pulmonary edema can be classified into two types:

1. Cardiogenic pulmonary edema: Also known as hydrostatic pulmonary edema, often associated with a history of heart disease.
2. Non-cardiogenic pulmonary edema: Also referred to as permeability pulmonary edema, including neurogenic pulmonary edema, high-altitude pulmonary edema, infectious pulmonary edema, and toxic pulmonary edema.

Is pulmonary edema common?

Yes. Pulmonary edema is one of the common complications in hospitalized patients. A retrospective study showed that the incidence of pulmonary edema among hospitalized patients is 7.6% (meaning approximately 76 out of 1,000 hospitalized patients develop pulmonary edema)^[3].

SYMPTOMS

What are the common symptoms of pulmonary edema?

Pulmonary edema usually has a sudden onset and can severely affect respiratory function. The most common clinical symptoms include coughing, chest tightness, rapid breathing, difficulty breathing, and cyanosis (a bluish-purple discoloration of the skin and mucous membranes)^[4].

As the condition progresses, coughing worsens, producing white or pink frothy sputum. Symptoms such as orthopnea (being forced to sit upright or in a semi-recumbent position to relieve difficulty breathing), dizziness, and weakness may appear. In severe cases, coma and shock may occur.

What complications can pulmonary edema cause?

• Hypoxemia: Changes in pulmonary capillary pressure during pulmonary edema lead to interstitial and alveolar edema, impairing alveolar ventilation and gas exchange, resulting in hypoxemia. The main manifestations include shortness of breath and difficulty breathing.
• Acid-base imbalance: Pulmonary edema can cause cardiopulmonary failure, leading to severe hypoxia and acidosis, which may trigger acid-base imbalance.

CAUSES

What are the common causes of pulmonary edema?

Pulmonary edema has various causes, and its pathogenesis is relatively complex, mainly closely related to increased alveolar capillary permeability and imbalance of alveolar fluid balance. It often occurs secondary to certain diseases or may be caused by external factors. Common causes are as follows:

• Disease-related factors:

1. Cardiovascular diseases: Conditions such as hypertension, coronary heart disease, and mitral stenosis can easily lead to heart failure, obstructing blood reflux and causing accumulation in the pulmonary circulation. This increases pulmonary capillary hydrostatic pressure, leading to fluid leakage from blood vessels and resulting in pulmonary edema. This type is usually referred to as cardiogenic pulmonary edema.
2. Neurological diseases: Conditions such as brain tumors or traumatic brain injuries can stimulate adrenal sympathetic nerve activity, increasing pulmonary capillary pressure and permeability, thereby causing pulmonary edema.
3. Pulmonary diseases: Conditions such as lung injury or acute respiratory distress syndrome can damage the alveolar-capillary barrier, allowing proteins and large molecules to leak into the interstitial space, leading to pulmonary edema.

• External factors:

1. Infection: Pulmonary or systemic infections can increase pulmonary vascular permeability, leading to pulmonary edema.
2. Drowning: Inhaling water into the lungs disrupts fluid balance, preventing excess tissue fluid from being absorbed by the lymphatic and venous systems. This causes abnormal leakage from pulmonary capillaries and accumulation of fluid outside the vessels, forming pulmonary edema.
3. Environment: As altitude increases, atmospheric pressure decreases significantly. In high-altitude (above 3,000 meters) hypoxic environments, blood vessels constrict, and pulmonary fluid absorption becomes imbalanced. This lack of compensation can make sudden exposure to such conditions lead to pulmonary edema^[5].

Who is more prone to pulmonary edema?

• Patients with cardiovascular diseases: Conditions like hypertension, coronary heart disease, and mitral stenosis increase pulmonary capillary hydrostatic pressure and vascular permeability, making them more susceptible to pulmonary edema.
• Individuals entering high-altitude areas: The lower oxygen levels at high altitudes can cause hypoxia in those who suddenly ascend, increasing pulmonary capillary hydrostatic pressure and the risk of pulmonary edema.

Is pulmonary edema hereditary?

Generally, it is not hereditary.

DIAGNOSIS

How to diagnose pulmonary edema? What tests are needed?

When diagnosing pulmonary edema, doctors primarily rely on medical history, typical clinical manifestations, and imaging results. The following tests are usually required:

• Physical examination:

Inspection is used to determine whether the patient exhibits signs of respiratory distress, such as pale complexion or cyanosis of the lips. Auscultation helps detect the presence of wet rales in the lungs, suggesting possible pulmonary edema.

• Imaging tests:

1. Chest X-ray: Examines the basic condition of the lungs and heart morphology to aid in diagnosing pulmonary edema. Before the test, metal objects must be removed to avoid interference and ensure accurate results.
2. Lung ultrasound: The patient lies flat or semi-recumbent while the probe is placed between the ribs to scan the lungs and assess the severity of pulmonary edema.
3. Pulse indicator continuous cardiac output monitoring: Measures cardiac preload, afterload, and the extravascular lung water index to determine the presence of pulmonary edema^[6].

Which diseases can pulmonary edema be confused with? How to differentiate them?

Pulmonary edema may be confused with conditions such as lung abscess or pulmonary embolism, as they share symptoms like severe coughing and dyspnea. Doctors differentiate them by evaluating medical history, clinical symptoms, and imaging tests.

TREATMENT

Which department should I go to for pulmonary edema?

Respiratory Medicine, Emergency Department, Cardiology.

How is pulmonary edema treated?

The treatment of pulmonary edema varies depending on the specific cause. For severe, life-threatening conditions, immediate supportive measures must be taken while actively addressing the underlying disease.

• Oxygen therapy and ventilation support:

1. If the patient continues to experience hypoxemia, it can be corrected by inhaling high-concentration oxygen.

2. Non-invasive positive pressure ventilation (a ventilation method connecting the patient to a ventilator via a nasal mask) or mechanical ventilation with an artificial airway may be used to improve ventilation and hypoxemia^[4].

• Medication:

1. Diuretics: Drugs such as furosemide, bumetanide, and torsemide are effective for most cases of pulmonary edema. Furosemide, which also acts as a venodilator, can rapidly reduce preload and is the preferred diuretic. Possible side effects include dehydration, loss of appetite, and constipation^[4].

2. Nitrates: Medications like nitroglycerin and isosorbide dinitrate effectively dilate arteries and veins. They are suitable for patients with pulmonary edema accompanied by hypertension but may cause dizziness and headaches^[4].

3. Morphine: A short-acting venodilator, morphine is suitable for patients with acute left heart failure and can effectively relieve symptoms like dyspnea. Side effects may include nausea, vomiting, and drowsiness^[4].

4. Inotropic agents: Drugs such as dopamine and milrinone are used for cardiogenic pulmonary edema, stimulating myocardial contraction and promoting vasodilation. Possible side effects include headache, weakness, and palpitations^[4].

5. Corticosteroids: Medications like dexamethasone and hydrocortisone are used for high-altitude or toxic pulmonary edema, reducing inflammation and vascular permeability. However, they may cause lower limb edema, nausea, and vomiting^[4].

Does pulmonary edema require hospitalization?

Pulmonary edema typically has an acute onset and is a critical condition requiring hospitalization.

What happens if pulmonary edema is not treated promptly?

Without timely and standardized treatment, symptoms such as coughing and dyspnea may worsen, leading to complications like hypoxemia and acid-base imbalance. In severe cases, it can cause respiratory and circulatory failure or even death^[2].

DIET & LIFESTYLE

What should patients with pulmonary edema pay attention to in their diet?

• Maintain a balanced diet, eat more fruits and vegetables such as radishes, watermelon, cucumbers, and winter melon to help supplement vitamins and enhance immunity.
• For those with concurrent cardiovascular diseases, eat smaller, more frequent meals, control water and salt intake, and avoid aggravating edema.

What precautions should be taken after pulmonary edema treatment? How to care for it?

• Daily care: Ensure ventilation and keep the air fresh; maintain a regular routine and avoid high-oxygen-consuming activities.
• Medication care: Strictly follow the doctor's instructions for medication. Do not alter the dosage or stop medication without authorization. If adverse reactions such as nausea or vomiting occur, inform the doctor promptly for adjustments to the treatment plan.
• Psychological care: Some patients may experience negative psychological reactions such as anxiety or irritability. Learn self-regulation techniques, such as listening to music or watching movies, to divert attention and alleviate negative emotions.

Is follow-up necessary for pulmonary edema? How is it conducted?

Follow-up is necessary, with specific timing determined by the doctor's instructions. It is conducted through routine physical examinations and imaging tests.

PREVENTION

Can pulmonary edema be prevented? How to prevent it?

Due to the complex causes of pulmonary edema, it is difficult to prevent, but the risk can be reduced by avoiding high-risk factors. Specific measures include the following:

1. Avoid sudden travel to high-altitude areas. If necessary, prepare in advance by carrying oxygen tanks and essential medications. Seek medical attention promptly if symptoms like headache, chest tightness, or shortness of breath occur.
2. Patients with cardiovascular, neurological, or pulmonary diseases should actively treat their underlying conditions.