Pulmonary edema

Pulmonary edema is a critical condition that occurs when the alveoli of the lungs fill with fluid, preventing normal gas exchange. This condition can be caused by a number of factors, including heart disease, kidney disease, and inhalation of toxic substances. Pulmonary edema is acute severe left ventricular failure with pulmonary venous hypertension and alveolar edema. Pulmonary edema causes severe shortness of breath, sweating, wheezing, and sometimes foamy, blood-stained sputum. Diagnosis is clinical and based on chest X-ray data. Treatment includes oxygen inhalation, intravenous nitrates, diuretics, morphine, and sometimes endotracheal intubation and mechanical ventilation.

Epidemiology

When left ventricular filling pressures increase suddenly, there is a rapid shift of plasma from the pulmonary capillaries into the interstitial spaces and alveoli, causing pulmonary edema. Approximately half of all cases are due to acute coronary ischemia, and a quarter are due to decompensation of severe preexisting heart failure, including heart failure with diastolic dysfunction due to hypertension. The remaining cases are due to arrhythmia, acute valvular dysfunction, or acute volume overload, often due to intravenous fluid administration. Medication and dietary errors have also been suggested as causes.

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Causes pulmonary edema

Pulmonary edema is a medical emergency that occurs when fluid builds up in the air sacs of the lungs, preventing the normal exchange of oxygen and carbon dioxide in the blood. It can be caused by a variety of reasons, including:

Heart problems (Cardiogenic pulmonary edema):

• Heart failure
• Myocardial infarction
• Heart valve diseases
• Hypertension, especially pulmonary hypertension
• Cardiomyopathy and myocarditis

Non-cardiogenic causes:

• Acute respiratory distress syndrome (ARDS)
• Inhalation injury to the lungs, such as from inhaling smoke or toxic gases
• Inflammatory processes such as pneumonia or sepsis
• Chest injuries
• Transfusion of large volumes of fluid, including rapid blood transfusion

High altitude pulmonary edema:

• Occurs due to rapid ascent to high altitude without proper adaptation.

Drug-induced pulmonary edema:

• From certain medications, including cancer drugs, some anti-inflammatory drugs, and drugs given into a vein during surgery

Renal dysfunction:

• Such as acute renal failure or chronic kidney disease

Acute lung injury:

• May occur due to aspiration, such as when stomach contents enter the lungs

Risk factors

Risk factors for pulmonary edema can be divided into those associated with cardiogenic causes and those associated with non-cardiogenic causes. Here are some of them:

Cardiogenic risk factors:

1. Coronary heart disease: A history of angina pectoris or myocardial infarction increases the risk of developing pulmonary edema.
2. Arterial hypertension: Especially uncontrolled high blood pressure increases the strain on the heart and can lead to heart failure.
3. Heart valve disease: Problems with the mitral or aortic valves can increase the risk of pulmonary edema.
4. Cardiomyopathy: Diseases of the heart muscle can lead to dysfunction and pulmonary edema.
5. Arrhythmias: Abnormal heart rhythms can lead to ineffective cardiac output and pulmonary edema.

Non-cardiogenic risk factors:

1. Lung diseases: Such as pneumonia or chronic obstructive pulmonary disease (COPD).
2. Head or chest injuries: These can lead to increased pressure in the head or chest area, which can contribute to pulmonary edema.
3. High altitude sickness: Rapid ascent to high altitude without adaptation can lead to pulmonary edema.
4. Toxic substances: Inhaling toxic gases such as chlorine or ammonia can cause inflammation and swelling of the lungs.
5. Medicines: Some medications can cause pulmonary edema as a side effect.
6. Smoking: Not only does it contribute to COPD, it also increases the risk of pneumonia and other respiratory infections.
7. Chronic kidney disease: Impaired kidney function can cause fluid retention in the body, which increases the risk of pulmonary edema.
8. Sepsis: Systemic inflammation can compromise the permeability of blood vessels, including those in the lungs, leading to leakage and pulmonary edema.

Identifying and managing risk factors is key to preventing the development of pulmonary edema and reducing the likelihood of its recurrence.

Pathogenesis

The pathogenesis of pulmonary edema is the mechanism of development of the condition when fluid from the blood vessels enters the lung tissue and alveoli, preventing normal gas exchange. There are several key mechanisms that can lead to pulmonary edema:

• Increased hydrostatic pressure in the pulmonary capillaries: This is the most common cause of cardiogenic pulmonary edema, where the heart is unable to pump blood effectively, causing blood to pool in the pulmonary vessels and increase pressure in them. Fluid from the capillaries begins to leak into the alveolar spaces.
• Decreased oncotic pressure of blood plasma: When the level of proteins, especially albumin, in the blood decreases, the oncotic pressure also decreases, which can also lead to the release of fluid from the vessels into the lung tissue.
• Capillary endothelial damage: Inflammation or toxic exposure can damage the endothelium of pulmonary capillaries, increasing their permeability to fluid.
• Lymphatic failure: The lungs' lymphatic system helps remove excess fluid. When it becomes overloaded or damaged, fluid accumulates in the lung tissue.
• Impaired fluid flow: Excessive fluid administration (eg, through infusion therapy) can lead to pulmonary edema if the rate of administration exceeds the body's ability to remove it.
• Indirect lung injury: Conditions such as acute respiratory distress syndrome (ARDS) involve damage to the alveolar-capillary barrier caused by various pathological processes not directly related to cardiac activity.

Symptoms pulmonary edema

Patients complain of intense dyspnea, restlessness and anxiety, and a feeling of shortness of breath. Cough with blood-tinged sputum, pallor, cyanosis, and severe sweating often occur; some patients foam at the mouth. Pronounced hemoptysis is rare. The pulse becomes rapid, with low filling, and blood pressure changes. The developing arterial hypertension indicates a significant cardiac reserve; arterial hypotension is a threatening sign. Crepitation is heard on inspiration, scattered over the anterior and posterior surfaces over all the lung fields. Pronounced wheezing (cardiac asthma) may appear. Loud respiratory sounds often make cardiac auscultation difficult. A gallop rhythm may be determined due to a combination of III (S ₃ ) and IV (S ₄ ) heart sounds. Signs of right ventricular failure are possible (e.g., swelling of the neck veins, peripheral edema).

Stages

Pulmonary edema can progress through different stages depending on the underlying cause and how quickly symptoms develop. Below is a description of potential stages of pulmonary edema:

Initial stage (Interstitial edema):

1. Interstitial edema: In this early stage, fluid begins to accumulate in the interstitial space that surrounds the air sacs of the lungs. Symptoms at this stage may include mild shortness of breath, especially with exertion, fatigue, and possibly a feeling of tightness in the chest.

Progressive stage (Alveolar edema):

1. Alveolar edema: If interstitial edema is not corrected, fluid begins to fill the alveoli, which interferes with gas exchange. At this point, more severe symptoms occur, including significant shortness of breath even at rest, wheezing, coughing up foamy sputum, often pink in color.

Severe stage (Acute respiratory distress syndrome, ARDS):

1. ARDS: This is the most serious stage of pulmonary edema, in which severe inflammation and damage to the alveoli occurs, leading to significant problems with breathing and oxygen exchange. Symptoms include extreme shortness of breath, cyanosis (blue skin due to lack of oxygen), anxiety, and confusion. ARDS may require mechanical ventilation and other intensive care treatments.

Forms

Pulmonary edema can be classified according to various features and causes. The two main forms of pulmonary edema are cardiogenic and non-cardiogenic:

Cardiogenic pulmonary edema

It is the result of heart failure, where the heart cannot pump blood effectively, causing pressure in the pulmonary arteries to increase, which eventually causes fluid to leak out of the blood vessels into the alveoli and interstitial spaces of the lungs. It can be caused by a variety of conditions, including coronary artery disease, valvular heart disease, cardiomyopathy, and arrhythmias.

Non-cardiogenic pulmonary edema

This form of pulmonary edema is not associated with heart failure and can be caused by a variety of conditions, including:

• ARDS (acute respiratory distress syndrome): severe inflammation of the lungs, often in response to infection or injury.
• Toxic pulmonary edema: Inhaling toxic gases such as smoke from a fire, chlorine, or other chemicals.
• High altitude pulmonary edema: occurs when you quickly ascend to high altitude, causing a decrease in oxygen pressure and subsequent swelling.
• Neurogenic pulmonary edema: May develop after severe brain injury or extreme stress, causing rapid changes in blood pressure and circulation in the lungs.
• Aspiration pulmonary edema: Occurs when fluids, food, or vomit enter the lungs, causing inflammation and swelling.

Drug-induced pulmonary edema

Some medications can cause pulmonary edema as a side effect.

Pulmonary edema due to infections

Certain infectious processes, particularly severe pneumonia or sepsis, can also cause pulmonary edema.

Pulmonary edema in obstructive sleep apnea

Chronic conditions such as obstructive sleep apnea can lead to nocturnal pulmonary edema due to persistently elevated pressure in the pulmonary arteries.

Each form of pulmonary edema requires a specific approach to treatment, including treating the underlying cause, supporting respiratory function, and, in some cases, using medications. Prompt medical attention is critical to reduce the risk of complications and mortality.

Complications and consequences

Pulmonary edema is a serious and potentially life-threatening condition that can lead to a number of complications. Some of the possible complications caused by pulmonary edema include:

• Hypoxemia: The main complication of pulmonary edema is hypoxemia, or low oxygen levels in the blood. This can lead to damage to vital organs due to inadequate oxygen supply.
• Hypercapnia: A build-up of carbon dioxide in the blood, which can occur due to decreased gas exchange in the lungs.
• Acute respiratory failure: This is a critical condition where the lungs cannot provide adequate gas exchange to keep the body alive.
• Cardiogenic Shock: In cardiogenic pulmonary edema, which is caused by heart failure, the heart cannot pump blood effectively, which can lead to cardiogenic shock.
• Respiratory alkalosis or acidosis: Acid-base imbalances caused by abnormal breathing.
• ARDS (Acute Respiratory Distress Syndrome): A severe form of lung injury that can occur after severe injury, infection, or as a complication of pulmonary edema.
• Multiple organ failure: Prolonged hypoxemia can lead to failure of multiple organs because they do not receive enough oxygen to function properly.
• Pneumonia: Fluid buildup in the lungs can contribute to bacterial infection.
• Pleural effusion: Accumulation of excess fluid in the pleural space, which can further impair breathing function.

Treatment of complications of pulmonary edema involves not only addressing the underlying cause of the edema but also supporting bodily functions during this critical period. In severe cases, this may require the use of a ventilator, drug therapy to support the cardiovascular system, and specialized procedures such as hemodialysis for renal failure.

Pulmonary edema is a serious and potentially life-threatening condition that can lead to death for several reasons:

• Asphyxia: The most immediate threat from pulmonary edema is suffocation, or asphyxia. Excess fluid in the alveoli interferes with normal gas exchange, meaning that oxygen cannot be efficiently delivered to the blood and carbon dioxide cannot be removed. This causes hypoxia and hypercapnia, which can lead to cardiac and respiratory arrest.
• Cardiogenic shock: If pulmonary edema is caused by heart failure, the condition can progress to cardiogenic shock, in which the heart cannot maintain adequate circulation, causing critical hypoperfusion of vital organs.
• Acute respiratory failure: Prolonged oxygen deprivation and carbon dioxide accumulation can lead to acute lung injury and subsequent acute respiratory failure.
• Multiple organ failure: Hypoxia can lead to failure of other organs such as the kidneys, liver, and brain, which can lead to multiple organ failure.
• Septic shock: If pulmonary edema is associated with an infection or sepsis, it can lead to septic shock, a condition in which blood pressure drops to dangerously low levels and organs stop functioning normally.
• Pneumothorax: Sometimes, high intrathoracic pressure caused by pulmonary edema can lead to rupture of the alveoli and subsequent pneumothorax (accumulation of air in the pleural space), which further impairs breathing.

Diagnostics pulmonary edema

An exacerbation of COPD may mimic pulmonary edema due to left ventricular failure or both ventricles if the patient has cor pulmonale. Pulmonary edema may be the first clinical manifestation in patients without a history of heart disease, whereas patients with COPD with such severe manifestations have a long history of COPD, although they may be too short of breath to recognize this complication. The picture of interstitial edema on emergency chest radiographs is usually helpful in establishing the diagnosis. The level of brain natriuretic peptide is increased in pulmonary edema and normal in an exacerbation of COPD. ECG, pulse oximetry, and blood tests (cardiac markers, electrolytes, urea, creatinine, and, in severe patients, arterial blood gases) are also performed. Hypoxemia may be severe. CO2 retention is a late, ominous sign of secondary hypoventilation.

Differential diagnosis

Differential diagnosis of pulmonary edema involves considering the various conditions that can cause symptoms similar to pulmonary edema or differentiating between the different types of pulmonary edema. Here are some conditions that are commonly considered:

1. Cardiogenic pulmonary edema: Caused by heart failure when the heart cannot pump blood effectively, causing fluid to build up in the air sacs of the lungs.
2. Non-cardiogenic pulmonary edema:
   1. Acute respiratory distress syndrome (ARDS): Inflammation of the lungs that causes fluid to leak into the alveoli.
   2. High-altitude pulmonary edema: May occur when you quickly ascend to high altitude due to low atmospheric pressure.
   3. Toxic pulmonary edema: Inhaling toxic gases such as smoke or chlorine can cause inflammation and damage to the lungs.
   4. Acute interstitial pneumonitis: rapidly progressing inflammation and swelling of the lung tissue.
3. Obstructive pulmonary diseases:
   1. Chronic obstructive pulmonary disease (COPD): Can cause shortness of breath and hypoxia, which may be mistaken for pulmonary edema.
   2. Bronchial asthma: Severe asthma attacks can cause hypoxemia and shortness of breath.
4. Infectious diseases:
   1. Pneumonia: A lung infection can cause a buildup of pus-filled fluid and inflammation, the symptoms of which may resemble pulmonary edema.
   2. Tuberculosis: A progressive infection that can also cause symptoms similar to pulmonary edema.
5. Hemorrhage in the lungs:
   1. Pulmonary hemorrhage: may result from trauma or vasculitis.
6. Neurogenic pulmonary edema: May occur as a result of brain injury, seizures, or after resuscitation.

Various diagnostic methods are used to differentiate pulmonary edema from other diseases, including:

• Auscultation and percussion of the lungs: to detect wheezing, dry or wet.
• Chest X-ray: May show increased pulmonary markings, Kerley lines, or "butterfly" markings in the central lungs.
• Computed tomography (CT): for more accurate visualization of lung tissue.
• Echocardiography: to assess heart function.
• Pulmonary artery pressure measurement using a Swan-Ganz catheter: This method is often used in critical situations to assess pulmonary artery pressure and determine the presence of heart failure.
• Arterial blood gas (ABG) analysis: allows to assess the degree of hypoxemia and hypercapnia, which may be signs of respiratory failure.
• Pulse oximetry: A non-invasive way to monitor blood oxygen saturation.

The differential diagnosis also includes the patient's medical history, recent medical history, possible exposures (such as inhalation of toxic substances), known chronic diseases (such as heart or kidney failure), and other symptoms that may suggest a particular condition.

In addition to identifying the underlying cause of pulmonary edema, it is important to determine the degree of gas exchange and cardiorespiratory dysfunction, as this directly affects the choice of treatment methods and the urgency of medical intervention.

Treatment pulmonary edema

Emergency care for pulmonary edema requires a quick and effective medical response because the condition can be life-threatening. Here are the steps typically taken when pulmonary edema is suspected:

• Maintaining a clear airway: If the patient is conscious, he or she is assisted into a semi-sitting or sitting position, as this reduces venous return to the heart and facilitates breathing.
• Oxygen therapy: Immediate initiation of oxygen therapy to increase the concentration of oxygen in the blood and reduce the work of the respiratory muscles.
• Vital Signs Monitoring: Monitors heart rate, blood pressure and blood oxygen saturation levels.
• Intravenous access: Placement of an intravenous catheter to administer necessary medications.
• Drug therapy:
  • Diuretics: For example, intravenous furosemide to reduce circulating fluid volume and reduce pulmonary capillary pressure.
  • Nitrates: If the patient does not have low blood pressure, nitrates may be given to reduce atrial and postcardiac resistance.
  • Opioids: Morphine may be used to reduce shortness of breath and anxiety, although its use may be limited due to potential respiratory depression.
• Mechanical ventilation: In severe cases, placement on a ventilator may be necessary.
• Treating the underlying condition: It is important to identify and treat the underlying condition causing pulmonary edema (eg, heart failure, infection) as soon as possible.
• Ongoing monitoring: Monitoring the patient's response to treatment and adjusting therapy accordingly.
• Preparing for possible hospitalization: The patient may require urgent hospitalization in the intensive care unit for further treatment.
• Transportation: Safe and fast transportation of the patient to a medical facility.

In case of pulmonary edema, it is important to call an ambulance immediately. Until it arrives, everything possible should be done to maintain the patient's vital functions and reduce the level of discomfort.

Initial treatment includes inhalation of 100% oxygen through a one-way gas mask, elevated patient position, intravenous furosemide at a dose of 0.5-1.0 mg/kg body weight. Nitroglycerin 0.4 mg sublingually every 5 minutes is indicated, then intravenously by drip at 10-20 mcg/min with an increase in the dose of 10 mcg/min every 5 minutes, if necessary, to a maximum rate of 300 mcg/min or systolic blood pressure of 90 mm Hg. Morphine is administered intravenously at 1-5 mg 1 or 2 times. In case of severe hypoxia, noninvasive respiratory support with spontaneous breathing and continuous positive pressure is used, however, if there is CO2 retention or the patient is unconscious, endotracheal intubation and artificial ventilation are used.

Treatment for pulmonary edema involves the use of different groups of drugs, the purpose of which is to reduce the load on the heart, improve breathing, and eliminate the underlying cause of the condition. Here are some of the most commonly used drugs:

• Diuretics (water pills): These help reduce the volume of circulating fluid and the pressure in the pulmonary capillaries. Examples include furosemide (Lasix) and bumetanide.
• Nitrates: Drugs such as nitroglycerin help dilate blood vessels, which reduces the return of blood to the heart and improves its pumping function.
• Antihypertensive medications: If pulmonary edema is caused by high blood pressure, medications such as ACE inhibitors, calcium channel blockers, or beta blockers may be used.
• Opiates: In particular, morphine is used to reduce dyspnea and anxiety, although its use in modern clinical practice is limited due to the potential risk of respiratory depression.
• Vasodilators: Medicines that widen blood vessels help lower pressure in the arteries and improve blood flow.
• Oxygen therapy: Pure oxygen is given through a mask or nasal cannula to improve oxygenation of the blood.
• Cardiotonics: In some cases, drugs to stimulate the heart, such as digoxin, may be used.
• Drugs to support cardiac function: In case of heart failure, drugs that improve myocardial contractility may be prescribed, for example, inotropic agents (dopamine, dobutamine).
• Antiarrhythmic drugs: If pulmonary edema is associated with an arrhythmia, drugs to correct it may be needed.
• Antibiotics: If pulmonary edema is caused by an infection, appropriate antibiotics are selected.
• Glucocorticoids: In some cases, such as high-altitude pulmonary edema or pulmonary edema caused by inflammation, corticosteroids may be used.

The choice of specific drugs and their dosage should be made by a doctor based on the clinical picture and the patient's condition. This is an area where self-medication can be dangerous and is contraindicated.

Specific additional therapy depends on the etiology:

• thrombolysis or direct percutaneous coronary angioplasty with or without stenting in myocardial infarction or other type of acute coronary syndrome;
• vasodilators for severe arterial hypertension;
• cardioversion for supraventricular or ventricular tachycardia and intravenous administration of beta-blockers;
• intravenous digoxin or cautious use of intravenous calcium channel blockers to slow the ventricular rate in cases of frequent atrial fibrillation (cardioversion is preferred).

Other treatment options, such as intravenous MUNG (nesiritide) and new inotropic agents, are under investigation. If blood pressure drops sharply or shock develops, intravenous dobutamine and intra-aortic balloon pump are used.

After stabilization of the condition, further treatment of heart failure is carried out as described above.

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Prevention

Prevention of pulmonary edema involves monitoring and treating medical conditions that can lead to the condition, such as hypertension, heart failure, and kidney disease. Maintaining a healthy lifestyle, not smoking, and having regular checkups with a cardiologist are recommended.

Forecast

The prognosis for pulmonary edema depends on many factors, including the underlying cause of the condition, how quickly it is diagnosed and treated, and the patient's overall health and the presence of comorbidities. Here are the key aspects that affect the prognosis:

• Cause of pulmonary edema: If the edema is caused by acute heart failure and is treated promptly, the prognosis may be relatively good. Edema caused by more complex conditions, such as sepsis or acute respiratory distress syndrome (ARDS), has a worse prognosis.
• Speed of response to treatment: Prompt medical attention improves the prognosis. Delay may lead to worsening hypoxia and organ damage.
• Volume of lung involvement: The larger the area of the lung affected by edema, the worse the prognosis.
• Comorbidities: Patients with chronic medical conditions such as coronary artery disease, diabetes, or chronic lung disease may have a poorer prognosis.
• Patient age: Older adults generally have a worse prognosis due to decreased physiological reserve capacity and the presence of other chronic conditions.
• Quality and accessibility of medical care: Availability of modern medical services and technologies for intensive care significantly improves outcomes.

Given these factors, in some cases patients make a full recovery with no long-term consequences after successful treatment. In other cases, especially when pulmonary edema is part of a larger medical crisis, the condition can lead to severe organ damage or even death.

Patients who have experienced pulmonary edema should adopt a healthier lifestyle, undergo regular check-ups, and follow medical advice to minimize the risk of the condition recurring.

References

Vitaly Popov, Victor Topolyansky. Pulmonary edema, 1975

Vasiliev D. V. Pulmonary edema: Study guide, 2011

S. Chapman, G. Robinson, R. Srimanker. Pulmonology: Oxford reference book, GEOTAR-Media, 2024.

Chuchalin Alexander Grigorievich. Respiratory Medicine. Manual in 3 volumes. Volume 1, 2017