What Are the Causes of Pulmonary Edema?

Pulmonary edema refers to the imbalance in the generation and return of tissue fluid in the lung due to some reason, which prevents a large amount of tissue fluid from being absorbed by the pulmonary lymphatic and pulmonary venous systems within a short period of time. And small bronchial tubes, which cause severe obstacles to pulmonary ventilation and ventilation. The clinical manifestations are extreme dyspnea, sitting breaths, cyanosis, sweating, paroxysmal cough with a large amount of white or pink foamy sputum, and symmetrical wet rales in both lungs.

Basic Information

English name: pulmonary edema
Visiting department: Respiratory Medicine, Cardiology

Common causes: Cardiogenic and non-cardiogenic
Common symptoms: Difficulty breathing, sitting still, cyanosis, sweating, coughing
Contagious: no

Causes of pulmonary edema

The etiology of pulmonary edema can be divided into two categories, cardiogenic and noncardiogenic according to the anatomical location. The latter can be divided into several types according to different pathogenesis.

Cardiogenic pulmonary edema

In some pathological conditions, such as a sharp increase in return blood volume and right ventricular output or a sudden and severe decrease in left ventricular output, a large amount of blood accumulates in the pulmonary circulation, causing the pulmonary capillary venous pressure to rise sharply. When it exceeds the colloid osmotic pressure in the pulmonary capillaries, hemodynamic changes in the capillaries on the one hand, and pulmonary circulation congestion on the other hand, the permeability of the pulmonary capillary walls increases, and the liquid is filtered through the capillary walls to form the lung Edema. Acute pulmonary edema caused by hypertension heart disease, coronary heart disease and rheumatic heart valve disease clinically accounts for the majority of cardiogenic pulmonary edema. Myocarditis, cardiomyopathy, congenital heart disease, and severe tachyarrhythmia can also be caused.

2. Noncardiogenic pulmonary edema

(1) Increased pulmonary capillary permeability Infectious pulmonary edema: It is caused by infections of bacteria, viruses, fungi, mycoplasma, and protozoa in the whole body and / or lungs. Inhaling harmful gases: such as phosgene (COCl ₂ ), chlorine, ozone, carbon monoxide, nitrogen oxides, etc. blood circulation toxins and vasoactive substances: such as tetraoxopyrimidine, snake venom, organophosphorus, histamine, serotonin, etc. diffuse capillary leakage syndrome: such as endotoxemia, the application of a large number of biological agents. Severe burns and disseminated intravascular coagulation. Allergic reactions, plus drug-specific reactions, allergic alveolitis and so on. Radiation pneumonitis: Large-dose radiation therapy for malignant tumors of the chest can cause pulmonary edema. Uremic: Uremic pneumonia is a manifestation of pulmonary edema. Drowning: Drowning in freshwater and seawater can cause pulmonary edema. Acute respiratory distress syndrome: the most severe acute pulmonary interstitial edema caused by various reasons. Oxygen poisoning: Long-term inhalation of high-concentration oxygen (> 60%) can cause increase of reactive oxygen free radicals, causing lung injury and pulmonary edema. heat radiation sickness.

(2) Increased pulmonary capillary pressure Pulmonary vein occlusive disease or pulmonary vein stenosis. Excessive infusion.

(3) Decreased plasma colloid osmotic pressure Hepatic and renal diseases cause hypoproteinemia. protein-losing bowel disease. malnutrition hypoproteinemia.

(4) Lymphatic disorders

(5) Tissue interval negative pressure increases Pulmonary edema after retensioning: such as pneumothorax, pleural effusion, or lung collapse after thoracic surgery, rapid exhaustion, rapid lung re-expansion after pumping, tissue interval negative pressure increases, acute Pulmonary Edema. Pulmonary edema after upper airway obstruction: Upper airway obstruction caused by various reasons, tracheal intubation and tracheotomy, etc., acute pulmonary edema that occurs quickly after the obstruction is lifted.

(6) Other complex factors High altitude pulmonary edema: Pulmonary edema caused by high altitude and hypoxic environment is called high altitude pulmonary edema. Drug-induced pulmonary edema: such as aspirin, heroin, lidocaine, furantan, rimienine, terbutaline, methadone, etc. In addition to some drugs related to allergic factors, some drugs mainly cause direct damage to the lung tissue or a direct effect on the central nervous system and acute pulmonary edema occurs. Neurogenic pulmonary edema: Acute pulmonary edema caused by increased intracranial pressure caused by craniocerebral trauma, surgery, subarachnoid hemorrhage, cerebral embolism, and intracranial tumors.

Clinical manifestations of pulmonary edema

In the interstitial phase of pulmonary edema, patients often have cough, chest tightness, mild shallow breathing, and rapidness. On examination, wheezing sounds can be heard in both lungs, and signs of heart disease can be found in cardiogenic pulmonary edema. Both PaO ₂ and PaCO ₂ decreased slightly. After the pulmonary edema fluid has penetrated into the alveoli, the patient may present with pale complexion, cyanosis, severe dyspnea, coughing of large amounts of white or bloody foamy sputum, and two lungs covered with wet snoring. Blood gas analysis showed that hypoxemia worsened, and even CO ₂ retention and mixed acidosis appeared.

Pulmonary edema examination

Laboratory inspection

Including blood, urine routine, liver and kidney function, cardiac enzyme spectrum and electrolyte examination, provide a basis for the diagnosis of infection, hypoproteinemia, kidney disease, heart disease.

2. Arterial blood gas analysis

Partial oxygen pressure is mainly manifested by hypoxia in the early stage of the disease. The partial pressure of carbon dioxide is mainly manifested as low CO ₂ in the early stage of the disease, and high CO _{2 in the} later stage, with respiratory acidosis and metabolic acidosis.

3.X-ray inspection

Alveolar edema is mainly manifested as dense alveolar shadows, which are irregularly blended with fuzzy shadows. The diffuse distribution is confined to one side or one leaf, or it spreads outward from the sides of the hilum and gradually fades into a typical butterfly shadow. Sometimes accompanied by a small amount of pleural effusion. However, the above symptoms can only occur if the lung content is increased by more than 30%.

4.Swan-Ganz catheter inspection

Examination of pulmonary capillary wedge pressure (PCWP) by venous Swan-Ganz catheter at the bed can determine pulmonary edema with increased pulmonary capillary pressure, but the height of PCWP does not necessarily match the degree of pulmonary edema.

5. Other inspections

In the past, many extravascular water (EVLW) measurement methods, such as X-rays, thermal indicator dilution technology, soluble gas inhalation, transpulmonary electrical impedance, CT, magnetic resonance imaging, etc., were used to determine early the microvascular-alveolar barrier injury of pulmonary edema and Not sensitive. In recent years, the permeability of pulmonary vascular endothelium was evaluated by measuring the net flow of isotope-labeled proteins (usually ^99m Tc) through the pulmonary capillary endothelium in vitro; the clearance of small molecules of isotopes (radiolabeled proteins, ^99m Tc-DTPA) by measuring alveoli To evaluate the permeability of the alveolar epithelium, the degree of lung injury can be judged earlier.

Diagnosis of pulmonary edema

According to medical history, clinical symptoms, signs and X-ray findings, general clinical diagnosis is not difficult. However, there is still no satisfactory and reliable method for early quantitative diagnosis of pulmonary edema. Clinical symptoms and signs are used as the basis for diagnosis, and the sensitivity is low. When the extravascular fluid of the lung increases by 60%, abnormal signs appear clinically. X-ray examination also showed abnormal shadows only when the lung water volume increased by more than 30%. CT and MRI are helpful for quantitative diagnosis and distinguishing pulmonary congestion and pulmonary edema. Plasma colloid osmotic pressure-pulmonary capillary wedge pressure gradient measurement, radionuclide scanning, indicator dilution method for pulmonary extravascular fluid measurement, chest electrical impedance measurement, etc., are helpful for early diagnosis, but have not yet been applied to the clinic. Blood gas analysis can help understand the severity of imbalances in arterial oxygen pressure, carbon dioxide pressure, and acid-base balance, and can be used as a dynamic follow-up indicator.

Pulmonary Edema Treatment

It was discovered in time that adopting active and effective treatment measures to quickly reduce pulmonary venous pressure and maintain sufficient blood gas exchange are the keys to successful rescue. Treatment measures should be accompanied by symptomatic treatment while actively treating the etiology and inducing factors.