What Are the Causes of Atelectasis?

Atelectasis refers to a decrease in the volume or air content of one or more lung segments or lobe. Due to gas absorption in the alveoli, atelectasis is usually accompanied by reduced light transmission in the affected area. Adjacent structures (bronchus, pulmonary blood vessels, interstitial lungs) gather toward the atelectasis, sometimes the alveolar cavity is consolidated, and other lung tissues are compensated Emphysema. Atelectasis can be classified as congenital or acquired. Congenital atelectasis refers to the absence of gas filling in the alveoli of a baby at birth, clinically severe dyspnea and cyanosis, and most children die of severe hypoxia after birth.

Basic Information

English name

pulmonaryatelectasis

Visiting department

Respiratory Medicine

Common causes

Endobronchial obstruction

Common symptoms

Chest tightness, shortness of breath, dyspnea, dry cough, etc.

Causes of atelectasis

The main cause of acute or chronic atelectasis in adults is bronchial lumen obstruction. Common causes are mucus plugs, tumors, granulomas, or foreign bodies formed by viscous bronchial secretions. Atelectasis can also be caused by bronchoconstriction or distortion, or exogenous compression of the bronchus by swollen lymph nodes, tumors or hemangiomas, or exogenous compression of lung tissue by fluids and gases such as pleural effusion and pneumothorax.

Clinical manifestations of atelectasis

The clinical manifestations of atelectasis vary depending on the etiology, the extent and extent of atelectasis, the time of occurrence, and the severity of the complications. The more severe side of the large lobe atelectasis may be chest tightness, shortness of breath, dyspnea, dry cough and so on. When combined with infection, it can cause chest pain on the ipsilateral side, sudden dyspnea and cyanosis, cough, wheezing, hemoptysis, purulent sputum, chills and fever, tachycardia, increased body temperature, decreased blood pressure, and sometimes shock. Slowly occurring atelectasis or small areas of atelectasis can be asymptomatic or mild, such as right middle lobe atelectasis. Physical examination of the chest showed that the thoracic activity of the lesion was weakened or disappeared, the trachea and heart moved to the affected side, and the percussion was dull to solid, and the breath sounds weakened or disappeared. Diffuse tiny atelectasis can cause dyspnea, shallow breathing, hypoxemia, and reduced lung compliance, and is often an early manifestation of respiratory distress syndrome in adults and newborns. Auscultation of the chest can be normal or smell the twisting sounds, dry sounds, wheezing sounds. When the scope of atelectasis is large, there may be cyanosis, dullness of percussion in the diseased area, and decreased respiratory sounds. During inhalation, dry or wet rustling sounds can be heard.

Atelectasis

Imaging examination

(1) X-ray examination There are two types of X-ray manifestations of atelectasis: direct X-ray signs and indirect X-ray signs. Direct X-ray signs of atelectasis The atelectic lung tissue has reduced transparency and increased uniformity density, and may have uneven density during recovery or with bronchiectasis (cystic translucent area). Volume reductions to varying degrees, atelectasis of subsegments and below may not be significantly reduced due to ventilation of other collaterals. Leaf segmental atelectasis is generally a blunt triangle, with a wide, pure surface facing the costal pleura, and the tip pointing toward the hilum, with fan-shaped, triangular, band-shaped, and round shapes. The indirect X-ray signs of atelectasis shift the interlobular fissure to the atelectic side of the lung, such as right pleural translobar pleural shift, bilateral oblique fissure pleural shift, etc .; due to lung volume shrinkage, lesions The bronchial and vascular texture of the area are gathered, and the compensatory swelling of the adjacent lungs means that the vascular texture is thinned and bowed to the atelectic lung lobe; Separated from the dense shadow of atelectasis; mediastinal, heart, trachea shift to the affected side, especially when the whole atelectasis is obvious, sometimes the healthy side pulmonary hernia moves to the affected side, and the mediastinal hernia appears; the diaphragmatic muscle is elevated, The thorax narrowed and the intercostal space narrowed.

(2) CT examination has greater diagnostic value, especially for clarifying the location or nature of obstructive lesions in the bronchial cavity, exploring enlarged mediastinal lymph nodes, and identifying mediastinal masses and atelectasis around the mediastinum.

(3) Bronchography is mainly used to understand whether there is bronchiectasis in non-obstructive atelectasis, but it has been basically replaced by CT. If atelectasis is suspected to be caused by a pulmonary thrombus, pulmonary ventilation-perfusion imaging or pulmonary angiography may be considered.

(4) Others In patients with atelectasis caused by fibrotic mediastinitis, superior vena cava angiography has certain value. When cardiovascular disease causes compressive atelectasis, multiple imaging methods can be selected.

2. Laboratory inspection

Routine blood tests have limited diagnostic value for atelectasis. Asthma and Aspergillus pneumoniae with mucus impaction increase blood eosinophils and occasionally can be seen in Hodgkin disease, non-Hodgkin lymphoma, bronchial lung cancer, and sarcoidosis. In the secondary obstruction, secondary neutrophils increased and erythrocyte sedimentation increased. Chronic infections and lymphomas often have anemia. Sarcoidosis, amyloidosis, chronic infections, and lymphoma show elevated gamma globulin.

Serological tests for anti-Aspergillus antibodies have higher sensitivity and specificity for the diagnosis of pulmonary allergic Aspergillus infection. Specific complement binding test can be positive when bronchial stenosis caused by histoplasmosis and coccidioidosis. Detection of serotonin in blood and urine has diagnostic value for carcinoid syndrome caused by bronchial lung cancer.

3. Sputum and bronchial aspiration

Because the secretions produced by the cough are mainly from the lungs without atelectasis, which cannot reflect the pathological process that causes bronchial obstruction, the sputum examination has little significance for the diagnosis of atelectasis. Bacterial, fungal, and Mycobacterium tuberculosis smear examinations and cultures should be performed, as well as routine cytological examinations. Allergic Aspergillus infection can sometimes cultivate Aspergillus, but it should be noted that the laboratory is often contaminated with Aspergillus. If a sputum plug is coughed and a large amount of mycelium is found under the microscope, the diagnosis can be established.

Bronchial lung cancer has a positive cytology test, while most adenocarcinomas and benign tumors have a negative cytology test. Tumor cells are occasionally found in the sputum of lymphoma patients.

4. Skin test

Skin tests have little significance in the diagnosis of atelectasis. A tuberculin, coccidiomycin, or histoplasmin skin test for atelectasis caused by bronchial tuberculosis can be positive and provide clues for diagnosis. If the atelectasis is caused by hilar lymphadenopathy, the tuberculin skin test has recently turned positive, especially in children or adolescents, and has certain diagnostic value. The skin test for an allergic Aspergillus infection is typically an immediate skin reaction, and some patients show a biphasic reaction.

5. Bronchoscopy

Bronchoscopy is one of the most valuable diagnostic methods for atelectasis and can be used in most cases. In most cases, obstructive lesions can be seen directly under the microscope and biopsied.

For obstructive atelectasis caused by a mucus plug, fiberoptic bronchoscopy (fibrobronchoscope) aspiration is both diagnostic and therapeutic. Bronchoscopic biopsy and brushing are also diagnostic for benign and malignant tumors, sarcoidosis, and specific inflammation that cause obstruction.

6. Lymph node biopsy and extrathoracic biopsy

If the atelectasis is caused by bronchial lung cancer or lymphoma, subdiagonal and mediastinal lymph node biopsy is helpful, and bronchoscopy is often negative.

7. Pleural effusion and pleural biopsy

There are several reasons for the formation of pleural effusion during atelectasis. Pleural effusion may mask radiological signs of atelectasis. Pleural effusion and pleural biopsy have diagnostic value for malignant lesions and some inflammatory lesions. Hemothorax is seen in chest trauma or aneurysm rupture, and bloody pleural effusions suggest tumors, pulmonary embolism, tuberculosis, or trauma.

Atelectasis diagnosis

The diagnosis of atelectasis is mainly based on chest imaging and etiology, and the diagnosis needs to be combined with medical history.

Atelectasis

The cause of acute atelectasis (including acute large-scale atelectasis after surgery) should be eliminated. If mechanical obstruction is suspected, coughing, suction, or 24-hour active breathing and physical therapy can alleviate the condition. If a bronchial obstruction is identified, it should be managed for obstructions and commonly associated infections. Bronchoscopy can be used to remove mucus plugs or thick secretions, so that atelectic lungs can be re-inflated. Chest physiotherapy and other measures need to be continued. If foreign body inhalation is suspected, bronchoscopy should be performed immediately.

Patients diagnosed with atelectasis should take the position with the affected side at the highest position to facilitate drainage; appropriate physical therapy; and encourage coughing, patient turning over and deep breathing. Frequently (every 1 to 2 hours) guide the use of intermittent positive pressure breathing (IPPB) or spirometry to ensure deep breathing. Antibiotics were given according to drug sensitivity tests.

Repeated severe respiratory infections or repeated hemoptysis should consider surgical resection of atelectic lobes or segments. Lung atelectasis caused by tumor should be based on the cell type and the extent of the lesion, the patient's general condition, and lung function. Comprehensive consideration should be given to surgery, radiation therapy or chemotherapy to relieve obstruction.

Atelectasis prevention

Acute massive atelectasis is preventable. Because of the original chronic bronchitis, a large amount of smoking increases the risk of atelectasis after surgery. Therefore, smoking should be encouraged to stop before surgery, and measures to enhance bronchial clearance should be taken. Avoid using long-acting anesthetics, and less analgesics after surgery, because they suppress cough reflexes.