Atelectasis

Introduction to atelectasis Atelectasis refers to a decrease in the volume or volume of one or more lung segments or lobes. Due to gas absorption in the alveoli, atelectasis is usually associated with reduced transmittance in the affected area, adjacent structures (bronchial, pulmonary vasculature). , pulmonary interstitial) accumulate in the infertile area, sometimes visible alveolar cavity consolidation, compensatory emphysema in other lung tissue. The collateral gas communication between the lobules of the lungs and the segments (even the lobes of the lungs) allows the fully obstructed area to still have a certain degree of light transmission. Atelectasis can be divided into congenital or acquired acquired two. Congenital atelectasis refers to the absence of gas filling in the alveoli at birth, clinically severe breathing difficulties and cyanosis, and children mostly die after birth. The lack of oxygen, the majority of clinical atelectasis is acquired, the focus of this chapter. basic knowledge The proportion of the disease: the incidence rate of the middle-aged and elderly people over 50 years old is about 1.5% - 2.5% Susceptible people: no special people Mode of infection: non-infectious complication:

Cause of atelectasis

Cause:

There are many causes of atelectasis, which can be roughly divided into congenital and acquired. 1. A fetus with a congenital atelectasis may have some of the alveoli not inflated at birth, but gradually inflates and expands in the next few days. Congenital atelectasis can occur if the fetus has more alveoli in the lungs after birth and cannot be inflated normally. 2. Acquired atelectasis indicates that the inflated lung has become partially or completely deflated, and may be caused by bronchial obstruction (including internal or external factors) or external pressure of the lungs. The most common causes of endobronchial obstruction are inhalation of foreign bodies, thick mucus, inflammatory exudate, bronchial tumor, bronchial granulomatous tissue or inflammatory bronchoconstriction. External bronchial obstruction can be caused by swollen lymph nodes (including tuberculosis, tumors, and sarcoidosis), peribronchial tumors, aortic aneurysms, enlarged heart (such as enlargement of the left atrium), and pericardial effusion. Lung atrophy caused by external pressure in the lungs, may be due to a large amount of chest fluid or pneumothorax, intrathoracic tumor. Caused by thoracic subsidence (congenital, traumatic or postoperative) and assault.

pathology:

After bronchial obstruction, the gas in the surrounding alveoli is absorbed through the alveolar capillary blood circulation, forming an airless state and contraction of the lung tissue within a few hours. In the absence of infection, the lungs can completely contract and collapse. In the early stages, blood perfusion passes through the airless lung tissue, resulting in arterial hypoxemia. Capillary and tissue hypoxia leads to fluid leakage and pulmonary edema; the alveolar cavity is filled with secretions and cells, so that the atelectasis cannot completely collapse. Although the unexpanded peripheral lung tissue expansion can partially compensate for the reduction of lung volume, in the case of large areas of atelectasis, there is also a squat elevation, a flat chest wall, and the heart and mediastinum move toward the affected side.

A variety of stimuli can affect the respiratory center and the cerebral cortex to create an air rush. When a large area of atelectasis causes a significant decrease in PaO2, this stimulation comes from chemoreceptors; when the gas in the lungs decreases, the lung compliance decreases (stiffness), and when the work of breathing increases, the stimulus comes from the lungs and respiratory muscle receptors. PaO2 may be improved during the first 24 hours or after the onset of atelectasis, possibly due to reduced blood flow in the atelectasis. PaCO2 tends to be normal or decreased due to increased ventilation of the remaining normal lung parenchyma.

If the bronchial obstruction is relieved, the gas re-enters the lesion and the concomitant infection dissipates and the lung tissue eventually returns to normal. Recovery time depends on the degree of infection. If the blockage persists and there is an infection, local airlessness and no blood flow can lead to fibrosis and bronchiectasis.

Even if there is no airway obstruction, alveolar surface tension changes, alveolar volume shrinks, and airway-thoracic pressure changes can cause local hypoventilation and small-scale flaky atelectasis or diffuse micro atelectasis, resulting in Light to severe gas exchange barriers. Accelerated atelectasis occurs in military pilots because when the high-acceleration pressure keeps the sagging airway closed, the gas remaining in the alveoli is absorbed and the atelectasis occurs .

Atelectasis prevention

1, acute extensive arrhythmia can be prevented. Because of the original chronic bronchitis, a large number of cigarettes increase the risk of postoperative atelectasis, so it is encouraged to stop smoking before surgery and take measures to enhance bronchial clearance.

2, avoid the use of long-acting anesthetics, postoperative analgesics should also be used, because these drugs inhibit cough reflex. At the end of anesthesia, the lungs should be filled with a mixture of air and oxygen, as slow absorption of nitrogen improves the stability of the alveoli. Encourage patients to roll over once a second and encourage coughing and deep breathing; early activities are important.

Atelectasis Complication

If the atelectasis persists for a long time, it is easy to have secondary infection on the basis of atelectasis, causing bronchial damage and inflammatory secretion retention. Bronchiectasis and lung abscess may occur over time.

Atelectasis symptoms common symptoms mediastinal widening of asthma, pulmonary embolism, cough, dryness, cough, dyspnea, breath sounds, weakened rat tail sign, lung infection, interlobular shift

The signs and symptoms of atelectasis depend on the rate at which bronchial obstruction occurs, the extent of involvement, and whether or not the infection is combined.

Symptom

Blockage formed in a short period of time with large area of lung collapse, especially in the case of co-infection, the affected side may have obvious pain, sudden breathing difficulties, cyanosis, and even blood pressure drop, tachycardia, fever, and even shock, Slowly formed atelectasis can be asymptomatic or only mild, and mid-leaf syndrome is mostly asymptomatic, but often has a severe irritating dry cough.

Some clinical conditions may indicate the possibility of bronchial obstruction and atelectasis. If some children with asthma continue to have wheezing, they may have atelectasis. If there is fever, it will prompt diagnosis, allergic aspergillosis with mucus The plug is mainly seen in asthma patients. Fever and tachycardia (pneumonia after surgery) at 48 hours after surgery are often caused by atelectasis.

After heart surgery, the left lower lobe is at best, and patients with chest wall disease cannot have effective cough. It is a risk factor for atelectasis. In patients with respiratory symptoms, the possibility of atelectasis should be considered. Atelectasis can occur in multiple rib fractures, especially in the presence of chronic bronchitis.

Children should think of the possibility of inhalation of foreign body when they have respiratory symptoms. Especially in the medical history, they have to talk about cough, suffocation or cough. Patients often cannot provide such information on their own initiative. They need to be excluded through purposeful inquiry, and should be noted in foreign bodies. After inhalation, there is an asymptomatic period of varying lengths. Adults often provide a clear history of foreign body inhalation, with the exception of those who are slow or unconscious.

The atelectasis secondary to bronchial lung cancer is mainly seen in middle-aged or elderly men with a history of smoking. There is often a history of chronic cough. This type of condition is often accompanied by infection. Patients often have fever, chills, chest pain and cough and sputum. Hemoptysis is more characteristic. When the tumor is transferred to the thoracic cavity, obvious symptoms may occur. The female bronchial adenoma is more than the male. The age of onset is smaller than that of bronchial lung cancer. The respiratory symptoms are not specific, but there are many hemoptysis. Occasionally, the patient can show Carcinoid syndrome suggests a broad metastasis of the tumor.

If there is tuberculosis, pulmonary fungal infection, foreign body inhalation or chronic asthma in the medical history, attention should be paid to the presence or absence of bronchoconstriction. Previous history of chest trauma should be noted to exclude the presence of undiscovered bronchial laceration and bronchoconstriction, secondary to bronchial stones. About 50% of patients with a history of coughing out calcified substances, patients often do not pay attention, need a doctor's prompt, some patients think that doctors do not believe that they will cough up "stone", so intentionally miss this history, bronchial stones Other common symptoms include chronic cough, wheezing, repeated hemoptysis, and repeated lung infections. In addition, patients in the intensive care unit are also prone to atelectasis.

2. Signs

Typical signs of obstructive atelectasis are evidence of decreased lung capacity (decreased tactile tremor, diaphragmatic uplift, mediastinal shift), turbidity, tremors and respiratory sounds weakened or disappeared, if a small amount of gas enters the collapse Area, audible and wet, can have obvious cyanosis and difficulty breathing. After surgery, the patient is characterized by repeated coughing and weakness of cough, if the affected area is small, or the surrounding lung tissue is adequate Effectively compensated excessive expansion, at this time the signs of atelectasis may be atypical or absent, non-obstructive atelectasis, the main bronchus is still unobstructed, so the voice tremor is often enhanced, the breath sounds exist, the upper lobe is atelect Because of its proximity to the trachea, it can be heard in the lungs and bronchial breath sounds. The signs of inferior atelectasis are similar to those of pleural effusion and unilateral diaphragmatic elevation.

Signs related to underlying diseases found during physical examination may provide diagnostic clues, mucus plugs, mucus caulking or atelectasis caused by bronchoconstriction secondary to asthma, auscultation audible and characteristic expiratory wheezing, bronchi Lung cancer may have clubbing or other signs of metastasis. Lymphoma-induced atelectasis can be found in different parts of the lymph nodes, atelectasis with jugular vein dilatation or engorgement and liver growth often suggest fibrotic mediastinal inflammation. Compressive atelectasis caused by cardiovascular disease can detect heart murmur, galloping, cyanosis or signs of heart failure. It is easy to find one or more rib fractures when palpation in chest trauma, and even chest when inhaling. Elevation of atelectasis due to weakness of the chest wall often has evidence of underlying neuromuscular disease.

Insufficient examination

1. Radiological examination Radiological examination is the most important means of diagnosing atelectasis. Conventional chest radiographs usually identify the presence of leaf or atelectasis and its location. The radiological manifestations of atelectasis vary greatly, often Atypical, in the anterior or posterior position of the lack of projection conditions, due to the cover of the heart, the left lower lobe is often easily missed, the upper lobe can be mistaken for the mediastinum widening, the parenchy effusion is also with atelectasis Similar, and a large number of pleural effusion can cover the inferior lobe, bronchial air sign can rule out complete bronchial obstruction, but can not remove the lung lobe collapse.

Calcified lymph nodes are found in the inferior segment of the lung or at the top of the lobes, which is important for the diagnosis of bronchial stones. Mediastinal calcification can be found in fibrotic mediastinal inflammation and various inflammatory lymph nodes.

Allergic aspergillosis, mucoid viscid, lymphoma, X-rayed foreign body and bronchial laceration have corresponding radiological abnormal signs. When foreign body obstructs the main bronchus, conventional chest radiographs can be found that one side of the lung becomes smaller. The transmittance is reduced, the lung volume on the other side is increased, and the transmittance is increased. This phenomenon may indicate

1 One side of the lung is over-expanded due to obstruction of the valve, and the contralateral lung is compressed to make it absent;

2 Absorptive insufficiency after obstruction of one side of the lung, compensatory hyperexpansion of the contralateral lung, fluoroscopy and comparison of inhalation and end-tidal chest X-ray can identify the above two situations, because only the bronchial smooth lung is sucking There is a significant change in the volume between gas and exhalation.

CT scan of the chest is helpful for the following situations: description of the location and shape of the collapsed lobe, presence or absence of bronchial air, presence or absence of calcification and its location, obstruction of the lesion, and presence or absence of obstruction in the lumen Block, CT examination is more valuable for the diagnosis of such problems, especially for the following cases is better than tomography, including: to determine the location or even the nature of obstructive lesions in the bronchial lumen, to explore the enlarged mediastinal lymph nodes, to identify the mediastinum The mass and the lungs around the mediastinum are atelect.

Bronchography is mainly used to understand whether there is bronchiectasis in non-obstructive atelectasis, but it has been basically replaced by CT.

Pulmonary ventilation-perfusion imaging If the suspected atelectasis is caused by pulmonary thrombosis, pulmonary ventilation-perfusion imaging or pulmonary angiography may be considered, and the specificity of angiography is relatively high.

Radionuclide angiocardiography has a certain value in patients with atelectasis caused by fibrotic mediastinal inflammation. The vena cava angiography has certain value. When cardiovascular disease causes oppressive atelectasis, a variety of imaging methods can be selected.

2. sputum and bronchial aspirate examination sputum bacterial smear examination sputum bacterial culture because the cough secretion mainly comes from the lungs that do not occur atelectasis, can not reflect the pathological process that causes bronchial obstruction, so sputum examination for the lungs The diagnostic value of Zhang is very small. It should be used for smear examination and culture of bacteria, fungi and Mycobacterium tuberculosis, and routine cytological examination. Allergic Aspergillus infection can sometimes produce Aspergillus, but it is necessary to pay attention to the laboratory. Mold contamination, if you cough up the sputum and find a large number of hyphae under the microscope, you can establish a diagnosis.

Cytological examination of bronchial lung cancer can have a positive finding, while most adenocarcinoma and benign tumors are negative for cytology, and tumor cells are occasionally found in lymphoma patients.

3. Skin test The delayed skin allergic skin test has little significance for the diagnosis of atelectasis. The tuberculin, coccidiostat or histoplasmin skin test can be positive when the bronchial stones are caused by atelectasis. Provide clues for diagnosis, such as pulmonary atelectasis caused by hilar lymphadenopathy, tuberculin skin test turned positive in the near future, especially in children or adolescents, has a certain diagnostic value, skin when allergic Aspergillus infection The test is typically an immediate skin reaction and some patients exhibit a biphasic response.

4. Bronchoscopy bronchoscopy is one of the most valuable diagnostic methods for atelectasis. It can be used in most cases. In most cases, obstructive lesions can be directly seen under the microscope and biopsy can be performed if a rigid bronchoscope is used. , can expand the stenosis and remove exogenous foreign bodies or endogenous stones, such as foreign bodies or bronchial stones surrounded by granulation tissue, it is not easy to confirm the diagnosis under the microscope.

The surface of bronchial adenocarcinoma is usually covered with a normal epithelial tissue. If the tumor is pedunculated, it is easy to be mistaken for the pressure lesion in the cavity, but most of the adenocarcinoma has pedicles, which helps to determine the origin of the bronchi, bronchial carcinoid blood vessels. Rich, easy to hemorrhage during biopsy, should be left to be removed during thoracotomy, and should not be blind biopsy, sometimes the surface of bronchial lung cancer can also be covered with a layer of granulation tissue, microscopic biopsy can only get inflammatory tissue, at this time if the obstructed bronchus There are still small gaps, and the oncological evidence can be obtained by deep brush examination. For the extra-bronchial compression lesions, the bronchial mucosa biopsy can occasionally find histological abnormalities related to the underlying lesions, but the pulsatile mass outside the tube should not be avoided. Biopsy.

For obstructive atelectasis caused by mucus plugs, bronchoscopy is both diagnostic and therapeutic. Fibrobronchoscopy biopsy and brushing for benign and malignant tumors, sarcoidosis and specific inflammation There is also diagnostic value.

5. Lymph node biopsy and extrathoracic biopsy Histopathology If atelectasis is caused by bronchial lung cancer or lymphoma, the biopsy of the oblique and mediastinal lymph nodes is helpful for diagnosis, while the bronchoscopy biopsy is often negative, if there is a clear When the hilar or mediastinum grows, lymph node biopsy often has a positive finding. If the radiological changes only the distal lung tissue collapses, it is difficult to obtain a positive result. When the sarcoidosis, tuberculosis, fungal infection causes atelectasis, the scalene muscle There are occasional positive findings in the lower and mediastinal lymph node biopsy. Extrathoracic biopsy (liver, bone, bone marrow, peripheral lymph nodes) can sometimes provide diagnostic assistance for certain diseases such as sarcoidosis, infectious granuloma, lymphoma and metastatic bronchogenic lung cancer.

6. Pleural effusion examination and pleural biopsy There are many reasons for the formation of pleural effusion during atelectasis. Pleural effusion may mask the radiological signs of atelectasis, pleural effusion examination and pleural biopsy for malignant lesions and some inflammatory diseases. The lesion has diagnostic value, the blood chest is seen in the chest trauma or the aneurysm rupture, and the blood pleural effusion indicates the tumor, pulmonary embolism, tuberculosis or trauma.

7. Exploratory thoracotomy A considerable number of patients with atelectasis need to undergo thoracotomy for diagnostic or therapeutic purposes. 35% of bronchial stones require open chest to be diagnosed, including bronchial lung cancer, adenocarcinoma, bronchoconstriction, and chronic inflammation. Some cases of pulmonary atelectasis caused by lung shrinkage, localized bronchitis and exogenous compression can be diagnosed by thoracotomy.

Diagnosis of atelectasis

Diagnosis can be made based on clinical manifestations and examinations.

Differential diagnosis:

A considerable number of patients with atelectasis need to undergo thoracotomy for diagnostic or therapeutic purposes. 35% of bronchial stones require open chest to be diagnosed, including bronchial lung cancer, adenocarcinoma, bronchoconstriction, chronic inflammation with lung shrinkage, and limitations. Some cases of bronchitis and extrapulmonary atelectasis due to exogenous compression require a thoracotomy to confirm the diagnosis.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.