Aspiration pneumonia is an infectious and toxic damage to the pulmonary parenchyma that develops as a result of the contents of the oral cavity, nasopharynx, and stomach entering the lower respiratory tract. Aspiration pneumonia is manifested by cough, tachypnea, cyanosis, tachycardia, chest pain, fever, and the appearance of fetid sputum. The diagnosis of aspiration pneumonia is based on auscultative and radiological data, the results of bronchoscopy, microbiological examination of the contents of the lower respiratory tract and pleural effusion. Treatment of aspiration pneumonia requires oxygen therapy, antibiotic therapy, endoscopic rehabilitation of the tracheobronchial tree; if necessary, drainage of developed abscesses or empyema of the pleura is carried out.
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Aspiration pneumonia in pulmonology refers to inflammation of the lungs resulting from an established episode of accidental ingestion of the contents of the oropharynx or stomach into the lower respiratory tract. Among the various forms of pneumonia, aspiration pneumonia has a fairly large proportion: it accounts for about 23% of cases of severe forms of lung infection. Aspiration syndrome is often found in practically healthy individuals during sleep. Thus, in studies with nasopharyngeal irrigation with a solution labeled with radioactive isotopes, aspiration was recorded in 45-50% of healthy people and in 70% of elderly patients aged over 75 years with impaired consciousness.
Aspiration pneumonia causes
Aspiration pneumonia develops against the background of accidental ingress of solid particles or liquid into the airways. However, the mere fact of aspiration is not enough to cause aspiration pneumonia. The number of aspirated contents and its nature, the number of microorganisms entering the terminal bronchioles, their virulence, and the state of the body’s protective factors play a role in the mechanism of the development of pneumonia.
In most cases, the etiology of disease is polymicrobial in nature. More than 50% of cases of aspiration pneumonia are caused by anaerobic flora (bacteroids, Prevotella, fusobacteria, porphyromonads, veilonella, etc.); about 10% – only aerobic species (Staphylococci, Hemophilus bacillus, Klebsiella, E. coli, Enterobacteria, proteus, Pseudomonas aeruginosa); in other cases – combined flora. An important microbiological substrate in the development of apathology is the presence of pathogenic microflora in the oral cavity and upper respiratory tract in caries, periodontal disease, gingivitis, tonsillitis, etc.
Most often, the premorbid background for aspiration pneumonia is:
Disorders of consciousness caused by various factors:
- alcohol intoxication
- general anesthesia
- traumatic brain injury
- overdose of medicines
Diseases of the peripheral and central nervous system:
- myasthenia gravis
- multiple sclerosis
- Parkinson’s disease
- metabolic encephalopathy
- brain tumors
Diseases accompanied by a violation of the act of swallowing (dysphagia) and regurgitation:
- achalasia of the cardia
- esophageal stenosis
- gastroesophageal reflux disease
- hernia of the esophageal orifice of the diaphragm
Injuries and iatrogenic injuries:
- traumatic and iatrogenic injuries of the respiratory tract in wounds
- of foreign bodies of the trachea and bronchi
- vomiting of various genesis
- tracheostomy, intubation
- of endotracheal manipulations.
- aspiration of meconium
- force-feeding a child
- inhalation of foreign bodies into the bronchi
The scenario of events unfolding during aspiration of the contents into the tracheobronchial tree can vary from complete absence of disorders to the development of respiratory distress syndrome, respiratory failure and death of the patient. The conditions leading to the development of aspiration pneumonia are violations of local protection factors in the respiratory tract and the pathological nature of aspiration masses (quantity, chemical properties and pH, degree of infection, etc.). The main pathogenetic links leading to aspiration pneumonia are mechanical obstruction of the respiratory tract, acute chemical pneumonitis and bacterial pneumonia.
When inhaling a large volume of aspirate or large solid particles, mechanical obstruction of the tracheobronchial tree occurs. The resulting protective cough reflex promotes even deeper penetration of the aspirated substrate into the bronchi and bronchioles, which can lead to the development of pulmonary edema. Mechanical obstruction is accompanied by the development of lung atelectasis and stagnation of bronchial secretions, against which the risk of infection of the pulmonary parenchyma increases.
In response to the aggressive effect of the aspirated contents, acute chemical pneumonitis develops, characterized by the release of biologically active substances, activation of the complement system, release of tumor necrosis factors, cytokines, etc. Further pathological changes in the pulmonary parenchyma are caused by its damage by biologically active substances, and not by the direct action of the aspirate. Hypoxemia develops rapidly against the background of reflex bronchospasm, atelectasis of a part of the lung, a decrease in pulmonary perfusion and direct damage to the alveoli. With the addition of the bacterial component, respiratory failure, fever, cough increases, i.e. all signs of bacterial pneumonia appear. At this stage of aspiration pneumonia, infiltration foci are radiologically determined, pulmonary abscesses and pleural empyema often occur.
Aspiration pneumonia symptoms
In the clinical course, aspiration pneumonia goes through the stages of pneumonitis, necrotizing pneumonia, abscess formation and empyema of the pleura. Unlike bacterial lung infection, the aspiration pneumonia clinic unfolds gradually and is erased. Within a few days after the aspiration episode, subfebrility, weakness, dry painful cough may occur. In the future, dyspnea, chest pain, fever, tachycardia, cyanosis, the release of foamy sputum with an admixture of blood when coughing increase. Often, after 10-14 days with aspiration pneumonia, lung tissue abscess and pleural empyema occur. At the same time, a productive cough appears with the release of purulent sputum with a putrid smell, hemoptysis, chills.
Aspiration pneumonia is indicated by the presence in the anamnesis of an aspiration episode, confirmed by physical, X-ray, endoscopic and microbiological data. Examination reveals signs of hypoxemia (shortness of breath, cyanosis, tachycardia), lagging of the affected side of the chest when breathing, sometimes putrid breath. To find out the causes that led to aspiration pneumonia, in addition to examining the patient by a pulmonologist and a thoracic surgeon, a consultation of a gastroenterologist, neurologist, otolaryngologist may be required.Confirmatory diagnostics include:
- X-ray. Lung x-ray in 2 projections allows us to determine the typical localization of disease in the so-called dependent segments of the lung: the posterior upper lobe and upper lower lobe segments (when the contents are aspirated in a horizontal position) or the lower lobes (when the patient is in a horizontal position during aspiration). In addition, lung atelectasis, foci of destruction in the pulmonary parenchyma, accumulation of gas above the exudate in the pleural cavity are determined.
- Isolation of the pathogen. An important stage in the diagnosis of aspiration pneumonia is the bacteriological sowing of sputum on the microflora with the determination of sensitivity to antibiotics, as well as bacteriological examination of bronchial flushing waters. Therefore, for diagnostic purposes, bronchoscopy is usually resorted to with sputum sampling, taking washing waters from the tracheobronchial tree.
- Blood test. To determine the severity of hypoxemia in aspiration pneumonia, the gas composition of the blood, the blood braid is examined. The biochemical parameters of blood are being studied, blood is being seeded for sterility, for aerobic and anaerobic bacteria.
Aspiration pneumonia treatment
When aspiration of foreign bodies leading to obturation of the lumen of the airways, urgent endoscopic removal of a foreign body from the trachea / bronchus is indicated. Oxygen therapy is carried out – the supply of moistened oxygen, in severe cases – intubation and ventilation. The basis for the treatment of aspiration pneumonia is antibacterial therapy. When prescribing antimicrobials, the sensitivity of anaerobic and aerobic pathogens to them is taken into account. In aspiration pneumonia, combinations of several antibacterial drugs (for example, fluoroquinalones or cephalosporins and metronidazole) are usually prescribed. The duration of the course of antibacterial treatment for aspiration pneumonia is 14 days.
In the presence of abscesses in the lungs, their drainage is performed, vibration massage, percussion chest massage is performed. If necessary, repeated tracheal aspiration of the secretion, sanitization bronchoscopy and bronchoalveolar lavage are performed. Surgical intervention is resorted to in the organization of large abscesses (more than 6 cm), pulmonary bleeding, the formation of bronchopleural fistula. With aspiration pneumonia complicated by pleural empyema, drainage of the pleural cavity is performed, sanitation washings are performed, antibiotics and fibrinolytics are injected into the pleural cavity. It is possible to perform open drainage (thoracostomy), pleurectomy with lung decortication.
Prognosis and prevention
With small volumes of aspirated contents, a stable general background and timely competent treatment, the prognosis for aspiration pneumonia does not cause concern. In the case of massive pneumonitis, pulmonary abscesses, pleural empyema, bronchopleural fistulas, sepsis, the prognosis is extremely serious. Mortality in the complicated course of aspiration pneumonia is 22%.
Given the high risk of disease among people suffering from diseases of the nervous and digestive systems, it is necessary to treat the underlying pathological condition. Patients with dysphagia and a tendency to aspiration are recommended fractional nutrition and a gentle diet. To prevent reflux in patients with dysphagia, seriously ill and postoperative patients, it is necessary to lift the head end of the bed at an angle of 30-45 °. Special attention should be paid to patients who are on a ventilator, probe feeding. Hygiene and timely sanitation of the oral cavity, regular visits to the dentist play an important role in the prevention of aspiration pneumonia.
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