Aspiration pneumonia

  Aspiration pneumonia  Department of inhaled acidic substances, such as animal fat after food, stomach contents and other irritating liquids and play nature of hydrocarbons due to chemical pneumonia. In severe cases, respiratory failure may occur, or respiratory distress syndrome.

Etiology
    Aspiration of gastric contents clinically due to pneumonia caused by gastric acid is more common than the inhalation of hydrocarbon liquid and more important. Kerosene, gasoline, dry cleaners, furniture polish and the like sometimes aspiration, more common in children. Since normal laryngeal protective reflex and synergies swallowing, general food and foreign matter into the lower respiratory tract is not easy, even if a small amount of liquid aspiration can also be discharged by coughing. When delirious as general anesthesia, cerebrovascular accidents, seizures, alcoholism, excess anesthesia or sedated, the defense weakened or disappeared, can be inhaled foreign body trachea; esophageal lesions such as esophageal loss flaccid disease, upper esophageal carcinoma swollen, Zenker diverticulum, esophageal swallow not all stomach, reflux into the trachea; tracheoesophageal fistula caused by various reasons, food can transesophageal directly into the trachea; iatrogenic factors such as the stomach to stimulate the throat to induce vomiting; trachea intubation or tracheostomy affect laryngeal function, inhibit the normal movement of throat may be vomit inhaled airway. The reaction of the elderly poor are more likely to aspiration pneumonia.

After inhalation of stomach contents, due to the stimulation of gastric acid, resulting in acute lung inflammation, the severity and the concentration of hydrochloric acid, gastric juice intake and distribution in the lungs related. Inhalation of gastric acid pH≤2.5, 25ml intake that can cause severe lung damage. Animal experiments demonstrated that inhalation of pH <1 .5="" 3ml="" be="" body="" can="" damage.="" deadly.="" distributed="" font="" inhalation="" kg="" liquid="" more="" of="" range="" serious="" solution="" the="" weight="" when="" widely="">

Pathological changes
    After inhalation of stomach contents, stomach acid can cause the airways and lungs chemical burns immediately. Stimulate bronchial spasm caused by strong wall, ensuing acute inflammatory reaction of the bronchial epithelium and bronchial inflammatory infiltration around. The rapid spread of gastric fluid into the alveoli to the lung tissue, causing the bubble now epithelial cell damage, degeneration, and involving the capillary wall, increased permeability of the blood vessel wall, intravascular fluid leakage, causing edema and hemorrhagic pneumonia. At the same time due to the destruction of the alveolar capillary membrane, forming interstitial pulmonary edema. A few days later alveolar edema and hemorrhage gradually absorbed, and was replaced by a transparent film. A long time can the formation of pulmonary fibrosis. If inhalation of food or foreign body throat dwelling bacteria into the lungs can lead to anaerobic bacteria mainly of secondary bacterial infection, abscess formation. Pulmonary edema, decreased elasticity of the lung tissue, reduced compliance, reduce lung capacity, coupled with the reduction of pulmonary surfactant, so that small airway closure, alveolar collapse caused by micro-atelectasis, can produce insufficient ventilation, ventilation / perfusion imbalance and static arterial shunt increased, leading to hypoxemia or with metabolic acidosis. Intravascular large number of leaking fluid or reverse vasodilation, can produce hypotension. Pathological process hydrocarbon inhalation and inhalation of gastric acid is similar, because of its low surface tension, immediately diffusion in the lungs after inhalation of a large area, and surfactant inactivation, easily produce atelectasis, lung water species, leading to serious hypoxemia.

Clinical manifestations
    Patients often have symptoms after inhalation inducement history, rapid onset, more than 1 to 3 hours, and the clinical manifestations induced etiologies, as from tracheal - esophageal fistula due to aspiration pneumonia, each after eating there spasmodic cough, shortness of breath . In the confusion, the suction is often no obvious symptoms, but 1 to 2 hours after a sudden difficulty in breathing, rapid cyanosis and hypotension, cough often serous foamy sputum may be blood. Lungs heard and wet rales, may be associated with addicted beeps. Severe respiratory distress syndrome can occur.

Check test
    Chest X-ray showed that in 1 to 2 hours after inhalation that can be seen scattered in both lungs irregular flakes edge blur shadows, when lung lesions related to the distribution and absorption position, common in the lower lung fields, right lung is more common. Pulmonary edema, the lungs appear flaky, flocculent cloud shadows confluent sheet, spread out from two hilar to the lungs within the band is obvious, and acute cardiogenic pulmonary edema X-ray similar, but normal heart size and shape, no signs of pulmonary venous hypertension.

Treatment
    In case of emergency, it should be immediately given a high concentration of oxygen inhalation, application or fiberoptic intubation foreign body aspiration, plus PEEP Respiratory Therapy "acute respiratory distress syndrome." Correct hypovolemia albumin or low molecular weight dextran. In order to avoid an excessive burden between the left ventricle and colloid fluid leakage into the lungs quality, use of diuretics. Application of adrenocorticotropic hormone therapy is still controversial, there is that extensive use of inhaled corticosteroids within 12 hours at 3-4 in favor of absorption of lung inflammation, but there are those who hold the opposite view. Antibiotics to control secondary infection, rather than advocate for the prevention of bacterial infection, medication because neither reduce secondary bacterial infection and prone to drug-resistant strains. Principles after inhalation of hydrocarbon liquids as described above.

Prognosis and Prevention
    The main measures to prevent aspiration pneumonia to prevent inhalation of food or stomach contents, such as gastric emptying should be fully let before anesthesia, coma patients can take the low head and lateral position, tube placement as soon as possible, the need for intubation or trachea cut. Strengthening care is more important.