Aspiration pneumonia is a bronchopneumonia resulting from the inhalation or inappropriate passage of foreign solid or liquid material into the respiratory tract.
When the gastric contents or oropharyngeal contents seek passage to the lower airways, it is defined as aspiration.
The passage of the foreign materials to the lungs may cause several syndromes depending on the nature, frequency, host factors and quantity of the material aspirated. Pneumonia that accompanies aspiration is called aspiration pneumonia .
Three different types of materials cause three different types of aspiration pneumonia. They are as follows:
The authentic data for chemical pneumonia is not known, some studies, however, suggest that around 5 to 15% of all the community acquired pneumonia (CAP) results from aspiration pneumonia. The 30-day mortality rate of the aspiration pneumonia was found to be around 21%.
It has been estimated that 1 in every 10 patient hospitalized post drug-overdose were found to have aspiration pneumonitis.
Nosocomial bacterial pneumonia is more common among males than females. Adults were found to be more frequently affected by this disease than the children. The predisposing factors are common among the elderly, making them susceptible to this disease .
In patients who develop aspiration pneumonia, the infiltrate increases the risk of oropharyngeal aspiration. The risk is greatly increased in patients with the lower level of consciousness. The three most important determinants of the severity and extent of aspiration pneumonia are nature, and volume of the material aspirated, along with the host defenses.
Chemical pneumonia: This aspiration leads to acute respiratory distress within one hour. The chances of development of this type of pneumonia depend on the levels of consciousness. Since the gastric fluid is acidic in nature, it results in chemical burns. Studies have revealed that if the pH of the aspirated fluid is less than 2.5 and volume aspirated is greater than 0.3 mL/kg of body weight, the chances of chemical pneumonia increase several fold.
Bacterial pneumonia: In persons with impaired airway defense, there is an increased risk of bacterial pneumonia as the inherent mechanism of removing the bacteria is compromised. This type of pneumonia occurs both in community and hospital acquired pneumonia. Anaerobic and micro-aerophilic organisms are believed to play significant role in this disease
Causative microorganisms: The common causative micro-organisms of community acquired aspiration pneumonia are: Streptococcus species (pneumoniae, aureus), Haemophilus influenzae, and Enterobacteriaceae. However, the hospital acquired pneumonia (especially intubated patients) is caused by gram-negative organisms such as Pseudomonas aeruginosa  .
Prognosis of the bacterial and chemical pneumonia depends on the underlying diseases or complications as well as host status. If the bacterial pneumonia is not treated, it can lead to severe complications such as lung abscess and bronchopleural fistula. Longer period of hospitalization is associated with nosocomial pneumonia .
Physical Examination: The findings of the physical examination depend on the severity of the disease and the presence of complications. Aspiration pneumonia shows the following signs: fever, tachypnea, tachycardia, decrease in breath sounds, rales, hyporexia, and/or hypotension.
Host Factors: The decreased ability to protect the airway of the host results from previous cerebro-vascular accident (CVA), esophageal diseases, esophageal web, or if the patient is chronically fed by feeding tube.
The physical symptoms of this type of pneumonia range from tachypnea, tachycardia, wheezing or cyanosis.
The clinical presentation of bacterial aspiration pneumonia includes nonspecific symptoms such as headache or nausea/vomiting, and weight loss. Fever, absence of rigors, chest pain, chills and cough with sputum are some of the other symptoms manifested by the patients .
From the data obtained from the radiographic evidence of an infiltrate, the diagnosis of aspiration pneumonia can be ascertained. The exact location of the infiltrate is determined by the chest radiograph. Laboratory studies are guided by the symptoms and clinical presentation of the patients.
Antibiotics: In aspiration pneumonia, antibiotics form the first line in the management procedure. The important points to consider while administering antibiotics in patients with aspiration pneumonia are as follows:
Managing Chemical Aspiration Pneumonia: Important step for the management of chemical pneumonia is maintaining the airways of the secretions by tracheal suctioning and oxygen supplementation. The routine use of corticosteroid must be avoided.
Aspiration pneumonia is a serious disease and there are certain conditions that can worsen or increase the chances of complications such as alcoholism, drug overdose, stroke and seizures, trauma to head, dysphagia, esophageal neoplasm, gastroesophageal reflux disease, myasthenia gravis, Parkinson disease and dementia.
Critical illness and use of mechanical devices also contribute to the disease. Hence, awareness of the condition in such patients is advisable.