Signs, Symptoms, and Complications
- Increased respiratory rate
- Foul-smelling sputum
- Hemoptysis
- Fever
- Complications such as exudative pleural effusion, empyema, and lung abscesses

Causes and Risk Factors
- Defective swallowing mechanism
- Neurological diseases
- Injuries impairing swallowing or consciousness
- Impaired consciousness due to anesthesia or medical conditions
- Poor oral hygiene leading to bacterial colonization
- Impaired swallowing
- Neurologic conditions affecting swallow mechanism
- Anatomical changes in the chest
- Altered mental status
- Bacterial colonization
- Ethnicity
- Other factors like age, gender, diabetes, malnutrition, medication use, and respiratory conditions

Bacteria
- Common aerobic bacteria: Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, Klebsiella
- Anaerobic bacteria: Bacteroides, Prevotella, Fusobacterium, Peptostreptococcus
- Anaerobic coverage is typically included in treatment regardless of culture results

Pathophysiology and Diagnosis
- Aspiration defined as inhalation of oropharyngeal or gastric contents into the lungs
- Complications: chemical pneumonitis, aspiration pneumonia, airway obstruction
- Severity of chemical pneumonitis depends on pH and quantity of aspirate
- Location of aspiration is often gravity dependent, with right middle and lower lung lobes most commonly affected
- Chest x-ray is typically performed to detect pneumonia, including aspiration pneumonia
- Findings on chest x-ray can support the diagnosis of aspiration pneumonia
- Sputum cultures are not used for diagnosing aspiration pneumonia
- Clinical symptoms and physical exam findings can increase suspicion of aspiration pneumonia
- Lung biopsy specimens can diagnose aspiration pneumonia caused by food particles or other substances
- Differentiation from Chemical Pneumonitis
- Chemical pneumonitis and aspiration pneumonia have similar findings but require different management
- Chemical pneumonitis is caused by damage to the inner layer of lung tissue
- Inflammation triggers fluid influx in chemical pneumonitis
- Treatment of chemical pneumonitis involves removal of inflammatory fluid and supportive measures
- Antibiotics are reserved for chemical pneumonitis complicated by bacterial infection

Prevention, Treatment, and Prognosis
- Oral hygiene practices can decrease the incidence and severity of aspiration pneumonia
- Reduction of oral bacteria through antimicrobial use and dental professional interventions is beneficial
- Post-pyloric feeding may reduce the risk of aspiration pneumonia in critically ill patients with feeding tubes
- Training and assistance in swallowing can reduce episodes of aspiration pneumonia
- Identifying conditions causing upper gastrointestinal dysfunction before surgery is essential in preventing aspiration
- Adjusting the patient's posture and suctioning oropharyngeal contents are initial treatment steps
- Humidified oxygen and elevated head end of the bed are recommended for patients not intubated
- Antibiotics are the main treatment for aspiration pneumonia
- Broad antibiotic coverage is necessary due to diverse types of bacteria causing the infection
- Drainage of fluid within the lungs may aid in the healing process
- Alteration of dietary regimens and head positioning can be recommended for dysphagia patients
- Thickening liquids may decrease aspiration but increase the risk of delayed aspiration
- Clinical interventions' impact on reducing pneumonia incidence is relatively unknown
- Aspiration pneumonia is associated with increased in-hospital mortality compared to other forms of pneumonia
- Individuals diagnosed with aspiration pneumonia have an increased risk of future episodes and higher mortality rates

Aspiration pneumonia (Wikipedia)

Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may include lung abscess, acute respiratory distress syndrome, empyema, and parapneumonic effusion. Some include chemical induced inflammation of the lungs as a subtype, which occurs from acidic but non-infectious stomach contents entering the lungs.

Aspiration pneumonia
Microscopic image of aspiration pneumonia in an elderly person with a neurologic illness. Note foreign-body giant cell reaction.
Specialty	Emergency medicine, pulmonology
Symptoms	Fever, cough
Complications	Lung abscess
Usual onset	Elderly
Risk factors	Decreased level of consciousness, problems with swallowing, alcoholism, tube feeding, poor oral health
Diagnostic method	Based on presenting history, symptoms, chest X-ray, sputum culture
Differential diagnosis	Chemical pneumonitis, tuberculosis
Medication	Clindamycin, meropenem, ampicillin/sulbactam, moxifloxacin
Frequency	~10% of pneumonia cases requiring hospitalization

Infection can be due to a variety of bacteria. Risk factors include decreased level of consciousness, problems with swallowing, alcoholism, tube feeding, and poor oral health. Diagnosis is typically based on the presenting history, symptoms, chest X-ray, and sputum culture. Differentiating from other types of pneumonia may be difficult.

Treatment is typically with antibiotics such as clindamycin, meropenem, ampicillin/sulbactam, or moxifloxacin. For those with only chemical pneumonitis, antibiotics are not typically required. Among people hospitalised with pneumonia, about 10% are due to aspiration. It occurs more often in older people, especially those in nursing homes. Both sexes are equally affected.