Introduction
Background
Aspiration is defined as the inhalation of either oropharyngeal or gastric contents into the lower airways. Inhalation of these contents can lead to aspiration pneumonia and aspiration pneumonitis. Although these two entities are managed differently, they are often interchangeably referred to as aspiration pneumonia.
Aspiration pneumonitis represents chemical damage to the tracheobronchial tree caused by acute, often witnessed, inhalation of regurgitated gastric contents in patients with an acute change in mental status. Aspiration pneumonia results from chronic, usually unwitnessed, inhalation of small amounts of oropharyngeal contents leading to an infectious process.
Chest radiograph of a patient with massive aspiration pneumonia of the right lung.
Pathophysiology
Aspiration pneumonitis represents an acute, chemical lung injury resulting from the inhalation of gastric contents. This disease occurs in people with altered levels of consciousness resulting from seizures, cerebrovascular accident (CVA), CNS mass lesions, drug intoxication or overdose, and head trauma.
The risk of aspiration is indirectly related to the level of consciousness of the patient (ie, decreasing Glasgow Coma Scale [GCS] score is related with increased risk of aspiration).1 The extent and severity of this disease is directly related to the volume and acidity of the fluid aspirated. Aspiration of a massive amount of gastric contents, also know as Mendelson syndrome, can produce acute respiratory distress within 1 hour. The acidity of gastric contents results in chemical burns to the tracheobronchial tree involved in the aspiration.
Because of the relative sterility of normal gastric contents, bacteria do not play an important role in the early stages of the disease. This does not hold true in patients with gastroparesis or small-bowel obstruction or in those using antacids (proton pump inhibitor [PPI], H2-receptor antagonists). Regardless of the bacterial load of the inoculum, bacterial superinfection may occur after the initial chemical injury.
Aspiration pneumonia is defined as the development of an infiltrate in a patient at increased risk of oropharyngeal aspiration. It occurs when a patient inhales material from the oropharynx that is colonized by upper airway flora.
Initial bacteriologic studies into the causative organisms revealed the anaerobic species to be the predominant pathogens in community-acquired aspiration pneumonia. However, subsequent studies revealed that Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae, and Enterobacteriaceae are the most common organisms.2 Hospital-acquired aspiration pneumonia, on the other hand, is often caused by gram-negative organisms including Pseudomonas aeruginosa, particularly in intubated patients. These studies demonstrated a limited role of anaerobic pathogens in both the community and nosocomial variants of the disease.
This syndrome most commonly occurs in individuals with chronically impaired airway defense mechanisms. This includes gag reflex, coughing, ciliary movement, and immune mechanisms, all of which aid in removing infectious material from the lower airways. Other risk factors include poor dentition and poor oral care, which both increase the bacterial burden of oropharyngeal secretions. Clinicians must thus surmise this diagnosis when a patient presents with risk factors and radiographic evidence of an infiltrate suggestive of aspiration pneumonia. The location of the infiltrate on chest radiograph depends on the position of the patient when the aspiration occurred.
Frequency
United States
Few studies have been designed that distinguish between aspiration pneumonia and aspiration pneumonitis. Several studies suggest that 5-15% of the 4.5 million cases of community-acquired pneumonia result from aspiration pneumonia.2
Approximately 10% of patients who are hospitalized after drug overdoses will have an aspiration pneumonitis.
International
Aspiration pneumonia is considered a common disease, but no statistics are available.
Mortality/Morbidity
- The mortality associated with aspiration pneumonia mimics that of community-acquired pneumonia: approximately 1% in the outpatient setting and up to 25% in those requiring hospitalization. This mortality range depends on complications of the disease.
- The mortality rate for severe chemical pneumonitis (Mendelson syndrome) can be up to 70%.
- Without treatment, aspiration pneumonia is associated with a high incidence of cavitation and abscess formation in comparison to community-acquired pneumonia. Other complications of both aspiration pneumonia and pneumonitis include empyema, acute respiratory distress syndrome, and respiratory failure. Aspiration pneumonitis can rapidly progress to respiratory failure.
Sex
Aspiration pneumonia is more common in males than in females.
Age
Aspiration pneumonia is more common in extremely young or old patients.
Clinical
History
The clinical presentation of both aspiration pneumonitis and pneumonia ranges from mildly ill and ambulating to critically ill with signs and symptoms of septic shock and/or respiratory failure.
Patient history in aspiration pneumonia is similar to that of community-acquired pneumonia and may include the following:
- Cough
- Fever or chills
- Malaise, myalgias
- Shortness of breath, dyspnea on exertion
- Pleuritic chest pain
- Putrid expectoration
- Nonspecific symptoms including headache, nausea/vomiting, anorexia, weight loss
- Host factors - Chronic conditions resulting in decreased ability to protect one's airway
- Previous CVA
- History of esophageal diseases including achalasia,3 esophageal web
- Nursing home patients
- Patients chronically fed by feeding tube (NG tube or gastric tube)
- Patients brought in after witnessed large-volume vomitus and subsequent aspiration pneumonitis will have a history consistent with an acute change in mental status. This history may include the following:
- Seizure
- Alcohol abuse
- Drug overdose
- Head trauma
Physical
Physical examination findings vary depending on severity of the disease, presence of complications, and host factors. Patients with aspiration pneumonitis secondary to seizure, head trauma, or drug overdose should be inspected for signs related to these processes. Both aspiration pneumonia and pneumonitis can present with the following:
- Fever or hypothermia
- Tachypnea
- Tachycardia
- Decreased breath sounds
- Dullness to percussion over areas of consolidation
- Rales
- Egophony and pectoriloquy
- Decreased breath sounds
- Pleural friction rub
- Altered mental status
- Hypoxemia
- Hypotension (in septic shock)
- In addition, patients may exhibit signs associated with the underlying disease that lead to their aspiration.
Causes
Any condition that reduces a patient's gag reflex, ability to maintain an airway, or both increases the risk of aspiration pneumonia or pneumonitis.
- CVA
- Intracranial mass lesion
- Head trauma
- Alcohol abuse
- Drug overdose
- Isolated alteration of the swallowing reflex associated with pharyngeal disease
More on Pneumonia, Aspiration |
 Overview: Pneumonia, Aspiration |
| Differential Diagnoses & Workup: Pneumonia, Aspiration |
| Treatment & Medication: Pneumonia, Aspiration |
| Follow-up: Pneumonia, Aspiration |
| Multimedia: Pneumonia, Aspiration |
| References |
| Next Page » |
References
Adnet F, Baud F. Relation between Glasgow Coma Scale and aspiration pneumonia. Lancet. Jul 13 1996;348(9020):123-4. [Medline].
Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. Mar 1 2001;344(9):665-71. [Medline].
Akritidis N, Gousis C, Dimos G, Paparounas K. Fever, cough, and bilateral lung infiltrates. Achalasia associated with aspiration pneumonia. Chest. Feb 2003;123(2):608-12. [Medline].
Marom EM, McAdams HP, Erasmus JJ. The many faces of pulmonary aspiration. AJR Am J Roentgenol. Jan 1999;172(1):121-8. [Medline].
Drakulovic MB, Torres A, Bauer TT, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. Lancet. Nov 27 1999;354(9193):1851-8. [Medline].
Lumpkin JR, Westfall MD. Aspiration pneumonia. In: Emergency Medicine: Concepts and Clinical Practice. 1992:1112-20.
Marik PE, Careau P. The role of anaerobes in patients with ventilator-associated pneumonia and aspiration pneumonia: a prospective study. Chest. Jan 1999;115(1):178-83. [Medline].
Mier L, Dreyfuss D, Darchy B. Is penicillin G an adequate initial treatment for aspiration pneumonia? A prospective evaluation using a protected specimen brush and quantitative cultures. Intensive Care Med. 1993;19(5):279-84. [Medline].
Moll J, Kerns W 2nd, Tomaszewski C. Incidence of aspiration pneumonia in intubated patients receiving activated charcoal. J Emerg Med. Mar-Apr 1999;17(2):279-83. [Medline].
Pennza PT. Aspiration pneumonia, necrotizing pneumonia, and lung abscess. Emerg Med Clin North Am. May 1989;7(2):279-307. [Medline].
Preston AJ, Gosney MA, Noon S. Oral flora of elderly patients following acute medical admission. Gerontology. Jan-Feb 1999;45(1):49-52. [Medline].
Sasaki H, Sekizawa K, Yanai M. New strategies for aspiration pneumonia. Intern Med. Dec 1997;36(12):851-5. [Medline].
Vadeboncoeur TF, Davis DP, Ochs M. The ability of paramedics to predict aspiration in patients undergoing prehospital rapid sequence intubation. J Emerg Med. Feb 2006;30(2):131-6. [Medline].
Further Reading
Keywords
aspiration pneumonia, aspiration pneumonitis, aspiration pneumonia treatment, Mendelson syndrome, pneumonitis, altered level of consciousness, abnormal swallowing reflexes, acute respiratory distress syndrome, acute respiratory failure, bacterial pneumonitis, chemical pneumonitis, community-acquired aspiration pneumonia, Staphylococcus aureus, nosocomial infection, empyema, stress dyspnea, rest dyspnea, cyanosis, putrid expectoration, tachypnea, tachycardia, bradycardia, crackles, bronchial rales, pleural effusion, egophony, cerebrovascular accident, intracranial mass lesions, sepsis, meningitis
