eMedicine Specialties > Pulmonology > Aspiration and Atelectasis
Pneumonia, Aspiration
Updated: Aug 7, 2009
Introduction
Background
Aspiration, ie, the act of taking foreign material into the lungs, can cause a number of syndromes determined by the quantity and nature of the aspirated material, the frequency of aspiration, and the host factors that predispose the patient to aspiration and modify the response. Three types of material cause 3 different pneumonic syndromes. Aspiration of gastric acid causes chemical pneumonia (CP). Aspiration of bacteria from oral and pharyngeal areas causes bacterial pneumonia (BP). Aspiration of oil, eg, mineral oil or vegetable oil, causes exogenous lipoid pneumonia, a rare form of pneumonia. In addition, aspiration of a foreign body may cause an acute respiratory emergency and, in some cases, may predispose the patient to bacterial pneumonia.
Aspiration pneumonia, according to common usage, includes both CP and BP, although the pathophysiology, clinical presentation, treatment, and complications of CP and BP are different.
Aspiration pneumonia. An 84-year-old man in generally good health had fever and cough. Posteroanterior radiograph demonstrates a left lower lobe opacity.
Pathophysiology
Aspiration, particularly during sleep, is a common event in healthy individuals. No disease ensues because the aspirated material is cleared by mucociliary action and alveolar macrophages. The nature of the aspirated material, volume of the aspirated material, and state of the host defenses are 3 important determinants of aspiration pneumonia.
CP, also known as Mendelson syndrome, is due to the parenchymal inflammatory reaction caused by a large volume of gastric contents independent of infection. If the pH of the aspirated fluid is less than 2.5 and the volume of aspirate is greater than 0.3 mL/kg of body weight (20-25 mL in adults), it has a greater potential for causing CP. The initial chemical burn is followed by an inflammatory cellular reaction fueled by the release of potent cytokines, particularly tumor necrosis factor–alpha and interleukin-8.
BP caused by aspiration can occur in the community or in the hospital (ie, nosocomial). In both situations anaerobic organisms alone or in combination with aerobic and/or microaerophilic organisms play an important role. Nosocomial BP caused by aspiration is common, and the major pathogens involved are hospital-acquired flora through oropharyngeal colonization (eg, enteric gram-negative bacteria, staphylococci).
In anaerobic pneumonia, the pathogenesis is related to the large volume of aspirated anaerobes (eg, as in persons with periodontal disease) and to host factors (eg, as in alcoholism) that suppress cough, mucociliary clearance, and phagocytic efficiency. Selection and colonization of gram-negative organisms in the oropharynx, sedation, and intubation of the patient's airways are important pathogenetic factors in nosocomial pneumonia.
Frequency
United States
A reliable estimate of incidence of CP is not available. BP caused by aspiration is reported to cause 5-15% of community-acquired pneumonia (CAP) cases. Nosocomial BP is the second most likely cause of nosocomial infections, second only to urinary tract infection, and is the leading cause of death from hospital-acquired infections.
Mortality/Morbidity
In Mendelson's original series in 1946, Mendelson described 61 obstetric patients who aspirated gastric acid during anesthesia, all of whom had a complete clinical recovery within 24-36 hours.1 In subsequent studies, which have included older sicker patients, CP has a reported mortality rate of 30-62% because CP often leads to acute respiratory distress syndrome (ARDS).
- If BP is not treated early, it can lead to development of complications, including lung abscess and bronchopleural fistula.
- Nosocomial pneumonia is associated with a longer period of hospitalization and increased mortality rates.
Age
Nosocomial BP caused by aspiration is much more frequent in adults than in children. Predisposing factors (see Causes) are more common among elderly people; therefore, this population is more prone to develop aspiration pneumonia.
Clinical
History
- Chemical pneumonitis
- Acute onset
- Abrupt development of symptoms within a few minutes to 2 hours of the aspiration event
- Respiratory distress and rapid breathing
- Audible wheezing
- Cough with pink or frothy sputum
- Bacterial pneumonia
- Subacute or insidious onset: Symptoms occur in a matter of days when aerobic organisms are the pathogens and in days to weeks when anaerobic organisms are the pathogens.
- Cough with purulent sputum
- Absence of rigors
- Putrid odor of sputum (a clue to anaerobic bacterial pneumonia)
- Weight loss
Physical
- Chemical pneumonia
- Tachypnea
- Tachycardia
- Fever
- Rales
- Wheezing
- Cyanosis (possibly)
- Bacterial pneumonia
- Periodontal disease (primarily noted as gingivitis)
- Bad breath
- Clubbing of fingers (possibly)
- Fever
- Bronchial breath sounds and rales over a consolidated posterior area
Causes
Almost all patients who develop aspiration pneumonia have one or more of the predisposing conditions listed below. While all the listed conditions predispose the patient to chemical pneumonia (CP), conditions that alter consciousness and periodontal disease specifically predispose the patient to bacterial pneumonia (BP).- Conditions associated with altered or reduced consciousness
- Alcoholism
- Drug overdose
- Seizures
- Stroke
- Head trauma
- General anesthesia
- Esophageal conditions
- Dysphagia
- Esophageal strictures
- Esophageal neoplasm
- Esophageal diverticula
- Tracheoesophageal fistula
- Gastroesophageal reflux disease
- Neurologic disorders
- Multiple sclerosis
- Dementia
- Parkinson disease
- Myasthenia gravis
- Pseudobulbar palsy
- Mechanical conditions
- Nasogastric tube
- Endotracheal intubation
- Tracheostomy
- Upper gastrointestinal endoscopy
- Bronchoscopy
- Gastrostomy or postpyloric feeding tubes
- Other types of conditions
- Protracted vomiting
- Prolonged recumbency
- General deconditioning and debility
- Critical illness
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| Multimedia: Pneumonia, Aspiration |
| References |
| Further Reading |
| Next Page » |
References
Mendelson CL. The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol. 1946;52:191.
[Guideline] Coffin SE, Klompas M, Classen D, Arias KM, Podgorny K, Anderson DJ, et al. Strategies to prevent ventilator-associated pneumonia in acute care hospitals. Infect Control Hosp Epidemiol. Oct 2008;29 Suppl 1:S31-40. [Medline].
[Guideline] Tablan OC, Anderson LJ, Besser R, Bridges C, Hajjeh R. Guidelines for preventing health-care--associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep. Mar 26 2004;53:1-36. [Medline].
American Thoracic Society. Hospital-acquired pneumonia in adults: diagnosis, assessment of severity, initial antimicrobial therapy, and preventive strategies. A consensus statement, American Thoracic Society, November 1995. Am J Respir Crit Care Med. May 1996;153(5):1711-25. [Medline].
Bartlett JG. Anaerobic bacterial infections of the lung and pleural space. Clin Infect Dis. Jun 1993;16 Suppl 4:S248-55. [Medline].
Bynum LJ, Pierce AK. Pulmonary aspiration of gastric contents. Am Rev Respir Dis. Dec 1976;114(6):1129-36. [Medline].
Fang GD, Fine M, Orloff J. New and emerging etiologies for community-acquired pneumonia with implications for therapy. A prospective multicenter study of 359 cases. Medicine (Baltimore). Sep 1990;69(5):307-16. [Medline].
Huxley EJ, Viroslav J, Gray WR. Pharyngeal aspiration in normal adults and patients with depressed consciousness. Am J Med. Apr 1978;64(4):564-8. [Medline].
Janssens JP. Pneumonia in the elderly (geriatric) population. Curr Opin Pulm Med. May 2005;11(3):226-30. [Medline].
Kadowaki M, Demura Y, Mizuno S, Uesaka D, Ameshima S, Miyamori I. Reappraisal of clindamycin IV monotherapy for treatment of mild-to-moderate aspiration pneumonia in elderly patients. Chest. Apr 2005;127(4):1276-82. [Medline].
LaForce FM. Hospital-acquired gram-negative rod pneumonias: an overview. Am J Med. Mar 1981;70(3):664-9. [Medline].
Levison ME, Mangura CT, Lorber B. Clindamycin compared with penicillin for the treatment of anaerobic lung abscess. Ann Intern Med. Apr 1983;98(4):466-71. [Medline].
Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. Mar 1 2001;344(9):665-71. [Medline].
Marrie TJ, Durant H, Yates L. Community-acquired pneumonia requiring hospitalization: 5-year prospective study. Rev Infect Dis. Jul-Aug 1989;11(4):586-99. [Medline].
Matthay MA, Rosen GD. Acid aspiration induced lung injury. New insights and therapeutic options. Am J Respir Crit Care Med. Aug 1996;154(2 Pt 1):277-8. [Medline].
Sullivan RJ Jr, Dowdle WR, Marine WM. Adult pneumonia in a general hospital. Etiology and host risk factors. Arch Intern Med. Jun 1972;129(6):935-42. [Medline].
Tietjen PA, Kaner RJ, Quinn CE. Aspiration emergencies. Clin Chest Med. Mar 1994;15(1):117-35. [Medline].
van Westerloo DJ, Knapp S, van't Veer C, Buurman WA, de Vos AF, Florquin S. Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia. Crit Care Med. Aug 2005;33(8):1770-8. [Medline].
Varkey B, Kutty K. Pulmonary aspiration syndromes. In: Kochar's Concise Textbook of Medicine. Baltimore, Md:. Lippincott Williams & Wilkins;1998:902-906.
Wynne JW, Ramphal R, Hood CI. Tracheal mucosal damage after aspiration. A scanning electron Microscope study. Am Rev Respir Dis. Dec 1981;124(6):728-32. [Medline].
Further Reading
Clinical guidelines
Coffin SE, Klompas M, Classen D, Arias KM, Podgorny K, Anderson DJ, Burstin H, Calfee DP, Dubberke ER, Fraser V, Gerding DN, Griffin FA, Gross P, Kaye KS, Lo E, Marschall J, Mermel LA, Nicolle L, Pegues DA, Perl TM, Saint S, Salgado CD, Weinstein RA, Wise R, Yokoe DS. Strategies to prevent ventilator-associated pneumonia in acute care hospitals. Infect Control Hosp Epidemiol 2008 Oct;29 Suppl 1:S31-40. 2
Tablan OC, Anderson LJ, Besser R, Bridges C, Hajjeh R. Guidelines for preventing health-care--associated pneumonia, 2003: recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep 2004 Mar 26;53(RR-3):1-36. 3
Keywords
aspiration pneumonia, Mendelson syndrome, chemical pneumonitis, anaerobic bacterial pneumonia, chemical pneumonia, CP, aspiration of gastric acid, bacterial pneumonia, BP, aspiration of bacteria from oral and pharyngeal areas, exogenous lipoid pneumonia, aspiration of oil, aspiration of a foreign body, acute respiratory emergency, parenchymal inflammatory reaction, community-acquired pneumonia, CAP, nosocomial pneumonia, acute respiratory distress syndrome, ARDS
