Aspiration Pneumonia or Aspiration Pneumonitis

Posted by | January 2, 2011 | Articles, Dyphagia Evaluation

Aspiration Pneumonia vs. Aspiration Pneumonitis- How to decipher between the Two

Aspiration pneumonia and aspiration pneumonitis are important for the speech-language pathologist to be able to decipher between.  Aspiration is the inhalation of oropharyngeal or gastric contents into the larynx and lower respiratory tract.  Aspiration pneumonitis is a complication caused by inhalation of sterile gastric contents. It leads to acute lung injury from the inhaled acidic and particulate material.  Aspiration pneumonia is when there is inhalation of colonized oralpharyngeal material and is associated with an acute pulmonary inflammatory response to bacteria and bacterial products.  (Marik, 2001). In aspiration pneumonitis the degree of lung injury caused by the aspiration is influenced by the pH and volume of the aspirate (Cavallazzi, R. 2010).

ASPIRATION PNEUMONIA

Aspiration pnuemonias are caused by microaspiration of pathogenic oropharyngeal bacteria.  This diagnosis is used when a patient develops pneumonia who has risk factors for oralpharyngeal aspiration.   Healthy individuals commonly aspirate their saliva during sleep or when drinking quickly.  No disease ensues in healthy persons 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. Aspiration in larger amounts or in patients with compromised immune systems,  can cause problems.  Patients may develop aspiration pneumonia or lung abscess.

Lung abscess is a necrotizing lung infection characterized by a pus-filled cavitary lesion. It is almost always caused by aspiration of oral secretions by patients who have impaired consciousness. Symptoms are persistent cough, fever, sweats, and weight loss. Diagnosis is based primarily on chest x-ray. Treatment usually is with clindamycin or combination β-lactam/β-lactamase inhibitors.

Empyma may also complicate aspiration.  Empyema is a collection of pus in the pleural spaces (space between the lung and the pleural wall).

Symptoms and Signs of aspiration pneumonia

Symptoms and signs of pneumonia and abscess are similar to that for aspiration pneumonia and include chronic low-grade dyspnea, fever, weight loss, and cough productive of putrid, foul-tasting sputum. Shortness of breath, elevated white blood cell count and hypoxemia are other signs.  Patients may have signs of poor oral hygiene.

Risk Factors of Aspiration Pneumonia

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.  Patients with neurological disorders, critically ill, and elderly are at risk for aspiration.  Patients with malignancy, especially head and neck cancer, are at risk for aspiration, due to obstruction or the effects of chemoradiation.  Almost half of patients who undergo chemotherapy and radiation develop severe dysphagia leading to increased risk of aspiration pneumonia. Patients with enteral feeding tubes are also at risk of aspiration. This is because they have some of the above factors that predispose the patients to aspiration pneumonia.  They can still aspirate the oralpharyngeal secretions and are at high risk for gastro-esophageal reflux.

Diagnosis of aspiration pneumonia

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.

Right lower lobe infiltrate

Chest x-ray shows an infiltrate, frequently but not exclusively, in the dependent lung segments, ie, the superior or posterior basal segments of a lower lobe or the posterior segment of an upper lobe.  The infiltrate location mostly depends on the position ofthe patient at the time of aspiration.  Patients who aspirate in the recumbent position usually have infiltrates in the posterior segments of the upper lobe.  Those who aspirate in an upright position have infiltrates in the basal segments of the lower lobes.  (Marik, 2001).  Overlap with community aquired pneumonia and aspiration pneumonitis can occur.  The presense of risk factors for aspiration helps to distinguish aspiration pneumonia from community acquired pneumoia.  The inhaltion of colonized material (as opposed to sterile material) helps to distinguish aspiration pneumonia from aspiration pneumonitis.

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.  Klebsiella pneumoniae, Escherichia coli are also common.  Hospital-acquired aspiration pneumonia, on the other hand, is often caused by gram-negative organisms including Pseudomonas aeruginosa, particularly in intubated patients.The most common anaerobes include gram-negative bacteria.

Treatment of Aspiration Pneumonia

Antiobiotic therapy is the typical treatment for aspiration pneumonia.   Antiobiotics should cover typical community-acquired pathogens in patients without a toxic appearance. Ceftriaxone plus azithromycin, levofloxacin, or moxifloxacin are appropriate options.  A recent clinical trial demonstrated that moxifloxacin is as effective and safe as ampicillin/sulbactam and has the advantage of a simplified once daily dosing regimen (Ott et al., 2008).  Patients with a toxic appearance or who were recently hospitalized, antiobiotics covered the community-acquired pathogens, as well as gram-negative bacteria including Pseudomonas aeruginosa and Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus must be covered as well. Piperacillin/tazobactam or imipenem/cilastatin plus vancomycin would be appropriate.  Add clindamycin for purulent sputum.

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