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ICD-9 480


Pneumonia is defined as "inflammation of the lungs."[1]


Pneumonia can be classified along various dimensions including clinical setting, underlying etiology, and its gross appearance (bronchopneumonia versus lobar pneumonia).

Aspiration pneumonia

Community acquired pneumonia

The most common cause, streptococcus pneumonia, causes about a third of episodes.[2]

Atypical pneumonia

Nosocomial pneumonia

Ventilator associated pneumonia


Community acquired pneumonia

History and physical examination

A clinical prediction rule found the five following signs from the medical history and physical examination best predicted infiltrates on the chest radiograph of 1134 patients presenting to an emergency room:[3]

  • Temperature > 100 degrees F (37.8 degrees C)
  • Pulse > 100 beats/min
  • Crackles
  • Decreased breath sounds
  • Absence of asthma
The probability of an infiltrate based on the number of findings.[4] [3]
Number of findings Primary care[4] Emergency Room[3]
5 47% 75%
4 27 56
3 8 22
2 4 11
1 1 3
0 1 2

  • 5 findings - 84% to 91% probability
  • 4 findings - 58% to 85%
  • 3 findings - 35% to 51%
  • 2 findings - 14% to 24%
  • 1 findings - 5% to 9%
  • 0 findings - 2% to 3%

A subsequent study[5] comparing four clinical prediction rules to physician judgment found that two clinical prediction rules, the one above[3] and another[6] were more accurate than physician judgment because of the increased specificity of the prediction rules.

Blood tests

Some, but not all[7] experts recommend prompt blood cultures.

Procalcitonin levels may help prognosticate.

Diagnostic imaging

Ultrasonography can diagnose community acquired pneumonia in one study with accuracy of:[8]

  • Sensitivity 93%
  • Specificity 98%

Nosocomial pneumonia

The accuracy of findings for ventilator-associated pneumonia.[9]
Finding Sensitivity Specificity
Fever 45%-67% 33%-76%
Purulent sputum 50%-83% 33%-67%
Chest x-ray showing new infiltrate 87%-91% 33%-50%

Bronchoalveolar lavage with quantitative culture of the bronchoalveolar-lavage fluid or endotracheal aspiration with nonquantitative culture of the aspirate can help diagnose ventilator-associated pneumonia.[10]


Clinical practice guidelines are available.[11]


Some, but not all[7] experts recommend prompt antibiotics.


In a randomized controlled trial of adults with community-acquired pneumonia, the relative risk ratio of prednisone 50 mg daily for 7 days, as compared to placebo, reduced the time to median time to clinical stability from 4.4 to to 1.3 days. [12]

In another randomized controlled trial of adults with community-acquired pneumonia, dexamethasone can reduce length of hospital stay. [13]

One trial reported increase in late-failures.[14]

Aspiration pneumonia

Community acquired pneumonia

The 'respiratory quinolones' (levofloxacin, moxifloxacin, gemifloxacin) may be the best choices[15] although the evidence is not clear[16] and some studies show macrolides may be better[17].

The optimal duration of antibiotic treatment for community acquired pneumonia is not clear.[18]

Ventilator associated pneumonia

Treatments that are ineffective

Chest physiotherapy includes postural drainage, percussion, and vibration and has been call the 'ketchup-bottle method'[19] of treating pneumonia. Chest physiotherapy and intermittent positive-pressure breathing have been shown not to help in a small randomized controlled trial.[20] A subsequent systematic review did not find benefit.[21]


Short term prognosis and the decision to hospitalize

The prognosis of community acquired pneumonia can be estimated with several clinical prediction rules of similar accuracy:[22][23]

  • Pneumonia severity index (PSI) - the PSI may[24] or may not[23] be more accurate than the CURB-65 and is available online (Pneumonia Severity Index Calculator).
    • Patients with PSI Risk groups I-III can usually be treated as an outpatient.[25]
  • CURB-65
  • SMART-COP is a new clinical prediction rule that may be better according to a single study.[26] Patients are high risk if they have three or more points from the following:
    • systolic blood pressure < 90 (2 points)
    • multilobar chest radiography involvement (1 point)
    • albumin level < 3.5 mg/dl (1 point)
    • high respiratory rate. 25 or more breaths per minute if less than 50 years old, else 30 or more breaths per minute (1 point)
    • tachycardia of 125 or more bpm (1 point)
    • confusion, new onset (1 point)
    • poor oxygenation. Either of the following adds 2 points:
      • PaO2 < 70 mm Hg if less than 50 years old, else < 60 mm Hg
      • PaO2/FiO2 < 333 if less than 50 years old, else if less than 250.
    • arterial pH < 7.35 (2 points)
  • SCAP score is a new clinical prediction rule that may be better than the Pneumonia severity index and CURB-65[27]
  • PIRO is another clinical prediction rule specifically for severe pneumonia.[28]

C-reactive protein and procalcitonin

Several studies have compared the c-reactive protein and procalcitonin in the prognosis of pneumonia.[29][30][31][32] The procalcitonin may[33][32][30][31] or may not[29] be more accurate.

Prognosis at the time of discharge

Abnormal medical signs at discharge are associated with higher mortality with 30 days.[34]

Long term prognosis


For more information, see: Pneumococcal vaccine.

Clinical practice guidelines are available for administering vaccines for pneumonia at


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