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  • Pneumonia: acute infection of pulmonary parenchyma
  • Route of entry: aspiration of oropharyngeal contents, inhalation of aerosolized particles, hematogenous spread from extrapulmonary site
  • Alteration in host defenses: ↓ alveolar macrophage function, ↓ mucociliary clearance

Table 26-1 Pneumonia Definitions (Am J Respir Crit Care Med 2005;171:338)

Diagnosis & Evaluation

(JAMA 1997;278:1440)

  • Required: acute infiltrate on chest radiography
  • Signs & symptoms of acute infection (↑ temp, ↑ WBCs), respiratory complaints (productive cough, dyspnea, pleuritic chest pain), systemic complaints (fatigue, anorexia, myalgias); auscultatory findings (dullness to percussion, Δ in breath sounds, wheezes, crackles, egophony)

Microbiological Diagnosis

  • Blood cultures (preantibiotics) = low positive yield (5–14%)—obtain if severe CAP/ICU admission & selected hospitalized patients (cavitary infiltrates, leukopenia, active EtOH abuse, severe liver disease, asplenia, pleural effusion)
  • Gram stain & sputum culture: variable yield, influenced by quality; in intubated patients: collect endotracheal aspirate
  • Urinary antigen tests → S. pneumoniae: sensitivity 50–80%, specificity >90% (Arch Intern Med 2011;171:166); L. pneumophila serogroup 1: sensitivity 70–90%, specificity 99%

Table 26-2 Prognostic Scoring Systems in CAP
Table 26-3 Criteria for Severe CAP

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