What are the typical physical exam findings in a patient with community-acquired pneumonia (CAP)?

Physical Examination Findings in Community-Acquired Pneumonia

A patient with community-acquired pneumonia typically presents with abnormal breath sounds and crackles on auscultation, accompanied by tachypnea and fever, though elderly patients may present atypically with only tachypnea and altered mental status without fever. 1

Classic Respiratory Findings

The respiratory examination reveals several key abnormalities:

• Crackles (rales) are the most common auscultatory finding and significantly increase the likelihood of pneumonia 1, 2
• Abnormal breath sounds including bronchial breathing or decreased breath sounds over the affected area 1, 2
• Egophony (E-to-A changes) is highly specific when present, with a positive likelihood ratio of 6.17, making it one of the most valuable physical exam findings 3
• Dullness to percussion over consolidated areas increases the probability of CAP with a positive likelihood ratio of 2.62 3

Vital Sign Abnormalities

Vital signs are critical for both diagnosis and severity assessment:

• Tachypnea (respiratory rate ≥30 breaths/minute in severe cases) is particularly important as it correlates with disease severity and is usually present even when other findings are absent 1, 2
• Fever (temperature >38°C) increases the likelihood of pneumonia with a positive likelihood ratio of 2.52, though its absence does not exclude the diagnosis 4, 3
• Tachycardia may be present and contributes to severity scoring 1
• Hypotension (systolic blood pressure <90 mmHg) indicates severe disease requiring aggressive management 1

Atypical Presentations in High-Risk Populations

Elderly patients (>65 years) frequently present without classic findings:

• Confusion or altered mental status may be the primary presenting symptom rather than respiratory complaints 1, 2
• Fever may be absent in older adults despite significant infection 1
• Tachypnea remains the most reliable finding even when other signs are absent 1
• Nonrespiratory symptoms including failure to thrive, worsening of chronic illness, or falls may be the only manifestations 1

Critical Diagnostic Pitfall

The absence of all vital sign abnormalities AND the absence of all abnormal lung examination findings substantially reduces the likelihood of pneumonia (negative likelihood ratio = 0.25), making further evaluation potentially unnecessary in low-risk patients 3, 5. However, if ANY vital sign is abnormal OR ANY lung examination finding is present, chest imaging should be obtained 5.

Overall Clinical Impression

The gestalt clinical impression of an experienced clinician that pneumonia is present has the highest diagnostic accuracy of any single assessment, with a positive likelihood ratio of 6.32 and an area under the ROC curve of 0.741 3. This emphasizes that pattern recognition combining multiple subtle findings often outperforms individual signs.

Severity Assessment Findings

Physical examination findings that indicate severe disease requiring hospitalization or ICU admission include:

• Respiratory distress with use of accessory muscles 1
• Cyanosis or inability to maintain oxygen saturation 1
• Signs of septic shock including hypotension, altered perfusion, and organ dysfunction 1
• Hypothermia (core temperature <36°C) paradoxically indicates severe disease 1