Breath Sounds of Pleural Effusion

Physical Examination Findings

Decreased or absent breath sounds are the hallmark auscultatory finding in pleural effusion, with the degree of reduction proportional to the size of the effusion 2, 3
Percussion reveals dullness over the fluid-filled area 3, 4
Tactile fremitus is typically decreased or absent over the effusion 3
Egophony (E to A change) and increased vocal resonance may be heard at the upper border of the effusion 5, 3
Contralateral tracheal deviation may occur with large effusions due to mediastinal shift 1, 6

Simple parapneumonic effusions may have preserved breath sounds if the effusion is small 5, 7
Complete absence of breath sounds is common in complicated parapneumonic effusion/empyema 7
Malignant pleural effusions typically present with progressive diminishment of breath sounds as the effusion accumulates 1, 6

The extent of decreased breath sounds generally correlates with the size of the effusion seen on imaging 3, 8
Moderate to large effusions (500-2,000 ml) typically produce clearly detectable auscultatory changes 1, 6
Small effusions (<500 ml) may have subtle or no auscultatory findings, requiring imaging for detection 1, 6
Loculated effusions may produce patchy areas of decreased breath sounds 7, 9

Breath sounds may be transmitted through fluid, especially in thin patients, leading to false-negative auscultatory findings 3
Underlying lung consolidation can modify the auscultatory findings of pleural effusion 5, 3
Bilateral effusions with normal heart size should raise suspicion for malignancy rather than heart failure 2, 6
Absent breath sounds with hyperresonance suggests pneumothorax, not pleural effusion 3, 9
Auscultation alone is insufficient for diagnosis - always confirm with imaging (chest radiograph, ultrasound, or CT) 3, 8
Ultrasound is more sensitive than auscultation for detecting small pleural effusions 8, 9

The fluid in the pleural space creates a barrier to sound transmission from the lung to the chest wall 1, 3
The decreased lung volume due to compression by the effusion contributes to reduced breath sounds 1, 6
The pathogenesis of dyspnea in pleural effusion involves decreased chest wall compliance, mediastinal shift, decreased ipsilateral lung volume, and reflex stimulation from the lungs and chest wall 1, 6