Physical Assessment of the Respiratory Tract IV: Auscultation

Normal breath sounds are categorized into three types based on pitch and location. Vesicular sounds are soft, low-pitched, and rustling, heard over most lung areas with inspiration three times longer than expiration. Bronchovesicular sounds are medium-pitched with equal inspiration and expiration duration. Bronchial sounds are loud, high-pitched, and resemble air through a hollow pipe, heard over the trachea with a gap between inspiration and expiration.

Begin auscultation at the lung apices and systematically move toward the bottom of the lungs while comparing both sides of the chest. Listen for at least one complete breath cycle at each placement, noting pitch, sound duration, and any abnormal sounds. This systematic approach ensures comprehensive assessment of airflow and potential obstructions throughout the respiratory tract.

Diminished or absent breath sounds may signal bronchial obstruction, pleural effusion, or tissue separation from the air passages. These findings suggest impaired airflow or sound transmission through the lungs. Identifying these abnormalities during auscultation helps clinicians detect serious respiratory conditions requiring further investigation and intervention.

Adventitious sounds are additional abnormal sounds indicating conditions affecting the bronchial tree and alveoli. Crackles are brief popping sounds during inspiration caused by fluid in airways, seen in pneumonia and heart failure. Wheezes are continuous sounds during expiration from narrowed airways in asthma or COPD. Rhonchi are low-pitched gurgling sounds from secretions in larger airways, while stridor is a high-pitched sound indicating upper respiratory tract narrowing requiring emergent attention.

In normal physiology, voice sounds are faint and indistinct when transmitted through healthy lung tissue. However, respiratory pathologies that increase lung density, such as pneumonia and pulmonary edema, alter voice sound transmission. Abnormal voice sounds include bronchophony (intense, clear vocal resonance), egophony (distorted voice sounds), and whispered pectoriloquy (clearly heard whispered sounds that should be inaudible).

Pleural friction rub is a low-pitched, grating sound heard during both inspiration and expiration, caused by inflamed pleural surfaces rubbing together. This abnormal sound is common in pleuritis, pulmonary embolism, and infections like pneumonia. Detecting pleural friction rub during auscultation indicates significant pleural inflammation requiring clinical attention and appropriate treatment.

Instructing the patient to take slow, deep breaths through their mouth ensures optimal airflow for accurate assessment. Proper breathing technique allows clinicians to hear breath sounds clearly and detect subtle abnormalities in airflow patterns. This patient cooperation is essential for reliable auscultation findings and accurate diagnosis of respiratory conditions.