Physical Assessment of the Respiratory Tract III: Percussion

Position the patient upright and leaning forward with arms folded across the chest. This positioning optimizes access to the posterior thorax and helps relax the shoulder muscles. Starting percussion across the shoulder allows you to identify the zone of resonance approximately 5 centimeters above the lung apices, establishing a baseline for systematic downward assessment.

Begin percussion in the supraclavicular area, then progress downward intercostally, moving one space at a time. Percuss symmetric areas at 5 to 6 centimeter intervals, avoiding bony structures like ribs. Dullness noted to the left of the sternum between the third and fifth intercostal spaces is normal, as this marks the heart's location.

Ask the patient to inhale deeply and hold their breath while you percuss and mark the transition from resonance to dullness at maximum diaphragm descent. Then ask the patient to exhale fully and percuss again to locate the dullness level. The distance between these two marks indicates the extent of diaphragmatic motion and lung health.

Hyperresonance is a loud, lower-pitched sound heard over hyperinflated lungs, commonly found in conditions like chronic obstructive pulmonary disease and acute asthma. This abnormal sound indicates increased air content in lung tissue compared to normal resonance. Detecting hyperresonance helps identify respiratory system abnormal findings during physical assessment.

Dullness, a medium-pitched sound, indicates areas of mixed solid and lung tissue or fluid-filled pleural space. This sound may suggest partially consolidated lung tissue from pneumonia or other pathology. Dullness over the lung represents a departure from normal resonance and signals potential respiratory abnormalities requiring further investigation.

Percussion uses audible and tactile vibrations to distinguish among air, fluid, and solid material within the thorax. Different tissue densities produce characteristic sounds that reveal whether lung tissue is air-filled or replaced by fluid or consolidation. This non-invasive technique allows healthcare providers to identify potential abnormalities and assess the physiology of respiration functions the respiratory system.

Flat is a soft, high-pitched sound of short duration heard over very dense tissue where air is absent. This sound is normally found over the posterior chest below the diaphragm level. Flat sounds indicate solid tissue rather than air-filled lung, helping clinicians distinguish normal anatomical boundaries from pathological consolidation.