What is the normal finding when percussing the posterior lung fields?

Resonance is the normal percussion sound heard over healthy lung tissue. It is characterized by a low-pitched, hollow sound that indicates the presence of air-filled alveoli within the lungs. Rationale: Percussion is used during respiratory assessment to evaluate the density of underlying tissues. Normal lung tissue contains a large amount of air, which produces a resonant sound when percussed. This finding is expected over the majority of the posterior lung fields in a healthy individual. Deviations from resonance can indicate underlying pathology. For example, dullness may suggest fluid accumulation (such as in pneumonia or pleural effusion) or solid tissue (such as a tumor), while hyperresonance may indicate increased air trapping as seen in conditions like emphysema or pneumothorax. The posterior lung fields are particularly important to assess because fluid or consolidation often accumulates in the lower lobes due to gravity, especially when a client is in an upright or semi-recumbent position. The presence of resonance during percussion of the posterior lung fields indicates normal, air-filled lung tissue without evidence of consolidation, fluid, or excessive air trapping.