Definition: Percussion of the thorax attempts to examine the quality of intra-thoracic contents by evaluating the quality of sounds produced.
Test procedure: There are two methods; direct and indirect. Over a bony prominence such as the clavicles percussion can be done directly. Over soft tissues firmly place your middle finger of your non dominant hand in the intercostal spaces along the ribs. Percuss with your dominant middle or index finger or with both fingers the finger which is on the chest wall. Perform percussion with a hammer-like action coming from your wrist. Start from above the clavicles, then on the clavicles and progress until the costal margin by percussing at least at 5 different positions. Repeat on the back with the patient moving his scapulae out of the way by pulling their shoulders forward. On the back percuss about 5 positions. Repeat this in at the mid-axillary line 2-3 positions. To expose the sides ask the patient to place their arms over their head or neck.
Test findings: Normal lung tissue will produce resonant sound, fluid dull sounds and solid masses stony dull. Take into account the physiological dull sounds produced when percussing over the heart and liver.
Considerations: Percussion of the lungs will be affected by: Increase in the thoracic volume as in barrel chest and by excessive obesity. In these situations more assertive percussion may be necessary. Between a full inhalation and a full exhalation the diaphragm will descend and ascend by about 5-6 cm. (see diaphragmatic expansion).