Diaphragmatic Excursion

The technique of percussion is used to determine the degree to which the diaphragm moves during inhalation and exhalation, referred to as diaphragmatic excursion.
When the diaphragm is relaxed at the end of exhalation it forms a dome and sits higher in the thorax, usually around the level of the thoracic vertebra.
When a person inhales, the diaphragm contracts, flattens, and moves lower in the thorax, usually around the thoracic vertebra.
The percussion sound heard over expanded lung tissue will yield a resonant sound in the healthy lung and dull sound over solid tissue. Thus, resonance will be heard at a lower level of the thorax when the patient inhales and at a higher level when they exhale.
When percussing for diaphragmatic excursion have the patient sit with the back of their thorax exposed. Have them arch their shoulders forward to help expand the intercostal spaces.
Have the patient take a deep breath, exhale, and hold it. Place the percussing finger at the intercostal space at the midscapular line near the lower end of the scapula.
Begin percussing. Continue moving down the same side of the thorax between the intercostals spaces until you notice the sound change from resonant to dull. Mark the spot where the sound changed to dull with a pen. Instruct the patient to breath.
Then have the patient inhale and hold their breath. Continue percussing from the spot you mark as dull. That spot should now sound resonant because the diaphragm is flattened and lower in the thorax during inhalation. Continue percussing between each intercostal space until you notice the sound change again from resonant to dull. Mark this spot with a pen.
Repeat the entire procedure on the other side of the thorax.
When the right and left sides have been tested, use a ruler to measure the distance between the pen marks on each side. The distance is the diaphragmatic excursion and is normally 3-5 cm.