Diaphragmatic excursion is the movement of the

thoracic diaphragm The thoracic diaphragm, or simply the diaphragm ( grc, διάφραγμα, diáphragma, partition), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the ...

during breathing. Normal diaphragmatic excursion should be 3–5 cm, but can be increased in well-conditioned persons to 7–8 cm. This measures the contraction of the diaphragm. It is performed by asking the patient to exhale and hold it. The doctor then percusses down their back in the intercostal margins (bone will be dull), starting below the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

, until sounds change from resonant to dull (lungs are resonant, solid organs should be dull). That is where the provider marks the spot. Then the patient takes a deep breath in and holds it as the provider percusses down again, marking the spot where the sound changes from resonant to dull again. Then the provider will measure the distance between the two spots. Repeat on the other side, is usually higher up on the right side. If it is less than 3–5 cm the patient may have a

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...

or a

pneumothorax A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve ...

in which a chest x-ray is diagnostic for either.

References

Respiratory physiology {{anatomy-stub