How is diaphragmatic paralysis diagnosed ? who is at risk for it?

Sniff test: Easy to diagnose by ordering a "sniff rest" from radiology. Patients who have had prior thoracic surgery are at risk.

Sniff test: A radiologist does fluoroscopy and ask a person to sniff to see the initial downward movement of the diaphragm. Paralysis can be from lesion interrupting the phrenic nerve on its way from the neck down, or trauma or surgery (most common). There is the idiopathic one which can be from above anyway.