The sniff test is sometimes used when paralysis or diaphragmatic paresis is suspected. Under fluoroscopy, the patient makes a rapid, brief, and strong inspiratory effort ("sniff"). This maneuver decreases the contribution of other breathing muscles (eg, intercostal muscles). The weakening of a hemidiaphragm can result in a decrease in the stroke of a cupola compared to that of the opposite side or in a paradoxical upward movement. An electromyogram of the diaphragm and phrenic nerve is sometimes performed, but the interpretation of this test requires considerable expertise and its diagnostic accuracy is uncertain.