Thoracic outlet syndrome The Adson maneuver is used to determine a thoracic outlet compression. To conduct the Adson maneuver, a massage therapist places the clients arm into horizontal abduction on the affected side to a 45 degree angle while rotating their head toward the affected side. The massage therapist then instructs the client to extend their head which tightens the scalene muscles, which should magnify any preexisting compression of the subclavian artery and brachial plexus. The massage therapist palpates for a decrease in the radial pulse while the client takes deep breathes to exaggerate the compression.