Allen test performed with pulse oximeter

A modified Allen test can be performed using a pulse oximetry probe, which should be placed on the patient's index finger. The ulnar and radial arteries are compressed. The loss of the pulse oximeter waveform is an objective measure that compression is adequate. A return of a pulse wave following the release of the ulnar artery indicates a negative test (ie, a patent ulnar artery). The test can then be repeated by compressing the ulnar artery again and then releasing the radial artery to demonstrate its patency.