Allen Test Protocol
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This exam uses photoplehysmography to assess palmar arch patency (ie the adequacy of hand
perfusion from the radial and ulnar arteries)
It may be performed alone, with a segmental pressure examination, or with an UEA duplex exam.
It is often ordered prior to harvesting the radial artery for use as a dialysis graft or CABG.
Protocol
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Apply PPG sensor to each middle finger, with patient sitting comfortably on the bed.
Establish baseline waveforms that have uniform height.
Record the PPG trace before, during, and after the following compression techniques.
Palpate the radial and ulnar artery pulses. Then use your thumbs to compress both arteries
simultaneously.
o You should see abrupt cessation of PPG waveforms when both arteries are compressed.
Next, release compression of the radial artery, keeping the ulnar artery compressed.
o You are looking for the waveform to return with delivery of blood through the radial artery.
Compress both arteries again until the PPG waveform flat lines again.
Then, release compression of the ulnar artery, keeping the radial artery compressed.
o You are looking for the waveform to return with delivery of blood through the ulnar artery.
Results
o Normal study – Waveforms are normal at baseline, when neither vessel is compressed, and
when only one vessel is compressed. Waveforms should only be flattened when both
vessels are compressed.
o Abnormal study – Waveform flattens while one of the arteries is compressed on its own. If
it flattens while the ulnar artery is compressed but the radial artery is not, lack of hand
perfusion through the radial artery is indicated. If it flattens while the radial artery is
compressed but the ulnar artery is not, lack of hand perfusion through the ulnar artery is
indicated.
o An example of PPG waveforms recorded during an Allen test is shown below. Abnormal
responses are indicated by the arrows.
AK \backup\Vascular II\protocols