The fingertip pulse oximeter is used to monitor the content of percutaneous blood oxygen saturation. Usually, the electrodes of the fingertip pulse oximeter are set on the index fingers of both upper limbs. It depends on whether the electrode of the fingertip pulse oximeter is clamp or the sheath of the fingertip pulse oximeter. The finger usually selected for clamp is with rich blood vessels、good circulation, and with easy clamps. In comparison, the index finger is large area, small volume, easy to clamp, and the blood flow on the clamp is rich, but some patients may not have good local circulation of the index finger, so they can choose other fingers.

In clinical practice, most of the fingertip pulse oximeter is placed on the finger of the hand of the upper limb, not on the toe, mainly considering that the finger circulation is better than the toe circulation, which can more accurately reflect the true content of oxygen in the pulse of the finger. In a word, which finger clamped depends on the size of the finger, the part of the blood circulation situation, and the type of finger pulse oxygen electrode. Usually choosing local circulation and moderate finger.