There’s a lot of improvising with the finger clip pulse oximetry when it’s difficult to get a good reading. Changing fingers is the obvious thing. Putting it on the ear lobe or auricle is often used. And although it looks silly, the nose can be a good place for the clip. Buccal readings, placing the clip in the lateral angle of the mouth opening, also works. Here’s one I hadn’t seen: MacGyvering a paediatric pulse ox taped to a pharyngeal airway.
The idea to tape a soft tape pulse ox to a pharygeal airway seems to come from case reports and a study taping pulse ox to LMAs. I’m not sure if these tricks measures pharyngeal or soft palate oxygenation, but both areas should be well perfused. I would think the pulse ox probe could also be places on the opposite side, to measure tongue oxygenation.
The case reports are interesting, as they get pulse trace and a saturation reading that compares well to the measured arterial saturation in patients where standard pulse oximetry didn’t give any reliable readings. Something to think about for monitoring severely shocked patients or patients with low output states.
Then the LMA versions. Based on the same principal. The case studies are on two shocked patients, while the study from Anesthesia and Analgesia is on healthy, well perfused subjects, but has more detail on the technique, as well as references to papers documenting different sites of obtaining pulse oximetry, for the ones with a special interest:
Successful pharyngeal pulse oximetry in low perfusion states, Can J Anesth, 2000