Anyone have a good resource for learning about possible sources of airway obstructions and normal values for those measurements? Also, any experience making these measurements yourself? I've got two cephs and on both I was able to measure 9-10mm minimum posterior airway space (also the minimum distance along the whole airway). Yet, two surgeons told me my space is 7mm-8mm. Am I supposed to subtract 1mm from each side or something?