One suffix — -pnea — plus a handful of prefixes of rate and amount generates almost everything you will ever write about a patient’s breathing. Snap the parts together and watch the combining vowel survive before a consonant and vanish before a vowel. Then switch to Plurals, because respiratory anatomy is a graveyard of irregular ones and charting demands you get them right.
Prefix optional · rate, amount, position
Combining form optional · the root idea
Second combining form optional · for two-root terms
Suffix required · it decides the vowel
Pick a singular every one appears in ordinary respiratory documentation