hypercapnea

Usage notes
The spellings "hypercapnea" and "hypocapnea" are occasionally seen in published medical articles (46 results and 5 results, respectively, in a PubMed search in 2021), but they are not entered in major dictionaries and are not tied to any etymology that involves the -pnea ("breathing") suffix. They are misspellings by writers who misunderstand that the words and  do not end in the same suffix that the words, , and  end in. In contrast, the -capn- syllable of the words comes from.