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Mild hypoxia ( SO2 < 90 % ) was the most common event ( 11 patients ) ; 3 patients ( 2 % ) presented transient hypoxia due to upper airway obstruction by probe introduction and 8 ( 5 . 8 % ) due to hypoxia caused by MZ use .
 hypoxia, hypoxia, airway obstruction, hypoxia, MZ
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 hypoxia, hypoxia, airway obstruction, hypoxia, MZ