Definition of acute respiratory failure,”1. Hypoxia PaO2 <60 mmHg2. Hypercapnia June 22, 2017 mfadmin Medicine Average Rating 0 out of 5 stars. 0 votes.You must log in to submit a review. Definition of acute respiratory failure,”1. Hypoxia PaO2 <60 mmHg2. Hypercapnia PCO2 >50 mmHg”