Controlled oxygen therapy at 60% concentration. Why and how

In a number of circumstances pulmonary function is so disturbed that inspired oxygen concentrations of about 60% are needed to combat arterial hypoxaemia. Rational therapy requires that the inspired concentration be controlled and not vary with the patient's breathing. An exploration of the interaction between gas flow, ventilation, breathing pattern, and mask volume shows that a mask of 300 ml volume supplied with a flow of 30 1/min (15 1 O2, 15 1 air) can meet the need.