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February 9, 1970

Control of Inspired Oxygen Concentration in Pressure Cycled Ventilators

Author Affiliations

From the Pulmonary Division of the Medical Service, Lemuel Shattuck Hospital; Massachusetts Department of Public Health; and the Department of Physiology, Harvard School of Public Health (Drs. Lewinsohn, Grassino, and Tyler), Boston.

JAMA. 1970;211(6):961-963. doi:10.1001/jama.1970.03170060025005

During ventilation with pressure cycled ventilators, we have found that it is possible to predict the inspired oxygen concentration from a standard graph when the ventilators are driven by compressed air and oxygen is added to the inspiratory line. We found no significant difference between the predicted and observed inspired oxygen concentrations when (1) expired minute ventilation was measured accurately, (2) the flowmeter for oxygen delivery had a scale from 0 to 6 liters per minute and was calibrated and used with a constant pressure delivery system, (3) there was no leakage of oxygen from the line, and (4) the mixing volume of the inspiratory line was large.