Plots of alveolar PO2, hemoglobin saturation, and alveolar PCO2 as a function of alveolar ventilation in a normal subject at sea level (inspired oxygen pressure of 150 mm Hg). Plots of alveolar PO2, hemoglobin saturation, and alveolar PCO2 as a function of alveolar ventilation in a normal subject at sea level (inspired oxygen pressure of 150 mm Hg). The dashed line indicates normal values. Adapted from Reference 2. Neil R MacIntyre Respir Care 2014;59:1590-1596 (c) 2012 by Daedalus Enterprises, Inc.