Introduction/Background Normal minute ventilation is from 4-7 L/min. Normal deadspace ventilation makes up 30% of that. The shape of the oxygen/hemoglobin curve starts to flatten at SpO2 of 90% – for this reason, PaO2 is a poor indicator of oxygen content; however, the A-a gradient is an excellent indicator of gas exchange. PAO2 = FiO2 […]