Nomogram for estimating standard PaO2 and alveolar-arterial gradient for oxygen during ventilation with room air

Standard arterial oxygen pressure is a calculated value which must be in arterial blood in the given lung function when all conditions of estimation are standard--PACO2 40 mm Hg, barometric pressure 760 mm Hg and respiratory exchange ratio 0.85. For practical purposes, a nomogram was constructed for estimating SPaO2 and arterial alveolar oxygen difference during breathing with room air. It will give us a possibility of comparing estimations made in different conditions. The mean error for AaDO2 is 0.4 mm Hg, which is acceptable for clinical purposes.