Lab studies ■ Arteria| blood gas Pao2 levels should remain normal. Oxygen saturation is accurate only if directly measured but not if calculated from Pao2, which is common in many blood gas analyzers PCO, levels is normal or mildly decreased◼ Arterial blood gas – PaO2 levels should remain normal. Oxygen saturation is accurate only if directly measured but not if calculated from PaO2 , which is common in many blood gas analyzers. – PCO2 levels is normal or mildly decreased Lab Studies