tokens: The model therefore predicts that 1 ) on - line calculation of airway dead space and end - expired lung volume can be made by the addition of an oxygen sine - wave perturbation component to the mean FIO2 ; and ( 2 ) QS / QT can be measured from the resultant oxygen perturbation sine - wave amplitudes in the expired gas and in arterial and mixed - venous blood and is independent of the mean blood oxygen partial pressure and oxyhemoglobin saturation values .