Background: The international organization for standardization (ISO) 80601-2-61 dictates that the accuracy ofa pulse oximeter should be assessed by a controlled desaturation study. We aimed to characterize the relationshipbetween the fraction of inspired oxygen (FiO2) and peripheral oxygen saturation (SpO2) using a turnover modelby retrospectively analyzing the data obtained from previous controlled desaturation studies. Materials and Methods: Each volunteer was placed in a semi-Fowler’s position and connected to a breathingcircuit to administer the hypoxic gas mixture containing medical air, oxygen, nitrogen, and carbon dioxide.Volunteers were exposed to various levels of induced hypoxia over 70-100% arterial oxygen saturation (SaO2).The study period consisted of two rounds of hypoxia and the volunteers were maintained in room air betweeneach round. FiO2 and SpO2 were recorded continuously during the study period. A population pharmacodynamicanalysis was performed with the NONMEM VII level 4 (ICON Development Solutions, Ellicott City, MD,USA). Results: In total, 2899 SpO2 data points obtained from 20 volunteers were used to determine the pharmacodynamiccharacteristics. The pharmacodynamic parameters were as follows: kout = 0.942 1/min, Imax = 0.802, IC50 =85.3%, γ = 27.3. Conclusion The changes in SpO2 due to decreases in FiO2 well explained by the turnover model with inhibitoryfunction as a sigmoidal model.