Quantitative analysis of the effect of fraction of inspired oxygen on peripheral oxygen saturation in healthy volunteers

BACKGROUND: The international organization for standardization (ISO) 80601-2-61 dictates that the accuracy of a pulse oximeter should be assessed by a controlled desaturation study. We aimed to characterize the relationship between the fraction of inspired oxygen (FiO(2)) and peripheral oxygen saturation (SpO(2)) using a turnover model by 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 breathing circuit 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 (SaO(2)). The study period consisted of two rounds of hypoxia and the volunteers were maintained in room air between each round. FiO(2) and SpO(2) were recorded continuously during the study period. A population pharmacodynamic analysis was performed with the NONMEM VII level 4 (ICON Development Solutions, Ellicott City, MD, USA). RESULTS: In total, 2899 SpO(2) data points obtained from 20 volunteers were used to determine the pharmacodynamic characteristics. The pharmacodynamic parameters were as follows: k(out) = 0.942 1/min, I(max) = 0.802, IC(50) = 85.3%, γ = 27.3. CONCLUSION: The changes in SpO(2) due to decreases in FiO(2) well explained by the turnover model with inhibitory function as a sigmoidal model.