Fig. 2

Method for inducing desaturation and resaturation in healthy subjects. Desaturation was induced by adjusting the gas mixture of oxygen and nitrogen through a facemask in healthy subjects. (1) Subjects breathed room air until a stable baseline rSO₂ was achieved. (2–3) FiO₂ was titrated down slowly to achieve a stable plateau SpO₂ of approximately 70%. (4–5) FiO₂ was increased instantly to 1 to achieve a stable FeO₂ of 0.85. Steps (6) through (9) represent a second desaturation and resaturation cycle, after which (10) the subjects were returned to room air