Volunteers were monitored using end-tidal carbon dioxide partial pressure and fraction of inspired oxygen. Each volunteer was placed in a semi-Fowler's position and connected to a breathing circuit to administer the nitrogen-air-carbon dioxide mixtures. A nose clip was applied to prevent breathing of room air. For frequent blood sampling, an arterial cannula was placed in the radial artery of each volunteer. Pulse oximeter probes were simultaneously attached to each volunteer's fingers. Each volunteer was exposed to various levels of induced hypoxia from 70~100% of SaO2. Each plateau of oxygen saturation was maintained for at least 30 s until stabilization, after which 1 ml of arterial blood was drawn into a heparinized syringe. The study period consisted of two rounds of hypoxia, and the volunteers were maintained on room air between each round. SaO2 measurements using a CO-oximeter were used as a reference for the SpO2 accuracy.

Volunteers were monitored using end-tidal carbon dioxide partial pressure and fraction of inspired oxygen. Each volunteer was placed in a semi-Fowler's position and connected to a breathing circuit to administer the nitrogen-air-carbon dioxide mixtures. A nose clip was applied to prevent breathing of room air. For frequent blood sampling, an arterial cannula was placed in the radial artery of each volunteer. Pulse oximeter probes were simultaneously attached to each volunteer's fingers. Each volunteer was exposed to various levels of induced hypoxia from 70~100% of SaO2. Each plateau of oxygen saturation was maintained for at least 30 s until stabilization, after which 1 ml of arterial blood was drawn into a heparinized syringe. The study period consisted of two rounds of hypoxia, and the volunteers were maintained on room air between each round. SaO2 measurements using a CO-oximeter were used as a reference for the SpO2 accuracy.

The root-mean-square of the difference between the observed pulse oximetry value (SpO2) and the carbon monoxide-oxygenometer arterial blood reference value (SRi) within the range of 70-100% of arterial oxygen saturation