A pulse oximeter is used for continuous monitoring of peripheral oxygen saturation (SpO2) and plays an important role in the early detection of hypoxia, guiding the titration of supplemental oxygen, and reducing the need for blood gas analysis. Therefore, the SpO2 accuracy of a pulse oximeter should be validated for patient safety. The objective of this study is to evaluate whether the CART-I pulse oximeter with a ring-type wearable PPG sensor (Sky Labs Inc., Seoul, Korea) provides clinically reliable SpO2 readings over the range of 70-100% SaO2, during steady-state, non-motion conditions.

Inclusion Criteria:

• Healthy adults aged 20-50 years2
• COHb < 3 %
• MetHb < 2 %
• ctHb > 10 g/dl
• Non-smoker
• An individual deemed fit by the investigators to be included in the clinical trial

Exclusion Criteria:

• History of respiratory disease
• History of cardiovascular disease
• Smoker
• Pregnant
• History of fainting
• History of diabetes
• Obesity (defined as BMI > 30 kg/m2)
• Allen's test positive (poor collateral blood supply of hand)
• An individual who is judged to be difficult for the collection of normal PPG signals because CART-I is loose when being worn on fingers other than the thumb and little finger