Calibration of a software module that computes SpO2 based on photoplethysmography (PPG) traces acquired by a reflectance-based pulse oximeter which can be placed on the index finger or the forehead.

The study is designed in accordance with Medical electrical equipment - Part 2-61: Particular requirements for basic safety and essential performance of pulse oximeter equipment (ISO 80601- 2-61:2011)

Inclusion Criteria:

• healthy subjects (ASA 1 and ASA 2) upon signing the informed consent. (ASA : american society of anesthesiologist's health score)

Exclusion Criteria:

• smokers or individuals exposed to high levels of carbon monoxide that result in elevated carboxyhaemoglobin levels.
• individuals subject to conditions that result in elevated levels of methaemoglobin.
• individuals with arterial cannulation or hypoxia at FiO2 = 0,21