A non-invasive monitoring device for electro-mechanically monitoring arterial oxygen saturation. During the administration of conscious sedation it enables the operator to detect the early signs of hypoxia. Its use is mandatory for intravenous, oral, and intranasal conscious sedation. It consists of a probe with a light emitting diode and photosensor, a digital display, an audible alarm, and a battery backup. It may in addition provide a graphic display of the pulse pressure. It works on the principle that the oxygenated blood is a brighter colour of red than the deoxygenated blood.