. . "Current pulse oximeters employ two wavelengths to detect blood oxygenation, as discussed in this report:The pulse oximeter calculates the absorption based on two physical principles: the two wavelengths of light are absorbed differently by oxygenated hemoglobin and deoxygenated hemoglobin; and tissues such as bone and fat and venous blood absorb a relatively constant amount of light, producing a r" . . . .