Nihon Kohden Corporation is a Tokyo-based leading manufacturer, developer and distributor of medical electronic equipment, which include EEGs, EMG measuring systems, ECGs, patient monitors, Invasive and Non-Invasive Ventilators, Defibrillators, AEDs and clinical information systems, with subsidiaries in the U.S., Europe and Asia. The company's products are now used in more than 120 countries, and it is the largest supplier of EEG products worldwide. In 1972, Takuo Aoyagi, a researcher at the company, invented and patented the basic principles of pulse oximetry. Two years later he developed the world's first pulse oximeter, the OLV-5100, which has helped improve patient safety during anaesthesia. Wikipedia