At present the FDA have adopted the standards published in 2005 by the International Organization for Standardization (ISO), entitled ISO 9919. This is a set of technical specifications and guidelines for pulse oximeters, which share certain technical similarities to cerebral oximeters. In particular, Annex EE details the conduct of a controlled desaturation study for the calibration of pulse oximeter equipment. Specifically, the fraction of inspired oxygen delivered to test subjects is varied to achieve a series of targeted steady state saturation periods over a range of arterial oxygen saturation of 70 - 100%.