Accuracy of the EvieMED Ring Pulse Oximeter in Profound Hypoxia

The goal of this study was to evaluate the accuracy of pulse oximeters over the range of 70-100% per the International Organization for Standardization (ISO) 80601-2-61:2019. Four test devices were placed on each subject on the left or right hand with two at the finger base and two at the fingertip. Motion equipment was used to control motion of the test devices. In addition, two test devices were placed on the contralateral hand on the base of a finger and also on the fingertip. Finally, a test wrist device was placed on either the left or right wrist. SpO2 measurements from these devices were compared to sampling of arterial blood during brief stable oxygen desaturation in healthy volunteers to evaluate the claimed range.

The study is an open enrollment, single-center, single blinded design using four test rings in motion compared to arterial blood gas measurements (SaO2) and to two commercially available hospital grade reference pulse oximeters (Masimo Radical-7 and Nellcor N-595) and at rest for two test rings and the test wrist device. To be included in the study, subjects had to meet all the inclusion criteria and not meet any of the exclusion criteria and to sign the written consent. Demographic data were obtained.

The investigational (7/subject) and reference devices were placed. A radial arterial cannula was placed in either the left or right wrist of each subject for arterial blood sampling and blood pressure monitoring. Each subject had two control blood samples taken at the beginning of each experiment, while breathing room air. Hands with test devices and reference pulse oximeters were maintained in motion or motionless on arm boards throughout the test. Hypoxemia was then induced to different and stable levels of oxyhemoglobin saturation (between 70-100%) by having subjects breathe mixtures of nitrogen, air, and carbon dioxide. The mixture of gases was controlled by the study physician by adjusting gas flows according to breath-by-breath estimates of oxygen saturation calculated from end-tidal partial pressure of oxygen (PO2) and partial pressure of carbon dioxide (PCO2). Each plateau level of oxyhemoglobin saturation was maintained for at least 30 seconds or until readings were stable. Two arterial blood samples were then obtained, approximately 30 seconds apart. Each stable plateau was maintained for at least 60 seconds with SpO2 fluctuating by less than 2-3%. All investigational, control, and reference data were recorded.