Low blood oxygen, or hypoxemia, is a life-threatening complication of many illnesses such as pneumonia and malaria, as well as preterm birth, surgery, labor and delivery, and other conditions. Hypoxemia contributes to over a million preventable deaths in low-income countries every year. Providing concentrated medical oxygen, known as oxygen therapy, can prevent many of these deaths. But treatment in low-income countries is often limited by poor hypoxemia diagnosis and unreliable oxygen supplies, due to high prices and weak maintenance systems. Pulse oximeters, simple handheld devices that measure blood oxygen saturation to identify which patients need oxygen, aren’t available in over 90 percent of facilities, and fewer than half of all facilities have access to oxygen.