Pre-term infants -less than 37 weeks gestational age --usually had immature lungs' development, which resulted of poor oxygen saturation in red blood cells. A blood oxygen saturation level was measured in percent of Peripheral capillary oxygen saturation (SpO2). Medical doctors needed to order an oxygen therapy to maintain SpO2 of the infants between 90-95% while SpO2 of normal infants is 99-100%. Oxygen therapy was a procedure to stimulate lung functions and to maintain life. A registered nurse (RN) was responsible for adjusting levels of a fractional of inspired oxygen (FiO2) from 21% to 100% which was a proportion of oxygen gas provided to the infants periodically. In real situation, the adjustment could only be made as often as every 20-30 minutes, which might not be adequate. This caused ineffectiveness of an oxygen therapy and result in a longer hospital stay. A critical error of this adjustment could also cause blindness due to oxygen toxicity or dead due to hypoxia. This research was to develop a reliable embedded system that allowed automatically control of FiO2 according to an order of SpO2 by medical doctors. As a result, risks of oxygen toxicity and hypoxia could be minimized. The system also allowed medical doctors to use recorded data for future care planning in oxygen therapy.

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Premature babies of less than 37 weeks gestation might require oxygen therapy as an integral part of treatment and respiratory support. Because of their under-developed lungs, these socalled "preemies" might contract respiratory distress syndrome (RDS). To treat RDS, neonatal oxygen therapy is administered, where controlled oxygen gas is measured as a fraction of inspired oxygen (FiO 2 ). However, exposure to high oxygen content during long treatment could cause oxygen intoxication, which might cause permanent blindness due to retinopathy of prematurity (ROP), whereas insufficient oxygen exposure could cause severe hypoxia. A doctor would use oxygen saturation (SpO 2 ) data and prescribe a dose of FiO 2 to maintain SpO 2 within a suitable range. One objective is to maintain SpO 2 within the acceptable range using FiO 2 that is as low as possible. Adjustment of FiO 2 would normally be done by nurses every 15 to 30 minutes, which might not be safe in many situations. An error in FiO 2 adjustment during a manual procedure could be as large as +/-2.5%. This paper presents a system that can determine an FiO 2 value suitable to the current SpO 2 and that automatically adjusts FiO 2 with an error clearance of +/-0.25%.