The development of a computer controlled system to simulate in rats, the rapid, frequent changes in oxygen experienced by preterm infants developing retinopathy of prematurity

Preterm infants that develop sever ROB have significantly more fluctuations in their transcutaneous oxygen compared to mild or no ROP, despite the fac t that all these infants are kept within clinically 'safe' limits. Current animal models do not accurately reflect this oxygen environment. Our aim wa s to custom build equipment capable of reproducing the transcutaneous oxyge n (TcPO2) levels recorded by infant cotside monitoring equipment in a rat m odel and assess the equipment's precision. Using previously published data for the rt that translates TcPO2 into the equivalent inspired FiO(2), a pro file was derived from a datalog of TcPO2 values recorded every minute for 1 4 days in an infant that had developed severe ROP. This profile was control led in the animal chamber by software algorithms which calculated the amoun t and type of gas to be injected to move oxygen to each new set-point CO2 r egulation within the chamber was also possible. Absolute differences betwee n the datalog set-points (n = 17,465) and the oxygen sensor were median 0.3 % oxygen. IQR 0.2-0.7% oxygen, with 95% of the differences <+/- 2% oxygen. The equipment is capable of reproducing the oxygen environment experienced by a preterm ventilated infant, giving a satisfactory level of precision.