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The development of a computer controlled system to simulate in rats, the rapid, frequent changes in oxygen
1Edinburgh University, UK.
Insights
This study developed novel equipment to precisely replicate fluctuating transcutaneous oxygen (TcPO2) levels found in preterm infants with severe retinopathy of prematurity (ROP). This new animal model accurately mimics the critical oxygen environment, aiding ROP research.
Area of Science:
- Biomedical Engineering
- Neonatology
- Ophthalmology
Background:
- Preterm infants with severe retinopathy of prematurity (ROP) exhibit significant transcutaneous oxygen (TcPO2) fluctuations within clinically safe limits.
- Existing animal models fail to accurately replicate the dynamic oxygen environment experienced by these infants.
Purpose of the Study:
- To engineer and validate custom equipment for precisely controlling transcutaneous oxygen (TcPO2) levels in a rat model.
- To simulate the specific oxygen profiles observed in preterm infants who develop severe ROP.
Main Methods:
- Derived an inspired oxygen (FiO2) profile from infant TcPO2 datalogs (1-minute intervals over 14 days) for severe ROP cases.
- Utilized software algorithms to control gas injection within an animal chamber, replicating the derived TcPO2 profile.
- Enabled simultaneous carbon dioxide (CO2) regulation within the chamber.
Main Results:
- The custom equipment demonstrated high precision in reproducing target TcPO2 levels.
- Median absolute difference between set-points and sensor readings was 0.3% oxygen (IQR 0.2-0.7%).
- 95% of differences were within +/- 2% oxygen, indicating satisfactory accuracy.
Conclusions:
- The developed equipment successfully recreates the transcutaneous oxygen environment of ventilated preterm infants.
- This precise animal model offers a valuable tool for studying the mechanisms and potential treatments of ROP.
Abstract:
Preterm infants that develop severe ROP have significantly more fluctuations in their transcutaneous oxygen compared to mild or no ROP, despite the fact that all these infants are kept within clinically 'safe' limits. Current animal models do not accurately reflect this oxygen environment. Our aim was to custom build equipment capable of reproducing the transcutaneous oxygen (TcPO2) levels recorded by infant cotside monitoring equipment in a rat model and assess the equipment's precision. Using previously published data for the rat that translates TcPO2 into the equivalent inspired FiO2, a profile was derived from a datalog of TcPO2 values recorded every minute for 14 days in an infant that had developed severe ROP. This profile was controlled in the animal chamber by software algorithms which calculated the amount and type of gas to be injected to move oxygen to each new set-point. CO2 regulation within the chamber was also possible. Absolute differences between 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.