Measurement and Control of Oxygen Saturation Levels in Neonates http://vubme.vuse.vanderbilt.edu/group13_00 Group Members Charlie Artime Kit Eward Suzanne Flanary Heather Sweeney Advisors John Penn, PhD Paul King, PhD

Background Studies published by our advisor, Dr. John Penn, and others concluded that variability in blood oxygen saturation levels, along with prolonged exposure to hypoxic conditions, increases the risk for retinopathy of prematurity.1,2,3 Penn JS, et al. “The range of PaO2 variation determines the severity of oxygen-induced retinopathy in newborn rats.” Invest. Ophthalmol. Vis. Sci. 1995 Sep;36(10):2063-70. Yoshihiro Saito, et al. “The Progression of retinopathy of prematurity and fluctuation in blood gas tension” Graefe's Archive for Clinical and Experimental Ophthalmology 1993, 231:151-156 Penn JS, et al. “Arterial Oxygen Fluctuation and Retinopathy of Prematurity in Premature Infants”

Retinopathy of Prematurity Develops in over 20% of all very low birth weight premature infants (<1500g). Characterized by abnormal blood vessel growth in the peripheral regions of the retina. Leads to detachment of the retina and, in severe cases, blindness (13% of all ROP cases). Leading cause of blindness in children.

How Our Device Will Help Currently, when neonates exhibit a significant change in blood oxygen saturation, adjustments to the fraction of oxygen in the inspired air must be made by hand. Typically, this results in an overshoot of the blood oxygen saturation of the neonate, and stabilization to the acceptable SaO2 range can take hours. This device can be used to help over 50,000 premature infants born each year at risk for developing ROP.

Project Definition Team project goal: design a computer- based integrator that recommends the proper adjustment in FiO2 to avoid fluctuation in SaO2. Ultimate goal: monitor and control, with minimum variation, the blood oxygen saturation level of neonates in order to avoid development of retinopathy.

Device Specifications Pulse Oximeter Heart Rate Oxygen Saturation Level (SaO2) Integrator Amount of O2 needed to adjust inspired air (FiO2) Oxygen Blender New FiO2

IWB Diagram

Work Completed Literature research Preliminary experimentation with the respiratory gas monitor Established liaison with NICU Data cable constructed Data collection/analysis Program outline

PR not usefully correlated to SaO2. Data Analysis PR not usefully correlated to SaO2.

Data Interpretations Physiological responses: relationship between heart rate, SaO2 , and respiratory rate. Respiratory rate information might make correlation between pulse rate and SaO2 more meaningful. Best option for this project using available data is to base control on SaO2 and change in SaO2.

Current Work Continued data analysis Literature research to determine whether there is a basic relationship between FiO2 and SaO2 Integrator program development Designsafe analysis

Program Components Calculate rate of change of SaO2 over 10 second intervals Control loops with output being a command to increase or decrease FiO2 , with relative amount indicated (more exact adjustments if satisfactory relationship between FiO2 and SaO2 can be determined) Control loops based on SaO2 and rate of change of SaO2 Choose a reasonable time delay for an adjustment in FiO2 to affect SaO2, and only allow a second adjustment to be made after this time.

Control Parameters Slight Adjustment Moderate Adjustment Great Adjustment SaO2 slope 97-98 0.1 SaO2 slope >98 0.1 80-90 >= 0.3 >94 >0.2 94-95 -0.1 93-95 0 <94 -0.1 94-95 -0.2 to -0.3 90-92 0 <94 -0.2 to –0.3 <95 <-0.3 <90 0 decrease increase

Future Work and Timeline Task March April Designsafe analysis * Determine relationship between FiO2 and SaO2 . *** Write program to interpret data and determine necessary adjustments Test and Debug

Acknowledgements Dr. Paul King and Dr. John Penn - project advisors Dr. Dan Lindstrom, Dr. Bill Walsh, Dr. Kendall Graham, and Dr. Jackie York -NICU Patrick Norris Dr. Richard Fries and Datex-Ohmeda