Measurement and Control of Oxygen Saturation Levels in Neonates

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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
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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 Sep36(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, 231151-156
• Penn JS, et al. Arterial Oxygen Fluctuation and
  Retinopathy of Prematurity in Premature Infants

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Retinopathy of Prematurity

• Develops in over 20 of all very low birth weight
  premature infants (lt1500g).
• 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.

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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.

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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.

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Device Specifications

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

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IWB Diagram
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Work Completed

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

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Data Analysis

• PR not usefully correlated to SaO2.

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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.

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Current Work

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

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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.

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Control Parameters
Slight Adjustment Moderate Adjustment Great Adjustment
SaO2 slope 97-98 0.1 SaO2 slope gt98 0.1 80-90 gt 0.3 SaO2 slope gt94 gt0.2
94-95 -0.1 93-95 0 lt94 -0.1 94-95 -0.2 to -0.3 90-92 0 lt94 -0.2 to 0.3 lt95 lt-0.3 lt90 0
decrease
increase
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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
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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