SURF Grant Proposal:
Medical Inequality, Pulse Oximeter Use in Dark-Skinned Individuals
Principle Investigator: Madison Rackear
The University of North Carolina at Chapel Hill
Office of Undergraduate Research at UNC
220 Graham Memorial, CB #2800, UNC-Chapel Hill
Chapel Hill, NC 27599-2800
Project Dates: May 9– July3, 2016
Funding Requested: $1700
Specific Aims:
The objective of this study is to discover if two types of pulse oximeters – those with transmission probes and those with reflectance probes – have significant differences in the accuracyof blood oxygen saturation readings for individuals with relatively dark skin. To accomplish this objective, I will use three methods to measure the oxygen saturation of two sample groups, one with dark skin and one with light skin. First, I will use arterial blood gas to determine a baseline SpO2 reading for each patient. Then I will use a transmission-probed oximeter followed by a reflectance-probed oximeter to obtain two additional SpO2 readings and compare these to the patient’s baseline to determine each oximeter’s accuracy.
Background and Significance:
Oximeters measure amount of red and infrared light in an area of pulsatile blood flow. Oximeters with transmission probes have the light emitter and sensor placed on opposite sides of some thin bodily tissue, while with reflectance probes have the light emitter and sensor placed on the same side of a flat bodily surface. These two general types of oximeters are used on different areas of the body (simply due to physical and spatial characteristics of different body parts), and measure oxygen saturation and pulse rate using slightly different forms of data.
Since both types of oximeters utilize light to determine O2 saturation and heart rate, anything that interferes with the transmission or absorbance of light can cause errors in these readings, including sufficiently dark skin pigmentation. Feiner (2007) and a team of researchers have demonstrated that individuals with darker skin are more likely to experience overestimations of oxyhemoglobin at oxygen saturation levels below 80%, butthere has been no investigation into the differences in accuracy of transmission-probed versus reflectance-probed oximeters.
My research will involve determining if either transmission-probed or reflectance-probed oximeters can provide more accurate readings in dark-skinned patients whose oxygen saturation level, as determined by arterial blood gas sampling, falls below 80%.
The significance of this research is self-evident. If one type of oximeter is found to be more accurate for use on dark-skinned patients than another, this could greatly improve health care standards among an already marginalized group of people, generally speaking. Additionally, pulse oximeters are cheap and easy to produce, and correspondingly are some of the only technology that developing countries currently have to detect certain diseases in their early stages. Therefore, this research could improve entire countries’ ability to detect and treat diseases among disproportionately large groups of dark-skinned patients.
Methods:
The first step of this study requires the creation of groups of patients at UNC Hospitals. Individuals will be selected based on the likelihood that their oxygen saturation will fall below 80%, and groups will be divided based on skin albedo (ie. skin pigmentation) as determined by a pigmentometer. Each individual will then receive three oxygen saturation tests: a baseline assessment using arterial blood gas, and two readings using transmission- and reflectance-probed pulse oximeters.
The second step of this study involves using statistical analysis to measure the proximity of an individual’s oximeter SpO2 results to said individual’s arterial blood gas value; that is, the accuracy of each pulse oximeter for each individual. I will then examine the data for accuracy across groups based on skin albedo. I will also determine new groups based on “true” oxygen saturation readings using each individual’s arterial blood gas sample, and will then compare accuracy data across these groups as well. This will allow me to determine statistically significant correlation among multiple variables: transmission-probed oximeter accuracy and skin pigmentation; reflectance-probed oximeter accuracy and skin pigmentation; transmission-probed oximeter accuracy and “true” SpO2 readings; and reflectance-probed oximeter accuracy and “true” SpO2 readings.
Timeline:
Week 1: May 9 – May 15Identify Patient Groups
Weeks 2-4: May 16 – June 5Collect Patient Data
Weeks 5-6: June 6 – June 19Data Analysis
Weeks7-8: June 20 – July 3Develop and Finalize Deliverables
Budget:
Oximetry Other Lab Equipment:$200
On-Campus Summer Housing:$1100
Patient Monetary Incentive:$400
Preliminary Work Experience:
As a senior in high school last year I was enrolled in AP Physics. My final project and presentation for the class focused on identifying the cause of technological issues that tattooed users had been experiencing with their Apple watches. During my research period I learned that the Apple watch utilizes pulse oximetry technology to measure a user’s heart rate when he or she is wearing the device. For my final thesis, I proposed an innovative design (featuring a reflectance-probed rather than a transmission-probed oximeter) that would eliminate problems in accuracy for Apple watch users with tattooed wrists. Thus, I have a good background in and experience with oximetry technology.
I also have first-hand experience working with patients. In the summer of 2015 I was a paid intern at High Quality Home Therapy, a physical therapy office located within a holistic health center. I received HIPPA training and gained experience shadowing physical and occupational therapists, neurologists, and research assistants. Each of these professionals saw a wide variety of cases each day, including patients with chronic headaches, sleep disorders, Alzheimer’s disease, and moderate physical trauma. Thus, I am qualified to handle the face-to-face interactions with patients associated with this study.
Dissemination Plan:
With the information obtained in this study, I plan on determining statistically significant differences in the accuracy of oxygen saturation readings of transmission-probed pulse oximeters and reflectance-probed pulse oximeters when used on dark-skinned patients. I will write and attempt to publish a paper concerning my findings.
Word Count:859
References:
Feiner, J.R., Severinghaus, J.W., Bickler, P.E. (2007). Dark skin decreases the accuracy of pulse oximeters at low oxygen saturation.Anesthesia & Analgesia, 105 (6), S18-23.
Korol, B., Bergfeld, G.R., Goldman, H., McLaughlin, J. (1977). Use of the pigmentometer, a new device for measuring skin albedo.The Pavlovian Journal of Biological Science, 12 (1), 19-31.
List of Scholarships and Honors:
- AP Scholar Award
- President’s Award for Educational Excellence
- Mount Holyoke College Book Award
- Yale Physics Olympics Honorable Mention
- National Merit Scholarship Committee Commended Student
- National Honor Society
- Math Honor Society