Principles of Pulse Oximetry FIG. 1 Introduction
Pulse oximeters provide a spectrophotometric
assessment of functional arterial hemoglobin
oxigenation (SpO2). Pulse Oximetry is based
hemoglobin (Hb) and oxygenated hemoglobin
(HbO2) differ in their absorption of red and infrared light. Second, the volume of arterial
blood in tissue (and therefore light absorption by
the hemoglobin) changes during the pulse. A pulse oximeter passes red and infrared light into Photo Diodes
an arteriolar bed, measures changes in light
FIG. 2 How Pulse Oximeters Work Pulse oximeter sensors have red and infrared low voltage
light emitting diodes (LEDs) wich serve as light sources. The
emitted light is transmitted through the tissue, then detected by the photodetector and sent to the microprocessor of the
pulse oximeter (Figure 1) All constituents of the human
body, venous and arterial blood, and tissue absorb light (Figure 2). The pulsating of arterial blood results in changes Absorptionin the absorption to to added hemoglobin (Hb) and oxygenated hemoglobin (HbO2) in the path of the light.
Since HbO2 and Hb absorb light to varying degrees, this varying absorption is translated into plethysmographic waveforms at both red and infrared wavelengths (Figure 3).
The relationship of red and infrared plethysmographic signal amplitude can be directly related to arterial oxygen saturation. For example, when the plethysmographic amplitude ad 660nm and 910nm are equal and the ratio R/IR=1, the SpO2 is approximately 85% (Figure 4). FIG. 3 FIG. 4 Calibration of Pulse Oximeters
red and infrared wavelengths are tightly
Validation of Accuracy Mediaid Inc. pulse oximeters and sensors are tested for accuracy at the Anesthesia Research Laboratory at the University of California Medical Center in San Francisco. Validation consists of inducing hypoxemia in healthy subjects and comparing pulse oximeter readings (SpO2) using arterial samples. Figure 5 & 6 compare results from a typical Mediaid pulse oximeter and a Nellcor N-200. Both instruments show a small bias and similar distribution of sampling points. FIG. 5 FIG. 6 Linear Fit Linear Fit Summary of Fit Summary of Fit Clinical use of Pulse Oximetry Pulse oximeters may be used in a variety of situations that call for monitoring oxygenation and pulse rates. Pulse oximeters increase patient safety by alerting the hospital staff to the onset of h y p o x i a d u r i n g o r f o l l o w i n g s u r g e r y. O x i m e t e r s c o n f i r m a d e q u a t e o x y g e n a t i o n d u r i n g mechanical ventilation. Physician and dental offices utilize pulse oximetryfor spot checking respiratory status, as well as for monitoring during procedures that call for sedation. Truly, pulse oximetry is the fifth vital sign, essential to complete patient monitoring. 17517 Fabrica Way Suite H; Cerritos, CA 90703 USA P 714.367.2848 - F 714.367.2852 www.mediaidinc.com - [email protected]
Elizabeth Ann Becker Psychology, 220 Post Hall, Philadelphia, PA 19131 Tel:(610)660-2894 * Email: [email protected] ________________________________________________________ EDUCATION Ph.D. University of Wisconsin, Madison, WI Delta Certificate in Research, Teaching and Learning University of Wisconsin, Madison, WI B.A., June 2005. Lawrence University, Appleton, WI B.M.
WARFARIN NECROSIS TREATMENT with TRANSDERMAL CONTINUOUS OXYGEN THERAPY Stephanie Wu, DPM, MSc* and Donald Kemp, MD# * Associate Professor of Surgery, Dr. William M. Scholl College of Podiatric Medicine, Center for Lower Extremity Ambulatory Research, Chicago IL #Renfrew Victoria Hospital, Wound care Clinic, Renfrew, ON, Canada Warfarin (Coumadin; DuPont Pharma, Wilmington, DE) is a sy