Novametrix Medical Systems OXYPLETH 520A, Service Manual

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5-Jun-01 Model 520A Service Manual
1
PRELIMINARY
1
Introduction
Purpose
1.1
This manual has been prepared for technicians servicing the Novametrix Model
520A Pulse Oximeter monitor. It presents technical information relating to the
monitor’s theory of operation, maintenance, calibration and repair. Refer to the
Pulse Oximeter Model 520A User’s Manual (Catalog Number 5693-23) for
additional information.
Technology Description
1.2
Pulse oximetry is a non-invasive method of monitoring the oxygen saturation of
arterial blood. Oxygen saturation monitoring is intended to be used in a variety of
clinical situations including, respiratory therapy, anesthesia, the intensive care unit
(ICU) and neonatal (NICU) and pediatric (PICU) intensive care units.
The Model 520A Pulse Oximeter provides reliable continuous measurement,
display, and alerts for oxygen saturation (SpO
2
) and pulse rate. The monitor can be
powered from its rechargeable internal battery or from the AC Mains.
The Model 520A utilizes sensors containing two light emitting diodes (LEDs) and
a photodiode. Each LED emits a specific wavelength of light (660 and 940
nanometers) through a pulsating vascular bed to the photodiode. Oxygen saturated
blood absorbs different amounts of light at each wavelength as compared to
unsaturated blood. Therefore, the amount of light absorbed by the blood in each
pulse can be used to calculate saturation.
The Model 520A is calibrated to display “functional” saturation. This differs from
the “fractional” saturation value displayed by most co-oximeters. Functional
saturation is defined as:
This can be considered to represent the amount of oxyhemoglobin as a percentage
of the hemoglobin that can be oxygenated. Dysfunctional hemoglobins (COHb and
METHb) are not included.
Functional Saturation =
HbO
2
100 - (COHb + METHb)
HbO
2
= Fractional Hemoglobin
COHb = Carboxyhemoglobin
METHb = Methemoglobin