Nonin CO-Pilot H500, Operator'S Manual

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55
Technical Information
Low Perfusion Accuracy Testing
This test uses an SpO
2
Simulator to provide a simulated pulse rate, with
adjustable amplitude settings at various SpO
2
levels for the oximeter to read.
The oximeter must maintain accuracy in accordance with ISO 80601-2-61 for
pulse rate and SpO
2
at the lowest obtainable pulse amplitude (0.3%
modulation).
rSO
2
Principles of Operation
Regional oximetry uses calculations based on the Beer-Lambert law or Beer’s
law, to determine cerebral and tissue oxygenation. The Beer-Lambert law
relates the absorption of light to the properties of the material through which the
light is traveling. The law states that there is a logarithmic relationship between
the concentration of compounds and the transmission of light through it. By
utilizing wavelengths of light that are absorbed by the compounds to be
measured, the concentration of the compounds can be determined. For cerebral
and tissue oximetry, the compounds of interest are hemoglobin, deoxygenated
hemoglobin, and tissue.
The oximetry sensors use a proprietary, patented arrangement of light emitters
(LEDs) and light detectors (photodiodes). This arrangement effectively provides
a “deep tissue” absorption measurement focused on the cerebrum. The
absorption measurement is largely unaffected by surface or near-surface
features, irregularities, or substances.
rSO
2
Accuracy Testing
At an independent research laboratory, rSO 2 accuracy testing was conducted
during induced hypoxia studies on healthy, non-smoking, light- to dark-skinned
subjects that were 18 years of age and older. The measured cerebral and tissue
hemoglobin saturation value (rSO
2 ) of the sensors was compared to arterial/
venous hemoglobin oxygen (SavO 2 ) value, determined from venous and arterial
blood samples. The model used for blood in the brain was 70% venous and 30%
arterial, which is applicable under normocapnic conditions. The venous blood
was drawn from the right jugular bulb. The accuracy of the sensors in
comparison to the blood gas analyzer samples measured over the rSO
2 range
of 45 – 100%. Accuracy data was calculated using the root-mean-squared
(A
rms value) for all subjects, per ISO 80601-2-61, Medical Electrical
Equipment—Particular requirements for basic safety and essential performance
of pulse oximeter equipment.