Automatic Calibration - Covidien Nellcor OxiMax N-600x Operator's Manual

Principles of Operation

Automatic Calibration

162
Because oxyhemoglobin and deoxyhemoglobin differ in light
absorption, the amount of red and infrared light absorbed by
blood is related to hemoglobin oxygen saturation.
The monitor uses the pulsatile nature of arterial flow to identify
the oxygen saturation of arterial hemoglobin. During systole, a
new pulse of arterial blood enters the vascular bed, and blood
volume and light absorption increase. During diastole, blood
volume and light absorption reach their lowest point. The pulse
oximeter bases its SpO
2
maximum and minimum absorption (measurements at systole
and diastole). By doing so, it focuses on light absorption by
pulsatile arterial blood, eliminating the effects of nonpulsatile
absorbers such as tissue, bone, and venous blood.
Because light absorption by hemoglobin is wavelength
dependent and because the mean wavelength of LEDs varies, an
oximeter must know the mean wavelength of the O
sensor's red LED to accurately measure SpO
During monitoring, the instrument's software selects coefficients
that are appropriate for the wavelength of that individual O
sensor's red LED; these coefficients are then used to determine
SpO .
2
Additionally, to compensate for differences in tissue thickness,
the light intensity of the O
automatically.
Note: During certain automatic calibration functions, the N-600x
may briefly display a flat line on the plethysmographic waveform.
This is a normal operation and does not require any user
intervention.
measurements on the difference between
.
2
M sensor's LEDs is adjusted
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N-600x Operator's Manual
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