Nellcor OxiMax N-550, Руководство оператора

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Principles of Operation
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difference between 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.
There are various matrixes within the OxiSmart XL algorithm. Some
are used to assess the severity of conditions presented to the N
- 550 in
measuring SpO
2
and pulse rate. These individual matrixes or
combinations of these matrixes are used to drive the LED indicators
on the N
- 550 front panel.
During challenging measurement conditions, which could be caused
by low perfusion, motion, external interference, like ambient light, or
a combination of these, the OxiSmart XL algorithm automatically
extends the amount of data required for measuring SpO
2
and pulse
rate. If the resulting dynamic averaging time exceeds 20 seconds, the
pulse search indicator is lit solid and SpO
2
and pulse rate will
continue to be updated every second. As these conditions become
even more challenging, the amount of data required continues to
extend. If the dynamic averaging time reaches 40 seconds, the pulse
search indicator begins flashing, the SpO
2
and pulse rate displays
flash zero indicating a loss - of - pulse condition.
Automatic Calibration
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 sensor's red LED to accurately
measure SpO
2
. During manufacturing, the mean wavelength of the
red LED is encoded in an integrated circuit in the sensor. The
wavelength range of the light emitted is within the range of 250 nm to
1,000 nm with the energy not exceeding 10 mW.
During monitoring, the instrument's software reads this resistor value
and selects coefficients that are appropriate for the wavelength of that
individual sensor's red LED; these coefficients are then used to
determine SpO
2
. This resistor value is read when the monitor is
turned on, periodically thereafter, and each time a new sensor is
connected.
Additionally, to compensate for differences in tissue thickness, the
light intensity of the sensor's LEDs is adjusted automatically.