Automatic Calibration; Functional Testers And Patient Simulators - Covidien Nellcor Operator's Manual

Theory of Operations
rial blood enters the vascular bed, and blood volume and light absorption
increase. During diastole, blood volume and light absorption reach their lowest
point. The monitoring system bases its SpO
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.

Automatic Calibration

10.3
Because light absorption by hemoglobin is wavelength dependent and
because the mean wavelength of LEDs varies, a monitoring system must know
the mean wavelength of the pulse oximetry sensor's red LED to accurately
measure SpO
During monitoring, the monitoring system's software selects coefficients that
are appropriate for the wavelength of that individual sensor's red LED; these
coefficients are then used to determine SpO
Additionally, to compensate for differences in tissue thickness, the light inten-
sity of the sensor's LEDs is adjusted automatically.

Note:
During certain automatic calibration functions, the monitoring system may briefly
display a flat line on the plethysmographic waveform. This is a normal operation and
does not require any user intervention.

Functional Testers and Patient Simulators

10.4
Some models of commercially available bench top functional testers and
patient simulators can be used to verify the proper functionality of Covidien
Nellcor™ monitoring systems, sensors, and cables. Reference the individual
testing device's operator's manual for the procedures specific to the model of
tester used. While such devices may be useful for verifying that the sensor,
cabling, and monitoring system are functional, they are incapable of providing
the data required to properly evaluate the accuracy of a system's SpO
surements.
Fully evaluating the accuracy of the SpO
mum, accommodating the wavelength characteristics of the sensor and repro-
ducing the complex optical interaction of the sensor and the patient's tissue.
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measurements on the difference
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measurements requires, at a mini-
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mea-
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Operator's Manual