Covidien Nellcor GR101704, Руководство по обслуживанию

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Automatic Calibration
Service Manual 3-3
3.4
Automatic Calibration
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 sensor's red LED to accurately measure SpO
2
.
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
2
.
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.
3.5
Functional Testers and Patient Simulators
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
2
mea-
surements.
Fully evaluating the accuracy of the SpO
2
measurements requires, at a mini-
mum, accommodating the wavelength characteristics of the sensor and repro-
ducing the complex optical interaction of the sensor and the patient’s tissue.
These capabilities are beyond the scope of known bench top testers. SpO
2
measurement accuracy can only be evaluated in vivo by comparing monitoring
system readings with values traceable to SaO2 measurements obtained from
simultaneously sampled arterial blood using a laboratory CO-oximeter.
Many functional testers and patient simulators have been designed to inter-
face with the monitoring system's expected calibration curves and may be suit-
able for use with monitoring systems and/or sensors. Not all such devices,
however, are adapted for use with the OxiMax™ digital calibration system.