GE TruSat, Руководство пользователя

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Overview
1–3
The photodetector in the sensor converts the light intensity information into an
electronic signal. Since O
2
Hb and HHb absorb different amounts of the light that is
emitted from the oximeter sensor, different amounts of light reach the photodetector at
the selected wavelengths. The electronic signal varies according to which light source is
“on” (red or infrared) and the oxygenation of the arterial hemoglobin. This information is
used to calculate the relative percentage of O
2
Hb and HHb. The monitor processes the
electronic signal it receives from the photodetector. The SpO
2
and pulse rate
measurements are continuously calculated as a 12-second “moving” average.
Interfering substances
Increased patient carboxyhemoglobin may falsely increase SpO
2
readings in all brands
of pulse oximeters. Therefore, saturation readings may be higher for smokers, victims of
smoke inhalation, and patients with carbon monoxide (CO) intoxication. The level of
increase is approximately equal to the amount of carboxyhemoglobin present.
Methemoglobin from certain therapies, dyes that change arterial pigmentation, and
substances at the sensor site that contain dyes ( fingernail polish, for example) may also
cause erroneous readings.
Calibration
The TruSat pulse oximeter uses the functional calibration method. Functional saturation
is represented mathematically as the percentage of hemoglobin capable of carrying
oxygen that is carrying oxygen.
Functional SpO
2
=
( )
x 100 =
( )
x 100
The calculation of SpO
2
assumes 1.6% carboxyhemoglobin (COHb), 0.4%
methemoglobin (MetHb), and no interfering dyes. These values are based on the Datex-
Ohmeda Pulse Oximeter Empirical Calibration Study. Appreciable variation from these
values will influence SpO
2
accuracy.
NOTE: A hospital-grade CO-oximeter, which requires a sample of arterial blood and
typically uses four or more wavelengths of light, calculates carboxyhemoglobin (COHb)
and methemoglobin (MetHb) as well as O
2
Hb and HHb. CO-oximeter readings and pulse
oximeter readings will differ when COHb or MetHb is present.
O2Hb
O2Hb + HHb
O2Hb
HbTOTAL – COHb – MetHb