CareFusion Alaris 8210 Series, Техническое и сервисное руководство

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4-2 Alaris
®
SpO
2
Modules
Technical Service Manual
PRINCIPLES OF OPERATION
By doing so, it focuses on light absorption
by pulsatile arterial blood, eliminating the
effects of nonpulsatile absorbers (such as,
venous blood, tissue and bone).
Because light absorption by hemoglobin
is wavelength dependent and the mean
wavelength of
LED
s varies, an oximeter
must know the mean wavelength of the
sensor’s red
LED
to accurately measure
S
p
O
2
. During monitoring, the instrument’s
software selects coefficients that are
appropriate for the wavelength of that
individual sensor’s red
LED
. Those
coefficients are then used to determine
S
p
O
2
.
To compensate for differences in tissue
thickness, the light intensity of the sensor’s
LED
s is adjusted automatically.
The
S
p
O
2
Module measures functional
saturation (oxygenated hemoglobin
expressed as a percentage of the
hemoglobin that can transport oxygen).
It does not detect significant amounts
of dysfunctional hemoglobin (such as,
carboxyhemoglobin or methemoglobin). In
contrast, hemoximeters (such as,
IL482
)
report fractional saturation (oxygenated
hemoglobin expressed as a percentage
of all measured hemoglobin, including
measured dysfunctional hemoglobin).
To compare functional saturation
measurements to those from an instrument
that measures fractional saturation,
fractional measurements must be converted
as follows:
functional saturation =
fractional saturation
100 - (%carboxyhemo %methemoglobin)
When saturation is calculated from a
blood gas partial pressure of oxygen
(
PO
2
), the calculated value may differ
from the
S
p
O
2
measurement of the
S
p
O
2
Module. This usually occurs because the
calculated saturation was not appropriately
corrected for the effects of variables that
shift the relationship between
PO
2
and
pH, temperature, the partial pressure
of carbon dioxide (
PCO
2
),
2
,
3
-
DPG
, and
fetal hemoglobin. To compare functional
saturation measurements to those from
an instrument that measures fractional
saturation, fractional measurements must be
converted as follows:
Oxyhemoglobin Dissociation Curve
4.4 8220 Series (Masimo Technology)
The
S
p
O
2
Module uses the Masimo
®
Signal Extraction Technology
®
(
SET
® ) to
decompose the red and infrared pulsatile
absorbance signal into an arterial signal plus
a noise component. Its value is used to find
the
S
p
O
2
saturation in an empirically derived
equation in the Masimo ®
SET ®
software. The
values in an internal look-up table are based
on human blood studies against a laboratory
co-oximeter on healthy adult volunteers in
induced hypoxia states during motion and
nonmotion conditions.
4.3 8210 series (Nellcor Technology)
(Continued)
x 100
­ pH
Temperature
PCO
2,3-DPG
Fetal Hb
2
¯
¯
¯
­
­
pH
Temperature
PCO
2,3-DPG
2
¯
¯
¯
100
50
0
50 100
PO (mmHg)
2
Saturation
(%)
¬
®