Mediana YM6000, Руководство по обслуживанию

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92 System Processing Description
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
SpO
2
sensor’s red LED to accurately measure SpO
2
. During monitoring, the
instrument’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 intensity of
the sensor’s LEDs is adjusted automatically.
Measured versus Calculated Saturation
The measured SpO
2
value from an oximeter may differ from the saturation value that
is calculated from a blood gas partial pressure of oxygen (PO2). This usually occurs
because the calculated saturation was not appropriately corrected for the effects of
variables that shift the relationship between PO2 and saturation: pH, temperature,
partial pressure of carbon dioxide (PCO2), 2, 3 ‐ DPG, and fetal hemoglobin.
100
50
0
50 100
S
a
tu
ratio
n
(%)
PO
2
(mmHg)
pH
Temperature
PCO2
2,3-DPG
Fetal Hb
pH
Temperature
PCO2
2,3-DPG
Figure 44. Oxyhemoglobin Dissociation Curve
Functional versus Fractional Saturation
This monitor 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 the 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 – (%carboxyhemoglobin + %methemoglobin)
SpO
2
Accuracy
The saturation (SpO
2
) accuracy specification and/or pulse rate (PR) performance were
analyzed by comparative oximetry performance (COPS) tests between YM6000 SpO
2
module and MP506 module with the same version of the oximetry algorithm from
Nellcor. This was to demonstrate that the performance of YM6000 SpO
2
module was
equivalent to that of MP506, which had been validated during both standard motion,
combined motion and cold ‐ induced peripheral vasoconstriction (low perfusion)
conditions by direct comparison to measurements of arterial oxygen saturation (SpO
2
)
obtained from arterial blood samples analyzed with Instrumentation Laboratory (IL)
CO ‐ Oximeters under Nellcor’s clinical protocol, Invasive Controlled Hypoxia Studies.
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