Measured Versus Calculated Saturation - Nellcor N-180 Manual

N-180 Pulse Oximeter Service Manual

MEASURED VERSUS CALCULATED SATURATION

2-2
functional SpO =
2
100 - (% carboxyhemoglobin + % methemoglobin)
When saturation is calculated from a blood gas measurement of the partial
pressure of arterial oxygen (PaO
sured SpO . This is because the calculated saturation may not have been cor-
2
rected for the effects of variables that shift the relationship between PaO
and saturation (figure 2-1). The variables are: pH, temperature, the partial
pressure of arterial carbon dioxide (PaCO
2,3-DPG and fetal hemoglobin.
100
50
0
Figure 2-1:
fractional saturation
), the calculated value may differ from mea-
2
), and the concentrations of
2
}
pH
Temperature
PCO
2
2,3-DPG
}
pH
Temperature
PCO
2
2,3-DPG
50
PaO (mmHg)
2
Oxyhemoglobin Dissociation Curve
x 100
2
100