Functional Versus Fractional Saturation; Measured Versus Calculated Saturation - Nellcor OxiMax N-65 Operator's Manual

Additionally, to compensate for differences in tissue
thickness, the light intensity of the O
is adjusted automatically.

Functional versus Fractional Saturation

This pulse oximeter 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 hemoglobins.
To compare functional saturation measurements to those
from an instrument that measures fractional saturation,
fractional measurements must be converted as follows:
functional saturation =

Measured versus Calculated Saturation

When saturation is calculated from a blood gas partial
pressure of oxygen (PO
from the SpO
usually occurs because the calculated saturation was not
appropriately corrected for the effects of variables that
shift the relationship between PO
the partial pressure of carbon dioxide (PCO
and fetal hemoglobin. See Figure 12 on page 116.
O Max N-65 Operator's Manual
XI
Principles of Operation
M
XI
fractional saturation
100 - (%carboxyhemoglobin + %methemoglobin)
), the calculated value may differ
2
measurement of a pulse oximeter. This
2
and pH, temperature,
2
sensor's LEDs
AX
x 100
), 2,3-DPG,
2
115