Circuit Analysis; Functional Overview - Mallinckrodt NELLCOR NPB-195 Service Manual

Section 11: Technical Supplement
11.2.2 Measured Versus Calculated Saturation

11.3 CIRCUIT ANALYSIS

11.4 FUNCTIONAL OVERVIEW

11-2
Consequently, before comparing NPB-195 measurements with those obtained by
an instrument that measures fractional saturation, measurements must be
converted as follows:
functional fractional
saturation = saturation x
When saturation is calculated from a blood gas measurement of the partial
pressure of arterial oxygen (PaO
NPB-195 SpO measurement. This is because the calculated saturation may not
2
have been corrected for the effects of variables that can shift the relationship
between PaO and saturation.
2
Figure 11-1 illustrates the effect that variations in pH, temperature, partial
pressure of carbon dioxide (PCO
hemoglobin may have on the oxyhemoglobin dissociation curve.
100
50
0
Figure 11-1: Oxyhemoglobin Dissociation Curve
The following paragraphs discuss the operation of each of the printed circuit
boards within the NPB-195 pulse oximeter. (Refer to the appropriate schematic
diagram at the end of this supplement, as necessary.)
The functional block diagram for the NPB-195 monitor is shown in Figure 11-2.
Most of the functions of the NPB-195 are performed on the UIF PCB. Functions
on the UIF PCB include the SpO
Other key components of the NPB-195 are the Power Entry Module (PEM),
Power Supply, and the LCD Display.
100-(% carboxyhemoglobin +%methemoglobin)
), the calculated value may differ from the
2
), and concentrations of 2,3-DPG and fetal
2
pH
Temperature
PCO
2
2,3-DPG
Fetal Hb
50
PO (mmHg)
2
module, 331 and 196 CPUs, and Memory.
2
100
pH
Temperature
PCO
2
2,3-DPG
100