Philips M3015A - Page 52

Arterial Oxygen Saturation and Pleth (SpO
2
/PLETH) Measurement
36
Introduction to the Instrument
SpO
2
Algorithm Software on the System CPU
The SpO
2
Algorithm receives the demodulated and filtered red and infrared signals, and the
transducer coding information from the SpO
2
measurement frontend. The red and infra-red
wave is transformed into the frequency domain. An adaptive signal analysis of the frequency
information eliminates artifact and noise from the patient signal that is then used to calculate
the SpO
2
and Pulse numeric values.
The SpO
2
algorithm also detects non-pulsatile or noisy signals, and generates the appropriate
INOPs.
The wave is communicated to the Monitor (via the operating system), the SpO
2
and pulse
rate are communicated to the average calculation software, and INOPs are communicated to
the alarming software.
•The Average Calculation software receives the SpO
2
value for each beat from the SpO
2
algorithm, and calculates the average over the time interval configured by the user. This
value is communicated to the Monitor via the operating system, and to the Alarming
software.
•The SpO
2
Alarming software gets the average SpO
2
value from the average calculation
software and compares it against the limits set by the user.
This software also gets INOP messages from the SpO
2
algorithm software.
Alarms are communicated to the Monitor via the operating software.
•The SpO
2
Controller software receives the red and infrared signals, the transducer coding
information, the INOP and error messages and the status information from the SpO
2
CPU.
It receives the operating controls and the user settings from the Monitor. The user settings
are stored in non-volatile memory.
S
pO
2
C
PU
SpO
2
Algorithm
SpO
2
Control
Average
Calculation
SpO
2
Alarming
Pleth, Wave
SpO
2
Value
Pulse Rate
SpO
2
Alarms
SpO
2
Controls