B: Theory of Operation Assemblies Descriptions
198
NBP Module
The NBP module handles the following functions:
• Inflation and deflation of the NBP cuff.
• Measurement of pressure in cuff.
• Detection of pressure waveform, and extraction of the systolic and diastolic values from that
waveform.
• Calculation of mean pressure from waveform, systolic, and diastolic data.
The NBP module communicate with the Processor PCA via a full duplex 9600 baud serial link and uses
5 V signaling.
SpO
2
PCA
The SpO
2
PCA serves as the interface to the SpO
2
sensor, including:
• Generation and control of voltages to drive the LEDs in the sensor.
• Receiving and processing signals from the SpO
2
sensor.
• Derivation of the SpO
2
waveform, SpO
2
value, and pulse rate.
• Providing the digital SpO
2
value to the Processor PCA.
The SpO
2
signal from the sensor is carried by the external SpO
2
cable to the SpO
2
port, and then to the
SpO
2
PCA. There it is analyzed to derive SpO
2
saturation level, pulse rate, and the waveform. This
information is then passed to the Processor PCA via an 18-pin connector (power for the SpO
2
PCA and
sensor is provided by the Processor PCA via the same 18-pin connector). The Processor PCA provides
the patient isolation and power supply for SpO
2
.
The Processor PCA is then responsible for:
• Formatting and presenting the O
2
saturation level, pulse rate and waveform to the display.
• Generating O
2
saturation level alarms.
• Reporting on the status of the sensor and its connections, and alerting the user to measurement
problems.
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