Sphygmomanometer Dynamic Pressure Measurement Using a Condenser Microphone

Area of Science:

• Biomedical Engineering
• Metrology
• Cardiovascular Health

Background:

• Hypertension diagnosis relies on accurate blood pressure (BP) measurement, but current errors of 3 mmHg are insufficient.
• Cardiovascular diseases are a leading cause of death and significant healthcare cost.
• Lack of dynamic pressure measurement standards hinders accurate BP assessment.

Purpose of the Study:

• To introduce a novel method for measuring air pressure within sphygmomanometer tubing during BP measurement.
• To develop and test a system utilizing a condenser microphone and radiofrequency (RF) modulation for pressure sensing.
• To establish traceability for BP measurement devices to acoustic standards.

Main Methods:

• Designed and constructed an RF modulation system to convert microphone capacitance changes into pressure signals.
• Tested the system using a low-frequency (LF) sound source, a BP simulator, and a piezoresistive pressure sensor.
• Conducted comprehensive tests to determine the uncertainty budget of the developed system.

Main Results:

• The RF microphone prototype demonstrated a functional frequency range of 0.5 Hz to 280 Hz.
• The system accurately measured pressure within the 0 to 300 mmHg range.
• The total expanded uncertainty (k=2, p=95.5%) of the RF microphone was determined to be 4.32 mmHg.

Conclusions:

• The proposed RF microphone method offers a potential solution for improving BP measurement accuracy.
• This technology could enable traceability of BP devices to established acoustic standards (IEC 61094-2).
• The system may contribute to the development of crucial dynamic BP measurement standards.