Authors: Noor Mohammed Dr. M.Z. Hossain Dr. Sumon Saha

Indigenous Development of Auscultatory Method Based Semi Automatic Blood Pressure

Monitor

Authors:Noor Mohammed

Dr. M.Z. HossainDr. Sumon Saha

11th International Conference on Mechanical Engineering, 2015

Blood Pressure

• The term ‘blood pressure’ refers the arterial blood pressure exerted by the circulating blood upon the walls of blood vessels.

• In human body, arterial blood pressure is pulsatile in nature.

• During each heartbeat, blood pressure varies between maximum (systolic) and minimum(diastolic) value

11th International Conference on Mechanical Engineering, 2015

Blood Pressure

11th International Conference on Mechanical Engineering, 2015

Blood Pressure Measurement

• Place of measurement: Brachial artery at left upper arm.

• Measurement Methods: a) Invasive b) Non invasive

• Non Invasive Methods:Two popular techniques.

a) Auscultatory method b) Oscillometric method

11th International Conference on Mechanical Engineering, 2015

Auscultatory Method

• The auscultatory method involves the use of inflatable arm cuff with a stethoscope to listen the Korotkoff sound (a special tapping sound having five phases but not the sounds of heartbeat) during the blood pressure measurement.

11th International Conference on Mechanical Engineering, 2015

Auscultatory Method

11th International Conference on Mechanical Engineering, 2015

The Proposed BP Monitor

• The proposed method is the modified electronic version of the mechanical Auscultatory method.

• Device architecture: Divided into two partsa) Digital Stethoscope: To listen K-sound

b) Control and Processing Unit:

11th International Conference on Mechanical Engineering, 2015

Measurement Algorithm

The BP Monitor

Pumping Unit

Control and Processing

Unit

Digital Stethoscope

Power supply

11th International Conference on Mechanical Engineering, 2015

Stethoscope Performance Analysis

• Stethoscope circuit output:

Fig.1: Input recorded K- sound

Fig.2: Amplified and Filtered Signal

11th International Conference on Mechanical Engineering, 2015

Pressure Sensor Calibration

Calibration result: a) Best fitted correlation: E=0.012P+0.196b) Sensitivity, S= 89.44 mv/kPa

Fig.3: Calibration curve for the pressure sensor

11th International Conference on Mechanical Engineering, 2015

Sensor Model:MPXV 5050GP

Result Analysis

Fig.4: Comparison between the standard device value and the designed device value.

Higher error in systolic pressure reading relative to diastolic pressure readings.

11th International Conference on Mechanical Engineering, 2015

Limitations of the device

• Shows error in detecting the starting phase and the ending phase of K-sound during the measurement which can be evidenced from the errors in the measured pressure readings. This results from the less sensitivity of the microphone to the low sound pressure level(SPL).

• The sensor requires periodic calibration as the calibration changes after a certain period of time.

• Amplification of the noise hence deteriorates the signal to noise ratio(SNR).

11th International Conference on Mechanical Engineering, 2015

Recommendations & Future Scope

• A capacitive microphone can be used instead of condenser microphone for better pickup of the low decibel sounds.

• A higher order filter is required to improve the signal to noise ratio.

• Instead of using single ended amplifier, we can use differential amplifier to remove the common noise results from the 50Hz interference.

• A proper shielding is required for the digital stethoscope circuit.

11th International Conference on Mechanical Engineering, 2015

A better visualization of the whole method

Fig.5: The pressure graph and the K-sound graph during the measurement (captured using LabTutor data acquisition device).

Here Bp reading is 123/78 mm HgP.

11th International Conference on Mechanical Engineering, 2015

QUSETIONS?11th International Conference on Mechanical Engineering, 2015

THE END

THANKS