Respiratory parameter measurement and analysis using differential pressure sensor

Force Vital Capacity (FVC) of lungs and respiration rate is measured using single differential pressure sensor. MPXV7025DP pressure sensor of range -3.6 psi to +3.6 psi(-25Kpa to +25Kpa) is selected. Sensor gives output proportional to differential pressure in terms of voltage. Sensor is connected to MLT1000L flow head using plastic tubing. MLT1000L flow head functions as a pneumotachometer and gives output signal proportional to airflow during breathing. Signal conditioning is done using dual supply AD623 instrumentation amplifier. Air is blown into the MLT1000L flow head through mouthpiece. HEPA filter is attached to disposable mouthpiece. It will reduce the infection risk while breathing into the system. In this system, sensor is calibrated for different flow rates. AM4201 digital anemometer is used in calibration process to measure the velocity of the air flow in terms of m/sec. Simultaneously, sensor output is measured in terms of voltage. In order to show the effectiveness of the proposed system a real life experimentation is carried out on the five male and five female subjects to demonstrate the Force Vital Capacity (FVC) and Respiration rate (RR). Forced vital capacity (FVC) for female subject is in between 3 litres to 5 litres and for male subject it is in between 4 litres to 6 litres. From measurement it is observed that male subjects are having more force vital capacity than female subjects. Respiration rate is measured for both male and female subjects and it is in between 12 to 14 breaths per minute.