Masters Thesis Defense - Respiratory Airflow Sensor
Date: May 9, 2005
Time: 9:00 AM
Location: Baiada Center, Room: Wedge Room
Ryszard Lec, Ph.D. and Dov Jaron, Ph.D.
Constant monitoring of respiratory function is very useful for doctors during and after anesthesia and often required especially for infants, children and adults with respiratory disorders. Information about respiration is needed for infants and children with chronic respiratory failure, which requires long-term use of a tracheostomy tube and mechanical ventilation.
Currently no device can provide real time information based on direct measurement of air flowing into and out of lungs. Even respirators used in hospitals do not measure actual air flow during expiration, instead they often measure pressure drops. Existing airflow sensors, based on thermal, mechanical and ultrasonic technologies, are large in size, expensive, and often slow and unreliable.
This thesis presents an effort to design a prototype of a novel sensor, which utilizes a highly sensitive piezoelectric resonator structure for measuring of gas flow. Active mode of operation was be utilized, in which the piezoelectric resonator structure excited to high frequency oscillation produces the change in the resonant frequency proportional to airflow; this mode of operation features high accuracy and reliability.
The sensor was tested over a broad range of operating conditions. The sensor is able to monitor respiratory rate of 10-50 breaths/min and tidal volumes of 20-700cm3 that cover a physiological range of both child and adult respiratory airflow. Also, the sensor is capable of determining the direction of airflow in contrast to existing technologies, which often provide only the magnitude of airflow. In addition, monitoring of the breathing pattern is taken into consideration as a future enhancement. It is known that the breathing pattern is related to different respiratory conditions; therefore monitoring the pattern could allow detection of various pulmonary disorders.
Piezoelectric sensors are miniature, rugged, stable and can be manufactured with integrated circuit technology, which results in low cost in mass production. They can be easily integrated with a wireless system to provide remote monitoring of airflow, which is very important for continuous monitoring infants and small children, especially those free to walk around. The piezoelectric airflow sensor technology is very promising and may revolutionize airflow measurement in both medical and as well as industrial applications.
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