(280g) Development of a Mobile CO2 Breath Sensor for Pulmonary Assessment

Obstructive pulmonary disease is an extremely common disease in the United States, yet lacks heavily in consumer-level medical devices. The measurement of Carbon Dioxide and volumes in breath give direct indicators of pulmonary obstruction, but require very rapid and non-intrusive analysis, which brings high-cost and user-unfriendly designs. We have developed an inexpensive and user friendly sensor which takes advantage of colorimetric carbon dioxide detection, the Confined Pitot Tube flow meter, and precision temperature compensation in a smartphone-based device. With the use of advanced regression methods, we have made a low-cost device that is capable of accurate analysis of characteristic parameters, such as End-Tidal carbon dioxide and volume, along discriminating minute details in carbon dioxide breathing waveforms. The colorimetric detection platform utilizes a highly porous substrate and ultrafast carbamate reaction system in order to provide CO₂ response times on the order of less than 100ms, with simple and robust transmission LED/photodiode electronics for signal acquisition. The Confined Pitot Tube flow meter allows for accurate flow measurements at a low back-pressure for optimal breath flow measurements using an inexpensive differential pressure sensor. Using a precision temperature model, we are able to compensate for large temperature swings which otherwise bring large deviations in sensor readings. Combining these technologies, we are able to demonstrate an inexpensive, robust, and user-friendly device that has a demonstrated capability to discriminate between varying degrees of lung obstruction, providing a new tool for monitoring chronic obstructive disease and a potentially very powerful tool for monitoring episodic pulmonary disorders, such as Asthma.