(413d) A Portable Ultra-Fast Response Gas Detector for Breath-By-Breath Measurement of Carbon Dioxide

The analysis of breath CO₂ provides valuable information of pulmonary and cardiovascular functions, and plays a crucial role in monitoring patients with respiratory problems. Most of the existing breath CO₂ monitors not only are expensive and bulky, but also require substantial training for correct operation and maintenance. In this work, we developed a low cost and high performance breath CO₂ analyzer for the personal use at home. This portable analyzer features an accurate colorimetric CO₂ sensor that can analyze end tidal CO₂ concentration in real time and a pressure transducer that can measure the tidal volume and breath frequency. The reversible colorimetric sensor changes color immediately (response time < 200 ms) from blue to yellow once exposed to expired air. The concentration of breath CO₂ can be determined by the color change of sensor cartridge. The pressure transducer measures expiratory flow rate, which can be used to determine the tidal volume and respiratory frequency through an intelligent signal-processing algorithm. The device was validated using a commercial capnometer based on infrared techniques and a good correlation was observed between the commercial CO₂ analyzer and our sensor. In addition, the device can be wirelessly paired to the users’ cell-phone, computer, notebook, netbook or tabloid, providing a seamless information gateway between patients and medical care professionals and maximizing its benefit to the large and growing chronic respiratory disease patients.