A Simple and Sensitive Airflow Sensor for Sleep Studies

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Sleep disorders affect more than 40 million Americans. Excessive daytime sleepiness is a major health problem contributing to the increasing vehicular fatalities, and reduced work productivity. A polysomnograph (PSG) is the only effective way to diagnose sleep disorders. PSG relies on accurate detection of many physiological parameters. One of the important parameters to monitor is airflow. Currently, airflow is measured indirectly by sensing temperature fluctuations during breathing using thermistors. Many studies showed that sensing pressure, instead of temperature, is more sensitive; it reveals subtle but important clinical signals often missed by thermistors. Studies also showed that pressure-based airflow is correlated to actual airflow offering a better quantitative measure. So far, however, current pressure- based devices use nasal cannula for pressure reading. Nasal cannula are bulky, more intrusive to the patient, susceptible to condensation and can generate artifacts. Also, nasal cannula are more expensive on per use basis. We propose to develop a novel and simple pressure-based airflow sensor that will replace the cannula with a cable having sensitive micromachined (MEMS) pressure sensors integrated at the tip. The sensor elements will be proximal to the patient, which will allow better signal detection. Improved sensitivity will also eliminate the need for prongs making the device less intrusive than cannulae systems. The device will have multiple sensors offering separate nasal and oral airflow signals. We will capitalize on cost efficient and highly sensitive MEMS solutions already established for many applications to produce inexpensive and fast to market product. In Phase I, we will construct prototypes using existing sensors and evaluate them on the bench and on volunteers. In Phase II, final packaging of the sensor and associated electronics will be developed and tested, and regulatory approval obtained. PROPOSED COMMERCIAL APPLICATIONS: Provide a brief summary of the potential commercial applications of the research. We estimate the existing U.S. market size for this device at 15,000 sensors per year. The market has a huge growth potential. Out of the estimated 12 million people who suffer from OSA only 1 million patients are diagnosed. This leaves a large population in need of PSG and therefore creates a large potential demand for PSG accessories such as the proposed device. Other sleep segments are also witnessing growth due to the heightened appreciation of its implications. Overall, the sleep devices market is expected to grow at 17%.