SpiroSense: A Deskilled Spirometer for Low-Resource Settings

To better assess pulmonary function and inform patients with respiratory diseases and their providers of the necessity of treatment, we designed and prototyped a fluidic oscillation spirometer. The device inputs a patient’s exhaled air and outputs a unique air pattern that is sensed by two microphones and processed in a mobile device application. Our current prototype contains an obstacle inside that traps inputted exhaled air and creates two vortices that, due to changes in the pressure inside the device, cause airflow to switch rapidly between the device’s channels. Microphones, which pick up the out-of-phase pattern, are placed at the bottom of the device and powered by a battery. The audio signal is then processed to remove ambient noise and develop a flow vs. volume and a volume vs. time graph typical of spirometers. These graphs are then sent through telemedicine to pulmonologists in a remote location, who can examine the results and determine key pulmonary values such as FEV1 (Forced Expiratory Volume after 1 second), FEV6, and FVC (Forced Vital Capacity). With all its parts, the device falls under $25, requires minimal calibration, and has no moving parts, making it a low-cost, easy-to-use solution that approaches clinical standards. Tests planned include mechanical testing of the prototype to examine durability under varied conditions (drop testing, temperature/humidity testing, mucus testing), flow testing to determine linear correlation between frequency and flow, and accuracy testing to meet standards of spirometry set by the American Thoracic Society. In addition, improvements to the design are planned, such as designing a more sustainable method of powering the device (e.g. with solar power) and developing a real-time graph output for our mobile application.