Smart phone-based peak expiratory flow meter

The design and performance of a smart-phone-based device, called AudioFlow, that measures and records peak expiratory flow (PEF) is presented. PEF is a measure used by asthma sufferers to monitor their asthma conditions. The device is comprised of a custom 3D printed airtube and a minimal number of electronic components that communicate with a smartphone via a custom app. A pressure-dependent frequency signal generated when the user blows into the tube is sent to a smartphone app via the headphone jack. The custom designed app reads the signal and converts the frequency to a flow rate, which is displayed for the user to see and logged for condition tracking. The device has been validated with a commercial gas flow meter and is ready for human subject testing.