FIG. 3.

ELF Tracker app developed by Oregon State University. (A) Initial prototype. On the top left, a screenshot from the opening page of the ELF Tracker app, detailing the recent global positioning system (GPS) coordinates and data transmissions. The instruction page could be accessed by tapping the [+] button at the top right of the first screen. (B) Secondary prototype following west Eugene focus groups. Sequential screenshots before, during and after successful data transmission from the spirometer to the phone. (C) Third prototype following Carroll County focus groups. Sequential screenshots before, during and after successful data transmission from the spirometer to the phone. Note changes to the color of the buttons, and the text in the transmission sequences. A progress bar was added to track the number of spirometry replicates recorded.