Technical validity and usability of a novel smartphone-connected spirometry device for pediatric patients with asthma and cystic fibrosis. - Kruizinga MD; Essers E; Stuurman FE; Zhuparris A; van Eik N; Janssens HM; Groothuis I; Sprij AJ; Nuijsink M; Cohen AF; Driessen GJA (Pediatric pulmonology, 2020)