take https://www.mathworks.com/matlabcentral/fileexchange/55289-respiratory-rate-estimation 2. The PLUX Biosignals respiration belt & software: Inductive Respiration (RIP) Sensor Respiration (PZT & RIP) Analysis Add-on 3. And the Vernier Spirometers & software: https://www.vernier.com/product-category/?category=spirometers