Abstract: A method and a system for determining the amount of oxygen required by a user with respiratory problems are disclosed. First data about several users with respiratory problems is stored in a database. The method a) collects second data from a monitored user while (s)he is performing a test at a first location; b) computes a user’s behavioral model executing a first algorithm on the first and second data; c) collects, every period of time t1, third data of the user while (s)he is performing an activity at a second location; d) adjusts, every period of time t2, the computed user’s behavioral model using the first algorithm, providing a customized user’s behavioral model as a result; and e) computes an estimator of the quantity of oxygen to be delivered to the user by executing a second algorithm on the customized user’s behavioral model.