A system for determining the amount of oxygen required by a user with respiratory problems, comprising: a memory or database configured to store first data about a plurality of users with respiratory problems, the first data at least including oxygen saturation and heart beat frequency parameters of the plurality of users which were acquired while the plurality of users were performing a cardiorespiratory function test; a wearable data acquisition device configured to be placed on a monitored user having respiratory problems; and one or more processing units operatively associated with the wearable data acquisition device, the one or more processing units being configured to: a) compute a user's behavioral model that characterizes user behavior in terms of user oxygen support needs vs an effort to be done by implementing at least one first artificial intelligence algorithm on the first data and second data, the second data being collected from one or more sensors in the wearable data acquisition device while the monitored user is performing the cardiorespiratory function test at a first location, the second data at least including oxygen saturation and heart beat frequency parameters; b) provide a customized user's behavioral model by adjusting, every certain second configurable period of time t2, the computed user's behavioral model by means of implementing the at least one first artificial intelligence algorithm on third data, the third data being collected, every certain first configurable period of time t1, from the one or more sensors while the monitored user is performing an activity at a second location, the third data at least including oxygen saturation and heart beat frequency parameters; c) compute an estimator of the quantity of oxygen to be delivered to the monitored user by implementing at least one second artificial intelligence algorithm on the customized user's behavioral model, wherein steps b)-c) are repeated every certain third configurable period of time, such that the customized user's behavioral model is repeatedly trained with updated data. a memory or database configured to store first data about a plurality of users with respiratory problems, the first data at least including oxygen saturation and heart beat frequency parameters of the plurality of users which were acquired while the plurality of users were performing a cardiorespiratory function test; a wearable data acquisition device configured to be placed on a monitored user having respiratory problems; and one or more processing units operatively associated with the wearable data acquisition device, the one or more processing units being configured to: a) compute a user's behavioral model that characterizes user behavior in terms of user oxygen support needs vs an effort to be done by implementing at least one first artificial intelligence algorithm on the first data and second data, the second data being collected from one or more sensors in the wearable data acquisition device while the monitored user is performing the cardiorespiratory function test at a first location, the second data at least including oxygen saturation and heart beat frequency parameters; b) provide a customized user's behavioral model by adjusting, every certain second configurable period of time t2, the computed user's behavioral model by means of implementing the at least one first artificial intelligence algorithm on third data, the third data being collected, every certain first configurable period of time t1, from the one or more sensors while the monitored user is performing an activity at a second location, the third data at least including oxygen saturation and heart beat frequency parameters; c) compute an estimator of the quantity of oxygen to be delivered to the monitored user by implementing at least one second artificial intelligence algorithm on the customized user's behavioral model, a) compute a user's behavioral model that characterizes user behavior in terms of user oxygen support needs vs an effort to be done by implementing at least one first artificial intelligence algorithm on the first data and second data, the second data being collected from one or more sensors in the wearable data acquisition device while the monitored user is performing the cardiorespiratory function test at a first location, the second data at least including oxygen saturation and heart beat frequency parameters; b) provide a customized user's behavioral model by adjusting, every certain second configurable period of time t2, the computed user's behavioral model by means of implementing the at least one first artificial intelligence algorithm on third data, the third data being collected, every certain first configurable period of time t1, from the one or more sensors while the monitored user is performing an activity at a second location, the third data at least including oxygen saturation and heart beat frequency parameters; c) compute an estimator of the quantity of oxygen to be delivered to the monitored user by implementing at least one second artificial intelligence algorithm on the customized user's behavioral model,