Abstract: A method, system and software for monitoring a signal from a living subject to measure a function of the living subject. Specifically, a computer method, computer system and software for accurately calibrating respiratory inductance plethysmography and esophageal manometry signals to measure effort of breathing before and after extubation of a patient to provide an automated real-time interpretation for a clinician of whether or not the patient has upper airway obstruction, and severity of the same. The method, system and software can be adapted specifically for a child or infant.