A
system for monitoring the
respiratory activity of a subject, which comprises one or more movement sensors, applied to the
thorax of a subject, for generating first signals that are indicative of movement of the
thorax of the subject; a
receiver for receiving the first generated signals during
breathing motion of the subject; and one or more computing devices in data communication with the
receiver, for analyzing the
breathing motion. The computing device is operable to generate a first
breathing pattern from the first signals; divide each
respiratory cycle experienced by the subject and defined by the first pattern into a plurality of portions, each of the portions delimited by two different time points and calculate, for each of the plurality of portions of a given
respiratory cycle of the first pattern, a slope representing a
thorax velocity; derive, from the given
respiratory cycle of the first pattern, a pulmonary air flow rate of the subject during predetermined portions of the respiratory cycle; compare between corresponding portions of the first pattern and average flow rates during different phases of the
breathing cycle, to calibrate a thorax velocities of the subject with pulmonary air flow rates; and determine respiratory characteristics of the subject for subsequent respiratory cycles experienced by the subject, based on a calculated thorax velocity and the calibration.