A method of calculating a subject's breathing volume, comprising the steps of:
- a) providing on the thorax of a subject a marker comprising one or more signal generating elements fixed to said base, for generating signals that are indicative of movement of the thorax of said subject;
- b) by a receiver, receiving said generated signals from said one or more signal generating elements during breathing motion of said subject;
- and
- c) analyzing said received generated signals by one or more computing devices in data communication with said receiver, said analysis comprising the steps of:
- i. calculating, in response to said received generated signals, the magnitude of a maximum displacement in 3D space of said one or more signal generating elements during a cycle of said breathing motion;
- and
- ii. calculating the magnitude of a current displacement in 3D space of said one or more signal generating elements during said breathing motion with respect to a reference tidal volume associated with said maximum displacement in 3D space,
- wherein each of the one or more signal generating elements is a light source assembly which comprises two or more spaced light sources suitable to generate light, and the receiver is a stationary camera for tracking movement of, and imaging, said two or more light sources during breathing motion of the subject, the method further comprising the steps carried out by the one or more computing devices of:
- iii. calculating, in response to receiving imaged data taken by said camera at a predetermined orientation, the magnitude of a maximum displacement in 3D space of said two or more light sources during said breathing motion related to first and second reference breathing vectors associated with a same respiration cycle of said subiect, said second reference breathing vector being complementary to said first reference breathing vector and originating from a maximal light source location corresponding to exhalation conditions and terminating at a minimal light source location corresponding to inhalation conditions;
- iv. calculating a reference tidal volume that is related to said first and second reference breathing vectors;
- v. storing data associated with said reference tidal volume in memory;
- vi. calculating in a monitoring stage, for each of said two or more light sources, the magnitude of a current displacement in 3D space of said two or more light sources during said breathing motion related to corresponding complementary first and second monitored breathing vectors that are indicative of thorax movement and extend between a minimal light source location and a maximal light source location associated with a same monitored respiration cycle of said subject;
- vii. calculating in a monitoring stage, for each of said two or more light sources, the magnitude of a current displacement in 3D space of said two or more light sources during said breathing motion related to corresponding complementary first and second monitored breathing vectors that are indicative of thorax movement and extend between a minimal light source location and a maximal light source location associated with a same monitored respiration cycle of said subject;
- and
- viii. calculating the value of a current tidal volume for said monitored respiration cycle by determining a function of the magnitude of reference displacements and reference tidal volumes, when the corresponding second monitored breathing vector is non-disregarded, with respect to the magnitude of a corresponding maximum displacement, and multiplying said function by the value of the corresponding reference tidal volume.