System for detecting changes in body posture

DETAILED DESCRIPTION We claim as our invention: 1.
A system for detecting changes in body posture comprising: means for recording electrocardiograms from a subject, said electrocardiograms exhibiting a changing morphology; and analyzer means, supplied with said electrocardiograms, for determining changes in body posture of said subject from changes in the morphology of said electrocardiograms.
2.
A system as claimed in claim 1 wherein said analyzer means comprises: averaging means for determining a first average value of a predetermined portion of electrocardiograms recorded during a predetermined, first number of cardiac cycles, and for determining a second average value of said predetermined portion of electrocardiograms recorded during a predetermined, second number of subsequent cardiac cycles; and means for identifying a relation between said first average value and said second average value and for identifying changes in body posture dependent on said relation.
3.
A system as claimed in claim 2 wherein said means for determining a relation comprises means for forming a difference between said first average value and said second average value, and means for comparing said difference with at least one threshold value for identifying said changes in body posture dependent on a magnitude of said difference relative to said threshold value.
4.
A system as claimed in claim 3 wherein said means for comparing comprises means for comparing said difference to an upper, first threshold value and for indicating a change in posture from supine to standing if said difference upwardly transgresses said upper, first threshold value, and for comparing said difference to a lower, second threshold value and for indicating a change in posture from standing to supine if said difference downwardly transgresses said lower, second threshold value.
5.
A system as claimed in claim 2 wherein said predetermined portion of said electrocardiograms comprises a T-wave of a cardiac cycle.
6.
A system as claimed in claim 1 further comprising an accelerometer which generates an accelerometer signal, and wherein said means for analyzing comprises means for identifying said changes in body posture from a combination of changes in the morphology of the electrocardiograms and said accelerometer signal