Patent ID: 8727991

Claim:
At least one non-transitory tangible processor-readable storage device having computer readable software embodied thereon for programming at least one processor to perform a method for monitoring a heartbeat period of a subject, the method comprising: obtaining velocity samples from a signal reflected from a subject for successive overlapping signal analysis windows, the velocity samples comprise velocity samples v(t) for a current signal analysis window centered at a time t, velocity samples v(t−1) from a prior signal analysis window and velocity samples v(t+1) from a future signal analysis window, the velocity samples obtained from the signal represent a velocity of blood flowing in the subject, and each window is shorter than the heartbeat period of the subject; determining a cepstrum x(t) of the velocity samples v(t), a cepstrum x(t−1) of the velocity samples v(t−1) and a cepstrum x(t+1) of the velocity samples v(t+1); providing a vector y(t) comprising x(t−1), x(t) and x(t+1); determining a vector z(t) by nonlinearly transforming the vector y(t); defining different heartbeat periods τ that begin at t−τ and end at t: for each heartbeat period τ of the different heartbeat periods: determining a probability β of the vector z(t), and determining a probability α that the heartbeat period τ is the heartbeat period of the subject given one or more previous heartbeat periods of the subject; and determining which of the heartbeat periods τ is most probable, based on the probabilities β and α.