Patent ID: 9675258
Date: 2017-06-13
CPC Classifications: A61B

Claim:
1. A computer readable storage medium having computer readable instructions stored thereon that are executable by a system to perform or control performance of operations comprising: receiving a data signal generated by a cardiac sensor that is configured to measure heart beats of a subject and generate the data signal that represents the measured heart beats; computing a standard deviation of a plurality of K−1 most recent heart beat intervals and a current heart beat interval (I1) from a plurality of consecutive heart beat intervals included in the data signal, from a sum (S1) of K most recent heart beat intervals squared and a sum (S2) of the K most recent heart beat intervals and a Kth oldest heart beat interval (I2); and calculating an updated sum (S1′) of S1 minus I2 squared plus I1 squared and an updated sum (S2′) of S2 minus I2 plus I1, and a square root of a sum of a ratio of S1′ to K and of a ratio of a square of S2′ to a square of K.