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A method and apparatus for measuring the breathing rate from the electrocardiograph signal (ECG) by measuring the frequency of modulation of the R-R intervals using auto-regressive modelling. The R peaks are detected using a standard QRS detection technique and the R-R intervals are measured to produce a time series of values. These are resampled evenly and the resulting series is windowed in overlapping windows of typically 30 seconds' length, overlapping by 25 seconds, to obtain discrete sections which are AR modelled using an all- pole auto-regressive (AR) model. The AR model allows identification of the dominant frequencies in the signal and the pole corresponding to the breathing rate is identified- by considering its magnitude and the breathing rate it represents.; Each 30 second window gives a breathing rate estimate and use of successive windows displaced by 5 seconds results in a breathing rate estimate every 5 seconds. The time series of breathing rate estimates can be Kalman filtered to reject measurements which have a large change in magnitude or represent a large change in breathing rate. The measurements may also be fused with measurements from another sensor.

Type

Journal article

Publication Date

18/02/2009

Addresses

OXFORD BIOSIGNALS LIMITED,