System and method for smoothing sampled digital signals

• US 9,008,789 B2
• Filed: 08/06/2012
• Issued: 04/14/2015
• Est. Priority Date: 03/26/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Corndorf, Eric D.
• Primary Examiner(s): Holmes, Rex R
• Application Number:
  US13/567,188
• Publication Number:
  US 20120303329A1
• Time in Patent Office: 981 Days
• Field of Search: 607/2, 607/6, 607/60, 600/323, 600508-509, 600515-519, 386/114, 341/67, 341106-107, 341/155
• US Class Current: 607/60
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

Abstract

Waveforms are digitally sampled and compressed for storage in memory. The compression of the data includes generating a truncated entropy encoding map and using the values within the map to obtain good compression. An encoder further sub-selects values to be encoded and values to remain unencoded to provide an overall compression of the data.

Claims

1. An implantable medical device comprising:

a sensor configured to sense a signal and to provide a digitally sampled signal; and

a smoothing filter configured to process the sampled signal and classify a given data point of the sampled signal into a first type or a second type and to;

apply a smoothing function to the given data point responsive to the given data point being classified as the first type, and

to retain a sampled value for the given data point responsive to the given data point being classified as the second type,

wherein the smoothing filter is configured to determine variability between the given data point and at least one sampled data point that is adjacent to the given data point, and

classify the given data point into the first type if the variability is less than a predetermined variability value and into the second type if the variability is equal to or greater than the predetermined variability value.

2. The implantable medical device of claim 1, wherein the smoothing function applied to the first type of data is to determine an average value for the given data point and the data points adjacent to the given value.

3. The implantable medical device of claim 1, wherein the smoothing function applied to the first type of data is to determine a weighted average value for the given data point and the data points adjacent to the given value.