Respiratory Signal Processing Method

• US 20100249611A1
• Filed: 05/21/2009
• Published: 09/30/2010
• Est. Priority Date: 03/26/2009
• Status: Abandoned Application

• Current Assignee: Edan Instruments, Inc.
• Original Assignee: Edan Instruments, Inc.
• Inventors: Wang, Min, Wang, Hongchun, Chen, Liu
• Application Number:
  US12/470,304
• Publication Number:
  US 20100249611A1
• Time in Patent Office: Days
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

This Invention relates to a respiratory signal processing method, including the following steps: A. Obtain the respiratory physiological signals by means of a specific respiratory circuit, AD collects and obtains the respiratory digital signals and applies the data preprocessing to such signals; B. Convert frequency spectrum of the preprocessed respiratory signals and obtain the distribution of their frequency domain; C. Judge whether there is asphyxia in accordance with the properties of respiratory signal'"'"'s physiological parameters; D. Introduce the physiological parameters of heart activities and analyze frequency spectrum distribution of respiratory signals and judge whether there is any interference from heart activities; E. Analyze the spectral energy envelop of respiratory waveform and find out the correct spectral peak, and then convert the frequency point corresponding to the spectral peak to the respiratory rate so as to obtain the value of current respiratory rate by integrating with the previous values of respiratory rate. The processing methods under this Invention can maximize the accuracy of results of respiratory rate and improve the stability of such result remarkably.

Claims

1. A respiratory signal processing method, including the steps as below:

A. Obtain the respiratory physiological signals by means of a specific respiratory circuit, AD collects and obtains the respiratory digital signals and applies the data preprocessing to such signals;

B. Convert frequency spectrum of the preprocessed respiratory signals and obtain the distribution of their frequency domain;

C. Judge whether there is asphyxia in accordance with the properties of respiratory signal'"'"'s physiological parameters;

D. Introduce the physiological parameters of heart activities and analyze frequency spectrum distribution of respiratory signals and judge whether there is any interference from heart activities (i.e. cardiovascular artifact);

E. Analyze the spectral energy envelop of respiratory waveform and find out the correct spectral peak, and then convert the frequency point corresponding to the spectral peak to the respiratory rate so as to obtain the value of current respiratory rate by integrating with the previous values of respiratory rate.

2. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said data preprocessing under the Step A means the band pass filter applied to the respiratory signals.

3. In accordance with the respiratory signal processing method described under claim 2 herein and its feature is shown as below:

the said band pass filtering means the bi-directional zero phase IIR filter.

4. In accordance with the respiratory signal processing method described under claim 2 herein and its feature is shown as below:

the said band pass filter means the multiplication-free elliptical IIR filter.

5. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said method of frequency spectrum conversion means the Fourier transform.

6. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said method of frequency spectrum conversion means the wavelet transform.

7. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said method of frequency spectrum conversion means the Hilbert transform.

8. In accordance with the respiratory signal processing method described under claim 5 herein and its feature is shown as below:

the said Fourier transform means the fast Fourier transform (FFT).

9. In accordance with the respiratory signal processing method described under claim 5 herein and its feature is shown as below:

the said Fourier transform means the Chirp Z-Transform (CZT).

10. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said asphyxia judging method means setting up the respiratory signal'"'"'s frequency domain-energy threshold line and respiratory signal'"'"'s time-domain waveform amplitude threshold line—

it is judged as respiratory signal asphyxia when the maximum value of respiratory signal'"'"'s spectral energy is less than the preset frequency domain-energy threshold line within a period of time while the time-domain waveform amplitude is less than the preset time-domain waveform threshold line.

11. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said introduced heart activity parameter means the value of heart rate.

12. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said introduced heart activity parameter means the value of pulse rate.

13. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said judging method of cardiovascular artifact means obtaining the maximum value and sub-maximum value of respiratory spectral energy—

the respiratory waveform is judged to be interfered by the palpitation interference to one degree or another if the corresponding value of respiratory rate falls into the current set range of heart rat and/or pulse rate values.

14. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said analyzing method of respiratory wave frequency domain-energy envelop means obtaining the maximum value point of respiratory SIG'"'"'s spectral energy and determining some spectral peaks.

15. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said finding out of the correct spectral peak means analyzing the obtained spectral peak so as to determine a correct spectral peak according to the ratio of energy of each spectral peak, respiratory rate value corresponding to each spectral peak and ratio of historical respiratory rate values and to convert the corresponding frequency point to the respiratory rate.

16. In accordance with the respiratory signal processing method described under claim 1 herein and its feature is shown as below:

the said method to obtain the current respiratory rate value means analyzing the obtained spectral peaks so as to determine a accurate spectral peak according to the ratio of energy of each spectral peak, respiratory rate value corresponding to each spectral peak and ratio of historical respiratory rate values, to convert the corresponding frequency point to the respiratory rate and calculate the weighted mean of the obtained respiratory rate values and historical respiratory rate values.