Method for generating a signal corresponding to the respiration volume per unit of time of a patient

• US 5,355,894 A
• Filed: 08/23/1993
• Issued: 10/18/1994
• Est. Priority Date: 08/26/1992
• Status: Expired due to Term

• Current Assignee: Pacesetter AB (Abbott Laboratories)
• Original Assignee: Siemens AG
• Inventors: Sivard, Ake
• Primary Examiner(s): ZELE, KRISTA MICHELLE
• Application Number:
  US08/110,772
• Time in Patent Office: 421 Days
• Field of Search: 128/716, 128/723, 128/725, 128/734, 128/671, 607/6, 607/8, 607/9, 607/20
• US Class Current: 600/538
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3704 Circuits specially adapted therefor, e.g. for sensitivity control

Abstract

For generating a signal corresponding to the respiration volume per unit of time of a patient, a signal component correlated with the respiration is filtered out of a measured impedance signal acquired in the region of the heart of the patient, and the zero-axis crossings of this signal component are detected and the maximum values respectively arising in between two successive pairs of zero-axis crossings are identified in terms of amplitude. These maxima are added during a prescribed time interval to form a value corresponding to the respiration volume per unit of time.

Claims

1. A method for generating a signal corresponding to the respiration volume per unit of time of a patient, comprising the steps of:

acquiring a measured impedance signal from an impedance measuring system including an electrode arrangement disposed in a region of the heart of said patient;

filtering a signal component out of said measured impedance signal correlated with the respiration of the patient, said signal component having a plurality of zero-axis crossings;

detecting said zero-axis crossings of said signal component;

identifying a maximum amplitude value of said signal component between each of two successive pairs of zero-axis crossings; and

forming a continuously updated average of said maximum amplitude value over a predetermined time interval, said average corresponding to the respiration volume per unit of time of said patient.

2. A method as claimed in claim 1 wherein the step of identifying said maximum value of said signal component between successive zero-axis crossings is further defined by:

sampling said signal component to obtain a sampled signal component signal;

supplying said sampled signal component signal to a first input of a comparator;

supplying a current content of a memory to a second input of said comparator and comparing said first input with said second input in said comparator; and

replacing said current content of said memory with said sampled signal component signal if the amplitude of said sampled signal component signal exceeds said current memory content.

3. A method as claimed in claim 1 wherein the step of forming an average is further defined by adding a plurality of said maximum values obtained in a plurality of successive zero-axis crossings in an adder to obtain a sum corresponding to said respiration volume per unit of time.