Method and apparatus for determining when a partially or completely collapsed lung has been opened

• US 6,116,241 A
• Filed: 07/08/1997
• Issued: 09/12/2000
• Est. Priority Date: 07/08/1996
• Status: Expired due to Term

• Current Assignee: Maquet Critical Care AB (Getinge AB)
• Original Assignee: Siemens-Elema AB (Siemens AG)
• Inventors: Bohm, Stephan, Lachmann, Burkhard, Huygen, Paul
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): SRIVASTAVA, VIRENDRA KUMAR
• Application Number:
  US08/889,389
• Time in Patent Office: 1,162 Days
• Field of Search: 128/204.23, 128/202.22, 128/205.23, 128/203.14, 128/204.18, 128/204.21, 600/529, 600/532, 600/533, 600/538, 600/586, 600/483
• US Class Current: 128/204.23
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise

Abstract

A method and an apparatus for determining when a partially or completely collapsed lung has been opened are based on the fact that in the course of opening an alveolus by supplying a gas pressure, the alveolus will generate a crackle sound. By listening to the crackle sounds via microphones, an apparatus can determine when the lung is completely open. The apparatus has a filter for filtering out the relevant frequencies for the crackle sounds and a determination unit for identifying the crackles and for determining when the lung is open based on the filtered out sounds.

Claims

1. An apparatus for determining when an at least partially collapsed lung of a subject has been opened by gas pressure supplied to the lung from a ventilator comprising:

means for obtaining an audio signal from a lung region of a subject, said audio signal including a distinctive component produced by opening of alveoli in the lung;

filtering means for filtering out said distinctive component; and

evaluation means supplied with said distinctive component filtered out of said audio signal for determining, from said distinctive component, a degree of opening of the lung.

2. An apparatus as claimed in claim 1 wherein said means for obtaining said audio signal comprises a plurality of microphones adapted for attachment to said subject, and wherein said evaluation means comprises means for determining a location of alveoli which have been opened.

3. An apparatus as claimed in claim 2 wherein said evaluation means comprises means for determining that said lung is opened when alveoli in predetermined locations in said lung are opened.

4. An apparatus as claimed in claim 1 wherein said evaluation means comprises means for determining that the lung is opened when said distinctive component reaches a predetermined threshold.

5. An apparatus as claimed in claim 4 wherein said predetermined threshold comprises a frequency threshold.

6. An apparatus as claimed in claim 4 wherein said predetermined threshold comprises a predetermined number of distinctive components.

7. An apparatus for ventilating a subject comprising:

ventilator means for supplying respiratory gas to the lungs of a subject;

means for obtaining an audio signal from a lung region of a subject, said audio signal including a distinctive component produced by opening of alveoli in the lung;

filtering means for filtering out said distinctive component;

evaluation means supplied with said distinctive component filtered out of said audio signal for determining, from said distinctive component, a degree of opening of the lung; and

control means for controlling supply of said respiratory gas from said ventilator dependent on the degree to which the lung is opened.

8. An apparatus as claimed in claim 7 wherein said means for obtaining said audio signal comprises a plurality of microphones adapted for attachment to said subject, and wherein said evaluation means comprises means for determining a location of alveoli which have been opened.

9. An apparatus as claimed in claim 8 wherein said evaluation means comprises means for determining that said lung is opened when alveoli in predetermined locations in said lung are opened.

10. An apparatus as claimed in claim 7 wherein said evaluation means comprises means for determining that the lung is opened when said distinctive component reaches a predetermined threshold.

11. An apparatus as claimed in claim 10 wherein said predetermined threshold comprises a frequency threshold.

12. An apparatus as claimed in claim 10 wherein said predetermined threshold comprises a predetermined number of distinctive components.

13. An apparatus as claimed in claim 7 wherein said control means comprises means for controlling supply of said respiratory gas by increasing a gas pressure of said respiratory gas until a predetermined distinctive component occurs in said audio signal.

14. An apparatus as claimed in claim 7 wherein said control means comprises means for determining a lowest gas pressure which maintains the lungs open during an entire respiratory cycle by controlling delivery of said respiratory gas for producing a sequence of respiratory cycles with respectively varying PEEP and correlating each PEEP with the distinctive component obtained during that respiratory cycle.

15. A method for determining whether an at least partially collapsed lung of a subject has been opened by gas pressure supplied to the lung, comprising the steps of:

recording an audio signal from a lung region of a subject, said audio signal including distinctive components produced by opening of alveoli in the lung;

filtering out said distinctive components from said audio signal; and

determining a degree of opening of the lung dependent on the distinctive components filtered out of said audio signal.

16. A method as claimed in claim 15 wherein the step of obtaining said audio signal comprises obtaining a plurality of audio signals from different locations in said lung region, and wherein the step of determining a degree to which the lung is opened comprises determining from which of said locations each distinctive component emanated, and determining that the lung is opened when a predetermined region of said lung has opened.

17. A method for ventilating a subject comprising:

supplying respiratory gas to an at least partially collapsed lung of a subject;

recording an audio signal from a lung region of a subject, said audio signal including distinctive components produced by opening of alveoli in the lung;

filtering out said distinctive components from said audio signal;

determining a degree of opening of the lung dependent on the distinctive components filtered out of said audio signal; and

controlling the supply of said respiratory gas dependent on the degree to which said lung is opened based on said distinctive components.