Respirometer having thermosensitive elements on both sides of a hot wire

• US 3,962,917 A
• Filed: 07/03/1974
• Issued: 06/15/1976
• Est. Priority Date: 07/03/1974
• Status: Expired due to Term

• Current Assignee: Minato Medical Science Co. Ltd.
• Original Assignee: Minato Medical Science Co. Ltd.
• Inventors: Terada, Hideshi
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US05/485,537
• Time in Patent Office: 713 Days
• Field of Search: 73/189, 73/204, 128/2.08
• US Class Current: 600/537
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/0878 using temperature sensing means
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow

Abstract

A respirometer for measuring the rate of an air flow of respiration includes a hot wire in a path of the air flow. For measuring the rate of the air flow with a discrimination made between the senses of the air flow, a pair of temperature sensitive elements are placed in the path of the air flow on respective opposite sides of the hot wire relative to the air flow.

Claims

1. A respirometer for use in measuring the rate of an air flow of respiration, comprising:

means for defining a one-dimensional path of air flow of respiration;

a hot wire in said respiration air flow path;

means coupled to said hot wire for maintaining said hot wire substantially at a predetermined temperature;

a pair of temperature sensitive elements in said respiration air flow path on respective opposite sides of said hot wire relative to the air flow of respiration in said air flow path, said temperature sensitive elements having an electrical characteristic which varies as a function of temperature;

first means electrically connected to said hot wire for producing an electrical output signal representative of the rate of said air flow but without discriminating between the senses of the direction of said air flow; and

second means electrically connected to said first means and to said temperature sensitive elements, said second means including;

third means electrically connected to said temperature sensitive elements for producing a control signal that assumes a first value during expiration and a second value during inspiration; and

fourth means electrically connected to said first and third means and including;

switching means responsive to said control signal;

first electrical operating means coupled to said switching means and having a first electrical characteristic for operating on said electrical output signal of said first means during inspiration for providing an inspiration output signal;

second electrical operating means coupled to said switching means and having a second electrical characteristic for operating on said electrical output signal of said first means during expiration for providing an expiration output signal, and combining means coupled to said first and second electrical operating means for combining the inspiration and expiration output signals thereof and producing a respiration rate signal representative of the rate of said air flow with discrimination between the senses of the direction of said air flow.

2. A respirometer as claimed in claim 1, wherein each of said temperature sensitive elements is spaced about 1 millimeter from said hot wire on said respective opposite sides of said hot wire.

3. A respirometer as claim in claim 1, further comprising a hot resistance wire in said air flow path on one side of a combination of said hot wire and temperature sensitive elements.

4. A respirometer as claimed in claim 3, further comprising means electrically connected to said hot resistance wire for producing an electrical output signal representative of the rate of said air flow but without discriminating between the senses of the direction of said air flow.

5. A respirometer as claimed in claim 1, wherein said means for maintaining the temperature of said hot wire substantially at said predetermined temperature includes means electrically connected to said hot wire for supplying a variable electric current to said hot wire.

6. A respirometer as claimed in claim 1, further comprising an integrator connected to said second means for integrating said respiration rate signal to produce a respiration quantity signal representative of the quantity of said air flow.

7. A respirometer as claimed in claim 1, wherein said third means comprises differential amplifier means connected to said temperature sensitive elements for producing a differential output signal that assumes substantially positive and negative values during one and the other of expiration and inspiration periods of respiration, respectively, and a transistor circuit responsive to said differential output signal for producing said control signal of said first and second values when said differential output signal assumes said positive and negative values, respectively.

8. A respirometer as claimed in claim 1 wherein said first electrical operating means comprises a first amplifier, said second electrical operating means comprises a second amplifier and said combining means comprises means for summing the electrical output signals from said first and second amplifiers.

9. A respirometer as claimed in claim 1 wherein said switching means includes a relay operable in response to said control signal for switching said electrical output signal of said first means between said first and second electrical operating means.

10. A respirometer for use in measuring the rate of an air flow of respiration, comprising:

means for defining a one-dimensional path of air flow of respiration;

a hot wire in said respiration air flow path;

means coupled to said hot wire for maintaining said hot wire substantially at a predetermined temperature;

a pair of temperature sensitive elements in said respiration air flow path on respective opposite sides of said hot wire relative to the air flow of respiration in said air flow path, said temperature sensitive elements having an electrical characteristic which varies as a function of temperature;

first means electrically connected to said hot wire for producing an electrical output signal representative of the rate of said air flow but without discriminating between the senses of the direction of said air flow; and

second means electrically connected to said first means and to said temperature sensitive elements, and responsive to said electrical output signal of said first means and to said electrical characteristics of said temperature sensitive elements for producing a respiration rate signal representative of the rate of said air flow with discrimination between the senses of the direction of said air flow, said second means including;

third means electrically connected to said temperature sensitive elements for producing a control signal that assumes a first value during expiration and a second value during inspiration; and

fourth means electrically connected to said first and third means, said fourth means comprising a first amplifier means for producing a first output signal with an amplification substantially equal to minus unity, a second amplifier means for producing a second output signal with an amplification substantially equal to plus unity, a combining circuit coupled to said first and second amplifier means and reponsive to said first and second output signals from said first and second amplifier means for producing a combined output signal, and relay means electrically connected to said first and third means and operative responsive to said control signal from said third means for supplying said electrical output signal from said first means to said first amplifier means when said control signal assumes one of said first and second values, and for supplying said electrical output signal from said first means to said second amplifier means when said control signal assumes the other of said first and second values, said combined signal thereby becoming said respiration rate signal.