SPIROMETER

• US 3,797,479 A
• Filed: 04/14/1972
• Issued: 03/19/1974
• Est. Priority Date: 04/14/1972
• Status: Expired due to Term

• Current Assignee: National Computer Systems, Inc. (Pearson plc)
• Original Assignee: Martin H. Graham
• Inventors: Graham, Martin H.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/244,202
• Time in Patent Office: 704 Days
• Field of Search: 128/2.08,2.5F 73/25L
• US Class Current: 600/538
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/0871 Peak expiratory flowmeters

Abstract

A spirometer including improved pneumotach and electronic circuitry for obtaining normalized linear output measuring forced vital capacity and maximum expiration flow rate with automatic zeroing feature before test. Display means are included to provide the patient with an immediate indication during a test of the patient'"'"''"'"'s rating compared to normal. Automatic zeroing circuitry and a starting circuit responsive to initial exhalation are also included.

Claims

1. A spirometer comprising a pneumotach tube including a screen disposed across the area of said tube for developing a differential pressure thereacross in response to a patient'"'"''"'"'s exhalation applied through said tube, sensing means connected to said tube on each side of said screen to develop an electrical signal indicative of said differential pressure, a non-linear amplifier means constructed and arranged to receive and modify the electrical signal from said sensing means so as to develop a second electrical signal indicative of flow and linearly related to flow through said tube, a normalizing circuit means connected to receive the output of said second electrical signal for developing a normalized value for said linearized flow signal based upon the size, age and sex of the patient such that subsequently developed values of the electrical signal indicative of the maximum expiration flow rate and the forced vital capacity of the patient are ratioed with the expected maximum flow rate and expected forced vital capacity to develop said normalized values;

flow display means for sensing and storing peak normalized flow data and including means for supplying an output display thereof visible to the patient, flow integrating and volume memory means for obtaining normalized maximum volume means for supplying an output display thereof visible to the patient, said last named means being independent of said flow display means, a timing circuit means for developing at least one timing pulse of a predetermined duration for controlling the period of operation of each of said flow sensing and storing means and said flow integrating and volume memory means, an auto-zeroing circuit means including an amplifier means having a first state for developing a signal for maintaining the integrating means and display output at a zero level and a second state for holding the last value of said first state in response to a predetermined signal, a starting circuit means responsive to initial exhalation of the patient to switch said auto-zeroing circuit from said first state to said second state and for initiating the beginning of said timing pulse.

2. A spirometer comprising a breath tube including a screen for developing a differential pressure thereacross in response to a patient'"'"''"'"'s exhalation applied through said tube, sensing means connected to said tube on each side of said screen to develop an electrical signal indicative of said differential pressure and said flow, a non-linear amplifier means constructed and arranged to receive and modify the electrical signal from said sensing means so as to develop a second electrical signal indicative of said flow which is linearly related to flow through said tube, a normalizing circuit means connected to receive the output of said second electrical signal and for developing a normalized signal for said linearized flow signal based upon the physical parameters of the patient, flow indicating means for sensing and storing peak normalized flow data and including means for developing an output display visible to the patient, flow integrating and volume memory means for obtaining normalized maximum volume and including means for developing an output display visible to the patient, timing circuit means for developing at least one timing pulse of a predetermined duration for controlling the period of operation of each of said flow sensing and storing means and said flow integrating and volume memory means, and trigger means responsive to the initial exhalation of the patient to start said timing circuit.

3. A spirometer as in claim 2 in which said timing circuit means includes means for developing a plurality of timing signals of progressively longer intervals and in which said volume memory includes means responsive to said timing signals for integrating the instantaneous normalized flow signal over each of said respective intervals.

4. A spirometer comprising pneumotach hAving sensing means for developing an electrical signal proportional to flow normalizing circuit means, indicating means for sensing and storing peak normalized flow data and including means for supplying an output thereof, flow integrating and memory means for obtaining maximum volume and including means for supplying an output thereof, a timing circuit means for developing at least one timing pulse of predetermined duration for controlling the period of operation of each of said flow sensing and storing means and said flow integrating and memory means, and an auto-zeroing circuit means connected across said flow integrating means and including an amplifier means switchable between a first state for adjusting the output of said integrating means to a zero level and a second state for holding the last value of said first state in response to a predetermined signal, a starting circuit means responsive to initial exhalation of the patient to switch said auto-zeroing circuit from said first state to said second state.