LUNG VENTILATOR

• US 3,741,208 A
• Filed: 02/23/1971
• Issued: 06/26/1973
• Est. Priority Date: 02/23/1971
• Status: Expired due to Term

• Current Assignee: Bjorn Jonsson, Sven Gunnar Olsson, Sven Ingelstedt
• Original Assignee: Bjorn Jonsson, Sven Gunnar Olsson, Sven Ingelstedt
• Inventors: Jonsson, Bjorn, Ingelstedt, Sven, Olsson, Sven Gunnar
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Dunne, G. F.
• Application Number:
  US05/117,889
• Time in Patent Office: 854 Days
• Field of Search: 128/145,145.5,145.6,145.8,147,142,142.2,188 137/102,87,88 73/198,274,279
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/0009 with sub-atmospheric pressure, e.g. during expiration
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/20 Valves specially adapted to medical respiratory devices
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit
• CPC Class Codes: Y10T 137/2278 Pressure modulating relays or followers
• CPC Class Codes: Y10T 137/2544 Supply and exhaust type

Abstract

A lung ventilator is provided with means for controlling the magnitude of a variable of the flow of respiratory gas in the inspiration line or in the expiration line or in both of them and means for automatically modulating said control means in response to the instantaneous magnitude of said variable of said flow thereby maintaining a desired pattern of said magnitude of the flow.

Claims

1. A lung ventilator comprising means for supplying respiratory gas, inspiration means including an inspiration line connectible to the patient, expiration means including an expiration line connectible to the patient, first means in at least one of said lines for measuring the instantaneous magnitude of at least one gas flow parameter from the group consisting of rate-of-flow and pressure, second means providing a signal proportional to said instantaneous magnitude of said flow parameter, means for providing a reference signal defining a desired flow pattern for said respiratory gas, third means for comparing the signal from said second means with the signal from said reference signal means for generating a signal proportional to the magnitude and sense of the difference therebetween, and fourth means actuated by said difference signal for automatically modulating said flow of respiratory gas, thereby to maintain a desired pattern of flow of the respiratory gas independently of the pressure of the respiratory gas furnished by said supply means and independently of the variable flow resistance and variable patient resistance.

2. A lung ventilator as defined in claim 1 wherein said first means comprises a flow meter unit, said third means comprises an error signal calculator receiving signals from said reference signal means and from said flow meter unit for generating an error signal defining the difference between the signal from said reference signal means and said flow meter unit, and said fourth means comprises a flow regulator unit for adjusting the flow of respiratory gas in response to said error signal.

3. A lung ventilator as defined in claim 2 comprising means for zeroing said flow meter unit, means in said flow regulator unit for indicating a closed position of said unit, and means for energizing said means for zeroing said flow meter unit in response to an indication from said indicator unit that said flow regulator unit is closed and that the flow consequently is zero.

4. A lung ventilator as defined in claim 3 wherein said zeroing means comprises an electrical capacitor, a field effect switch and said indicating means of said flow regulator unit.

5. A lung ventilator as defined in claim 2 wherein said flow meter unit comprising means Defining two parallel passages therein, a fine-mesh netting disposed in one of said passages, a disc disposed in the other passage carried at one end by a rigid thread, a pressure sensitive member contacting said rigid thread, said pressure sensitive member being constituted by a thin silicon plate, a resistor mounted at each side of said silicon plate, said resistors being connected in a bridge connection for generating a signal in response to deformation of said silicon plate which is deformed by said rigid thread in response to the force exerted on said disc by the flow of respiration gas through said passages of said flow meter unit.

6. A lung ventilator as defined in claim 1 wherein said first means comprises a flow meter unit and which further includes an integrator, means applying said reference signal to said integrator, means applying the signal from said flow meter unit to said integrator, means in said integrator for integrating the deviation between the said signals applied thereto to produce a deviation signal, and means applying said deviation signal to said third means which produces said difference signal in such sense as to reduce said difference signal to zero.

7. A lung ventilator as defined in claim 1 wherein the parameter of the respiratory gas measured is its rate-of-flow, and which further includes a servo valve, said servo valve comprising a step motor, a cam mounted on the rotatable shaft of said step motor, a cam follower, and means including a lever actuated by said cam follower for engaging and varying the gas flow rate through a flexible hose constituting at least a section of said inspiration and expiration lines in accordance with the operation of said step motor.

8. A lung ventilator as defined in claim 1 wherein the parameter of the respiratory gas measured is its rate-of-flow and wherein said means providing a reference signal defining a desired flow pattern for said respiratory gas comprises a clock pulse generator wherein a predetermined number of the pulses produced thereby is definitive of one breathing cycle, a first counter receiving clock pulses from said generator for determining the duration of the inspiration phase of the breathing cycle in response to a preset number of said clock pulses, means for generating a signal from said first counter in response to the duration of said inspiration phase, a second counter receiving clock pulses from said generator for determining the duration of the pause phase of said breathing cycle by counting a preset number of clock pulses corresponding to the duration of said pause time, and a logic circuit for generating an expiration signal when sensing that there is neither inspiration phase nor pause phase.

9. A lung ventilator as defined in claim 8 wherein said means providing a reference signal defining a desired signal flow pattern for said respiratory gas further includes a signal generator receiving signals from said clock pulse generator and from said signal generating means of said first counter, said signal generator comprising means for generating a voltage inversely proportional to the length of the inspiration phase of a respiratory cycle, means in said signal generator for integrating the clock pulses such that the area of the reference signal is independent of the relation between the length of the inspiration phase and the length of the entire respiratory cycle and that the area of the reference signal during the inspiration phase will vary with the clock pulse frequency so that the area of all reference signals will be constant during a predetermined period of time.

10. A lung ventilator as defined in claim 9 and which further includes means for generating a desired output signal form.

11. A lung ventilator as defined in claim 9 and which comprises a further counter connected to said clock pulse generator for counting the frequency cycles of said generator, each frequency cycle corresponding to one breathing cycle, and means for decreasing the pulse frequency of saId clock pulse generator after counting a preselected number of breathing cycles during the inspiration phase of the following breathing cycle thereby to simulate a sigh function.

12. A lung ventilator comprising means for supplying respiratory gas, inspiration means including an inspiration line connectible to the patient, expiration means including an expiration line connectible to the patient, first means in at least one of said lines for measuring the instantaneous magnitude of the rate-of-flow of said gas, second means providing a signal proportional to said measured gas flow rate, means generating a reference signal defining a desired flow pattern for the respiratory gas, third means for comparing the signal from said second means with the signal from said reference signal means for generating a signal proportional to the magnitude and sense of the difference therebetween, fourth means actuated by said difference signal for automatically modulating the gas flow rate, a monitoring unit for monitoring the magnitude of at least one other variable parameter of the gas in addition to its rate-of-flow for generating a signal proportional to said other monitored variable, means for indicating said last signal, and means for applying said last signal to said reference signal means to modify the signal produced therefrom.

13. A lung ventilator as defined in claim 12 wherein said monitoring unit comprises a mean value flow rate integrator, means applying the signal produced by said second means indicative of the instantaneous gas flow rate in said expiration line to said integrator, means applying clock pulses from a clock pulse generator of said reference signal generating means to said integrator, means for prolonging said clock pulses, means for energizing said integrator during the duration of the prolonged clock pulses and means for continuously generating an output signal from said integrator proportional to the integrated value of said signal produced by said second means during said prolonged clock pulses.

14. A lung ventilator comprising means for supplying respiratory gas, inspiration means including an inspiration line connectible to the patient, expiration means including an expiration line connectible to the patient, first means in at least one of said lines for measuring the instantaneous magnitude of the product of the gas pressure and of the gas flow rate, second means providing a signal proportional to said product, means providing a reference signal defining a desired flow pattern for said respiratory gas, third means for comparing the signal from said second means with the signal from said reference signal means for generating a signal proportional to the magnitude and sense of the difference therebetween, and fourth means actuated by said difference signal for modulating said flow of respiratory gas, thereby to maintain a desired pattern of flow of the respiratory gas independently of the pressure of the respiratory gas furnished by said supply means and independently of the variable flow resistance and variable patient resistance.