Respirator system and method

• US 3,903,881 A
• Filed: 04/12/1974
• Issued: 09/09/1975
• Est. Priority Date: 04/12/1974
• Status: Expired due to Term

• Current Assignee: Bear Medical Systems Inc. (Becton, Dickinson & Co)
• Original Assignee: James Weigl
• Inventors: Weigl, James
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Recla, Henry J.
• Application Number:
  US05/460,621
• Time in Patent Office: 515 Days
• Field of Search: 128/145.6,142.2-142.4,145.7,145.8,145.5,146.4,146.5,188,DIG.17,203,184
• US Class Current: 128/204.25
• CPC Class Codes: A61M 16/022 Control means therefor
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 16/206 Capsule valves, e.g. mushroom, membrane valves
• CPC Class Codes: A61M 16/208 Non-controlled one-way valves, e.g. exhalation, check, pop-off non-rebreathing valves
• CPC Class Codes: A61M 16/209 Relief valves
• 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

Abstract

A respirator system and method in which a constant pressure plenum communicates through a gas bleeder with the patient gas supply system. The bleeder is adjustable so that a gas flow can be established from the plenum to the gas conduits at a level sufficient to compensate for leaks from the patient'"'"''"'"'s mouth and trachea, but less than that required by the patient during voluntary inhalation. The pressure inside the conduit system, and hence in the patient'"'"''"'"'s lungs, is thereby maintained at a level at least as great as a minimum desired amount. A discrimination between patient attempts at breathing and leaks from the conduit system is achieved by sensing the gas flow rate towards the patient, and actuating a breath assist function only in response to that flow rate equaling or exceeding the expected inhalation rate, without reference to the absolute pressure within the conduit system.

Claims

1. A respirator system for assisting a patient'"'"''"'"'s breathing during alternate inhalation and expiration phases, said system including gas conduit means having an inlet port, an outlet port, and a patient supply tap intermediate said inlet and outlet ports, recyclable means for charging gas into said inlet port during inhalation phases for delivery to a patient, a control means for actuating said charging means, first valve means adapted to block an outward flow of gas through said inlet port during expiration phases, and second valve means adapted to block an inward flow of gas through said outlet port during inhalation phases, wherein the improvement comprises the provision of:

a pressure plenum, means for positively maintaining said plenum at a predetermined pressure level, bleeder means adapted to conduct gas from said plenum into said gas conduit means, and a gas flow sensing means adapted to sense a flow of gas through said conduit means towards the patient during expiration phases and to produce a control signal in response to said flow exceeding a predetermined threshold flow rate, said control means being connected to said sensing means for actuation by said control signal, and said bleeder means providing a gas flow path of sufficient conductance to enable a substantially unrestricted inflow of gas into said conduit means from said plenum at a maximum rate approximately equal to said threshold flow rate, whereby gas leaks from the patient supply tap at leak rates not exceeding the said threshold flow rate are replenished by a compensating gas flow into the conduit means from the pressure plenum without producing a control signal for actuating the gas charging means, and the pressure in said conduit means is maintained at a level substantially at least equal to said predetermined plenum level despite said gas leaks.

2. The respirator system of claim 1, wherein said bleeder means provides a gas flow path from said plenum to the outlet port of said conduit means, and said gas flow sensing means comprises a pressure differential sensor means operably connected to sense pressure differences between said plenum and said outlet port, said bleeder means including flow restriction means adapted to produce a predetermined pressure differential across said bleeder means when the gas flow rate therethrough to said outlet port equals said threshold flow rate, said pressure differential sensor means being adapted to produce a control signal in response to the sensed pressure differential exceeding said predetermined amount.

3. The respirator system of claim 2, said flow restriction means including adjustment means for adjusting the maximum gas flow rate through said bleeder means within a range corresponding to the expected range of voluntary inhalation flow rates produced by a patient.

4. The respirator system of claim 1, wherein said gas flow sensing means is interposed in line with said patient supply tap.

5. A respirator system for assisting a patient'"'"''"'"'s breathing during alternate inhalation and expiration phases, said system including gas conduit means having an inlet port, an outlet port, and a patient supply tap intermediate said inlet and outlet ports, recyclable means for charging gas into said inlet port during inhalation phases for delivery to a patient, a control means for actuating said charging means, first valve means adapted to block an outward flow of gas through said inlet port during expiration phases, and second valve means adapted to block an inward flow of gas through said outlet port during inhalation phases, wherein the improvement comprises the provision of:

first and second pressure plenums, means for positively maintaining the pressure in said first plenum at a predetermined level, adjustaBle bleeder means adapted to conduct gas from said first plenum to said second plenum to provide a pressure therein, said second plenum communicating with said conduit means during the expiration phases of said respirator so as to maintain said conduit means at a pressure substantially equal to the pressure of the second plenum during such expiration phases, and a pressure differential sensor means operably connected to sense pressure differences between said first and second plenums and to produce a control signal for actuation of the control means in response to the sensed pressure differential exceeding a predetermined amount.

6. The respirator system of claim 5, wherein said second plenum communicates with said conduit means through the outlet port thereof, said bleeder means providing a gas flow path from said first plenum to said second plenum and thereby to said conduit means during expiration phases when said second valve means is open, and further including vent means communicating with said first plenum to vent expired air from the system.

7. The respirator system of claim 6, and further including a passageway between said first and second plenums, said passageway including a check valve enabling a unidirectional gas flow from the second plenum to the first plenum in response to a pressure differential therebetween of appropriate polarity.

8. A respirator system for assisting a patient'"'"''"'"'s breathing during alternate inhalation and expiration phases, said system including gas conduit means having an inlet port, an outlet port, and a patient supply tap intermediate said inlet and outlet ports, recyclable means for charging gas into said inlet port during inhalation phases for delivery to a patient, a control means for actuating said charging means, first valve means adapted to block an outward flow of gas through said inlet port during expiration phases, and second valve means adapted to block an inward flow of gas through said outlet port during inhalation phases, wherein the improvement comprises the provision of:

means responsive to a predetermined flow rate of gas through said conduit means to said patient supply tap during an expiration phase for producing a control signal to actuate said control means, and pressure maintenance apparatus for said conduit means, said apparatus comprising a first plenum maintained at a predetermined pressure level, a second plenum in gas flow communication with said conduit means through said outlet port, check valve means enabling a unidirectional gas flow from the second plenum to the first plenum, and a bleeder conduit connected in parallel with said check valve means between said first and second plenums, said second plenum having a pressure during expiration phases determined by the pressure in said conduit means, said bleeder conduit including a gas flow restriction valve capable of being set to restrict the flow of gas between said plenums to a level no greater than the expected voluntary inhalation flow rate produced by a patient.

9. A respirator system for assisting a patient'"'"''"'"'s breathing during alternate inhalation and expiration phases, said system including gas conduit means having an inlet port, an outlet port, and a patient supply tap intermediate said inlet and outlet ports, recyclable means for charging gas into said inlet port during inhalation phases for delivery to a patient, a control means for actuating said charging means, first valve means adapted to block an outward flow of gas through said inlet port during expiration phases, and second valve means adapted to block an inward flow of gas through said outlet port during inhalation phases, wherein the improvement comprises the provision of:

a first chamber, a second chamber surrounding said conduit means outlet port and communicating therethrough with said conduit means when said second valve means is open, a check valve means enabling a unidirectional gas flow from the second to the first chamber, a bleeder conduit connected in parallel With said check valve means between said first and second chambers, said bleeder conduit including an adjustable gas flow restriction valve for controlling the gas flow rate therethrough, vent means communicating with said first chamber for venting expired air from the system, a venturi in gas flow communication with said first chamber, and jet means adapted to direct a substantially constant velocity gas jet through said venturi to said first chamber, thereby maintaining the pressure in said first chamber at a substantially constant level.

10. The respirator system of claim 9, and further including a pressure differential sensor means operably connected to sense pressure differences between said first and second plenums and to produce a control signal for actuation of the control means in response to the sensed pressure differential exceeding a predetermined amount.

11. The respirator system of claim 9, and further including a third chamber interposed between said jet means and said venturi, said third chamber including longitudinally opposed walls having ports therein enabling the gas jet to pass through the chamber, and at least one outlet orifice in a transverse wall of said third chamber providing a vent for expired gas transmitted through said check valve means.

12. The respirator of claim 9, wherein said second valve means comprises the combination of a diaphragm and means for releasably closing said diaphragm over said conduit means outlet port, said diaphragm forming a wall of said second chamber.

13. A method of operating a respirator system of the type which includes gas conduit means having an inlet port, an outlet port, and a patient supply tap intermediate said inlet and outlet ports, recyclable means for charging gas inwardly into said inlet port during inhalation phases for delivery to a patient, a control means for actuating said charging means, first valve means adapted to block an outflow of gas through said inlet port during expiration phases, and second valve means adapted to block an inward flow of gas through said outlet port during inhalation phases, said method comprising:

sensing the flow rate of gas toward a patient through said conduit means during expiratory phases when the inlet port is blocked by said first valve means, supplying gas to said conduit means during expiratory phases to compensate for gas leaks from the patient supply tap, limiting the compensating gas flow to a rate no greater than the patient'"'"''"'"'s expected voluntary inhalation flow rate, and actuating the control means to operate the charging means when the sensed gas flow rate exceeds a predetermined threshold level which is no greater than the patient'"'"''"'"'s expected voluntary inhalation flow rate.

14. The method of claim 13, and further including the step of maintaining a plenum at a substantially constant pressure, wherein said compensating gas flow is supplied from said plenum to said conduit means through the outlet port thereof, and the gas flow rate to the patient is sensed by sensing the gas flow rate from the plenum to the conduit means.

15. The method of claim 14, wherein said compensating gas flow is limited by restricting the gas flow from the plenum to the conduit means, and the rate of said restricted gas flow is sensed by sensing the pressure differential between said plenum and conduit means.