Pneumatic lung analog

Abstract

A vertically oriented bellows has a fixed plate at one end and a movable plate at the other end. As air flows into the bellows, the movable plate pivots relative to the fixed plate and the free end thereof is cooperative with a readout panel to indicate the volume of the bellows. The plates are interconnected by an adjustable spring urging the plates toward each other when the bellows are expanded to simulate lung compliance. Selected tubes having calibrated flow characteristics interconnect the bellows to a lung ventilator to simulate lung resistance. Preferably, a pair of bellows are arranged in mutual association together to simulate a pair of lungs in order to analyze their interdependency.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A pneumatic lung analog comprising, in combination: a frame; a bellows in said frame, said bellows simulating a lung, said bellows having a stationary end plate secured to said frame and a movable end plate secured to said frame, said movable end plate being pivotal relative to said stationary plate; said bellows having air inlet and air outlet means for inflating and deflating said bellows, said movable end plate pivoting away from said stationary end plate when the flow of air is into said bellows and moving toward said stationary end plate when the flow of air is out of said bellows, said air inlet means defining a passageway having a preselected cross section flow area to simulate a preselected flow resistance through the respiratory track; means biasing said movable end plate toward said stationary end plate, said biasing means .Iadd.including a spring connected at one end to said movable end plate and at the other end to said frame, said spring providing a force against said movable end plate urging it toward said stationary end plate when said bellows is expanded and .Iaddend.acting as a resistance to the expansion of said bellows, said biasing means simulating the respiratory compliance in a lung; .Iadd.adjustment means for adjusting the force of said spring acting on said movable end plate, said adjustment means including attachment means anchoring the ends of said spring at various locations radially from the axis of pivot of said movable end plate so that the tension on said spring can be varied for a given angular movement of said movable end plate; .Iaddend.and indicating means associated with said movable end plate, said indicating means providing a performance readout of said lung analog in response to flow through said air inlet means. .[. 
     
     
       2.  The lung analog according to claim 1 wherein said means biasing said movable end plate toward said stationary end plate is a spring connected at one end to said movable end plate and at the other end to said frame, said spring providing a force against said movable end plate urging it toward said stationary end plate when said bellows is expanded..].  .[.3. The lung analog according to claim 2 wherein the force of said spring acting on said movable plate is adjustable by an attachment means anchoring the ends of said spring at various locations radially from the axis of pivot of said movable end plate so that the tension on said spring can be varied for a given angular movement of said movable end plate..]. 
     
     
         . The lung analog according to claim .[.3.]. .Iadd.1 .Iaddend.wherein said attachment means includes a pair of spaced guide rails, one of said guide rails being anchored on said movable end plate and extending radially from the axis of pivot of said movable end plate, the other of said guide rails being anchored to said frame and aligned with said one guide rail, and clamp means movable along said guide rails for receiving the ends of said spring, said clamp means positioning said spring radially 
     
     
        with respect to the pivot axis of said movable end plate. 5. The lung analog according to claim 4 wherein said adjustment means includes a calibrated scale along one of said guide rails to provide a visual readout of the position of said spring relative the pivot axis of said movable end 
     
     
        plate. 6. The lung analog according to claim 1 wherein said analog is further characterized by an adjustable stop anchored to said frame and limiting the movement of said movable end plate toward said stationary plate to assure the exact position of said movable end plate relative said 
     
     
        stationary end plate when said bellows is deflated. 7. The lung analog according to claim 6 wherein said movable end plate is parallel to said 
     
     
        stationary end plate when said bellows is deflated. 8. The lung analog according to claim 6 wherein said adjustable stop is a shaft threadably anchored to said frame and extending toward said movable end plate, said shaft having a free end abutting said movable end plate when said bellows 
     
     
        is deflated. 9. The lung analog according to claim 1 wherein said analog is further characterized by a stop anchored to said frame and limiting the movement of said movable end plate away from said stationary plate when 
     
     
        said bellows is inflated. 10. The lung analog according to claim 9 wherein said stop is a wire means having a preselected length, one end of said wire means being anchored to said frame, the other end of said wire means being anchored to said movable end plate to limit the movement of said 
     
     
        movable end plate away from said stationary plate. 11. The lung analog according to claim 1 wherein the axis of said bellows extends vertically when said bellows is deflated and said end plates extending horizontally, said movable end plate extending parallel to and spaced above said stationary end plate when said bellows is deflated; and adjustment means cooperatively associated with said movable end plate to neutralize the effect of its weight as a force acting against said bellows when said 
     
     
        bellows is deflated. 12. The lung analog according to claim 11 wherein said adjustment means is comprised of a spring anchored at one end to said movable end plate and at the other end to said frame, said spring when tensioned exerting a force on said movable end plate urging it away from 
     
     
        said stationary plate. 13. The lung analog according to claim 12 wherein said movable end plate includes a bracket extending vertically downwardly, said one end of said spring being attached to said bracket at a point spaced below said movable end plate, said spring extending horizontally beneath said movable end plate so that when said spring is tensioned, the force of said spring acts on said movable end plate through said spacing to create a moment urging said movable end plate to pivot away from said 
     
     
        stationary end plate. 14. The lung analog according to claim 13 wherein the other end of said spring is movably anchored to said frame to permit selection of the degree of tension on said spring by movement thereof 
     
     
        relative said one end. 15. The lung analog according to claim 1 wherein said indicating means is comprised of a panel having printed indicia thereon, said panel being positioned adjacent the free end of said movable end plate and generally perpendicular thereto when said bellows is deflated, said printed indicia having a locus of visual readouts indicating the simulated compliance and volume of the bellows at the associated free end of said movable end plate when pivoted relative the 
     
     
        stationary end plate. 16. The lung analog according to claim 15 wherein said panel is curved to match the arcuate path of said free end of said movable end plate to permit a direct readout of the position of said 
     
     
        movable end plate. 17. The lung analog according to claim 15 wherein said panel is pivotally anchored to said frame and movable between a generally upstanding position for indicating the position of said movable end plate 
     
     
        to a generally horizontal position for storage and transportation. 18. The lung analog according to claim 17 wherein said indicating means further includes means retaining said panel in either of said selected positions to prevent unintentional movement towards the other of said positions. 
     
     
            The lung analog according to claim 18 wherein said indicating means further includes resilient bumper means engageable with said panel in said generally horizontal position to avoid vibration of said panel during 
     
     
        storing and transportation of said lung analog. 20. The lung analog according to claim 1 wherein said means defining a passageway is comprised of a tube having a preselected cross section and length thereby defining a preselected volume flow at a preselected pressure, said tube being replaceable by similar tubes of varying cross section in order to simulate various respiratory resistances. .[.21. The lung analog according to claim 1 wherein means are provided around the pleats of said bellows to restrain said bellows during inflation from bulging nonuniformly..].  .[.22. The lung analog according to claim 21 wherein said latter means are comprised of a plurality of thin wires encircling each of said pleats snugly when said bellows is deflated..].  .[.23. The lung analog according to claim 1 wherein said end plates extend horizontally and the axis of said bellows extends vertically when said bellows is deflated, the axis of said bellows forming an arc when said bellows is inflated, said lung analog being further characterized by a retaining means mounted intermediate said end plates for pivotal movement about the axis of pivot of said movable end plate, said retaining means encapsulating one of the pleats of said bellows to prevent said bellows from sagging or bulging while said bellows in inflated..].  .[.24. The lung analog according to claim 23 wherein said retaining means comprises an annular ring means positioned about said one of the pleats and pivotally anchored to said frame by one or more 
     
     
        brackets..].  25. A pneumatic lung analog comprising, in combination: a housing; a pair of bellows anchored at one end to said housing, said bellows each having a movable plate means secured to the other end, each of said plate means being pivotally anchored to said housing so that when said bellows are inflated, said plates pivot arcuately relative to said housing; air inlet and outlet means for inflating and deflating each of said bellows independently of each other; first means associated with each of said bellows for controlling the flow of air into said bellows at a preselected flow rate at a preselected differential pressure to simulate lung resistance; second means associated with each of said bellows resisting the inflation of said bellows to simulate lung compliance; .Iadd.said second means including spring means interconnected between said housing and movable plate means, said spring means resisting inflating of said bellows by urging said movable plate means toward said one end of said bellows as said bellows are inflated; adjustment means for adjusting the force of said spring acting on said movable plate means, said adjustment means including attachment means anchoring the ends of said spring at various locations radially from the axis of pivot of said movable end plate means so that the tension on said spring can be varied for a given angular movement of said movable end plate means; .Iaddend.and third means associated with each of said bellows for indicating the 
     
     
        differential pressure, volume and compliance of said bellows. 26. The lung analog according to claim 25 wherein said first means is comprised of one or more flow tubes connected to said inlet means and having an arbitrary length and cross section calibrated for a known volume flow at given 
     
     
        pressure differentials. 27. The lung analog according to claim 26 wherein each of said bellows includes separate air inlet means connected to a 
     
     
        common source of air by individual flow tubes. .[.28.  The lung analog according to claim 25 wherein said second means is comprised of a spring means interconnected between said housing and movable plate means said spring means resisting inflating of said bellows by urging said movable plate means toward said one end of said bellows as said bellows are 
     
     
        inflated..].  29. The lung analog according to claim .[.28.]. .Iadd.25 .Iaddend.wherein said spring means is adjustable along a radius extending from the axis of rotation of said plate means to vary the effective force of said spring means to arbitrarily vary the simulated compliance of said 
     
     
        lung analog. 30. The lung analog according to claim 25 wherein said third means includes a panel positioned adjacent the free end of said plate means, said panel including graphic indicia on its face calibrated to indicate the volume and compliance of said bellows at each position thereof during inflation by comparing the position of the free end of said 
     
     
        plate means along said graphic indicia. 31. The lung analog according to claim 30 wherein said panel is curved in accordance with the arcuate 
     
     
        movement of said plate means. 32. The lung analog according to claim 30 wherein said panel includes separate graphic indicia for each of said 
     
     
        bellows and plate means. 33. The lung analog according to claim 30 wherein said graphic indicia is calibrated for different differential pressures. 
     
     
          . The lung analog according to claim 30 wherein said third means further includes pressure gauges associated with each of said bellows to provide a 
     
     
        differential pressure readout. 35. The lung analog according to claim 25 wherein said analog further includes stop means limiting the pivotal 
     
     
        movement of said plate means in either direction. 36. The lung analog according to claim 25 wherein said bellows are mounted side-by-side, said 
     
     
        plate means being pivotal about a horizontal axis. 37. The lung analog according to claim 36 wherein said analog includes fourth means for neutralizing the gravitational weight of said plate means and bellows. 
     
     
            The lung analog according to claim 37 wherein said fourth means includes an adjustable spring means urging said plate means and bellows toward an inflated position, said adjustable spring means being preset to offset the gravitational weight of said bellows and plate means urging said bellows and plate means toward deflation.