Breath Sampler

Abstract

A breath sampler device for use with an air analyzer. The sampler includes a chamber, an intake port leading into the chamber, an outlet port exiting from the chamber, and a breathing port through which a subject inhales from and exhales into the chamber. An intake check valve provides for unidirectional air flow through the intake port into the chamber, and an outlet check valve provides for unidirectional air flow out of the chamber through the outlet port. An air reservoir having a sampling region is associated with the outlet port. Upon exhalation, the outlet check valve opens and the air which has just been exhaled from the subject's lungs is passed from the chamber into the air reservoir where it replaces the residual air contained in the reservoir sampling region from a previous exhalation. In order to discretely sample this expired air before it can be affected by conditions outside the subject's body, a pressure sensing membrane is provided which responds to the decrease in pressure inside the chamber on subsequent inhalation to actuate a switch which closes a circuit to an electric pump which draws a sample of this expired air from the reservoir sampling region into the analyzer.

Description

FIELD OF THE INVENTION

This invention relates generally to analytic apparatus, and particularly concerns a breath sampler device for use with a medical lung function analyzer.

THE PRIOR ART

Lung function analyzers are used to analyze samples of a patient's breath in order to determine its compositions, and changes in its composition which occur over a period of time, under various conditions. From this information, diagnosticians draw important conclusions as to the condition of the patient's lungs, in cases where emphysema or other lung pathology is suspected.

A device of this type commonly employs a breath sampler comprising a chamber from which the patient inhales and into which he exhales. The chamber has an intake port through which the inhaled air is drawn, and an outlet port through which the exhaled air leaves. These ports are controlled by check valves arranged so that only fresh air is drawn into the chamber on the inhalation cycle, and expired air passes only through the outlet port on the exhalation cycle. As exhaled air leaves the chamber through the outlet check valve, a small sample of it is withdrawn by mechanically actuated means from a point just downstream from the outlet check valve and delivered over a sampling conduit to the analyzer.

In the past, the sampling conduit has lacked consistent control. The prior art arrangement yielded a relatively poor response, since the exhaled air passes continuously to the analyzer, and discrete volumes of air from successive exhalations are mixed randomly during passage through the sampling conduit.

THE INVENTION

The present invention utilizes an electrically controlled pump in cooperation with the sampling conduit and an associated reservoir for the air which has just been exhaled from the patient's lungs, which is the air to be sampled, so that the passage of exhaled air to the lung function analyzer is positively controlled. This exhaled air displaces the residual air from a previous exhalation which is contained in the portion of the reservoir which is in cooperation with the sampling conduit so as to provide a discrete breath to be sampled. The operation of the pump is controlled by a diaphragm switch which is responsive to a pressure sensitive membrane. The pressure sensitive membrane senses the pressure changes which occur in the breath chamber during inhalation to close the switch and actuate the pump to draw air from the reservoir, which air is preferably the last part of the expired breath which reflects the capillary gas concentration in the alveolus of the lung. As a result the pump is operated in sharply responsive fashion to draw exhaled air through the sampling conduit when the patient inhales immediately subsequent to an exhalation, and to be inoperable during exhalation so as to prevent the drawing of air through the sampling conduit during exhalation.

This results in a fast and sensitive pump operation so that the air which has just been exhaled from the patient's lungs may be sampled selectively, and in addition provides the capability for segregating and accumulating the end portions of discrete breaths for analysis, which is necessary to avoid random mixing. Mixing tends to average out the breath concentration over a period of time, whereas under certain circumstances it may be desired to analyze the breath content as of a sharply defined point in the respiratory cycle.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE of the drawing includes a vertical section taken through a conventional T-shaped breath collection conduit and appropriate hose connections thereto; along with a partly schematic representation of a pump controlled breath sampling connection leading from the T-conduit to the analyzer, and automatic control apparatus therefor, in accordance with this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The patient's breath is collected in a T-shaped enclosure, generally designated 10. This includes a cylindrical member 11 defining a centrally located breath collecting chamber 12 which has three port openings 26, 32 and 20; and three cylindrical conduits 14, 16 and 18 connected thereto by means of threaded connections to appropriate openings in the member 11. Three gaskets 19 are provided for sealing purposes. Conduit 18 is a breathing conduit through which the patient inhales and exhales. It is threadedly connected to a breathing port 20 for communication with the breath chamber 12 so that the patient's respiration draws air from the chamber 12 into the conduit 18 during the inhalation cycle, as represented by arrow 22, and forces expired air through conduit 18 into the chamber 12 during the exhalation cycle, as indicated by arrow 24.

Conduit 14 is an intake conduit. It is threadedly connected to an intake port 26 for communication with the chamber 12 so that, on the inhalation cycle, fresh air, represented by arrow 28, is drawn in through the intake port and passes through the breath chamber 12 in the manner indicated by arrow 30. Subsequently the inhaled air passes through the breathing conduit 18 to reach the patient, as indicated by arrow 22.

Conduit 16 is an outlet conduit. It is threadedly connected to an outlet port 32 for communication with the breath chamber 12 so that, on the exhalation cycle, the expired air forced through the breathing conduit 18, as indicated by arrow 24, passes through the breath chamber 12 and outlet conduit 16 as indicated by arrows 34 and 35 respectively. Preferably, elastomeric intake and outlet hoses 36 and 38 are coupled to the inlet and outlet conduits 14 and 16 respectively. Outlet hose 38 and outlet conduit 16 act as a reservoir 39 for the most recently exhaled air, the reservoir 39, functioning in a manner to be described in greater detail hereinafter. The reservoir 39 should be of sufficient overall dimension to preferably retain at least a portion of the air just exhaled from the patient's lungs in the outlet conduit 16, where it may be sampled in a manner to be described in greater detail hereinafter, for a sampling interval, which is determined by the inhalation of the patient. The outlet hose 36 may be eliminated if the outlet conduit 16 is of sufficient overall dimension to function as a reservoir 39 by itself.

In order to insure the undirectional flow of fresh air into the breath chamber 12 through the intake port 26, and of exhaled air out of the breath chamber through the outlet port 32, there are provided intake and outlet check valves assemblies 40 and 42 respectively. The check valve assemblies each include a seating cylinder 44 provided with a radially outwardly extending annular flange 46. The flange 46 of the intake check valve assembly is received within an annular recess 47 formed in the internal surface of the intake conduit 14, and is held in place by being clamped against the annular end surface of the cylindrical chamber member 11 surrounding the intake port 26. Similarly the radial flange 46 of the outlet check valve assembly is received in an annular recess 49 formed in the interior wall of the chamber member 11 surrounding the outlet port 32, and is clamped in place by the outlet conduit 16. As shown and as presently preferred, the movable valving element of each assembly 40 and 42 is an integrally formed plastic member, generally designated 48, which comprises a circular diaphragm 50, an annular ring 52, and a plurality of spaced helically shaped resilient filaments 54 connecting the circular diaphragm 50 and annular ring 52.

The ring 52 surrounds the cylinder 44, and is friction fit thereon. The diaphragm 50 seats against the end wall of the cylinder 44 for sealing purposes when the check valve assembly is in its closed condition. It is held in that position by the resilience of the helical filaments 54 which tend to draw the diaphragm 50 axially toward the annular ring 52, and therefore toward the cylindrical member 44. When the filaments 54 resiliently yield to allow the diaphragm 50 to move axially away from the cylindrical member 44, the diaphragm 50 comes out of sealing engagement with the cylindrical member 44. When this happens, air within the interior of the cylindrical member 44 escapes between the end wall of the cylindrical member and the confronting surface of the circular diaphragm 50, and then passes through the spaces between the filaments 54. This constitutes the open condition of the check valve assembly 40 or 42.

Check valve assembly 40 opens on the inhalation cycle, in response to the reduced pressure in the chamber 12, to permit the air intake illustrated by arrows 28, 30 and 22. It closes on the exhalation cycle, in response to the increased pressure in chamber 12, to prevent exhaled air from escaping back through the intake port 26. Similarly, the outlet check valve assembly 42 opens on the exhalation cycle, in response to the increased pressure in breath chamber 12, to permit the outflow of expired air, which is preferably the air which has just been exhaled from the patient's lungs, in the manner illustrated by the arrows 24, 34 and 35; and closes during the inhalation cycle in response to the decreased pressure in the breath chamber 12 in order to prevent re-inhalation of expired air through the outlet port 32.

The internal wall of the outlet conduit 16 is formed with an annular groove 56 which is located a spaced distance downstream from the outlet check valve assembly 42. This groove 56 serves to retain and position a motion-limiting assembly 58 which extends transversely across the outlet conduit 16 and which serves to limit the opening motion (motion to the right in the FIGURE) of the diaphragm 50 in the outlet check valve assembly 42. The motion-limiting assembly 58 comprises a pair of circularly arcuate sections 60 (only one is visible in the Figure) which are compressively received along their circular arcuate edges by the groove 56 and it comprises a transverse arm 62 (seen in section view in the Figure) which extends between and is attached to each of the arcuate sections 60.

In accordance with the present invention, a sampling conduit, generally designated 64, is provided in cooperation with the reservoir 39 to conduct a small sample of the exhaled air, which has preferably just been exhaled from the patient's lungs, from a point 65 in the reservoir 39 along the outlet conduit 16 located just downstream from the outlet check valve assembly 42, to an analyzer 66 which is a conventional type of air analyzer; although the invention may be utilized with any type of air analyzer. The sampling conduit includes a short length of tubing 68 having an inlet 69 tapped into the reservoir 39 at the downstream point 65 in the outlet conduit 16, and a pair of connecting pipes 72 and 74. The location of the sampling conduit inlet 69 permits the exhaled air from the last part of the patient's expiration to be sampled and accumulated for analysis. Connecting pipes 72 and 74 have inlets 73 and 75, and outlets 77 and 79, respectively. The inlet 73 of pipe 72 is in communication with tube 68 through a chamber 70, and thus in communication with the reservoir 39. The outlet 79 of pipe 74 is in communication with the input 81 to the analyzer 66. The flow of expired air from connecting pipe 72 to connecting pipe 74 is controlled by an electrically actuated pump 76, which can be any appropriate type of pump structure but is preferably a diaphragm pump 76.

The diaphragm pump 76 prevents the passage of air therethrough when the pump 76 is off or inoperable. The intake end of pump 76 is in communication with the outlet 77 of connecting pipe 72 and the outlet end is in communication with the inlet 75 of connecting pipe 74. As shown and preferred, a reciprocating rod 80, of short stroke, is connected to the pump to operate it. The rod 80 is operatively connected to a vibrator 78 which controls the movement of the rod 80 and, hence, the movement of the flexible diaphragm within the pump so as to pump air from the inlet to the outlet. Air is thus passed between connecting pipes 72 and 74 and on to the analyzer 66.

The vibrator 78 is electrically actuated by a switch which controls the flow of electrical power from a suitable source, here shown illustratively as a D.C. battery 91 to the vibrator 78. The switch which is preferably a diaphragm switch 90, includes a pressure sensing, or pressure responsive flexible membrane or diaphragm 92, shown schematically in the figure by a dotted line, and a pair of contacts which close in response to small displacements of the diaphragm. The flexible member 92 is flexed to close the controls when the internal air pressure within the housing 94 decreases, and is returned to its rest state to reopen the contacts from the flexed state when the internal air pressure within the housing 94 is increased. A pressure communication hose 96 leads from the interior of the housing 94 and is coupled to a tube 98 which taps through the chamber-forming member 11 to communicate with the breath chamber 12 to sense pressure changes.

In the operation of the breath sampling device, as the patient exhales, the air just exhaled from the lungs follows the path indicated by arrow 24 through the breathing conduit 18 and breathing port 20, and the path indicated by arrow 34 through the breath chamber 12, the outlet port 32, and the outlet check valve assembly 42 to the outlet conduit 16 and the outlet hose 38 comprising the reservoir 39. The reservoir 39 retains at least a portion of this exhaled air in the area of point 65 for a sampling interval and the exhaled air displaces any residual air remaining in this area from a previous exhalation. At this time the outlet check valve assembly 42 is opened in the manner described as exhalation raises the pressure in the breath chamber 12 above ambient. The flexible membrane 92 which is flexed from its rest position due to a decrease in pressure, remains at rest and the switch 90 is therefore open and no power is supplied to vibrator 78 from power source 91. The pump 76 is, therefore, in the inoperative state and no air is drawn through the sampling conduit 64 to the analyzer 66.

After the exhalation cycle terminates, the pressure in the breath chamber 12 drops back to ambient and later goes below ambient as subsequent inhalation begins. The pressure reduction causes the internal pressure within the housing 94 to decrease thereby flexing the membrane 92 from the rest position and closing the switch 90. This connects power source 91 to the electrical circuit of the vibrator 78 turning the pump on. The exhaled air contained in the area of the inlet 69 of the sampling conduit 64, which is at point 65 in the outlet circuit 16 of the reservoir 39 is pumped through the conduit 64 to the analyzer 66. During the normal cycle of operation of exhalation and subsequent inhalation, the inhalation immediately follows the exhalation and the last part of the air which has just been exhaled from the lungs of the patient is accumulated and drawn into the analyzer 66 without being mixed with the remainder of the patient's exhaled breath.

When the inhalation cycle terminates, the pressure in the breath chamber 12 rises toward ambient, and later, goes above ambient as exhalation begins. This pressure increase causes an increase in the internal pressure within the housing 94 thereby returning the membrane 92 to the rest position and opening the switch 90, once again turning off the pump 76. As the exhalation cycle begins again, the exhaled air from the previous breath is displaced from the sampling region 65 and replaced by the exhaled air from the current exhalation cycle. The membrane 92 is returned to rest at the completion of the inhalation cycle promptly opening the switch 90 prior to the commencement of the exhalation cycle so that the last part of the exhaled air from discrete breaths is segregated and accumulated. As a result, the sampling cycle terminates under control of the switch 90 at the start of the patient's inhalation subsequent to exhalation, just as rapidly and with the same sensitive pressure response as it begain.

It will therefore be appreciated that the present system provides improved breath sampling apparatus for use in a medical lung function analyzer or any other gas sampling application in which speed and sharpness of response and high sensitivity to small pressure changes are required, along with the ability to accumulate the last part of successive breaths, to enable selective analysis of this part of the exhaled breath.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In breath sampler apparatus of the type including an enclosure having a breathing port, an intake port, an outlet port, an intake check valve arranged for unidirectional air flow through said intake port into said enclosure in response to inhalation at said breathing port, and an outlet check valve arranged for unidirectional air flow from said enclosure through said outlet port in response to exhalation at said breathing port; the improvement comprising:

a sampling conduit communicating with said enclosure downstream from said outlet check valve;

means for withdrawing air from said sampling conduit;

electrically controlled means for actuating said air withdrawing means;

an electrical circuit connected to energize said actuating means;

a switch connected to control said electrical circuit whereby to turn said actuating means on and off, said switch including means for sensing the air pressure in said enclosure;

said switch being responsive to said pressure sensing means to connect said electrical circuit in a manner to cause said actuating means to turn on said means for withdrawing air whereby to draw a breath sample through said sampling conduit when the air pressure in said enclosure decreases during inhalation through said breathing port, and to affect said electrical circuit and actuating means in a manner to turn off said means for withdrawing air when the pressure in said enclosure increases during exhalation into said breathing port.

2. Apparatus as in claim 1, wherein said means for withdrawing air includes a pump, and said electrically controlled means is connected to said pump for actuating and deactuating said pump.

3. Apparatus as in claim 2 wherein:

said switch includes a hollow housing, and said pressure sensing means is a flexible membrane and is disposed within said housing, a decrease in pressure in said enclosure causing a decrease in pressure in said housing and an increase in pressure in said enclosure causing an increase in pressure in said housing.

4. Apparatus as in claim 2 wherein:

said electrically controlled means is a vibrator and said vibrator is operatively connected to said pump for causing the reciprocation thereof when said vibrator is energized.