Gas flow regulating device

A gas flow regulating device including a housing assembly, an inlet tube assembly, and a biasing device. The housing assembly has a main housing, a valve seat body, and a distal plate forming an outlet orifice. The inlet tube assembly includes a proximal inlet end, a tube forming a lumen, and a flange, and is slidably disposed within the main housing, biased to an open state by the biasing device. The flange separates middle and constant pressure chambers within the housing assembly. The inlet tube assembly is transitionable to a closed state in response to pressure in the constant pressure chamber to generate a relatively constant flow rate of air exiting the device via the outlet orifice.

BACKGROUND

The present disclosure relates generally to a gas flow regulating device. More particularly, it relates to devices for regulating the flow of gaseous samples from a patient's respiratory system and suitable for various applications requiring a constant flow of air or other gaseous substance, independent of the originating volume and pressure.

The air exhaled from a patient is important for diagnosing many diseases through analysis of certain substance concentrations in the exhaled air. For example, it is often desirable to analyze the air exhaled from a patient to determine whether the breath contains a particular compound, such an ethyl alcohol or carbon dioxide, or a non-chemical such as a particular microorganism. However, since the pressure of the exhaled air varies from patient to patient, and also during the exhalation process, the volume of air passing through a testing unit during a given unit of time will vary considerably, leading to inconsistent and/or unreliable results. Therefore, there is a need for a device that will create a constant flow of exhaled air to a testing mechanism, independent of the pressure of the exhaled air.

In light of the above, a need exists for improved gas flow regulating devices used for patient air sampling.

SUMMARY

One aspect provides a gas flow regulating device for use as part of in a medical system for sampling a patient's breath, including a housing assembly, an inlet tube assembly, and a biasing device. The housing assembly has a main housing, a valve seat body, and a distal plate, and forms a middle chamber and a constant pressure chamber. The inlet tube assembly defines a proximal inlet end, and includes an inlet tube forming a lumen, and a flange. The inlet tube assembly is slidably disposed within the middle chamber, with the biasing device biasing the inlet tube assembly to an open state in which the lumen is open to the constant pressure chamber. With this construction, relatively constant flow from the constant pressure chamber via an outlet orifice in the distal plate is provided by the inlet tube assembly slidably transitioning to a closed state in which the lumen is sealed from the constant pressure chamber in response to an increase in pressure in the constant pressure chamber to generate a force greater than a biasing constant of the biasing device, and returning to the first state in response to a decrease in pressure in the constant pressure chamber.

DETAILED DESCRIPTION

Some aspects in accordance with the present disclosure relate to a gas flow regulating device for use in regulating flow of air from a patient as part of a medical system. One embodiment of a flow regulating device10in accordance with the present disclosure is shown inFIG. 1and includes a housing assembly12, an inlet tube assembly14, and a biasing mechanism16. Details on the various components are provided below. In general terms, however, the inlet tube assembly14and biasing mechanism16are disposed within the housing assembly12. Additionally, two chambers are formed within the housing assembly12, a constant pressure chamber18and a middle chamber20. The biasing mechanism16biases the inlet tube assembly14to an open state as shown, with the inlet tube assembly16being selectively slidable within the middle chamber20to a closed state (not shown) in response to pressures within the constant pressure chamber18.

With the above in mind, the housing assembly12includes a main housing22, a valve seat body24, and a distal plate26. As illustrated inFIG. 1, the main housing22may be generally cylindrical, forming an interior surface28and an exterior surface30. As illustrated inFIGS. 2 and 3, the main housing22includes a flow port46which is configured to connect directly to a patient's mouth, an artificial airway of a patient, or other medial device. The flow port46may be formed integrally with the main housing22, or assembled later. The main housing22may also include an interior guide52extending for a distance from proximal to the valve seat body24towards the distal plate26. The main housing22forms at least one bleed hole32extending from the interior surface28to the exterior surface30, and thereby open to ambient. The main housing22may be formed of any plastic, metal or hardened rubber or other suitable material.

With further reference toFIGS. 1 and 2, the interior surface28of the main housing22optionally forms a channel34, a groove36, and/or a circumferential recess38. The channel34and the groove36can extend about a perimeter of the interior surface28, with the groove36being formed radially outside of the channel34. The circumferential recess38also may extend about the perimeter of the interior surface28, and is configured to couple with the distal plate26. The distal plate26is described in greater detail below, and is generally configured for removable assembly to the main housing22at the circumferential recess38. The distal plate26may be threaded (not shown) or otherwise configured (e.g. snap-fit) at the circumferential recess38in order to form a sealed connection with the main housing22. In yet other constructions, the distal plate26is more permanently affixed to and/or formed integral with the main housing22. Further, additional components useful in establishing and maintaining the desired sealed connection, such as a coupling, a seal, an o-ring, etc. may be included with the housing assembly12.

The valve seat body24and the distal plate26are positioned at opposing ends of the main housing22. With additional reference toFIG. 3, the valve seat body24further forms through holes44for incoming airflow. The valve seat body24forms a seat48sized to receive and fluidly seal an end of the inlet tube assembly14, as described below. Thus, the valve seat body24, and in particular the seat48, is formed of a material capable of forming a fluid seal, such as rubber or similar materials.

Returning toFIGS. 1 and 2, the distal plate26may have at least one extension40, which when assembled with the main housing22, protrudes into the main housing22. The distal plate26also forms an outlet orifice42. As described below, air within the constant pressure chamber18is released from the device10via the outlet orifice42; thus, a diameter of the outlet orifice42dictates a flow rate of the outgoing air. Stated otherwise, a desired flow rate of air released from the device10can be achieved by employing a distal plate having an appropriate, correspondingly-sized outlet orifice42. In some embodiments, then, the device10of the present disclosure includes two or more distal plates26each with a different diameter outlet orifice42. The desired distal plate26is then selected by the user and assembled to the main housing22, with a diameter of the corresponding outlet orifice42appropriately sized to generate the desired outlet pressure/flow rate. Alternatively or in addition, the distal plate26can optionally include one or more adjustment components (not shown) associated with the outlet orifice42that allow a user to alter or select an effective diameter of the outlet orifice42. The distal plate26may include one or more additional features, such as hub43, extending proximal to the outer perimeter of the distal plate26for a distance in generally the same direction as the at least one extension40.

The housing assembly12is sized to receive the inlet tube assembly14. The inlet tube assembly14defines a proximal end50, and includes a tube54and a flange56. As illustrated inFIGS. 1 and 2, the tube54is cylindrically shaped and forms a lumen58that is open at the proximal end50and a distal end60of the inlet tube assembly14. In one embodiment, the lumen58has a uniform diameter. The proximal end50of the inlet tube assembly14is oriented to correspond with, and selectively fluidly seal against, the seat48of the valve seat body24. The tube54has a proximal region62terminating at the proximal end50. In one embodiment, the proximal region62forms a ridge64for assembly to a flexible membrane body as described below.

At the distal end60of the inlet tube assembly14, the flange56has a radial wall68, a distal face70, a proximal face71, and an outer groove72formed on the distal face70. The radial wall extends proximally from the proximal face72, and is radially spaced from the tube54to provide a surface for slidably engaging the interior surface28of the main housing22. The distal face70may be smooth or include variations in the surface.

The inlet tube assembly14is preferably made of the same material (a rigid or semi-rigid material such as plastic, metal or hard rubber, for example) and integrated as a single piece.

Also configured to fit within the housing assembly12is the biasing mechanism16. The biasing mechanism16may be a helical spring or other device which exerts a force. The biasing mechanism16is pretensioned to a force (e.g., a spring constant k) corresponding to a desired pressure in the constant pressure chamber18and will not compress until the pressure in the constant pressure chamber18generates a force on the inlet tube assembly14that exceeds the spring constant k.

As alluded to above, one or more sealing bodies can be provided with the flow control device10for establishing a fluid seal at the chambers18,20. For example, in one embodiment a lower membrane66and an upper membrane76can be included. The lower membrane66and the upper membrane76are flexible membranes placed in ring-like configurations. The upper and lower membranes66,76are expandable and/or contractable. In one embodiment, the upper and lower membranes66,76are configured with a width that allows the upper and lower membranes66,76to overlap upon themselves circumferentially. The upper and lower membranes66,76are formed in a diameter appropriate to seal the inlet tube assembly14against the interior surface28of the housing assembly12. The inner and outer perimeters of the upper and lower membranes66,76may have applied adhesives, stops, clips or other means of attaching the upper and lower membranes66,76within the housing assembly12.

The flow regulating device10forms the constant pressure chamber18and the middle chamber20within the housing assembly12. The middle chamber20is formed inside the main housing22between the valve seat body24of the housing assembly12and the flange56of the inlet tube assembly14. The middle chamber20is open to ambient at the at least one bleed hole32. As a point of reference,FIGS. 1 and 2illustrate that the middle chamber20is sealed within the interior surface28of the main housing22between the upper and lower membranes66,76. In one embodiment, the lower membrane66connects to the interior surface28of the main housing22as well as the ridge64on the proximal region62of the tube54. In another embodiment, the lower membrane66is attached to the flow port46instead of the main housing22. This may occur when the flow port46and the main housing22are fabricated separately and later assembled. This provides for a lower fluid seal of the middle chamber20.

Further, the middle chamber20is fluidly sealed from the constant pressure chamber18at the upper membrane76. The flange56of the inlet tube assembly14is further sealed to the interior surface28of the housing12by the upper membrane76. The upper membrane76is attached at the groove36of the main housing22and the groove72of the flange56. The upper membrane76may be further secured to the housing assembly12by the hub43of the distal plate26. Additionally, the upper membrane76may be further secured to the flange56by an O-ring78.

The constant pressure chamber18is further formed by the distal plate26and the flange56of the inlet tube assembly14, opposite the middle chamber20. The distal plate26is sealably, and removably, connected to the main housing22at the circumferential recess38. The constant pressure chamber18is positioned between the flange56of the inlet tube assembly14and the distal plate26. The at least one extension40projects into the constant pressure chamber18and prevents complete closure between the distal plate26and the distal face70of the flange56. As discussed previously, the upper membrane76provides a sealed body between the constant pressure chamber18and the middle chamber20formed within the housing assembly12.

As assembled, the housing assembly12is configured to enclose the working components of the flow regulating device10. In particular, the inlet tube assembly14is positioned within the housing assembly12. The inlet tube assembly14is oriented within the housing assembly12such that the proximal end50is adjacent to the valve seat body24and the flange56is adjacent to the distal plate26. As oriented, the radial wall68of the flange56extends beyond the channel34along the interior surface28of the main housing22and slidably moves along the interior surface28as the inlet tube assembly14is repositioned. Attached to the flange56along the outer rim72and the groove36of the main housing22, the upper membrane76expands and/or contracts within the channel34as needed to accommodate the position of the inlet tube assembly14. The upper membrane76is fluidly sealed to both the flange56and the housing assembly12. The lower membrane66also provides a fluid seal and expands and/or contracts in response to the movement of the inlet tube assembly14.

Additionally, the biasing mechanism16is enclosed within the middle chamber20of the flow regulating device10. Respective ends of the biasing mechanism16may abut the proximal face71of the flange56and the valve seat body24. In one embodiment, the radial wall68and the interior guide52maintain the position of the respective ends of the biasing mechanism16within the housing assembly12. In another embodiment, the inner rim wall74positions the biasing mechanism16against the flange56. The biasing mechanism16may also encircle the tube54.

The flow regulating device10described above functions in the following manner. In general terms, the inlet tube assembly14slides between a first, open position (FIG. 1) in which airflow to the constant pressure chamber18is permitted and a second, closed position in which airflow to the constant pressure chamber18is prevented in establishing a near constant pressure flow of air from the outlet orifice42. In the context of medical testing procedures, a patient's breath enters the gas flow regulating device10at the flow port46by means of an artificial airway (not shown) or directly from a patient's mouth, and is directed toward the proximal end50of the lumen58via the through holes44(FIG. 3) in the valve seat body24. An uneven flow of the patient's breath is regulated to a constant flow that exits the gas flow regulating device10at the outlet orifice42, allowing samples to be collected for analysis and testing (for example via a test tube (not shown) assembled to the distal plate26at the outlet orifice42). More specifically and as illustrated by the flow arrows80inFIG. 2, the patient's exhaled breath enters the flow regulating device10by way of the through holes44and into the lumen58at the proximal end50. The breath exits the lumen58at the distal end60of the inlet tube assembly14and is directed into the constant pressure chamber18. The inlet tube assembly14slidably repositions within the housing assembly12as the volume of air (and thus pressure) increases in the constant pressure chamber18.

In the one embodiment, a diameter of the outlet orifice42is smaller than a diameter of the lumen58of the inlet tube assembly14. In this manner, only a portion of the delivered air exits the constant pressure chamber18via the outlet orifice42. Pressure builds within the constant pressure chamber18as the volume of air in the constant pressure chamber18increases at a rate greater than the rate the contained air can exit through the outlet orifice42. Pressure within the constant pressure chamber18builds until the force against the flange56of the slidable inlet tube assembly14is greater than the constant k of the biasing mechanism16, forcing the inlet tube assembly14to slide proximally toward the valve seat body24. The bleed hole32relieves any build-up of pressure within the middle chamber20in response to movement of the inlet tube assembly14. When the proximal end50of the lumen58seals against the seat48, airflow into the inlet tube assembly14(and thus to the constant pressure chamber18) is prevented.

Conversely, as air is continuously released from the constant pressure chamber18, the corresponding pressure (and thus force on the flange56) will decrease; once the force drops below the spring constant k, the biasing device16forces the inlet tube assembly14back toward the open state. As a result, the flow rate of airflow exiting the outlet orifice42is constant, and is independent of any fluctuations from the patient. In this manner, a more constant volume of air passing through the flow regulating device10per unit time is achieved. Thereby, the flow of air through the critical orifice42is controlled at a constant rate, despite variations in the air pressure entering the flow control device10at the through holes44.

An alternate embodiment device10′ is provided inFIGS. 5 and 6that further illustrate optional aspects of the present disclosure. The device10′ is highly akin to the device10(FIG. 1), and includes a housing assembly12′ slidably maintaining an inlet tube assembly14′ relative to a constant pressure chamber18′ and a middle chamber20′ between an open or first state (FIG. 5) and a closed or second state (FIG. 6).

In the first, open state, the inlet tube assembly14′ permits communication of a lumen58′ with the constant pressure chamber18′. A flange56′ of the inlet tube assembly14′ is biased toward the open state by a biasing mechanism16′. As compared to the flange56(FIG. 1) previously described, the flange56′ may have an inner rim wall74positioned radially within the radial wall68′ that provides guidance and/or stability to the biasing mechanism16′ as it interfaces with the flange56′. Air exits through the distal plate26′ via the outlet orifice42′ defined by an outlet port45that otherwise extends from a major face of the distal plate26′ to provide convenient connection to a tube or medical device (not shown).

In the closed position ofFIG. 6, pressure within the constant pressure chamber18′ generates a force F onto the flange56′ greater than a spring constant k of the biasing mechanism16′. The biasing mechanism16′ is thus compressed by the flange56′ of the inlet tube assembly14′, and the inlet tube assembly14′ slides proximally to a sealed location with the seat98′ of the valve seat body24′. Thus, the lumen58′ is sealed from the through holes (not shown, but akin to the through holes44ofFIG. 3) such that the patient's breath cannot enter the constant pressure chamber18′ from the lumen58′.