Continuous Feed Medical Nebulizer

Abstract

A continuous feed nebulizer system for medical inhalation therapy in which a rigid dual lumen feed tube is connected with a liquid supply source and extends into a nebulizing chamber. This feed tube continuously replenishes liquid as it is nebulized and has a liquid drain lumen that is of a smaller cross sectional area and extends below an air return lumen. Constricted orifice structures adjacent a bottom of the liquid drain lumen and a top of the air return lumen damp out sudden changes of liquid level in the chamber as this level ranges between a bottom of the liquid drain lumen and a bottom of the air return lumen. This structure causes more uniform nebulization within the continuous feed nebulizer.

Description

BACKGROUND

In recent years it has become more prevalent to treat respiratory illnesses such as emphysema, lung disorders, etc., with inhalation therapy. The inhalation theapy used generally involves controlling the gases that a patient breathes and these gases may be room air or air enriched with oxygen. A liquid medication is usually added to the gases for absorption in the lungs and respirating system of the patient.

One particularly successful way of adding liquid medication to gases breathed by a patient is with an "ultrasonic nebulizer." An ultrasonic nebulizer applies a tuned ultrasonic energy source to a medical liquid and causes this liquid to form a geyser at its surface. The geyser is comprised of microscopic liquid particles that are readily inhaled by the patient and absorbed through his respiratory system.

Patients who are extremely ill sometimes require very prolonged inhalation therapy of several hours. In these instances, it has been the practice to set up a "continuous feed" ultrasonic nebulizer to continually replenish liquid that is being breathed in by the patient. Previous systems have included an inverted one or two liter liquid supply bottle hung above a nebulizing chamber. Liquid was drained from the liquid supply bottom into a nebulizing chamber through a liquid drain tube. An air return tube fed air from the chamber back into the supply bottle. The liquid drain tube extended below the air return tube to control the upper and lower limits of liquid level in the nebulizer chamber. This construction was sometimes called the "chicken feeder" for automatically keeping liquid in the nebulizing chamber within a specified range, because similar constructions have been used by the poultry industry for dispensing food and water to poultry.

In a nebulizer, the liquid drain tube and the air return tube work like this. When the nebulizing chamber dropped below the lower end of the liquid drain tube more liquid would flow into the chamber from the liquid supply bottle. Air in the liquid supply bottle was replaced with air moving up the air return tube. When the level reached the bottom of the air return tube it would cut off the air flow back to the bottle and a vacuum lock would occur and prvent additional liquid drainage.

One of the main problems with these continuous feed nebulizer devices was that their level surged up and down between its lower ends of the liquid and air tubes. This surging can cause changes in nebulizing rates and generally affect the geyser erupting from the surface of the liquid. These continuous feed nebulizer systems are used over very prolonged periods of time, on very ill patients, and this surging causes serious problems in accurately controlling the nebulization of medicament being continually breathed in by the patient.

SUMMARY OF THE INVENTION

I have overcome the problem of the up and down surging of the liquid in the nebulizing chamber when delivered through a continuous feed system. In my invention there is a dual lumen feed tube having a liquid drain passage and an air return passage to form the "chicken feeder." Both of these lumens are substantially larger than capillary dimensions so liquid can readily flow downwardly and air can readily flow upwardly with little resistance. One of the large area lumens has a fixed orifice construction therein, and I have found that this damps out the surging effect of the liquid being supplied to the nebulizing chamber. In the preferred embodiment the air return passage has a restricted orifice adjacent its top end and the liquid drain lumen has a restricted orifice adjacent its bottom end. These two restricted orifices tend to break up the air flowing back into the liquid supply bottle and also slowly dispenses liquid from the liquid drain tube. The combination of the large diameter tubes and the restricted orifices cause smooth changes in the liquid level within the nebulizing chamber and give much better control of nebulization within the nebulizing chamber.

THE DRAWINGS

FIG. 1 is a front elevational view partially in section showing the liquid supply source, the nebulizing chamber and the dual lumen feed tube;

FIG. 2 is an enlarged section taken along line 2--2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 1 showing the oval configuration of the feed tube and how it fits against a side of the nebulizer collecting cup;

FIG. 4 is an enlarged sectional view of the dual lumen feed tube showing its two constricted orifices;

FIG. 5 is a top view taken along line 5--5 of FIG. 4; and

FIG. 6 is a bottom view taken along line 6--6 of FIG. 4.

DETAILED DESCRIPTION

Referring to these drawings in detail, FIG. 1 shows a liquid supply source 1 in the form of a liquid filled bottle with an outlet closure system 2. Connected to this outlet are two flexible hollow lead tubes 3 and 4. As shown in FIG. 1, liquid drains down tube 3 and air bubbles flow up into liquid supply source 1 through flexible tube 4.

Spaced below the liquid supply source 1 is a hollow thermoplastic nebulizing chamber 5. This nebulizing chamber has an inlet tube 6 and an outlet tube 7 which connect to the apparatus to feed the nebulized liquid to the patient. Very often this apparatus includes a blower system that forces air in through tube 6 into chamber 5 where it picks up nebulized liquid particles in the chamber and thereafter forces them out through tube 7 and to the patient for breathing. Nebulization of a liquid 8 at a lower portion of the chamber causes a geyser (not shown) to erupt from the surface of the liquid 8 and be picked up by the air stream being fed to the patient. This nebulization takes place because of an ultrasonic energy source 9 spaced below a collecting cup 10 of the nebulizing chamber. Ultrasonic energy is transferred through liquid bath 11, cup 10 and nebulizable liquid 8 to where it causes a geyser to erupt at surface 20 of liquid 8.

As liquid 8 is nebulized within chamber 5 its level slowly decreases. When the level reaches a certain point the dual lumen rigid feed tube 12 will replenish the liquid. As shown in FIG. 1. feed tube 12 has two tubular connectors 13 and 14 at its upper end which telescopically fit into the two hollow flexible lead lines 3 and 4 from liquid supply source 1. The feed tube 12 also has an integrally formed cap member that includes a lateral top wall 15 and a depending skirt 16 that engages with and fits over an upstanding inlet port system 17 of the nebulizer container. Thus, the rigid feed tube forms a connecting link between the tubes 3 and 4 and the liquid 8 in the nebulizing chamber.

At a lower end of the feed tube 12 it is seen that a liquid drain lumen 18 extends a given distance below the air return lumen 19. This extension of the liquid drain lumen controls the range of vertical movement of the upper surface 20 of liquid 8. When the liquid level 20 drops below end 21 of the liquid drain lumen 18 the nebulizing chamber will begin to fill. This occurs because air will flow up the air return pass lumen 19 to replace air in liquid supply source 1 so liquid can drain. When level 20 of liquid 8 reaches the end of end 22 of the air return lumen the liquid will block off air passage therethrough. This causes a vacuum lock in the liquid supply source and liquid 18 will cease to flow. As liquid 8 is nebulized, surface 20 will drop and again let air flow back into bottle 1. This continuous process causes a "continuous feed" of liquid to the nebulizing chamber and provides a generally constant liquid level that can be efficiently nebulized.

As mentioned before, a serious problem of previous continuous feed systems of this "chicken feeder" type was the up and down surging of surface 20 of liquid 8. This surging changes the characteristics of the nebulized geyser within chamber 5 and also varied the rate at which the patient was receiving the nebulized medicaments.

In FIG. 1 this surging is substantially reduced by including a retricted orifice 23 at a top portion of the air return lumen 19. This causes air to be funneled in by the large lumen 19 with little resistance to flow and then slowly metered out through orifice 23. Preferably this orifice is between 0.040 and 0.100 inches in diameter. I have found this size of orifice tends to break up large slugs of air coming up air lumen 19. The air dispensed into liquid source 1 is in very fine metered bubbles which slowly release the vacuum lock in the liquid supply bottle 1. This causes the liquid to drain down liquid drain lumen 18 more slowly.

I've also discovered that elimination of the liquid surging is greatly benefited by a small orifice 24 of between 0.040 and 0.100 at a bottom of the liquid drain tube. This causes slow metering out of the liquid from the liquid drain tube. Thus, as the liquid is continuously supplied to the nebulizing chamber 5 the surface 20 of liquid 8 will slowly creep up and down between the two extremes of its range. Thus, a large slug of air entering air tube 19 at an instant the surface tension of surface 20 breaks the lower end 22 of the air return lumen will not cause a large gush of liquid to be delivered to the nebulizing chamber. As shown in FIGS. 1 and 4 the lower end of the air tube 19 is beveled to reduce the surface area of contact between the liquid surface and air tube at the critical opening and closing of the air passage. This improves the smoothness of the opening and closing of the air passage's lower port. The beveled lower end of the air tube is preferred but it could be made horizontal if desired.

For the non-surging feature of my invention to work very well the liquid drain passage 18 and the air return lumen 19 have cross sectional areas substantially larger than capillary sizes. This is to reduce friction as liquid is draining down lumen 18 and air is returning through lumen 19. It is also preferable to have lumen 19 with cross sectional area more than 3 times the size of liquid drain lumen 18. This allows large slugs of air to collect in lumen 19 before they are metered through fixed orifice 23. The diameter of lumen 18 is between 0.125 and 0.150 inch. Lumen 19 is of irregular cross sectional area but includes a cross section more than three times the cross sectional area of liquid drain lumen 18 as shown in FIGS. 2 and 3. As shown best in FIG. 3, the oval configuration of the feed tube fits against a side wall of the collecting cup so as not to interfere with an erupting geyser in a center portion of the collecting cup. The feed tube in FIG. 1 has been rotated from that of FIG. 2 to better show the tube's internal structure.

In FIGS. 4, 5 and 6 the feed tube of this invention is shown in enlarged sectional proportions so that its features may be readily visible. This rigid thermoplastic tube with its orifices 23 and 24 provide smooth liquid flow into the nebulizing chamber. These orifices are of fixed diameters within the rigid feed tube and thus do not depend on the variations caused by manually adjusting an orifice size.

In use the rigid dual lumen feed tube can be supplied to a hospital already connected to flexible leads 3 and 4. To assemble the apparatus as shown in FIG. 1 a nurse needs merely to connect leads 3 and 4 to a liquid supply bottle and insert the feed tube into a nebulizer container 5. This will supply a constant liquid feed to the nebulizer chamber 5 to replace liquid that is nebulized and consumed by the patient.

In the foregoing descriptions I have used a specific example to describe my invention. However, it is understood that persons skilled in the art can make certain modifications to this embodiment without departing from the spirit and scope of the invention.

Claims

I claim:

1. An anti-surging dual-lumen liquid feed assembly in combination with a nebulizer system comprising a gravity-feed liquid-supply source and a container having a pool of medical liquid below and fed by the supply source and in which the level of liquid in the pool is substantially maintained, said antisurging assembly comprising:

an elongated drain-tube lumen including means for connection to the liquid-supply source for the free flow of liquid therefrom,

said drain-tube lumen including a lower terminal end portion normally immersed in said pool of liquid for supplementing the liquid in the pool;

an elongated air-return lumen including means connected and communicating with said liquid-supply source below the surface thereof and having a free open lower end in fixed relation to the lower of said drain-tube lumen and disposed above the lowerend of said drain-tube lumen for substantially establishing the level of said pool,

said air-return lumen having a cross-sectional area substantially greater than that of the drain-tube lumen capacity whereby a greater amount of air is immediately available to replace liquid dispensed from the liquid-supply source to said pool than can be dispensed through the drain-tube lumen, each of the cross-sectional areas of said air-return and drain-tube lumen being greater than a capilary size; and

orifice means interposed between the lower open end of said air-return lumen and the means connected and communicating with the liquid-supply source whereby air replacing liquid in the liquid supply source passes through the liquid-supply source and is substantially dampened in its passage therethrough, said orifice means defining a constriction for limiting the size of bubbles of air passing into the source of liquid-supply.

2. The structure as claimed in claim 1 in which said orifice means constriction being located substantially at the upper end of said air-return lumen adjacent the lower portion of the liquid-supply source.

3. The structure as claimed in claim 1 in which the cross-sectional capacity of said air-inlet lumen is at least three times as great of the corresponding capacity of said drain-tube lumen.

4. The structure as claimed in claim 1 in which said drain-tube lumen includes constricted orifice means adjacent the lower end thereof.

5. The structure as claimed in claim 4 in which said constricted-orifice means of said drain-tube lumen is at the lower terminus thereof.

6. The structure as claimed in claim 1 in which said air-return lumen and drain-tube lumen are an integral unit with said drain-tube lumen being integrally connected to one side of said air-return lumen and along the inner surface thereof,

7. The structure as claimed in claim 6 in which said integral unit includes an integral adapter cap having a depending skirt integral with a transverse top wall for removable accomodation on a cooperating connector of the container, said top wall including integral tubular connectors for attachment to the liquid-supply source.

8. The structure as claimed in claim 6 in which the ower end of said air-return lumen is beveled upwardly from the lower end of said drain-tube lumen and forms a progressively smaller opening as the level of the pool rises.

9. The structure as claimed 3 in which said air-return lumen is oval shaped in cross section, the adjacent wall portions of said lumen being a common one, and an inner wall portion of said drain-tube lumen extending transversely between opposed side wall portions of said air-return lumen.