Percutaneous endoscopic gastronomy tube for optimized gastric sumping

An improved percutaneous endoscopic gastrostomy (PEG) tube that allows continuous suctioning/sumping without occlusion of the tube by the gastric wall. The PEG tube includes a hollow drainage tubing coupled to a ventilated bell cap. The bell cap can be open or closed to the external environment is ventilated via apertures, crenellations and grooves, and hemispherical arches. The PEG tube minimizes, or completely eliminates, the need for a user thereof to frequently flush the tube, thus also curtailing intermittent suctioning and allowing for longer periods of uninterrupted drainage. Furthermore, the PEG tubes of the current invention reduce clogging of the tube by larger gastric matter that is intended to be suctioned out of the patient or subject.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates, generally, to percutaneous endoscopic gastronomy (“PEG”). More specifically, it relates to an improved PEG tube for optimized gastric sumping.

2. Brief Description of the Prior Art

A standard PEG tube has an intragastric “bell” that resembles the underside of a mushroom cap which holds it in place and prevents it from being pulled free of the abdominal wall (seeFIGS. 1A and 1B). When a PEG tube is placed to suction for purposes of gastric drainage this bell frequently contacts the opposite stomach wall creating a seal and preventing further drainage (seeFIG. 1B), thus hindering the therapy.

As noted, PEG and nasogastric tubes are known in the art. For example, U.S. Pat. No. 5,356,391 to Stewart discloses a collapsible gastrostomy tube having a collapsible, internal retention flange. The gastrostomy tube is inserted into a patient's stomach by a percutaneous endoscopic or other suitable technique. However, the internal retention flange comprises a dome shape that would adhere to the contralateral stomach wall when suction is applied, effectively sealing off the tube.

U.S. Pat. No. 5,391,159 to Hirsch et al. discusses a gastrostomy tube is a flexible tube having on one inner end thereof an improved energy absorbent internal retaining member. The energy absorbent internal retaining member has a hollow body portion with two resiliently reversible physical forms or shapes, toroidal-like, and, goblet-like connected to a foreshortened hollow axial stem portion that is attached to or integrally made with the inward end of the flexible tube. The internal retaining member is made in the toroidal-like form. During intentional removal, when under pressure against the stomach mucosa, the internal retaining member snaps into the unrolled, dome-like shape and pulls out through the stoma tract. However, the dome-shaped retaining member still would adhere to the contralateral stomach wall when suction is applied, effectively sealing off the tube.

U.S. Pat. No. 3,421,510 to Kettenbach discloses a design for a temporarily placed surgical drain. These drains are placed around viscera or in the soft tissue as a temporary treatment after surgery and removed after several days. They cannot, however, be placed into the actual lumens of viscera.

U.S. Pat. No. 5,273,523 to Sozuki et al. discusses a design modification for a nasogastric tube. These tubes are placed through the nose into the stomach and are considered a temporary treatment. While these are well adapted for suctioning/sumping the stomach, they are temporary and cannot be inserted through an abdominal wall.

Similarly, U.S. Patent App. Pub. No. 2007/0060823 to Giroux et al. describes suction venting on a nasogastric tube provided by a sump lumen within the tube and not by a geometric property of the tube itself. These nasogastric tubes are not typically used for long term feeding, as is often done with a PEG tubes due to the long and narrow lumen which is prone to clogging. U.S. Pat. No. 3,999,554 to Kim et al. and U.S. Pat. No. 3,114,373 to Andersen describes a similar nasogastric tube as that seen in U.S. Pat. No. 5,273,523 to Sozuki et al. and U.S. Patent App. Pub. No. 2007/0060823 to Giroux et al. and include the same drawbacks as the described nasogastric publications. Similarly, U.S. Pat. No. 2,492,384 to Kaslow relates to nasogastric tubes as well. While the loop design at the end of this tube could theoretically help prevent occlusion, given the pliability of gastric mucosa, this is unlikely, and again this tube could not be used percutaneously.

U.S. Pat. No. 4,356,824 to Vazquez applies the principles of a nasogastric tube but placed through a gastric tube base. The suction tube utilizes a second interior sump tube to prevent sealing. This design facilitates the prevention of sealing or clogging, but does so by effectively adding several additional tubes and lumens, rather than any geometric alteration of the PEG tube bell itself. Additionally, this tube could not be placed percutaneously via an endoscope as it has multiple tubes and lumens on each end and could not be pulled through a single skin hole and would require a full surgical laparotomy.

U.S. Pat. No. 2,470,665 to Stiehl discloses a suction tip for a tube utilizing an inflatable hood to keep the stomach walls away from the suction tubing to prevent occlusion of the suction ports. However, this apparatus requires inclusion of additional ports on the proximal end of the tube, meaning that it cannot be placed percutaneously like a PEG tube.

Accordingly, what is needed is an improved PEG tube that can more effectively sump or suction out the contents of a body lumen, such as the stomach. However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.

BRIEF SUMMARY OF THE INVENTION

The long-standing but heretofore unfulfilled need for a ventilated PEG tube is now met by a new, useful, and nonobvious invention.

In an embodiment, the current invention is a percutaneous endoscopic gastrostomy tube apparatus. The apparatus includes an elongate, substantially hollow drainage tubing that has proximal and distal ends. The drainage tubing is configured to extend through a patient or subject's body with the distal end of the drainage tubing being positioned in a region of interest (e.g., stomach lumen) within the patient or subject's body. A bell cap is coupled to the distal end of the drainage tubing and has a substantially hollow interior in open communication with the interior the drainage tubing. The bell cap has a distal end and also a distal edge at the distal-most portion of the distal end of the bell cap. The apparatus further includes a means of ventilating the bell cap, where the ventilating means is positioned through and along a body of the bell cap and/or through and along the distal edge of the bell cap. This allows the interior of the bell cap to be in open communication with an external environment through the ventilating means.

Optionally, the drainage tubing can include a plurality of channels extending therethrough along a length of the drainage tubing, where one of the channels is a drainage lumen and the other channel is a ventricular lumen.

The distal end of the bell cap may be open or closed to the external environment. When open, the ventilating means may be a plurality of apertures disposed about the circumference of the body of the bell cap. In this case, each aperture can have a diameter that is equal to or less than a diameter of the distal end of the drainage tubing. Alternatively, when the distal end of the bell cap is open to the external environment, the ventilating means can be a plurality of crenellations disposed along the distal edge of the bell cap, such that a groove is formed between each pair of crenellations around the distal edge of the bell cap. In this case, the groove may have a width or length that is equal to or less than a diameter of the distal end of the drainage tubing.

Alternatively, when the distal end of the bell cap is open to the external environment, the ventilating means can be a hemispherical arch attached to the bell cap at two (2) distinct points on the bell cap and extending distally from the bell cap to a distal apex positioned at a spaced distance away from (distal to) the distal edge of the bell cap. These two (2) distinct points of connection between the hemispherical arch and the bell cap may be in diametric opposition to each other. Optionally, the ventilating means may include a second hemispherical arch attached to the bell at another two (2) distinct points on the bell cap and extending distally to a distal apex positioned at a spaced distance away from (distal to) the distal edge of the bell cap. In this case, these additional two (2) distinct points of connection between the second hemispherical arch and the bell cap may be in diametric opposition to each other. Further, the two hemispherical arches can intersect each other at the distal apexes, such that the spaced distances away from the bell cap are about the same distance away from the bell cap. In other words, the two hemispherical arches would share one apex. Alternatively, the hemispherical arches can intersect, such that one has a further distal apex than the other. In either case, the intersection between the hemispherical arches can form a ninety (90) degree angle between each other.

When the distal end of the bell cap is closed to the external environment, the ventilating means can be an array of apertures formed through and along a surface of the body of the bell cap. Each aperture can have a diameter that is equal to or less than a diameter of the distal end of the drainage tubing. Each aperture may be ovular or elongate in shape. The apertures may have a randomized or ordered arrangement around a circumference of the bell cap.

In another embodiment, the current invention is a percutaneous endoscopic gastrostomy tube apparatus for gastric sumping, comprising any one or more of the foregoing characteristics and features, individually or in combination.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In certain embodiments, the current invention is a vented percutaneous endoscopic gastrostomy (PEG) tube and/or a method of performing percutaneous endoscopic gastronomy, substantially as discussed herein.

More particularly, the PEG tube includes an elongate, hollow drainage tubing having a proximal end and a distal end, where the term “proximal” refers to a position closer to the user or physician and “distal” refers to a position closer to the patient or subject in which the PEG tube is inserted. The tubing extends through the patient or subject's body with the distal end positioned in a region of interest (e.g., stomach lumen) within the patient or subject. A bell cap is coupled to the distal end of the drainage tubing, where the interior of the bell cap and the interior of the tubing are in open communication with each other. The bell cap includes a structural means or mechanism for ventilation that is positioned through and/or along a surface of the bell cap, such that the interior of the bell cap is in open communication with the external environment or gastric environment through the means of ventilation.

The bell cap can have a distal end that is open to the gastric (or visceral) environment. In this case, the means of ventilation may be a plurality of apertures disposed along the circumference of the body or distal end of the bell cap, such that the interior of the bell cap is in open communication with the external environment or gastric environment through the apertures. Each aperture may have a diameter that is equal to or slightly less than the diameter of the hollow drainage tubing. A slightly smaller diameter for each aperture would prevent debris from entering the interior of the bell cap and subsequently plugging or clogging the entrance to the drainage tubing.

Alternatively, the means of ventilation may be a plurality of notches or crenellations formed along an edge or lip of the distal end of the bell cap. Each notch or crenellation may have a width and/or length that is equal to or slightly less than the diameter of the hollow drainage tubing. A slightly smaller width and/or length for each notch or crenellation would prevent debris from entering the interior of the bell cap and subsequently plugging or clogging the entrance to the drainage tubing.

Alternatively, the means of ventilation may be a hemispherical arch attached to the bell cap at two (2) distinct points and extending distally to a distal apex positioned a spaced distance away from and distal to the distal edge of the bell cap. The two (2) distinct points of connection between the arch and bell cap can be positioned in diametric opposition to one another on the bell cap. There may also be a second hemispherical arch attached at another two (2) distinct points of the bell cap at a spaced distance away from and distal to the distal edge of the bell cap. These two (2) distinct points of connection can also be positioned in diametric opposition to one another on the bell cap. In this case, the hemispherical arches can intersect with each other at their distal apexes to form a ninety (90) degree angle between each other. They can intersect such that their distal apexes are the same distance away from and distal to the distal end of the bell cap. In other words, they would share a distal apex, as the apexes would be co-planar with each other. Alternatively, the hemispherical arches can cross each other such that they do not share a common distal apex; rather, one arch has a slightly longer length than the other and has a further distal apex than the other. In this case, they do not necessarily “intersect” each other at all but would be positioned on top of each other to cross each other (i.e., the distal apexes are not co-planar).

Alternatively, the bell cap can have a distal end that is closed to the external environment or gastric environment. In this case, the means of ventilation may be an array of apertures formed through and along the surface of the body and/or closed distal end of the bell cap. Each aperture may have a diameter that is equal to or slightly less than the diameter of the hollow drainage tubing. A slightly smaller diameter for each aperture would prevent debris from entering the interior of the bell cap and subsequently plugging or clogging the entrance to the drainage tubing.

Alternatively, each aperture in the closed bell cap can be ovular or elongate in shape.

Optionally, the hollow drainage tubing may be multichanneled, or in other words include a plurality of channels extending through the length of the drainage tubing. These channels would terminate in a single tapered cone at the tube end to be passed percutaneously. Once passed through the skin this cone would be transected, and a multi-port adapter would be attached to the extraluminal end of the tube.

EXAMPLES

The current invention is an improved PEG tube that allows continuous suctioning/sumping without occlusion of the tube by the gastric wall. The PEG tube minimizes, or completely eliminates, the need for a user thereof to frequently flush the tube, thus also curtailing intermittent suctioning and allowing for longer periods of uninterrupted drainage. Furthermore, the PEG tubes of the current invention reduce clogging of the tube by larger gastric matter that is intended to be suctioned out of the patient or subject. This benefit reduces the time burden on nursing by reducing the need for manual examination and clearing of the tube. Even with the improvements of the PEG tubs of the current invention, the tube still permits standard endoscopic placement and feeding/medication administration by the nurse or physician.

In certain embodiments, the current invention has a form similar to the classic mushroom cap “bell” of a conventional PEG tube but includes several structural and functional modifications and improvements for improved sumping and gastric suctioning, while minimizing the time and frequency of flushing out the PEG tube.

As depicted inFIGS. 2A and 2B, hollow drainage tubing2can optionally be multichanneled (e.g., drainage channel4aand ventricular channel4bextending through the length of drainage tubing2), with each channel4a,4bhaving the same or different diameters. Channels4a,4bmay terminate in tapered cone6at the end of drainage tubing2, to be passed percutaneously.

Drainage channel4ais associated with the drainage lumen, and ventricular channel4bis associated with the ventricular lumen. Once cone6is passed through the skin, cone6can be transected, and a multi-port adapter (formed of ports8a.8b) would be coupled to the extraluminal end of drainage tubing2. Each lumen would respectively lead to one of ports8a,8bthat split off drainage tubing2, as seen inFIG. 2B. A multichannel PEG tube, such as this, performs similar to a nanogastric tube.

In an embodiment, the current invention is a PEG tube apparatus, generally denoted by the reference numeral10, including elongate, hollow drainage tubing12and a bell cap, generally denoted by the reference numeral16, in the form of a vented hemisphere. Hollow drainage tubing12has a proximal end closest to the nurse, physician or other user, and a distal end positioned within the stomach cavity/lumen of the patient or subject. Drainage tubing12includes distal tubing opening14that terminates in vented hemispherical bell cap14.

Bell cap16includes body18and distal edge20formed around distal cap opening22, which collectively form the boundaries of its hollow interior24. Bell cap16is shaped as an inverted mushroom cap or is otherwise cylindrically shaped with its body18lined with a plurality of apertures26,28formed radially around the entire circumference of body18of bell cap14. Bell cap16has a proximal end connected to and in open communication with distal tubing opening14of hollow drainage tubing12. Bell cap16further includes a distal end that is open to the external/gastric environment. Thus, the external/gastric environment is in open communication with hollow interior24of bell cap16through distal cap opening22and through apertures26,28disposed around body18of bell cap16.

Apertures26,28disposed radially around the entire circumference of body18of bell cap16can have any shape (see circular shape inFIG. 3Aand alternate/hexagonal shape inFIG. 3B) or size suitable for the function of PEG tube apparatus10or as desired by the user. Typically, though, each aperture26,28may have a diameter that is about the same as or slightly smaller than the diameter of distal tubing opening14of hollow drainage tubing12. This is done so that any particulates/matter that are suctioned through apertures26,28into hollow interior24of bell cap16and subsequently into hollow drainage tubing12through distal opening14cannot be so large that they can block or clog drainage tubing12, while still also maximizing the amount of particulates/matter that can be suctioned through bell cap16and drainage tubing12if distal cap opening22of bell cap16happens to be vacuum suctioned or sealed against an abdominal wall.

In an embodiment, the current invention is a PEG tube apparatus, generally denoted by the reference numeral30, including elongate, hollow drainage tubing32and a bell cap, generally denoted by the reference numeral36, in the form of a vented hemisphere. Hollow drainage tubing32has a proximal end closest to the nurse, physician or other user, and a distal end positioned within the stomach cavity/lumen of the patient or subject. Drainage tubing32includes distal tubing opening34that terminates in vented hemispherical bell cap34.

Bell cap36includes body38and distal edge40formed around distal cap opening42, which collectively form the boundaries of its hollow interior44. Bell cap36is shaped as an inverted mushroom cap or is otherwise cylindrically shaped with its distal edge40lined with a plurality of crenellations or notches46formed radially around the entire circumference of the cap with corresponding grooves47formed between crenellations46. Bell cap36has a proximal end connected to and in open communication with distal tubing opening34of hollow drainage tubing32. Bell cap36further includes a distal end that is open to the external/gastric environment. Thus, the external/gastric environment is in open communication with hollow interior44of bell cap36through distal cap opening42and through grooves47disposed around distal edge40of bell cap36.

Crenellations46disposed radially around the entire circumference of distal edge40of bell cap36can have any size suitable for the function of the PEG tube or as desired by the user. Typically, though, each groove47can have width48aand/or length48bthat is about the same as or smaller than the diameter of hollow drainage tube32and distal opening34thereof. This is done so that any particulates/matter that are suctioned through grooves47into hollow interior44of bell cap36and subsequently into hollow drainage tubing32through distal opening34cannot be so large that they can block or clog drainage tubing32, while still also maximizing the amount of particulates/matter that can be suctioned through bell cap36and drainage tubing32if distal cap opening42of bell cap36happens to be vacuum suctioned or sealed against an abdominal wall.

In an embodiment, the current invention is a PEG tube apparatus, generally denoted by the reference numeral50, including elongate, hollow drainage tubing52and a bell cap, generally denoted by the reference numeral56, in the form of a vented hemisphere or pseudo-sphere. Hollow drainage tubing52has a proximal end closest to the nurse, physician or other user, and a distal end positioned within the stomach cavity of the patient or subject. Drainage tubing52includes distal tubing opening54that terminates in vented hemispherical or pseudo-spherical bell cap56.

Bell cap56includes body58and distal edge60formed around distal cap opening62, which collectively form the boundaries of its hollow interior64. Bell cap56is shaped as an inverted mushroom cap or is otherwise cylindrically shaped with one or more hemispherical arches65a-65b(FIG. 5A),67a-67b(FIG. 5B) attached to its distal edge60. Bell cap56has a proximal end connected to and in open communication with distal tubing opening54of hollow drainage tubing52. Bell cap56further includes a distal end that is open to the external/gastric environment. Thus, the external/gastric environment is in open communication with hollow interior64of bell cap56through distal cap opening62and through the space between hemispherical arches65a-65b,67a-67b.

First hemispherical arch65a,67ahas a first end and a second end. The first end of hemispherical arch65a,67ais attached to a first side of bell cap56(e.g., at distal edge60of bell cap56, at the proximal end of bell cap56, along the exterior or interior surface of body58of bell cap56, etc.). Hemispherical arch65a,67afollows a path of travel, extending distally from the first side of bell cap56until it reaches distal apex66,68a, (seeFIG. 5Afor apex66andFIG. 5Bfor apex68a). Hemispherical arch65a,67acontinues to follow its path of travel, extending proximally from its distal apex66,68auntil it reaches a second side of the bell cap. As seen inFIGS. 5A-5B, the first and second sides of bell cap56typically are in diametric opposition to one another, or in other words are separated from one another by a distance equaling the diameter of the distal end of bell cap56if bell cap56has a circular distal end (seeFIG. 5A). Alternatively, if bell cap56has another shape (e.g., rectangular, square, etc.), the arches extend from one side to an opposite side of the bell cap (seeFIG. 5B).

In certain embodiments, second hemispherical arch65b,67bis connected to two (2) sides of bell cap56as well and extends distally from bell cap56, similar to the connection and disposition of first hemispherical arch65a,67a. In this case, the arches can intersect with one another at any angle desired.

In an embodiment, however, first and second hemispherical arches65a-65b,67a-67bwould intersect at approximately a ninety (90) degree angle, such that the paths of travel of arches65a-65b,67a-67bhave planes that are perpendicular to each other. Arches65a-65bcan completely intersect, as inFIG. 5Awhere arches65a-65bshare common apex66. Alternatively, arches67a-67bcan tangentially intersect, as inFIG. 5B, where first arch67aincludes distal apex68athat is further distally positioned than second arch67b, which includes distal apex68bthat is further proximally positioned than that of first arch67a. Thus, first arch67aalso has a steeper pitch than second arch67b.

Arches65a-65b,67a-67bare positioned along the distal end of bell cap56and form open spaces therebetween that are open distally to the external/gastric environment. Thus, the external/gastric environment is in open communication with hollow interior64of bell cap56through the space formed between arches65a-65b,67a-67band the space between arches65a-65b,67a-67band the distal end of bell cap56.

The length of arches65a-65b,67a-67band the space therebetween and between arches65a-65b,67a-67band the distal end of bell cap56can have any size suitable for the function of PEG tube50or as desired by the user. Arches65a-65b,67a-67b, which can be circular or rounded in certain embodiments, help prevent distal edge60of bell cap56from vacuum suctioning or sealing against an abdominal wall, thus allowing continuous suctioning of the particulates/matter desired.

In an embodiment, the current invention is a PEG tube apparatus, generally denoted by the reference numeral70, including elongate, hollow drainage tubing72and a bell cap, generally denoted by the reference numeral76, in the form of a vented sphere. Hollow drainage tubing72has a proximal end closest to the nurse, physician or other user, and a distal end positioned within the stomach cavity of the patient or subject. Drainage tubing72includes a distal tubing opening (not shown in these figures but shown in previous figures) that terminates in the vented spherical bell cap.

Bell cap76includes body78and closed distal edge80, which collectively form the boundaries of its hollow interior (not shown in these figures but shown in previous figures). Bell cap76is spherically- or otherwise cylindrically-shaped with a plurality of apertures82,84formed within body78of bell cap76. Bell cap76has a proximal end connected to and in open communication with the distal tubing opening of hollow drainage tubing72. Bell cap76further includes distal edge80that is closed to the external/gastric environment. Apertures82,84are formed generally along the distal end of bell cap76and along the sides of body78of bell cap76between the distal and proximal ends of bell cap76. Apertures82,84open outwardly to the external/gastric environment. Thus, the external/gastric environment is in open communication with the hollow interior of bell cap76through apertures82,84disposed around body78of bell cap76.

Apertures82,84disposed around the surface or body78of bell cap76can have any size suitable for the function of the PEG tube or as desired by the user. In an embodiment, though, each aperture82,84has a diameter or width that is about the same as or slightly smaller than the diameter of hollow drainage tube72. This is done so that any particulates/matter that are suctioned through apertures82,84into hollow drainage tubing72cannot be so large that they can block or clog drainage tubing72, while still also maximizing the amount of particulates/matter that can be suctioned through bell cap76and drainage tubing72if certain apertures82,84in bell cap76are vacuum suctioned or sealed against an abdominal wall.

Glossary of Claim Terms

Bell cap: This term is used herein to refer to the distal component or head of a PEG tube, through which matter or particulates from an anatomical region of interest are suctioned or sumped. It is contemplated herein that the bell cap can have any shape or form. Typically, the width or diameter of the bell cap is larger than the diameter of the proximally-positioned elongate, hollow drainage tubing attached thereto.

Closed to the external environment: This term is used herein to refer to a distal end of a bell cap having an edge that is closed or sealed, such as the side of a sphere.

Distal apex: This term is used herein to refer to the point of a hemispherical arch that is furthest away from a user (e.g., nurse, physician, etc.) of the PEG tube.

Distal: This term is used herein to refer to a relative position further from a nurse, physician, user, or other individual installing the PEG tube into a patient or subject

Distinct points: This term is used herein to refer to different connection points on or along a bell cap of a PEG tube according to certain embodiments of the current invention.

External environment: This term is used herein to refer to the surroundings (e.g., gastric environment) of a PEG tube when inserted into a region of interest of a patient or subject.

Less: This term is used herein to refer to a size of an aperture that optimizes the balance between not clogging the drainage tube with excessively large particulates or matter, while still permitting larger size particulates or matter to be removed from the region of interest of the patient or subject.

Means of ventilating: This term is used herein to refer to a structural mechanism that provides additional points of communication between the interior of the bell cap and the external/gastric environment. Examples include, but are not limited to, apertures or slits in the bell cap, notches or crenellations along the distal edge of the bell cap, among other suitable structures that provide open communication between the bell cap interior and external/gastric environment.

Open communication: This term is used herein to refer to a relationship between two (2) structural components of a system, where a fluid would be able to freely travel from the interior of one component to the interior of the other component.

Open to the external environment: This term is used herein to refer to a distal end of a bell cap having an edge that is free, such as the wider portion of a hemisphere.

Ordered arrangement: This term is used herein to refer to the positioning of apertures having a clear pattern around a bell cap.

Proximal: This term is used herein to refer to a relative position closer to a nurse, physician, user, or other individual installing the PEG tube into a patient or subject.

Randomized arrangement: This term is used herein to refer to the positioning of apertures having no clear pattern around a bell cap.

Region of interest: This term is used herein to refer to an anatomical area within a patient or subject from which a user (e.g., physician, nurse, etc.) desires to remove particulates or matter or to which the user desires to place a feeding tube or administer medication. An example of a “region of interest” is a stomach lumen of the patient or subject.

Spaced distance: This term is used herein to refer to a predetermined length or distance between a lip on the distal end of a bell cap and the distal apex of a hemispherical arch attached thereto.