GB2209129A

GB2209129A - Bubble trap

Info

Publication number: GB2209129A
Application number: GB8720508A
Authority: GB
Inventors: Alexander Harley
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-09-01
Filing date: 1987-09-01
Publication date: 1989-05-04
Anticipated expiration: 2007-09-01
Also published as: GB2209129B; GB8720508D0

Abstract

A device 1 for eliminating gas (air) bubbles from a liquid as the said liquid is passed through the said device 1 via passages 4 and 5. It is mainly for use in Percutaneus Transluminal Balloon Angioplasty or Valvuloplasty (and other vascular or intravenous applications). The Bubble Trap 1 consists of a transparent chamber 3 (e.g. acrillic) with a particular internal geometry of baffles 12 and 13, two leur connectors 8 and 9, and a stopcock 6 for expelling excess gas. The Bubble Trap 1 is connected in series between the inflation device (by leur connector 8) and the balloon catheter (by leur connector 9). <IMAGE>

Description

BUBBLE TRAP FOR CATHETER SYSTEMS: A DEVICE TO DCTRACZT BUBBLES FROM THE FLUID STRE#M IN # C#ThETER BACKGROUND OF THE INVENTION: The inventive device, will here and in what follows be called the bubble trap". It is designed to be coupled across a closed channel through which liquid is to flow. 'The purpose of the device Is' to extract bubbles from the flow stream of#.th#s-liquid as it passes through the device and hold them stationary within the device so they will no longer be carried by'the moving stream of fluid. Thus the device traps bubbles that may form in the a stream of flowing liquid.It may or may not also possess means to expell the bubbles from the fluid system once they are trapped.

The primary field of application for present invention is in cardiovascular catheterization work where it is important that no bubbles enter the catheter system as there is a possibility these could get into the bloodstream of the patient. More specifically' the bubble trap is needed in angioplasty and valvuloplasty operations.

Both angioplasty and valvuloplasty involve the use of a balloon mounted on the end of a catheter which is inserted percutaneousl'y into vascular system of the patient. The balloon is then 'positioned across the stenosis of an artery (angioplasty) or across a clogged heart valve (valvuloplasty). The balloon is then successively inflated and deflated with the purpose of removing or remolding the plaque which is causing the malfunction of the artery or heart valve.

In both procedures the catheter system is filled with a radio-contrast saline solution which is harmless to the patient and can be absorbed by the body in the case of a balloon rupture.

However as the operation proceeds it is generally necessary to inflate and deflate the balloon several times to obtain the desired result. In the course of deflation low pressure in the fluid allows dissolved air to enter bubbles consisting mostly of vacuum. These move to combine into large such bubbles. When normal pressure is returned these large bubbles reduce in size but do not disappear. The reason for this is that the ratio of the surface area of the free air to its volume is much less than it was before bubbles moved to combine. Hence the air which leaves solution can not redissolve because its surface contact with the liquid is not sufficiently large. Therefore nomatter how well sealed from the outside the fluid in the balloon catheter is, successive deflation; will produce successively larger air bubbles in the catheter fluid.In difficult operations the balloon may well rupture. It is then imperative that there be no air bubbles '#in that 'part of'the balloon catheter close 'enough to the balloon to empty into the patient's vascular system when the balloon bursts. > .

In this situation the bubble trap, the present inventive device, finds application. The bubble trap is inserted between the syringe or inflationdevice and the proximal end of the balloon catheter so that catheter fluid will pass through it on its way from the inflation device to the balloon and on its way from the balloon catheter back to the inflation device. Any bubble in the catheter will be drawn on deflation into the bubble trap and similarly any bubble in the inflation device that threatens to be swept into the catheter during inflation will be caught by the bubble trap and hence not enter the catheter. In this-way the bubbles formed, will inevitably, in the course of the operation be caught in the bubble trap and rendered harmless.

The trap will generally be equipped with a means for expelling trapped bubbles. Thus if for any reason in the course of the operation the inflation device develops lea#s which introduce large bubbles from the outside which might well exhaust the volume of the trap, the operation can proceed with only a periodic expulsion of the bubble from the trap. As this expulsion operation involves only a turn of a stopcock followed by a small push on the inflation device, the operation can proceed almost as normal. Without the bubble trap such a fault would require an immediate change of inflation device followed by a deflation and bubble clearing operation. What is worse, the fault might well not be detected especially if the inflation device and catheter are opaque as is often the case.

Moreover, at the start of a balloon catheter procedure, there is a point when the full inflation device is joined to the full but deflated catheter. At this juncture a bubble is formed which then has to be expelled either through a stopcock or through a number of tries at rejoining. This awkward and generally incomplete clearing of bubbles from the system can be eliminated by first attaching a bubble trap full of fluid to the inflation device, and then attaching the catheter to the distal end of the bubble trap.

The result is that all bubbles are eliminated from the catheter system as they are immediately caught in the bubble trap, and from there can be expelled.

Without a bubble trap what is generally presumed is that when a balloon ruptures the injection procedure will cease immediately with negative pressure applied as soon as possible. This measure forces any bubbles that may be lodged in the catheter to exit by being drawn into the inflation device but it also causes the inflation device to fill with blood with a resulting blood loss for the patient. This loss is 18 cc per balloon in the case of angioplasty and as much as 25 cc per balloon in the case of valvuloplasty. The use of the bubble trap would obviate the need for applying negative pressure when a balloon ruptures thereby saving the patient the accompanying blood loss.

4 system using the bubble trap would therefore be an improvement over prior art in balloon catheterization procedures since'the surgeon could be assured that throughout the operation the balloon catheter would be free of bubbles. This would maRe balloon rupturing a relatively safe event and so save the patient blood loss when this happens since the application of negative pressure to draw away any bubbles would no longer be necessary.

BRIEF DESCRIPTION OF THE oRv FIG.1 shows proximal end of a valvuloplasty system with inflation device fitted with bubble trap which in turn is fitted with the balloon catheter.

FIG.2 shows a cross section of the bubble trap along the axis of the bubble trap and through the bubble expulsion outlet.

DETAILED DESCRIPTION OF CONSTRUCTION AND USE OF BUBBLE TRAP FOR USE WITH 4 CATHETER SYSTEM FIG.1 shows a the proximal portion of a system for preforming valvuloplasty which has been fitted with the bubble trap 1. First we discuss the general features of the preparation and use of this system.

Female leur ending 8 on proximal end of bubble trap 1 is fitted to male leur ending 7 of inflation device 18 before the inflation device 18 is filled with radio contrast solution. Radio contrast solution is then drawn into the bubble trap 1 and the inflation device 18 through male leur ending 9. When the required volume is obtained in the syringe barrel of inflation device 18 any bubbles in the system are expelled via stopcock 6 through female leur ending 14. Any resulting deficiency of volume of injectable radio contrast solution is compensated for by drawing in more such fluid after the bubbles have been expelled. In this state inflation device 18 and bubble trap 1 connected as in FIG. 1 are ready for use. The proximal end of balloon catheter 11 is attached to male leur ending 9.Any bubbles introduced by this procedure are drawn into interior space 2 of bubble trap 1 and then expelled via stopcock 6.

With the balloon in position, the inflation - deflation procedure may now begin. On inflation, radio contrast solution is expelled through male leur ending 7 via female leur ending 8 into passage 5. It then passes into the interior 2 of bubble trap 1. If this interior 2 is full of fluid this fluid is then induced to flow through passage 4 via male leur ending 9 into the attached balloon catheter 11. This completes the description of the bubble trap's functioning on the first inflation cycle.

On deflation bubbles form in the radio contrast solution as a result of the imposed vacuum and generally collect in the proximal portion of the system. With the fluid moving from the balloon back into the inflation device 18 the high probability is that any bubbles formed on deflation will be drawn from the balloon catheter 11 and pass through passage 4 into the interior 2 of bubble trap 1. Having passed through passage 4 a bubble will float upwards towards stopcock 6 and will thereby be removed from the stream of fluid which will on reinflation be returned to the balloon catheter 11. If the interior 2 is more than half full of fluid then it will be impossible for a bubble, once trapped, to return into the balloon catheter 11 as long as the system is held horizontal.If the system is turned in any direction including the vertical then the bubble in interior 2 under atmospheric pressure must not have a volume exceeding the volume of that portion of interior 2 lying distal to the plane which passes through the proximal flat surface of baffle 13. If this condition on the size of the bubble in the trap is satisfied then no air can pass under any circumstances from the bubble trap 1 into the catheter 11 unless the bubble trap 1 and inflation device 18 are violently shaken during reinflation. Clearly this does not happen in the normal course of events. Accordingly, it is safe to assume the bubble will not be returned to the balloon catheter 11 as long as the baffles 12 and 13 remain submerged.

On reinflation the surgeon may want to-expell the bubble which was formed during deflation and now is lodged in the interior 2 of bubble trap 1. He may do this by opening stopcock 6 while holding the system so that stopcock 6 is vertical and pushing on the syringe handle of inflation device 18 until the bubble is removed.

He can then commence reinflation after closing stopcock 6.

Generally, unless there is a serious leak to the outside in the system, it is not necessary to remove the trapped bubble from bubble trap 1 before each successive reinflation. If the system is leak tight the bubble grows very slowly and will not approach a size to be of concern even after many inflation - deflation cycles. Therefore in the course of normal operations the surgeon need only push out the bubble once before the first inflation to be assured that the balloon catheter will be bubble free during the full course of the procedure.

If a bubble forms in inflation device 18 as a result of the imposed vacuum during deflation or is pulled out of the gauge, on reinflation, this bubble is pushed with the fluid in inflation device 18 through the joined leur endings 7 and 8 into passage 5 and finally into interior 2 of bubble trap 1. The bubble then floats upward and out of the stream of fluid flow and henceforth cannot pass on into passage 4 and balloon catheter 11.

As inflation; and deflations, especially in valvuloplasty operations, must occur quickly, considerable turbulance of fluid flow can result. If passage 5 were horizontal and in line with passage 4 then bubbles could easily be blown into passage 4 before they had a chance to float upward and out of the stream of flow leading into balloon catheter 11. The shape of baffle 12 further inhibits bubbles from entering passage 4 and induces them to collect into larger units thus facilitating their passage upward.

passage 15 between the plane faces of baffles 12 and 13 is made small so that the surface tension of the radio contrast solution will inhibit the passage of bubbles through this passage 15 and into passage 4. The formation of the narrow dist e passage 15 is the purpose for the plane face of baffle 13.

The bubble trap 1 in the here described preferred embodiment is constructed from clear plastic (either acrylic or polycarbonate) of medical grade. Leur endings 8 and 9 are standard pieces welded into passages 5 and 4 respectively at the points shown in Frog.2.

Stopcock 6 with female leur ending 14 is adapted from a standard high pressure stopcock and welded to any point where the plane parrallel to the faces of baffles 12 and 13 and midway between them intersects the outer surface of bubble trap 1. The thickness of wall 3 is chosen thin enough so that the bubble trap 1 will be light enough to facilitate use in the operating room on the end of inflation device 18. On the other hand, it is chosen thicks enough to withstand an internal pressure of 6 atmospheres for valvuloplasty and 15-28 atmospheres for angioplasty. The trap used for valvuloplasty should have interior 2 larger and wall 3 thinner than the corresponding trap used in angioplasty. The angioplasty trap can afford to have interior 2 of smaller volume because the amount of fluid from which a bubble could form is proportionately smaller in this case.

This completes the detailed description of the preferred embodiment of the present inventive device herein called the bubble trap. The scope of the present invention is in no way delimited or otherwise conditioned by the above description but only by what is put forth in the claims that follow.

Claims

BIIHHLE IRAM The preceding description and drawings of the present invention are intended to depict a particular embodiment of the invention only. The present invention is correctly described and delimited by the following claims and by these only.

We claim: 1. A device to trap and confine bubbles which may occur in a liquid within a catheter system, said device compriSing: an inner chamber being means to contain liquid and to contain gaseous bubbles which may occur in said liquid, a first and second means to provide fluid connection between said inner chamber and the fluid which can enter or leave said catheter system, said second means being disposed so that there is a percentage, P, P < P < 100, being such that if the liquid in said inner chamber fills more than P percent of the total volume of said inner chamber then when said device is stationary it is not possible for gaseous substance to pass out of said inner chamber via the second means, a third means to provide fluid connection between said inner chamber and the outside, said means permitting of being rendered operative or inoperative, a flow diverting means coupled to said first means, said flow diverting means being means to prevent gaseous substance leaving said inner chamber via said second means as a result of fluid entering said inner chamber via said first means while the liquid content of said inner chamber is at least F percent of the total volume of said inner chamber.
2. fi device as in claim 1. said first means allowing the formation of a fluid connection between said inner chamber and a fluid pressurizing device, said second means allowing the formation of a fluid connection between said inner chamber and said catheter system, said third means allowing the attachment of a fluid containing system in fluid connection with said inner chamber.
3. A device as in claim 2 said third means comprising a valve, said valve being means to expell bubbles from said inner chamber.
4. fi device for use in cardiac balloon catheterization, said device comprising: an inner chamber being means to contain liquid and gaseous bubbles which may occur in said liquid, first means. providing a fluid connection between said inner chamber and a source of pressurized fluid.

a second means, providing a fluid connection between said inner chamber and a balloon catheter, said second means being disposed in said inner chamber so that there is a percentage, P, O C P C 100, such that if the liquid content of said inner chamber exceeds P percent of the total volume of said inner chamber then it is not possible to pass a gaseous substance out of said inner chamber via said second means while said device is stationary a third means providing fluid connection between said inner chamber and a fluid containing system a flow diverting means coupled to said first means, said flow diverting means being means to prevent gaseous substance entering said inner chamber via said first means from leaving said inner chamber via said second means while the liquid content of said inner chamber fills at least P percent of the total volume of said inner chamber.
5. A device as in claim 4 said first means being a permanent fluid connection with said source of pressurized fluid.