The present invention relates generally to medical delivery systems. In particular, the invention relates to systems for delivering phase-change particulate slurries, such as ice slurry coolants to targeted areas or organs of the body.
Rapid inducement of protective hypothermia has been found to improve the survival rates of patients suffering from a variety of ailments. These include ischemia as a result of cardiac arrest, myocardial infarction, stroke, hemorrhage or traumatic injury and various medical procedures. More traditional methods for inducing protective hypothermia have included techniques such as ice water immersion; ice packs applied to a patient's head and torso; surface cooling of the head and neck; extracorporeal blood cooling; and cardio pulmonary bypass with a heat exchanger. More recently developed cooling techniques include endovascular heat exchange, and application of ice slurries to targeted areas or organs of the body.
Various methods for inducing hypothermia using phase-change particulate slurries are described in U.S. Pat. No. 6,597,811 to Becker et al., the entire disclosure of which is incorporated by reference in the present disclosure. According to the methods described by Becker et al., saline ice slurries, perfluorocarbon slurries or other types of slurries compatible with human tissue are used to directly cool various internal organs of the body. Ice slurries may be delivered to the body's internal heat exchangers, such as the lungs (endotracheal); G.I. (oral-gastric); carotid artery (peri-vascular); and peritoneal cavity (lavage). Ice slurries may also be delivered by direct intravenous insertion into the femoral vein or other blood vessels for rapidly cooling the blood. Recent experiments have demonstrated that targeted organs may be cooled by delivering ice slurry through a small tube guided by endoscope to prevent ischemia during surgery.
Methods for producing phase-change ice particulate slurries are described in U.S. Pat. Nos. 6,244,052 and 6,413,444, both to Kasza. U.S. Pat. No. 6,244,052 relates to the production of phase-change ice particulate perfluorocarbon slurries and U.S. Pat. No. 6,413,444 relates to the production of phase-change particulate saline slurries. Again the teaching of both of these references in their entirety is incorporated by reference into the present disclosure.
A wide variety of delivery tubes, syringes and other delivery devices are commonly used to deliver fluids into the body. However, commercially available delivery devices are designed only for the delivery of single-phase fluids. These devices do not function satisfactorily to deliver phase-change particulate slurries such as those described in the above referenced patents. Currently available delivery devices often become plugged when used to deliver phase-change particulate slurries. Plugging occurs even though the cross sectional area of the slurry particles are significantly smaller than the cross sectional area of the flow path through the various delivery tubes, valves, fittings, insertion tip and any other components of the fluid delivery system.
A factor that contributes to plugging of the delivery device when delivering phase-change particulate slurries is the quality of the phase-change particulate slurry itself. Conventional phase-change slurries have dendritic ice particles which are highly elongated with very sharp appendages. Such particles are easily entangled and can begin to clump together. As clumps draw more and more particles they can begin to clog the components that form the flow path of the delivery device. With such particles clumping can occur at particulate loading levels as low as 5%.
The characteristics of the delivery device can also contribute to particulate clumping and eventual plugging of the delivery system flow path. Plugging can occur due to particle build up along the walls of delivery tubing or injector tips. Particles, especially dendritic particles, can become lodged against imperfections in the sidewall of the tubing and other components of the delivery systems. For example, particles can become trapped in minute cavities in the walls of the delivery tubing or against small protrusions extending from the walls into the flow path. Trapped particles rapidly lead to particulate build-up which can eventually occlude the slurry flow path.
Particle trapping is particularly prevalent at the interfaces between various flow path components. Component interfaces such as between a delivery tube and a control value, or between a delivery tube and the insertion tip, or simply between two tubes of different diameter, are often accompanied by sudden changes in the cross sectional area of the slurry flow path. For example, when two tubes of different diameter are joined, a significant reduction in the cross sectional area of the flow path occurs at the transition from the larger tube to the smaller tube. Slurry particles can become trapped against the forward facing step created by the smaller diameter tube. Again trapped particles can quickly grow into piles which eventually occlude the flow path. Particle build up leading to plugging is most serious at the injector tip of the delivery device. The injector represents the smallest cross section of the entire flow path.
Additional problems with conventional fluid delivery systems include, overly aggressive narrowing of the flow path, such as in a nozzle or insertion tip device, multi-stage tapering of the flow path, or sudden sharp changes in the direction of flow. All of these conditions can lead to trapped particles and subsequent particulate buildup and eventual plugging of the slurry flow path.
Some of the problems regarding plugging can be alleviated by improving the qualities of the phase-change ice particulate slurries. The U.S. Pat. Nos. 6,413,444 and 6,244,052 mentioned above address these problems by providing ice slurries having high quality smooth globular shaped particles that exhibit much lower plugging tendencies than conventional slurries. Such slurries allow for higher particle loading levels than previously possible. Nonetheless, even with these improved phase-change particulate slurries, plugging can still be a problem. Slurries having high ice particle load levels are highly desired to achieve maximal cooling from the smallest amount of coolant. In order to effectively deliver such improved heavily loaded slurries to targeted areas or organs within a patient's body,. new delivery mechanisms must be provided. The improved delivery mechanisms must far exceed the performance capabilities of presently available single-phase fluid delivery mechanisms, remaining free of obstructions at the highest particulate loading concentrations.
The present invention relates to phase-change particulate ice slurry delivery systems for delivering ice slurry coolants to targeted areas of the body. A phase-change particulate ice slurry delivery system according to the invention includes a slurry reservoir and a conduit for conveying the slurry from the reservoir to the targeted area or organ of a patient. The delivery conduit may include multiple components. For example the delivery conduit may include an elongated section of flexible medical tubing, an insertion tip, and a transition fitting for adapting the medical tubing to the insertion tip. The slurry reservoir includes an exit port which allows for the out flow of slurry from the reservoir. The exit port forms an outwardly facing nipple that is insertable into a central lumen defined by the outer wall of the delivery tube. Slurry flows from the reservoir into the central lumen of the delivery tube. The internal interface between the exit port and the delivery tube is such that the cross sectional area of the flow path transitions from smaller to larger across the interface in the direction of flow away from the reservoir.
As noted above, the delivery conduit may comprise multiple components, including medical tubing, an insertion tip and one or more transition fittings. The interfaces between each component share the characteristic that the cross sectional area of the slurry flow path always transitions from smaller to larger across the interface in the direction of flow. With this geometry there are no forward facing steps at the interfaces which can trap particles and lead to plugging.
In some circumstances, such as in the insertion tip, and in some transition fittings, the flow path is necessarily narrowed. Whenever it is necessary to reduce the cross sectional area of the slurry flow path, the narrowing is accomplished via a gradual tapering of the flow path. Preferably the total included angle of taper does not exceed 20° relative to the central axis of the flow path.
Specially designed insertion tips are also provided. On example is a two port insertion tip. A first exit port is aligned axially with the central lumen extending through the insertion tip. The second exit port is off-axis in that the second exit port is formed in the side of the insertion tip. Preferably the second off-axis exit port is located within two lumen diameters of the first axially aligned exit port. A bevel surrounds the second exit port, forming an oblique surface to the direction of slurry flow at the downstream side of the second exit port. Accordingly slurry is caused to change direction gradually as it exits the second off axis exit port. Since there is no perpendicular impact surface, particulate will not become lodged against the downstream sidewall of the insertion tip that defines the second exit port.
A specially designed catheter for delivering slurry directly into blood vessels may also be employed as an insertion tip according to the invention. The specially designed catheter includes an input housing adapted to receive the output end of a tapered transition fitting. The transition fitting fits into a tapered bore formed in the input housing. Since the transition fitting is inserted into the housing and slurry flows from the transition fitting into the housing, the flow path maintains the proper geometry across interface between the transition fitting and the housing, transitioning from a smaller to a larger cross sectional area in the direction of flow.
The slurry reservoir may take on any number of different forms. For example the slurry reservoir may be a collapsible squeeze bag which is loaded with slurry and suspended from a rack. A plastic squeeze bottle has also been demonstrated, having an exit port formed in a threaded cap at the top of the bottle. Alternatively, the slurry reservoir may be a rigid container supplied with an agitator for maintaining uniform loading of the slurry particulate throughout the container.
The devices disclosed herein have proven effective for efficiently delivering phase-change particulate ice slurries to patients. The design of the various components, especially those that form the slurry flow path, is such that obstacles and protrusions into the flow path and other rapid changes in the flow path cross section are eliminated. Slurry particles flow freely from the reservoir to the targeted area without becoming trapped along the way at component interfaces and the like. Particles have no opportunity to accumulate and clog the system.
Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the appended claims.
These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein:
The present invention relates to devices for delivering phase-change particulate ice slurries to specific targeted areas or internal organs of a patient's body. The fundamental components of a phase-change particulate ice slurry delivery device are a slurry reservoir for storing and transporting the phase-change particulate ice slurry; a conduit for delivering the slurry from the reservoir to the patient, and an injector device for injecting the slurry in the targeted area or organ of the patient. The various embodiments of the invention described herein are adapted to effectively deliver phase-change particulate ice slurries to patients without plugging of the slurry flow path resulting from unwanted accumulation of particles within the various flow path components and at the interfaces therebetween.
An embodiment of a phase-change particulate ice slurry delivery device 10 according to the invention is shown in
According to the embodiment depicted in
A detailed cross section of the interface between the slurry reservoir exit port 14 and the delivery tube 16 is shown in
The proximal end of the delivery tube 16 fluidly connects to the nipple 34. The slurry delivery tube 16 is formed of an outer wall 42 that surrounds and defines a central lumen 44. The inner surface of the delivery tube wall 42 is substantially smooth, with no cavities or protrusions which can trap ice particles as the slurry flows through the delivery tube. The proximal end 24 of the slurry delivery tube 16 slides over the nipple 34, so that the hollow passage 36 through the nipple 34 communicates with the central lumen 44 defined by the delivery tube 16. The slurry delivery tube 16 frictionally engages the outer surface of the nipple 34 forming a snug-fit connection with the exit port 14. Slurry passes out of the reservoir 12, through the hollow passage 36, and into the central lumen 44 of the slurry delivery tube 16 and is delivered to the patient.
It must be noted that the tapered end of the nipple 34 is inserted into the central lumen 34 of the slurry delivery tube 16. The slurry delivery tube 16 is not inserted into the hollow passage 36. The diameter of the hollow passage 36 at the end of the nipple 34 is smaller than the diameter of the central lumen 44 of the slurry delivery tube 16. Therefore, the change in the cross sectional area of the flow path at the internal interface between the nipple 34 and the slurry delivery tube 16 transitions from smaller to larger in the direction of slurry flow away from the reservoir.
The internal interface between the exit port 14 and the deliver tube 16 is of critical importance to the effective delivery of phase-change particulate ice slurries. As slurry flows out of the squeeze bag slurry reservoir 12 through the hollow passage 36 and into the central lumen 44 of delivery tube 16, the slurry encounters no obstacles that could lead to particulate build up and eventual plugging of the flow path. The hollow passage 36 through the tapered extension 34 has a constant diameter (only the outer wall of the nipple 34 is tapered) as does the central lumen 44 of the delivery tube 16. Thus, the only change in the cross sectional area of the flow path occurs at the interior interface 46 where the flow path transitions the smaller diameter passage 36 through the nipple 34 to the relatively larger diameter central lumen 44 of the delivery tube 16. The step-like structure formed at the interface 46 faces away from the direction of flow. Thus the interface does not present a surface that can trap slurry particles or otherwise impede the flow of particles through the interface 46.
A feature of the present invention is that the interfaces between all components connected in the slurry flow path share this characteristic. There are no forward facing steps in the slurry flow path. Sudden changes in the cross sectional area of the slurry flow path are avoided as much as possible. Where they must occur they always transition from a smaller to a larger cross sectional area in the direction of flow. Where transitions from a larger to a smaller flow path must occur, such as within insertion tips or transitional fittings, the transitions occur gradually and smoothly. Preferably where a narrowing of the slurry flow path is required the total included angle of the tapered flow path will be less than about 20°. This will insure that particles do not bunch together in the area of taper and eventually clog the flow path.
Further illustrations of the proper interface between flow path components are found at the junctions between the distal end 22 of the slurry delivery tube 16 and the transition fitting 18 and between the transition fitting 18 and the insertion tip 20. A detailed view of these components is shown in
The distal end 22 of the delivery tube 16 is inserted into the flared tube receiving end 48 of the transition fitting 18. This connection forms the internal interface 66 between the delivery tube 16 and the transition fitting 18. Similarly, the exit end 50 of the transition fitting 18 is inserted into a receiving end 52 of the insertion tip 20. This connection forms the internal interface 68 between the transition fitting 18 and the insertion tip 20. The delivery tube 16 may be bonded to the transition fitting 18, or some other joining mechanism such as a snug-fit frictional connection may be provided to secure the transition fitting 18 to the distal end 22 of the delivery tube 16. Similar joining provisions may be applied between the transition fitting 18 and the insertion tip 20.
Like the delivery tube 16, the transition fitting 18 is formed of a generally cylindrical outer wall 56 which surrounds and defines a central lumen 58. When the transition fitting 18 is joined to the distal end 22 of the deliver tube 16, the central lumen of the delivery tube 16 is in fluid communication with the central lumen 58 of the transition fitting 18, thereby effectively extending the slurry flow path through the length of the transition fitting 18. At the internal interface 66 between the transition fitting 18 and the distal end 22 of the delivery tube, the diameter of the central lumen 58 of the transition fitting is greater than the diameter of the central lumen 44 of the delivery tube 16. Thus, the cross sectional area of the slurry flow path transitions from smaller to larger across the internal interface 66. The step-like structure formed at the interface 66 faces away from the direction of flow and does not present an obstacle to the flow of particles through the interface 66.
Unlike the delivery tube 16, the central lumen 58 of the transition fitting is tapered. The cross sectional area of the slurry flow is gradually reduced over the length of the transition fitting 18. In fact, the entire outer wall 56 of the transition fitting is tapered such that the outside diameter of the exit end 50 of the transition fitting 18 is substantially smaller than the outer diameter of the delivery tube 16. Thus, the exit end 50 of the transition fitting 18 may be inserted into the relatively small receiving end 52 of the insertion tip 20, whereas the distal end of the delivery tube 16 could not be.
Again, the insertion tip 20 may be bonded to the transition fitting, or a snug-fit frictional connection may be sufficient, or some of the connection mechanism may be employed to secure the insertion tip 20 to the transitional fitting 18. The insertion tip is formed by a tapered cylindrical outer wall 60 which surrounds and defines a central lumen 62. When the transition fitting 18 is inserted into the receiving end 50 of the insertion tip 20, the central lumen 58 of the transition fitting 18 is in fluid communication with the central lumen 62 of the insertion tip 20, thereby effectively extending the slurry flow path through the length of the insertion tip 20. At the internal interface 68 between the insertion tip 18 and the exit end 50 of the transition fitting 18, the diameter of the central lumen 62 of the insertion tip 20 is greater than the diameter of the central lumen 58 of the transition fitting 18. Thus, at the internal interface 68, the cross sectional area of the slurry flow path transitions from smaller to larger in the direction of flow. The step like structure formed at the interface 68 faces away from the direction of flow and does not present an obstacle to the flow of particles through the internal interface 68.
Like the transition fitting 18, the central lumen 62 of the insertion tip 20 is tapered. The slurry flow path is further narrowed along the length of the insertion tip 20. Preferably the amount of total included taper angle in the slurry flow path is less than about 20°. The entire insertion tip narrows to a relatively small point that can be inserted into various otherwise difficult to reach places that might not be accessible to wider instruments. Slurry exits the insertion tip 20 through a narrow nozzle-like exit port 64. The structure of the insertion tip provides for the directed flow of slurry from the slurry delivery apparatus 10.
Insertion tips having a single axial aligned aperture are preferred. Such insertion tips are the least likely to experience particulate build up and eventual plugging. However, in some applications dual port insertion tips are required. Dual ported insertion tips have the advantage that if one port is pushed against tissue, the tissue can block the delivery of slurry from that port. With two ports, even when one port is blocked the second port will continue to deliver slurry. Dual ports can also be advantageous during suctioning of slurry melt fluid for the same reasons.
In the phase-change particulate ice slurry delivery of the present invention, on/off flow control depicted in
In some situations it is desirable to introduce phase-change particulate ice slurry into a blood vessel through a catheter. However, traditional catheters designed to deliver single phase solutions are ineffective for delivering phase-change particulate ice slurries.
The inlet housing 102 of a traditional catheter such as catheter 100 is especially prone to plugging when used to deliver phase-change particulate ice slurries. The sealing ring 108 and especially the check valve 110 present obstacles to the slurry flow path which can trap particles and lead to plugging. Surfaces 116 and 118 associated with the second inlet port 106 and the entrance to the catheter tip 112 itself can also trap particles and lead to plugging. A new inlet housing was necessary to adapt traditional catheters for delivering phase-change particulate ice slurries.
An alternative embodiment of a slurry reservoir 130 is shown in
The tapered exit port 136 has all the same characteristics of the exit port 14 of the flexible squeeze bag 12 described above with reference to
The rigid container 202 includes an exit port 14 substantially identical to that described above with regard to the squeeze bag reservoir 12 and the squeeze bottle reservoir 132. The slurry delivery tube 16 fits over the exit port 14 also as previously described. In the previous embodiments, however, slurry was pumped through the delivery tube 16 by manually squeezing a flexible reservoir to force the slurry through the delivery tube 16. This manual pumping mechanism is not available with the rigid reservoir 202 of system 200. Accordingly, an in-line tube pump 210 is provided to pump the phase-change particulate ice slurry through the delivery tube 16. In-line tube pump 210 may be a 3 roller peristaltic pump such as Masterflex L/S Easy-Load pump head 7720-62 with Economy Digital Drive #07524-40. Preferably the in line tube pump will be capable of pumping 0-50% loaded ice slurries at a rate of between 10-700 ml/min.
Yet another embodiment of a phase-change particulate ice slurry delivery system 220 is shown in
It should be understood, and therefore included within the scope of this invention that the phase particulate delivery tubes and insertion tip devices can be replaced with a wide variety of different embodiments or devices including, automated or manual features. For example instead of using the manually operated slurry delivery containers the delivery tube can be interfaced with a slurry pumping system, for example a roller tubing pump. While the principles of the present invention have been made clear in illustrative embodiments, it will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, the elements, materials and components used in the practice of the invention and otherwise, which are particularly adapted to specific environments without departing from those principles. The following claims are intended to embrace and cover any and all such modifications with the limits only of the true spirit scope of the invention.
This invention was made with Government support under HIH HL 67630 from the National Institutes of Health. The Government may therefore have certain rights in this invention. The United States Government has rights in this invention pursuant to contract Number w-31-109-ENG-38 between the United States Government and Argonne National Laboratory.