WO2024220412A1

WO2024220412A1 - Low internal resistance polymer partitioned anesthetic vaporizer system and method

Info

Publication number: WO2024220412A1
Application number: PCT/US2024/024767
Authority: WO
Inventors: Bradley Fuhrman; Douglas P. Dufaux
Original assignee: Rheos Medical Corp.
Priority date: 2023-04-17
Filing date: 2024-04-16
Publication date: 2024-10-24

Abstract

A low-intemal-resistance vaporizer comprising a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vvaappoorr of the anesthetic aaggeenntt with the bypass gas.

Description

LOW INTERNAL RESISTANCE POLYMER PARTITIONED ANESTHETIC VAPORIZER SYSTEM AND METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial Number 63/496,533 filed on April 17, 2023, the entire contents of which are hereby incorporated by reference.

STATEMENT OF FEDERALLY FUNDED RESEARCH

[0002] None.

TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates in general to anesthetic vaporizers. In particular, the present invention relates to draw-over anesthetic vaporizers.

BACKGROUND OF THE INVENTION

[0004] It is common for anesthetic vaporizers to split the flow of incoming fresh gas into a stream that enters a vaporizer chamber, or “pot,” and a bypass stream. Within the pot, the incoming fresh gas is exposed to liquid anesthetic, which vaporizes into the gas stream. Gas exiting the pot, which has generally been fully saturated with anesthetic vapor, is diluted by the bypass stream after it exits. For example, isoflurane liquid has a vapor pressure of about 240 mmHg and the pot saturates gas to that vapor pressure. After dilution, the concentration suitable for patient anesthesia may be 7 to 20 mmHg. This diluted gas may then enter a rebreathing (circle) circuit from which the patient’s breathing gas is obtained. In this configuration, patient breathing is usually supported by positive pressure from either a mechanical ventilator or from an anesthesia bag. Special modifications are often provided by equipping the vaporizer with a temperature sustaining outer jacket (or heat sink), by modifying vaporizer output to alter gas flow as temperature changes, and by placing wicks and baffles within the vaporizer pot to ensure consistent anesthetic vapor saturation. In this configuration, the device is termed a “plenum” vaporizer, and, because of its high internal resistance, the patient cannot spontaneously inhale through it.

[0005] In other configurations, the patient may spontaneously inhale the diluted vaporizer output. Breathing may be supported by an anesthesia bag, but this configuration generally entails patient inspiration across the resistance of the vaporizer circuit. Fresh gas may be simply allowed to flow over the surface of the liquid anesthetic in the pot to avoid the high resistance of baffles and wicks. This embodiment is commonly referred to as a “draw- over” or “push-over” vaporizer. Such embodiments may have some disadvantages. If tipped or laid on their side, they may leak liquid anesthetic. They may not fully saturate with anesthetic at higher flows because of limited contact with the liquid pool in the pot. They generally have little or no temperature compensation, and may, therefore, deliver inaccurate anesthetic concentrations. Patient’s expired air is generally not returned to the device to prevent re-exposure to liquid anesthetic or contamination of the bypass air. This exhaust to atmosphere presents an environmental risk if used in poorly ventilated spaces. To their advantage, though, draw-over vaporizers are usually light in weight (lacking the heat sink) and easily carried. They may be used in settings lacking supplies of compressed oxygen, and their use does not require a mechanical ventilator. Draw-over vaporizers are then well-suited to military operations, mass casualty events, and remote or ill-equipped medical centers.

[0006] To take full advantage of the draw-over configuration, it would be desirable to: 1) overcome the low liquid-air contact area of the pot, 2) obviate the risk of leaks and spills, 3) provide some degree of temperature compensation through temperature dependent modification of gas flow through the pot, and 4) protect the configuration against contamination of the bypass path by gas flow containing anesthetic.

SUMMARY OF THE INVENTION

[0007] As embodied and broadly described herein, an aspect of the present disclosure relates to a low-intemal-resistance vaporizer comprising, consisting essentially of, or consisting of a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer to transfer the anesthetic agent to the inflowing gas by diffusion; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent. In one aspect, the polymer comprises one or more hollow polymer fiber bundles. In another aspect, the one or more hollow polymer fiber bundles is joined to the one or more anesthetic reservoirs at a first end, a second end, or both. In another aspect, the low-internal-resistance vaporizer further comprises, consists essentially of, or consists of a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the low-intemal-resistance vaporizer further comprises, consists essentially of, or consists of a sweat pump in fluid communication with an interior of the vaporizer pot and an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane. In another aspect, a gas exit from the vaporizer pot is configured to be enlarged or constricted by a temperature compensator. In another aspect, the low-intemal-resistance vaporizer is configured to be used as a draw-over vaporizer. In another aspect, the low-internal-resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit. In another aspect, the low-intemal-resistance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device. In another aspect, the low-intemal-resistance vaporizer is configured to receive the inflowing gas from a plurality of sources. In another aspect, the low-internal- resistance vaporizer is configured to receive the inflowing gas from an intermittent source. In another aspect, a single inflow gas conduit fully or partially surrounds the polymer of the vaporizer pot; or the single inflow gas conduit comprises holes that allow the inflowing gas to exit the single inflow gas conduit and impinge the surface of the polymer; or the single inflow gas conduit terminates within the vaporizer pot such that the inflowing gas flows across the polymer at a right angle to an axis of a structure that includes the polymer.

[0008] As embodied and broadly described herein, an aspect of the present disclosure relates to a low-intemal-resistance vaporizer comprising, consisting essentially of, or consisting of a vaporizer pot configured to hold a liquid anesthetic agent and comprising a polymer configured to contain a flowing gas, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring the flowing gas into fluid communication with the liquid anesthetic agent to transfer the anesthetic agent to the flowing gas by diffusion; an inflow gas conduit in fluid communication with the polymer, wherein the inflow gas conduit comprises a splitter to separate the flowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the polymer and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent. In one aspect, the polymer comprises one or more hollow polymer fiber bundles. In another aspect, the vaporizer pot is joined to the one or more anesthetic reservoirs at a first end, a second end, or both. In another aspect, the low-internal-resistance vaporizer further comprises, consists essentially of, or consists of a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the low-internal-resistance vaporizer further comprises, consists essentially of, or consists of a sweat pump in fluid communication with the polymer and an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane. In another aspect, a gas exit from the polymer is configured to be enlarged or constricted by a temperature compensator. In another aspect, the low-internal-resistance vaporizer is configured to be used as a draw- over vaporizer. In another aspect, the low-internal-resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit. In another aspect, the low-internal- resistance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device. In another aspect, the low-internal-resistance vaporizer is configured to receive the flowing gas from a plurality of sources. In another aspect, the low-intemal-resistance vaporizer is configured to receive the flowing gas from an intermittent source.

[0009] As embodied and broadly described herein, an aspect of the present disclosure relates to a method of introducing a vapor of an anesthetic agent to an air flow comprising, consisting essentially of, or consisting of providing a low-internal-resistance vaporizer comprising, consisting essentially of, or consisting of a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer to transfer the anesthetic agent to the inflowing gas by diffusion; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent; flowing air into the inflow gas conduit such that a first portion of the air flows into the vaporizer pot and a second portion of the air flows into the bypass gas conduit; adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the polymer; and flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit. In one aspect, the polymer comprises one or more hollow polymer fiber bundles. In another aspect, the one or more hollow polymer fiber bundles are joined to the one or more anesthetic reservoirs at a first end, a second end, or both. In another aspect, the low-internal resistance vaporizer further comprises, consists essentially of, or consists of a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the low-internal resistance vaporizer further comprises, consists essentially of, or consists of a sweat pump in fluid communication with an interior of the vaporizer pot and an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane. In another aspect, the method comprises, consists essentially of, or consists of enlarging or constricting a gas exit from the vaporizer pot to compensate for a temperature change. In another aspect, the low-internal-resistance vaporizer is configured to be used as a draw-over vaporizer. In another aspect, the low- internal-resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit. In another aspect, the low-intemal-resi stance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device. In another aspect, the low-internal-resistance vaporizer is configured to receive the inflowing gas from a plurality of sources. In another aspect, the low-intemal-resistance vaporizer is configured to receive the inflowing gas from an intermittent source. In another aspect, a single inflow gas conduit fully or partially surrounds the polymer of the vaporizer pot; or the single inflow gas conduit comprises holes that allow the inflowing gas to exit the single inflow gas conduit and impinge the surface of the polymer; or the single inflow gas conduit terminates within the vaporizer pot such that the inflowing gas flows across the polymer at a right angle to an axis of a structure that includes the polymer.

[0010] As embodied and broadly described herein, an aspect of the present disclosure relates to a method of introducing a vapor of an anesthetic agent to an air flow comprising, consisting essentially of, or consisting of providing a low-internal-resistance vaporizer comprising a vaporizer pot configured to hold a liquid anesthetic agent and comprising a polymer configured to contain a flowing gas, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring the flowing gas into fluid communication with the liquid anesthetic agent to transfer the anesthetic agent to the flowing gas by diffusion; an inflow gas conduit in fluid communication with the polymer, wherein the inflow gas conduit comprises a splitter to separate the flowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the polymer and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent; flowing air into the inflow gas conduit such that a first portion of the air flows into the polymer and a second portion of the air flows into the bypass gas conduit; adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the vaporizer pot; and flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit. In one aspect, the polymer comprises one or more hollow polymer fiber bundles. In another aspect, the vaporizer pot is joined to the one or more anesthetic reservoirs at a first end, a second end, or both. In another aspect, the low-internal resistance vaporizer further comprises, consists essentially of, or consists of a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the low-internal resistance vaporizer further comprises, consists essentially of, or consists of a sweat pump in fluid communication with the polymer and an anesthetic reservoir of the one or more anesthetic reservoirs. In another aspect, the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane. In another aspect, the method comprises, consists essentially of, or consists of enlarging or constricting a gas exit from the polymer to compensate for a temperature change. In another aspect, the low-intemal-resistance vaporizer is configured to be used as a draw-over vaporizer. In another aspect, the low-internal-resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit. In another aspect, the low-internal-resistance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device. In another aspect, the low-internal- resistance vaporizer is configured to receive the flowing gas from a plurality of sources. In another aspect, the low-internal-resistance vaporizer is configured to receive the flowing gas from an intermittent source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures, in which:

[0012] FIG. 1A is a photomicrograph of a silicone hollow fiber. FIG. IB is a photomicrograph of a closer view of a silicone hollow fiber.

[0013] FIG. 2 A shows loose hollow fibers, and FIG. 2B hollow fibers bundled in a cartridge.

[0014] FIG. 3 shows an array of hollow polymer fibers within a vaporizer pot.

[0015] FIG. 4 shows temperature compensation by modifying resistance of pot gas flow path and control of vaporizer flow path, preventing anesthetic pumping into the bypass line.

[0016] FIG. 5 shows use of a keyed system to refill a vaporizer.

[0017] FIG. 6 shows a thumb pump to return condensed vapor “sweat” to an anesthetic reservoir.

[0018] FIGS. 7A-7D show configurations for use of the present invention.

[0019] FIGS. 8A-8C show other embodiments of the present invention.

[0020] FIG. 9 shows a flowchart for a method embodiment of the present invention.

[0021] FIG. 10 shows a flowchart for another method embodiment of the present invention.

[0022] FIG. 11 shows another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] Illustrative embodiments of the system of the present application are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer’s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0024] In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

[0025] This disclosure entails: 1) use of a polymer highly permeable to anesthetic vapor to contain or exclude the liquid anesthetic, preventing leakage and spills, 2) provide a large, stable, enduring contact area for vaporization of the liquid anesthetic into the fresh gas flow traversing the pot, 3) provide some degree of temperature compensation to stabilize delivery of saturated vapor to the patient, and 4) protect against contamination of anesthetic free bypass gas by anesthetic-containing airflow inadvertently pumped into the bypass system.

[0026] The present invention according to this disclosure allows 1) safe and effective draw-over anesthesia, 2) replacement of high resistance plenum vaporizers by low resistance draw-over devices, and 3) the extra gas required to compensate for circuit air leaks to pass, at low pressure, through a vaporizer before entering the circle circuit, as described in U.S. Patent 11,173,262 B2, Fuhrman.

[0027] Hollow polymer fibers: The manufacture of polymer hollow fibers has been known since the 1960s. This technology with modifications has been applied to the manufacture of hollow fiber devices for, among other uses, dialysis, water purification, gas separation, and membrane oxygenation. When combined in a bundle, hollow fibers generally provide pathways (inside) for movement of a first fluid phase, and (outside, between fibers) a pathway for movement of a second fluid phase. This allows movement of selected permeable substances from one phase to another to achieve the desired end of purging one phase and enriching the other. This technology has been used to allow volatile anesthetics, in a gas phase generated by an anesthetic vaporizer diluted to partial pressures suitable to patient anesthesia, to pass beside the hollow fibers of a membrane oxygenator, which carry a stream of patient blood, and dosing and anesthetizing a patient by diffusion.

[0028] Prior art for delivery of volatile anesthetics using polymer containment of anesthetic vapor during extracorporeal circulation: Patients undergoing cardiopulmonary bypass may be anesthetized with isoflurane vapor administered into the cardiopulmonary bypass circuit. The patient’s lungs are often excluded from the circulation during cardiopulmonary bypass precluding inhalational anesthesia through the lungs. To anesthetize with isoflurane or another volatile agent, a standard vaporizer may be used to provide the target (diluted) concentration of anesthetic vapor to the fresh gas flow of the bypass circuit. This gas comes in contact with patient blood flowing within the cardiac bypass oxygenator, the blood and fresh gas separated by polymer. In practice, this often takes the form of blood, pumped through the hollow polymer fibers of a membrane oxygenator, that traverse a chamber supplied with continuous flowing oxygen and the dilute anesthetic-enriched output of an anesthetic vaporizer. It is known that only certain oxygenators provide adequate patient anesthesia. Some appear to be constructed of polymers not readily permeable to the anesthetic vapor. Yet it is clear that some oxygenators do allow sufficient anesthetic vapor to enter the patient’s blood, across the polymer barrier, to achieve anesthesia during cardiopulmonary bypass.

[0029] Polymer permeability to anesthetic vapor: Permeability of various polymers to anesthetic vapors has been studied, and uniqueness to each polymer under study, to thickness and diffusion area of the barrier, to porosity of the configured polymer, to solubility of vapor in the polymer and to diffusivity of anesthetic gas through the barrier, have all received some, but limited attention. Though not the only configuration that might meet the requirements of this disclosure, polymer hollow fibers have potential. In its simplest form, Q (the permeation rate of vapor across a membrane) is proportional (oc) to: AP (the partial pressure-drop of vapor across the barrier), to D (the diffusivity of the vapor in that membrane material) and to S (the surface area of the membrane), but is Q inversely related to T (the thickness of the membrane.) So, in general:

[0030] Q oc AP x D x S / T (1)

[0031] T. Marx, G. Froba, S. Bader, J. Villock and M. Georgieff [Acta Anaesthesiologica Scandinavica 40 (1996)] studied permeation of various gases, including isoflurane, through polymer barriers, including some made of silicone. In their study of silicone, AP for isoflurane (1%) was 7.6 mmHg, S was 54.7 cm², and T was 0.11 cm. Permeation for isoflurane was found to be 0.0088 ml/minute. Other polymers and vapors tested yielded different permeation rates.

[0032] In embodiments of the present invention, a polymer container may comprise an array of polymer hollow fibers and a pliable, refillable liquid reservoir, or some other polymer configuration, though the use of hollow fibers presents excellent surface area characteristics.

[0033] Photomicrographs of a silicone hollow fiber are shown in FIGS. 1 A and IB. For the fiber shown, if external diameter is 0.1 cm then a 10 inch (25.4 cm) tall hollow fiber would have roughly 3.14 x 0.1 x 25.4 cm² surface area (or S = 8.0 cm².) T would be 0.01 cm. A 6 inch = (15 cm or 150 mm) diameter bundle of such fibers could easily accommodate 17,663 such fibers. Bundling only 5,000 such fibers, to reserve greater than 13,000 mm² (130 cm²) for air space between fibers, would give the fiber array a surface area of S = 5,000 x 8 = 40,000 cm². The bundle would then provide 40000 / 54.7 = 730 times as much surface for permeation as the test surface in Marx. For each hollow fiber, T would be ~ 0.01 cm, one tenth the T of the material tested by Marx. This array might then have 730 x 10 = 7,300 times the permeation rate for isoflurane vapor found by Marx, or 7300 x 0.0088 = 64 ml/min at a AP of 7.6 mmHg.

[0034] FIG. 2A shows loose hollow fibers, and FIG. 2B hollow fibers bundled in a cartridge. Consider a vaporizer comprising a pot holding a bundle of hollow fibers like, that shown in FIG. 2B, filled with liquid isoflurane having a vapor pressure of 240 mmHg and a bypass line. A circle circuit receiving 2,000 ml/min fresh gas flow (only a fraction of which would traverse the pot) would need to draw 20 ml/min of isoflurane vapor from the pot to achieve a mixed anesthetic output of 20/2000 = 1.0 % (~1 MAC). To extract 20 ml isoflurane vapor from the pot would require a AP of 7.6 x 20 / 64 = 2.3 mmHg. So, at equilibrium for this flow rate, isoflurane partial pressure in the pot (Piso) would be 240 - 2.3 ~ 237.7 mmHg or Piso ~ 99% of its fully saturated vapor pressure.

[0035] Based on these assumptions, it is deemed feasible to construct a 6-inch diameter, 10 inch-high vaporizer containing a liquid isoflurane-filled hollow fiber bundle fabricated from silicone, sufficiently efficient to allow consistent delivery of several MAC of isoflurane with minimal impact on pot isoflurane concentration. It should be understood that not all polymers might be so efficient. Other choices of anesthetic liquid, optimal polymer, optimal pot and bundle dimensions, optimal polymer configuration, and optimal splitting range of vaporizer fresh gas inflow might also be applied in embodiments of the present invention.

[0036] Non-limiting examples of hollow fiber filters for use with the present invention will include materials that may vary in one or more properties, such as chemistry, porosity, morphology, geometry, configuration, modality, etc., that may affect the anesthetic. Generally, the feedstreams through each flow path are fed under substantially identical conditions. As such, the individual filter modules are subjected to substantially the same conditions, other than the differences among the materials. The present invention may leverage the filtering function of the hollow fiber filters, but that is not a requirement. The container from which the anesthetic is fed in accordance with various principles of the present disclosure may be referenced herein as a process vessel, a feed vessel, a feed reservoir, etc., and such terms may be used interchangeably herein without intent to limit, reference generally being made to a process vessel for the sake of simplicity without intent to limit.

[0037] A bundle of hollow fiber membranes for use with the present invention can be made from any number of polymers. Non-limiting examples of polymers include: polysulfone, polyethersulfone, poly(aryl)ethersulfone, polyvinylpyrrolidone (PVP), which have a polyamide layer on the lumen side of the hollow fibers. Hollow fiber filtration device for use with the present invention include, e.g., high-flux membranes, such as, for example, Polyflux® 170H (Baxter), Revaclear® (Baxter), Ultraflux®EMIC2 (Fresenius Medical Care), or Optiflux® F180NR (Fresenius Medical Care). Methods for their production have been described, for example, in U.S. Pat. No. 5,891,338 and EP 2 113 298 Al. In polysulfone or polyethersulfone based support membranes, the polymer solution generally comprises between 10 and 20 weight-% of poly ethersulfone or polysulfone as hydrophobic polymer and 2 to 11 weight-% of a hydrophilic polymer. In the case of PVP, these generally include a low and a high molecular PVP component. The resulting high- flux type membranes generally consist of 80-99% by weight of said hydrophobic polymer and 1-20% by weight of the said hydrophilic polymer. During production of the membrane the temperature of the spinneret generally is in the range of 25-55° C. However, the hollow fibers may also be made from a variety of flexible and rigid materials such as plastics, polymers, ceramics, and/or metals.

[0038] While the present disclosure discussion the present invention in terms of using isoflurane as the anesthetic liquid, other anesthetic liquids may be used with the present invention, including sevoflurane, halothane, and desflurane. If desflurane is used, a heater may be used in conjunction with the pot to vaporize the desflurane, which is a liquid at room temperature.

[0039] While an embodiment including a hollow fiber representation of the polymeric enclosure is described in detail below, it will be understood that there are other suitable configurations of a polymeric enclosure that might be used to separate a liquid volatile anesthetic from an air stream within a vaporizer to minimize resistance to airflow through the pot. Further, the skilled artisan will understand that in one embodiment the liquid may reside in the interior of the hollow fiber, but in another embodiment, the liquid may reside on the outside of the hollow fibers. Both are equivalents and contemplated herein. The liquid can reside in either the interior or exterior of the hollow fiber and, in fact, does not require any flow of the liquid in or about the hollow fibers to operate. In another embodiment, the fluids can flow in or about the hollow fibers.

[0040] As illustrated in FIG. 3, a bundle of polymer hollow fibers 1 may be cemented, passing through potting material 2 to open into pliable reservoirs 3. The bundle of polymer fibers 1, the potting material 2, and the pliable reservoirs 3 may be filled with liquid anesthetic 4, and filling intermittently maintained using a keyed refill receptacle 5 as anesthetic is consumed and reservoir volume declines. This configuration may be enclosed in a casing 6 supplied by fresh gas flow 7, continuously, intermittently, or both. This gas flow to the pot may be only a fraction of the gas flow provided to the entire vaporizer, the greater portion bypassing the pot 8. An alternative configuration of the polymer comprises an envelope rolled into a spool with gas space between the windings.

[0041] Because liquid cannot spill from this device, it may be positioned vertically as shown in FIG. 4, which depicts two paths for gas flow. The first path 11 enters the pot and takes up anesthetic vapor that diffuses through the polymer. The second path 10 bypasses the pot entirely. The two streams are separated at their inflow by a “splitter” 12, which may be set to determine the percentage of inflowing gas that enters the pot (to a first approximation). Check valves 13 are positioned in the two streams to prevent their admixing during abrupt pressure changes. Fresh gas flow then traverses the space surrounding the hollow fibers that contain liquid anesthetic 14, and recombines in the pot outlet 15. A temperature compensator 16 is positioned to vary the outflow resistance to airflow as temperature changes. After crossing another check valve 13, gas from the pot is recombined with gas from the bypass 10 and delivered to the vaporizer outlet 17. Note that unidirectional flow of gas flow paths by check valves 13 prevent anesthetic pumping into the bypass line during pressure changes.

[0042] FIG. 5 illustrates the use of a keyed system 20 to refill the polymer enclosure with anesthetic as it depletes by diffusion into the air within the pot.

[0043] As shown in FIG. 6, a “sweat pump” 30 may be incorporated into the pot, connecting the gas side of the pot 31 to the liquid reservoir 32. The sweat pump would include a pliable conduit 33 and a check valve 34. It could be used to return to the reservoir any vapor that might condense on the wall of the pot.

[0044] FIGS. 7A-7D show a variety of configurations of an embodiment 40 for patient care: a draw-over system for spontaneously breathing patients (FIG. 7A); a gas anesthetic source 42 for circle circuit (FIG. 7B); a gas anesthetic source 43 for ECMO/cardiopulmonary bypass circuit (FIG. 7C); a configuration 44 for inflow gas to the vaporizer coming from multiple sources; continuous, intermittent or both (FIG. 7D).

[0045] FIGS. 8A-8C show other configurations of the present invention. FIG. 8A shows a schematic representation of the low-internal-resistance vaporizer showing a single inflow gas conduit that fully or partially surrounds the polymer, where inflowing gas impinges a surface of the polymer to control a rate of mass transfer. FIG. 8B shows a schematic representation of the low-internal-resistance vaporizer showing a single inflow gas conduit comprising holes that allow the inflowing gas to exit the single inflow gas conduit and impinge the surface of the polymer to control a rate of mass transfer. FIG. 8C shows a schematic representation of the low-internal-resistance vaporizer showing a single inflow gas conduit that is terminated within the vaporizer pot such that the inflowing gas flows across the polymer at a right angle to an axis of a structure that includes the polymer to control a rate of mass transfer. Still another embodiment of the present invention (not shown) includes the polymer in flat plate, and the inflowing gas could impinge the flat plate directly or at an angle, or the inflowing gas could flow across the flat plate.

[0046] In some embodiments, the inflowing gas impinges the polymer at a range of velocities. In some embodiments, the inflowing gas stream impinges the polymer so as to modify a boundary layer and increase a net rate of vaporization. In some embodiments, a rate of mass transfer is equal to or greater than 0.3 microliters/minute/cm². In some embodiments, a pressure in each of the pliable anesthetic reservoirs can be controlled manually or automatically. [0047] FIG. 9 shows a flowchart for a method embodiment of the present invention. Method 900 includes block 905 which includes providing a low-internal-resistance vaporizer comprising a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer to transfer the anesthetic agent to the inflowing gas by diffusion; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent. Block 910 includes flowing air into the inflow gas conduit such that a first portion of the air flows into the vaporizer pot and a second portion of the air flows into the bypass gas conduit. Block 915 includes adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the polymer. Block 920 includes flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit.

[0048] FIG. 10 shows a flowchart for a method embodiment of the present invention. Method 1000 includes block 1005 which includes providing a low-internal -resistance vaporizer comprising a vaporizer pot configured to hold a liquid anesthetic agent and comprising a polymer configured to contain a flowing gas, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring the flowing gas into fluid communication with the liquid anesthetic agent to transfer the anesthetic agent to the flowing gas by diffusion; an inflow gas conduit in fluid communication with the polymer, wherein the inflow gas conduit comprises a splitter to separate the flowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the polymer and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent. Block 1010 includes flowing air into the inflow gas conduit such that a first portion of the air flows into the polymer and a second portion of the air flows into the bypass gas conduit. Block 1015 includes adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the vaporizer pot. Block 1020 includes flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit.

[0049] FIG. 11 shows another embodiment of the present invention. This is an embodiment of the low-internal-resistance vaporizer of method 1000. The illustration of the low-intemal-resistance vaporizer shown in FIG. 11 includes the bundle of polymer fibers 1, the potting material 2, a gas collector 4 in fluid communication with the polymer fibers 1, the refill receptacle 5, the casing 6, the pot fresh gas stream 7 with gas flowing into the polymer fibers 1, the gas bypassing the pot 8, the gas flowing within the polymer fibers 9, and the anesthetic liquid 10.

[0050] It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

[0051] All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0052] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.” Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0053] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. In embodiments of any of the compositions and methods provided herein, “comprising” may be replaced with “consisting essentially of’ or “consisting of.” As used herein, the phrase “consisting essentially of’ requires the specified integer(s) or steps as well as those that do not materially affect the character or function of the claimed invention. As used herein, the term “consisting” is used to indicate the presence of the recited integer (e.g., a feature, an element, a characteristic, a property, a method/process step, or a limitation) or group of integers (e.g., feature(s), element(s), characteristic(s), property(ies), method/process(s) steps, or limitation(s)) only.

[0054] The term “or combinations thereof’ as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof’ is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0055] As used herein, words of approximation such as, without limitation, “about,” “substantial” or “substantially” refers to a condition that when so modified is understood to not necessarily be absolute or perfect but would be considered close enough to those of ordinary skill in the art to warrant designating the condition as being present. The extent to which the description may vary will depend on how great a change can be instituted and still have one of ordinary skill in the art recognize the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding discussion, a numerical value herein that is modified by a word of approximation such as “about” may vary from the stated value by at least ±1, 2, 3, 4, 5, 6, 7, 10, 12 or 15%.

[0056] All of the devices and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the devices and/or methods of this invention have been described in terms of particular embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope, and concept of the invention as defined by the appended claims.

[0057] Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosure. Accordingly, the protection sought herein is as set forth in the claims below.

[0058] Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.

[0059] To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke 35 U.S. C. § 112(f) as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.

Claims

WHAT IS CLAIMED IS:

1. A low-internal-resistance vaporizer comprising: a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer to transfer the anesthetic agent to the inflowing gas by diffusion; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent.

2. The low-internal -resistance vaporizer of claim 1, wherein the polymer comprises one or more hollow polymer fiber bundles.

3. The low-internal -resistance vaporizer of claim 2, wherein the one or more hollow polymer fiber bundles is joined to the one or more anesthetic reservoirs at a first end, a second end, or both.

4. The low-internal -resistance vaporizer of claim 1, further comprising a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs.

5. The low-internal -resistance vaporizer of claim 1, further comprising a sweat pump in fluid communication with an interior of the vaporizer pot and an anesthetic reservoir of the one or more anesthetic reservoirs.

6. The low-internal -resistance vaporizer of claim 1, wherein the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane.

7. The low-internal -resistance vaporizer of claim 1, wherein a gas exit from the vaporizer pot is configured to be enlarged or constricted by a temperature compensator.

8. The low-internal-resistance vaporizer of claim 1, wherein the low-intemal- resistance vaporizer is configured to be used as a draw-over vaporizer.

9. The low-internal -resistance vaporizer of claim 1, wherein the low-internal - resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit.

10. The low-internal -resistance vaporizer of claim 1, wherein the low-internal - resistance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device.

11. The low-internal -resistance vaporizer of claim 1, wherein the low-internal - resistance vaporizer is configured to receive the inflowing gas from a plurality of sources.

12. The low-internal-resistance vaporizer of claim 1, wherein the low-intemal- resistance vaporizer is configured to receive the inflowing gas from an intermittent source.

13. The low-internal -resistance vaporizer of claim 1, wherein a single inflow gas conduit fully or partially surrounds the polymer of the vaporizer pot; or wherein the single inflow gas conduit comprises holes that allow the inflowing gas to exit the single inflow gas conduit and impinge the surface of the polymer; or wherein the single inflow gas conduit terminates within the vaporizer pot such that the inflowing gas flows across the polymer at a right angle to an axis of a structure that includes the polymer.

14. A low-internal-resistance vaporizer comprising: a vaporizer pot configured to hold a liquid anesthetic agent and comprising a polymer configured to contain a flowing gas, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring the flowing gas into fluid communication with the liquid anesthetic agent to transfer the anesthetic agent to the flowing gas by diffusion; an inflow gas conduit in fluid communication with the polymer, wherein the inflow gas conduit comprises a splitter to separate the flowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the polymer and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent.

15. A method of introducing a vapor of an anesthetic agent to an air flow comprising: providing a low-internal-resistance vaporizer comprising: a vaporizer pot comprising a polymer configured to contain a liquid anesthetic agent, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring an inflowing gas flowing through the vaporizer pot into fluid communication with the polymer to transfer the anesthetic agent to the inflowing gas by diffusion; one or more pliable anesthetic reservoirs in fluid communication with the polymer of the vaporizer pot; an inflow gas conduit in fluid communication with the vaporizer pot, wherein the inflow gas conduit comprises a splitter to separate the inflowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the vaporizer pot and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent; flowing air into the inflow gas conduit such that a first portion of the air flows into the vaporizer pot and a second portion of the air flows into the bypass gas conduit; adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the polymer; and flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit.

16. The method of claim 15, wherein the polymer comprises one or more hollow polymer fiber bundles.

17. The method of claim 16, wherein the one or more hollow polymer fiber bundles are joined to the one or more anesthetic reservoirs at a first end, a second end, or both.

18. The method of claim 15, wherein the low-internal resistance vaporizer further comprises a refill system in fluid communication with an anesthetic reservoir of the one or more anesthetic reservoirs.

19. The method of claim 15, wherein the low-internal resistance vaporizer further comprises a sweat pump in fluid communication with an interior of the vaporizer pot and an anesthetic reservoir of the one or more anesthetic reservoirs.

20. The method of claim 15, wherein the anesthetic agent is isoflurane, halothane, sevoflurane, or desflurane.

21. The method of claim 15, further comprising enlarging or constricting a gas exit from the vaporizer pot to compensate for a temperature change.

22. The method of claim 15, wherein the low-internal-resistance vaporizer is configured to be used as a draw-over vaporizer.

23. The method of claim 15, wherein the low-internal-resistance vaporizer is configured to be used as a source of anesthetic for a circle circuit.

24. The method of claim 15, wherein the low-internal-resistance vaporizer is configured to be used as a source for an anesthetic for an oxygenator of an extracorporeal oxygenation device.

25. The method of claim 15, wherein the low-internal-resistance vaporizer is configured to receive the inflowing gas from a plurality of sources.

26. The method of claim 15, wherein the low-internal-resistance vaporizer is configured to receive the inflowing gas from an intermittent source.

27. The method of claim 15, wherein a single inflow gas conduit fully or partially surrounds the polymer of the vaporizer pot; or wherein the single inflow gas conduit comprises holes that allow the inflowing gas to exit the single inflow gas conduit and impinge the surface of the polymer; or wherein the single inflow gas conduit terminates within the vaporizer pot such that the inflowing gas flows across the polymer at a right angle to an axis of a structure that includes the polymer.

28. A method of introducing a vapor of an anesthetic agent to an air flow comprising: providing a low-internal-resistance vaporizer comprising a vaporizer pot configured to hold a liquid anesthetic agent and comprising a polymer configured to contain a flowing gas, wherein the polymer is highly permeable to a vapor of the anesthetic agent, and wherein the vaporizer pot is configured to bring the flowing gas into fluid communication with the liquid anesthetic agent to transfer the anesthetic agent to the flowing gas by diffusion; an inflow gas conduit in fluid communication with the polymer, wherein the inflow gas conduit comprises a splitter to separate the flowing gas to the vaporizer pot from gas bypassing the vaporizer pot; a bypass gas conduit in fluid communication with the splitter to route bypass gas around the vaporizer pot; and an outflow gas conduit in fluid communication with the polymer and with the bypass gas conduit, configured to combine an outflowing gas containing the vapor of the anesthetic agent with the bypass gas for dilution and delivery of the vapor of the anesthetic agent; flowing air into the inflow gas conduit such that a first portion of the air flows into the polymer and a second portion of the air flows into the bypass gas conduit; adding the vapor of the anesthetic agent to the first portion of the air from the liquid anesthetic agent contained within the vaporizer pot; and flowing the first portion of the air comprising the vapor of the anesthetic agent into the outflow gas conduit to combine with the second portion of the air flowing through the bypass gas conduit.