Apparatus for tissue transport and preservation
12161110 ยท 2024-12-10
Assignee
Inventors
- Adam Collette (Somerville, MA, US)
- Melanie Jessel (Boston, MA, US)
- Lisa Maria Anderson (Cambridge, MA, US)
Cpc classification
A01N1/148
HUMAN NECESSITIES
International classification
Abstract
Systems and methods of the invention generally relate to prolonging viability of bodily tissue, especially an organ such as a lung, by adjusting pressure as needed to maintain a constant pressure within the organ even during external pressure fluctuations due, for example, to transportation of the organ in an airplane. Gas passing into and out of the organ may be conditioned to prolong tissue viability.
Claims
1. A system for storage of an organ, the system comprising: a transport container; a pump configured to direct gas through a channel into an airway of a lung; nested containers configured to be disposed within the transport container, the nested containers configured to contain the lung; a relief valve configured to release gas from the channel while the pump is directing gas through the channel; and a lung adapter configured to be in fluid communication with the channel, the channel configured to extend from an exterior of the nested containers to an interior of the nested containers, and the lung adapter operable to form a closed air system with the airway of the lung, wherein the nested containers are configured to only allow gas to pass from the exterior of the nested containers to the interior of the nested containers through the channel.
2. The system of claim 1, further comprising eutectic cooling material disposed within the transport container and outside the nested containers, the eutectic cooling material configured to maintain a temperature of the lung.
3. The system of claim 1, wherein the airway of the lung is selected from a group consisting of a trachea or bronchus of the lung.
4. The system of claim 1, further comprising one or more sensors configured to sense a parameter within the system.
5. The system of claim 4, wherein the parameter is selected from a group consisting of temperature and pressure.
6. The system of claim 2, wherein the eutectic cooling material is in-line between the pump and the airway of the lung and operable to cool gas traveling therebetween.
7. The system of claim 1, further comprising a humidifying element in-line between the pump and the airway of the lung and operable to humidify gas traveling therebetween.
8. The system of claim 1, further comprising a compressive sleeve operable to compress the lung.
9. The system of claim 2, wherein the eutectic cooling material comprises one or more pouches of phase change material (PCM) for surrounding and cooling the transport container.
10. A method for storage of an organ, the method comprising: providing an organ container comprising: a pump configured to direct gas through a channel into an airway of a lung; nested containers; a relief valve configured to release gas from the channel while the pump is directing gas through the channel; and a lung adapter configured to be in fluid communication with the channel, the channel configured to extend from an exterior of the nested containers to an interior of the nested containers, and the lung adapter operable to form a closed air system with the airway of the lung, placing the lung in the nested containers; coupling the airway of the lung to the lung adapter such that gas can only pass from the exterior of the nested containers to the interior of the nested containers through the channel; and placing the nested containers in the organ container.
11. The method of claim 10, further comprising arranging eutectic cooling material within the organ container and outside the nested containers, the eutectic cooling material configured to maintain a temperature of the lung.
12. The method of claim 10, wherein the airway of the lung is selected from a group consisting of a trachea or bronchus of the lung.
13. The method of claim 10, further comprising cooling the gas travelling between the pump and the airway of the lung with an in-line cooling element.
14. The method of claim 10, further comprising humidifying the gas travelling between the pump and the airway of the lung with an in-line humidifying element.
15. The method of claim 10, further comprising compressing the lung in a cyclic pattern to provide pulsatile compressive force on the lung by inflating and deflating one or more inflatable cavities in a compressive sleeve using a second pump.
16. The method of claim 11, wherein arranging the eutectic cooling material within the organ container comprises placing one or more pouches of phase change material (PCM) around the nested containers.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION
(45) Devices, systems and methods are described herein that are configured for extracorporeal preservation and transportation of bodily tissue. Specifically, devices for monitoring and stabilizing pressure within inflated lungs are described including organ connectors to filter air moving to and from the lung and to permit any leaked air to escape the preservation fluid-filled container. Systems and methods can compensate for pressure changes resulting from, for example, increases and decreases in altitude during air transport of the organ. By bleeding off and returning excess gases, volumetric expansion of the lung (i.e., over-inflation) may be prevented, avoiding damaging the organ which can result in decreased organ viability and decreased survival rates for transplant recipients. Additional aspects include contoured storage and transport chambers that can replicate the in-vivo anatomical orientation and geometry for a given organ. For example, a pair of donor lungs may be placed against a smooth, raised, central saddle designed to replicate the spine that the lungs would be resting against in vivo. Organs, such as lungs or hearts, may be suspended in an upright position to replicate the organ's orientation in a standing human and to prevent tissue damage caused by pressure from the organ's own weight resting on itself.
(46) Pressure modulation can be carried out using various combinations of compressed gas, pressure regulators, pressure relief valves, filters, pressure accumulators, and compressive features. The pressure modulating apparatuses may be connected to the interior airways of a stored lung in order to add and remove gas to maintain a desired pressure. The air connection is preferably sealed to allow the pressure regulation to function and to maintain a sterile environment. A coupled compressed gas source may comprise oxygen in order to provide oxygen to the living tissue being stored. A pressure regulator may sense pressure within the system and open a connection to the compressed gas source in order to increase pressure when the system pressure falls below a selected threshold that may result in tissue damage. Similarly, if pressure within the system is above a safe threshold to avoid tissue damage, one or more pressure relief valves may release excess gas volume until the desired internal pressure is achieved. Any point of access for adding or releasing gas may include a filter to avoid contamination of the sterile environment.
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(48) In various embodiments, cooling blocks may include eutectic cooling media or other phase change material (PCM) such as savENRG packs with PCM-HSOIP material commercially available from RGEES, LLC or Akuratemp, LLC (Arden, N.C.). Exemplary PCM specifications including a freezing temperature of 0 C.+/0.5 C., a melting temperature of 1 C.+/0.75 C., latent heat of 310 J/g+/10 J/g, and density of 0.95 gram/ml+/0.05 gram/ml. Pouch dimensions may vary depending on application specifics such as tissue to be transported and the internal dimensions of the transport container and external dimensions of the tissue storage device, chamber, or canister. PCM may be included in pouches approximately 10 inches by 6 inches having approximately 230 g of PCM therein. Pouches may be approximately 8.5 mm thick and weigh about 235 g to 247 g. In some embodiments, pouches may be approximately 6.25 inches by 7.75 inches with a thickness of less than about 8.5 mm and a weight of between about 193 g and about 201 g. Other exemplary dimensions may include about 6.25 inches by about 10 inches. Pouches may be stacked or layered, for example in groups of 3 or 4 to increase the total thickness and amount of PCM. In certain embodiments, PCM containing pouches may be joined side to side to form a band of coupled PCM pouches. Such a band may be readily manipulated to wrap around the circumference of a cylindrical storage container and may have dimensions of about 6 inches by about 26 inches consisting of approximately 8 individual pouches joined together in the band. Pouches may be formed of a film for containing the PCM having a desirable moisture vapor transmission rate to avoid PCM mass loss over time. Suitable films include X2030 EVOH and nylon pouch film available from Protect-all (Darien, Wis.) and plus plain laminate 162 OP nylon multilayer film 350 mm available from Shrinath Rotopack Pvt. Ltd. (India).
(49) One or more racks may be included below and/or above the organ and may include a pattern of holes. The holes may receive support rods which can be placed in different patterns of holes depending on the size and shape of the tissue being transported to maintain the tissue in a desired position and prevent lateral movement thereof during transportation and storage. Systems and methods of the invention may include sterile, nested containers for isolating stored tissue from the external environment and the potentially contaminated interior of various storage and transport apparatuses. In preferred embodiments as shown in
(50) The bags may have one or more connectors allowing gasses or other fluids to move between the bags, the tissue, and the external environment. For example,
(51) In certain embodiments, each nested container may include its own connector as shown in
(52) In certain embodiments, a single filter may be used on the air line (as shown in
(53) As discussed, nested containers may be configured in a series of 2 or more (preferably 3) sterile nested bags allowing for venting of air via 1-way check valves with integrated hydrophobic filtration media with communication allowed through a series of interconnected ports to a controlled plug (e.g., the accumulator element, relief valve, or gas source), system temperature can be monitored by a temperature probe placed in contact with the outside of the bag. Additional useful information regarding preservation solution temperature, pH, ionic chemistry, and other aspects may be obtained and monitored via a series of integrated probes (temp, pH, ion-specific, conductivity, etc.) which may pass into the bags through a series of bulkhead fittings or similar or be placed within the inner bag and communicate in a wireless fashion through near field communications or Bluetooth connectivity or similar to an external device which processes the signal. In certain embodiments, such probes may be affixed to the inner bag. In some embodiments, probes may be in a free-floating assembly placed into the bag prior to use. In certain embodiments, probes can be in communication with a user interface such as a display on the device or a remote display. Accordingly, user monitoring can be permitted to allow for environmental parameter recording and/or intervention. In certain embodiments, such probes can be in communication with a computer device including a non-transitory, tangible memory and a processor operable to receive information from the various probes and sensors and engage various apparatuses for maintaining or altering environmental parameters. For example, an active solution management tool may be used to dynamically adjust preservation solution properties to optimize the organ storage environment based on pH, ionic chemistry, or composition by adding or removing compounds from the preservation fluid. The computer may also manipulate cooling or heating elements and or the pressure control mechanisms described herein to maintain optimal storage conditions in response to changes detected via the connected probes.
(54) In certain embodiments, the containers or nested containers may be rigid cassettes instead of flexible bags. In such embodiments, it might be desirable to have a larger reservoir of aqueous solution for thermal reasons than might be economically or functionally practical. It might also be of advantage or necessary to provide a rigid container to an organ in transit which would not be provided by flexible bags. In such cases, a sterile, disposable, rigid enclosure may be used to contain the organ and some small volume of preservation solution directly, afterwards being inserted into the standard bag system containing a larger volume of aqueous media (preservation solution or otherwise) that may serve as a thermal reservoir/inertial dampener.
(55) In some embodiments, such enclosures may be completely sealed and may not communicate with the surrounding aqueous media in order to maintain an isolated sterile environment while still realizing certain thermal benefits of a larger fluid reservoir.
(56) In certain embodiments, such enclosures may be perforated such that the fluid inside the enclosure communicates passively with the surrounding aqueous media. In some embodiments, perforated enclosures can communicate actively with the surrounding aqueous media by means of a pump or other means of introducing fluid flow. In certain embodiments, active communication can occur with a reservoir of liquid or gas external to the sterile enclosures for a variety of reasons such as achieving gas exchange for the preservation medium, for example, to actively maintain either nominal equilibration with air or a gas-enriched environment (for example oxygen rich) for tissue preservation. Active communication with an external reservoir can also be used for chemistry exchange for the preservation medium including adjusting dissolved species in the aqueous species over time in either a fixed or dynamic fashion (e.g., introduction of a drug, therapeutic, dilute acid or base to maintain pH, etc.).
(57) Solution exchange (e.g., simply cycling out some fraction of spent solution for fresh) and thermal exchange (e.g., creating an isolated microenvironment either surrounding or potentially within the organ that is slightly different from nominal system temp) are other potential functions of an external reservoir in active communication with the sterile cassette. While pressure modulating apparatuses described herein are especially useful in lung storage and transportation, the aforementioned storage containers (e.g., flexible bags, rigid cassettes, or some combination) can also be used to store or transport other tissue or organs including heart, kidney, liver, or pancreas for example. In such embodiments, various organ-specific cassettes or bags may be used that are sized to accommodate the organ being stored or transported. Similarly, organ-specific preservation solutions may also be used and may be pre-loaded into the appropriate container.
(58) The gas entering and leaving the lung may be conditioned to create a favorable preservation environment. The gas may be oxygenated, cooled, humidity-controlled, and/or cycled to provide the preferred characteristics for tissue viability post-transport.
(59) In certain embodiments, the gas passing from the compressed gas source or pressure accumulator may be conditioned as described above.
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(62) The gas may be cooled as well to assist in maintaining a desired organ temperature for preservation. The overall organ is placed in cooled media or surrounded with cooling material but the repeated gas exchange of a warmer gas could raise the organ temperature, particularly at the internal points of contact, resulting in tissue degradation.
(63) Similarly, the gas used to initially inflate the lung at the donor site can be treated in any of the aforementioned ways (e.g., gas sources or lines may be heated, cooled, or humidified) to help ready the organ for storage or transport.
(64) Additionally, as air temperature, humidity, and pressure are interrelated, attempts to maintain a static pressure in a transported organ can be aided by also maintaining a desired humidity and temperature level.
(65) In various embodiments, constant or pulsatile compressive pressure may be applied to the organ to drive gas exchange in order to provide fresh humidified, oxygenated, and/or cooled gas to the internal lung. As shown in
(66) Alternatively, instead of passing air in and out of the same orifice via simulated breaths, additional outlets may be provided (either naturally occurring or surgically added) to allow air to pass through the passages of the tissue. By providing one or more outlets at the farthest points from the air inlet, penetration of treated gas throughout the tissue can be assured.
(67) In
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(69) The organ adapter 107 is coupled to an expandable accumulator 105 and the lumen of the organ adapter 107 is in fluid communication with a sealed interior volume of the expandable accumulator 105. The expandable accumulator 105 may be coupled by a valve 109, to an inlet 113. The inlet 113 has a lumen that, when the valve 109 is open, is in fluid communication with the interior volume of the expandable accumulator 105, the lumen of the organ adapter 107, and the airways of the lung 103. When the valve 109 is closed, the interior volume of the expandable accumulator 105, the lumen of the organ adaptor 107, and the airways of the lung 103 form an air-tight, closed environment that is sealed from the outside environment including, for example, any preservation fluid present within the organ container 111. The organ container 111 may include one or more boxes or bags configured to contain both the organ and any preservation fluid (e.g., temperature regulated, oxygenated fluid) in a sterilized environment. In preferred embodiments, the organ is placed into one or more sterile bags or boxes. For example, a lung may be placed in three concentric sterile bags fitted with a through-the-bag-wall cannula leading into the trachea plug. The cannula may include a filter for each bag (e.g., a 0.2-micron sterile filter). Accordingly, both the exterior surface and interior, pressure-dampened lumen of the organ are surrounded by three sterile layers.
(70) A filtration assembly may be placed in-line between the accumulator and the organ. The filtration assembly connects the lungs or other organ to the accumulator and provides filtration to the air moving therebetween.
(71) In various embodiments, the accumulator may have an interior volume (fully expanded) of about, 0.5, 0.75, 1, 1.25, 0.1.5, 1.75, 2, 2.5, 3, 3.5, 4, 4.5, or more liters. In preferred embodiments, the accumulator has a fully expanded interior volume of about 1 liter.
(72) System 101 is configured to permit gas to move back and forth between the airways of the lung 103 through the lumen of the organ adapter 107, and into the interior volume of the expandable accumulator 105. When the valve 109 is open, the system 101 is configured to permit gas flow from the inlet 113, through the valve 109, into the lumen of the organ adaptor 107, and finally into the airways of the lung 103. The expansion resistance of the expandable accumulator 105 may be adjustable, fixed, or progressive.
(73) The organ adapter 107 may be configured to substantially retain the bodily tissue (e.g., lung) with respect to the expandable accumulator 105. The organ adapter 107 may be configured to permit movement of a gas from the expandable accumulator 105, into the airways of the lung 103, and back. The organ adapter 107 can be configured to be coupled to a bodily tissue such as a lung 103. The organ adapter 107 can be coupled to the bodily tissue in any suitable manner. For example, in some embodiments, the organ adapter 107 can configured to be sutured to the bodily tissue. In another example, the organ adapter 107 is coupleable to the bodily tissue via an intervening structure, such as silastic or other tubing. In some embodiments, at least a portion of the organ adapter 107, or the intervening structure, is configured to be inserted into the bodily tissue such as the lumen of a trachea, bronchus, or other air passage of a lung 103. For example, in some embodiments, the lumen of the organ adapter 107 (or a lumen of the intervening structure) is configured to be fluidically coupled to a lumen of the bodily tissue such as an air passage of the lung 103.
(74) In various embodiments including the use of one or more sterile bags or other containers for the organ, the organ adapter may be contained in or integral to the inner most sterile bag and coupled to a through-the-bag-wall cannula that transverses each of the bags or other containers. The cannula, at the outer most bag or other container, may include an adapter to be removably coupled to the accumulator in the systems described herein. Accordingly, the bagged organ may be easily and quickly connected to the accumulator and inflated during loading and easily and quickly disconnected upon arrival at the transplantation site.
(75) In some embodiments, the organ adapter (or simply referred as the adapter) can be configured to support the bodily tissue when the bodily tissue is coupled to the adapter. For example, in some embodiments, the adapter can include a retention mechanism (not shown) configured to be disposed about at least a portion of the bodily tissue and to help retain the bodily tissue with respect to the adapter. The retention mechanism can be, for example, a net, a cage, a sling, or the like. In some embodiments, the system can include a basket (not shown) or other support mechanism configured to support the bodily tissue when the bodily tissue is coupled to the adapter or otherwise received in the system. The organ adapter may be rigidly coupled to an interior wall (e.g. a lid) of an organ container such that the organ may be suspended via its connection point to the adapter.
(76) The portion of the adapter that is inserted into a lumen of the organ may include a series of tapered steps such that a distal end of the adapter portion is narrower than a proximal end. In this manner, the adapter is configured to be inserted into a range of lumen sizes.
(77) The lumen may be secured or sealed to the organ adapter via any means including elastic tension in the organ lumen itself or through the use of sutures, elastic band, or other securing mechanisms on the outside of the lumen applying pressure thereupon to form an air-tight seal between the lumen of the organ and the lumen of the adapter.
(78) The expandable accumulator is configured to expand to accept relative increases in gas volume within the closed system in response to pressure differential changes between the closed system and the surrounding environment (e.g., during flight). The interior volume of the expandable accumulator should resist expansion with an opposing force that is less than that of the lung. Accordingly, decreases in internal pressure of the closed system due to decreases in the pressure of the surrounding environment (e.g. during flight) will be borne by the expandable accumulator such that the pressure within the system drops without volumetric expansion of the lung airways (which could cause tissue damage or rupture the airways).
(79) The expandable accumulator is configured to be in constant communication with the internal (closed system) pressure and the external (surrounding environment) pressure, and to establish a nearly-constant differential between the two while having compliance higher than the lung's compliance. The pressure differential is such that the internal pressure is greater than the environment pressure. The pressure differential keeps the lungs inflated. The pressure differential would commonly be referred to as the gauge pressure. When the system is initially prepared, the external pressure may be 1 bar (absolute) and the internal pressure would be 1+x bar, absolute (where the x is a suitable value chosen for best storage performance). The gauge pressure of the closed system is therefore x bar, and the differential pressure across the lung is also x bar. At a later time, in transport, the external pressure may be 0.75 bar for instance due to airplane cabin pressure when in flight. The internal pressure would be 0.75+x bar, so the gauge pressure is again x bar, as is the pressure across the lung. In this manner the expandable accumulator maintains a nearly-constant pressure differential across the lung (from inside to outside).
(80) In order to maintain the nearly-constant pressure differential the expandable accumulator will have a very high compliance, for example much higher than the lung compliance. In certain embodiments, the system may be configured to maintain about a 15 cm H.sub.2O gauge pressure inside the organ. The pressure may be fixed or may be tunable or adjustable using variable weight, spring tension, or other means depending on the accumulator mechanism. Pressure in the system may be set by filling the system to a desired fixed pressure or may be controlled using an adjustable accumulator which may be acted on by a computer based on inputs received from a pressure or other sensor as described below.
(81) An inlet of the system may be used to add or remove a gas from the lumen of the organ (e.g., airways of a lung). For example, where donor lungs are at least partially inflated for storage and transport, a retrieved lung may be secured to an organ adapter as shown in
(82) During inflation, as gas is admitted to the system, both the lungs and the expandable accumulator will inflate until reaching the desired gauge pressure (designated x above). As additional gas is thereafter admitted, the gas would preferentially fill the expandable accumulator given that component's higher compliance. When the expandable accumulator is entirely filled, the pressure would begin to rise above the x target, and the system would not have any remaining capacity. Therefore, when the system is filled the volume of gas may be adjusted such that a movable element of the expandable accumulator rests at a target position (for instance 25% of travel). Once the expandable accumulator is at that target position, the valve can be closed and the closed system is sealed and ready for transport.
(83) Once the lung has been inflated to a desired pressure, the valve may be closed, sealing off the closed system. The lung coupled to the expandable accumulator by the organ adapter along with the closed valve and the inlet may be then be placed in an organ container for storage or transport and may be at least partially submerged in a fluid such as a preservation fluid as known in the art. Examples of preservation fluid and static and perfusion-based tissue containers compatible with systems and methods of the invention are described in U.S. application Ser. No. 14/460,489, incorporated herein by reference.
(84) The fill of the accumulator can be adjusted at organ recovery according to the local ambient (e.g. barometric) pressure. A smaller accumulator would thereby be able to work identically whether filled in Denver Colo., or Boston Mass., whatever the weather conditions. The accumulator may include a scale or other indicator in customary barometric pressure units. An exemplary pressure indicator 1115 is shown in
(85) The expandable accumulator may be of any configuration that permits expansion of its interior volume with less resistance than that of the lung's airways. Examples of expandable accumulators are shown in
(86) The expandable accumulator 105 depicted in
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(89) The rolling diaphragm contributes to a low-friction, low-hysteresis accumulator advantageous to tissue preservation as described herein, especially in lung preservation and transport apparatuses. The diaphragm may be constructed of any suitable material including latex, rubber, or silicon. An exemplary accumulator 4401 including a pressure relief valve that may release excess gas volume until the desired internal pressure is achieved.
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(91) A diaphragm-type accumulator system as exemplified in
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(94) As noted, systems of the invention are compatible with and may include any static or perfusion-type preservation apparatus. An example of such a configuration is shown in
(95) The membrane 20 is disposed within the pumping chamber 14 along an axis A1 that is transverse to a horizontal axis A2. Said another way, the membrane 20 is inclined, for example, from a first side 22 to a second side 24 of the apparatus 10. As such, as described in more detail below, a rising fluid in the second portion 18 of the pumping chamber 14 will be directed by the inclined membrane 20 towards a port 38 disposed at the highest portion of the pumping chamber 14. The port 38 is configured to permit the fluid to flow from the pumping chamber 14 into the atmosphere external to the apparatus 10. In some embodiments, the port 38 is configured for unidirectional flow, and thus is configured to prevent a fluid from being introduced into the pumping chamber 14 via the port (e.g., from a source external to the apparatus 10). In some embodiments, the port 38 includes a luer lock.
(96) The second portion 18 of the pumping chamber 14 is configured to receive a fluid. In some embodiments, for example, the second portion 18 of the pumping chamber 14 is configured to receive a liquid perfusate. The second portion 18 of the pumping chamber 14 is in fluid communication with an adapter 26. The adapter 26 is configured to permit movement of the fluid from the pumping chamber 14 to a bodily tissue T. For example, in some embodiments, the pumping chamber 14 defines an aperture (not shown) configured to be in fluidic communication with a lumen (not shown) of the adapter 26. The adapter 26 is configured to be coupled to the bodily tissue T. The adapter 26 can be coupled to the bodily tissue T in any suitable manner. For example, in some embodiments, the adapter 26 is configured to be sutured to the bodily tissue T. In another example, the adapter 26 is coupleable to the bodily tissue T via an intervening structure, such as silastic or other tubing. In some embodiments, at least a portion of the adapter 26, or the intervening structure, is configured to be inserted into the bodily tissue T. For example, in some embodiments, the lumen of the adapter 26 (or a lumen of the intervening structure) is configured to be fluidically coupled to a vessel of the bodily tissue T.
(97) Where the tissue T is, for example a lung, the airways of the tissue T may be coupled to an expandable accumulator 705 and associated systems as described herein via an organ adapter 707 (e.g., via the trachea or bronchus).
(98) In some embodiments, the adapter 26 is configured to support the bodily tissue T when the bodily tissue T is coupled to the adapter. For example, in some embodiments, the adapter 26 includes a retention mechanism (not shown) configured to be disposed about at least a portion of the bodily tissue T and to help retain the bodily tissue T with respect to the adapter. The retention mechanism can be, for example, a net, a cage, a sling, or the like. In some embodiments, the apparatus 10 includes a basket (not shown) or other support mechanism configured to support the bodily tissue T when the bodily tissue Tis coupled to the adapter 26 or otherwise received in the apparatus 10.
(99) An organ chamber 30 is configured to receive the bodily tissue T and a fluid. In some embodiments, the apparatus 10 includes a port 34 that is extended through the apparatus 10 (e.g., through the pumping chamber 14) to the organ chamber 30. The port 34 is configured to permit fluid (e.g., perfusate) to be introduced to the organ chamber 30. In this manner, fluid can be introduced into the organ chamber 30 as desired by an operator of the apparatus. For example, in some embodiments, a desired amount of perfusate is introduced into the organ chamber 30 via the port 34, such as before disposing the bodily tissue T in the organ chamber 30 and/or while the bodily tissue T is received in the organ chamber. In some embodiments, the port 34 is a unidirectional port, and thus is configured to prevent the flow of fluid from the organ chamber 30 to an area external to the organ chamber through the port. In some embodiments, the port 34 includes a luer lock. The organ chamber 30 may be of any suitable volume necessary for receiving the bodily tissue T and a requisite amount of fluid for maintaining viability of the bodily tissue T. In one embodiment, for example, the volume of the organ chamber 30 is approximately 2 liters.
(100) The organ chamber 30 is formed by a canister 32 and a bottom portion 19 of the pumping chamber 14. In a similar manner as described above with respect to the membrane 20, an upper portion of the organ chamber (defined by the bottom portion 19 of the pumping chamber 14) can be inclined from the first side 22 towards the second side 24 of the apparatus. In this manner, as described in more detail below, a rising fluid in the organ chamber 30 will be directed by the inclined upper portion of the organ chamber towards a valve 36 disposed at a highest portion of the organ chamber. The valve 36 is configured to permit a fluid to flow from the organ chamber 30 to the pumping chamber 14. The valve 36 is configured to prevent flow of a fluid from the pumping chamber 14 to the organ chamber. The valve 36 can be any suitable valve for permitting unidirectional flow of the fluid, including, for example, a ball check valve.
(101) The canister 32 can be constructed of any suitable material. In some embodiments, the canister 32 is constructed of a material that permits an operator of the apparatus 10 to view at least one of the bodily tissue T or the perfusate received in the organ chamber 30. For example, in some embodiments, the canister 32 is substantially transparent. In another example, in some embodiments, the canister 32 is substantially translucent. The organ chamber 30 can be of any suitable shape and/or size. For example, in some embodiments, the organ chamber 30 can have a perimeter that is substantially oblong, oval, round, square, rectangular, cylindrical, or another suitable shape.
(102) In use, the bodily tissue T is coupled to the adapter 26. The pumping chamber 14 is coupled to the canister 32 such that the bodily tissue T is received in the organ chamber 30. In some embodiments, the pumping chamber 14 and the canister 32 are coupled such that the organ chamber 30 is hermetically sealed. A desired amount of perfusate is introduced into the organ chamber 30 via the port 34. The organ chamber 30 can be filled with the perfusate such that the perfusate volume rises to the highest portion of the organ chamber. The organ chamber 30 can be filled with an additional amount of perfusate such that the perfusate flows from the organ chamber 30 through the valve 36 into the second portion 18 of the pumping chamber 14. The organ chamber 30 can continue to be filled with additional perfusate until all atmospheric gas that initially filled the second portion 18 of the pumping chamber 14 rises along the inclined membrane 20 and escapes through the port 38. Because the gas will be expelled from the pumping chamber 14 via the port 38 before any excess perfusate is expelled (due to gas being lighter, and thus more easily expelled, than liquid), an operator of the apparatus 10 can determine that substantially all excess gas has been expelled from the pumping chamber when excess perfusate is released via the port. As such, the apparatus 10 can be characterized as self-purging. When perfusate begins to flow out of the port 38, the apparatus 10 is in a purged state (i.e., all atmospheric gas initially within the organ chamber 30 and the second portion 18 of the pumping chamber 14 has been replaced by perfusate). When the purged state is reached, the operator can close both ports 34 and 38, preparing the apparatus 10 for operation.
(103) Oxygen (or another suitable fluid, e.g., gas) is introduced into the first portion 16 of the pumping chamber 14 via the valve 12. A positive pressure generated by the introduction of oxygen into the pumping chamber 14 causes the oxygen to be diffused through the semi-permeable membrane 20 into the second portion 18 of the pumping chamber. Because oxygen is a gas, the oxygen expands to substantially fill the first portion 16 of the pumping chamber 14. As such, substantially the entire surface area of the membrane 20 between the first portion 16 and the second portion 18 of the pumping chamber 14 is used to diffuse the oxygen. The oxygen is diffused through the membrane 20 into the perfusate received in the second portion 18 of the pumping chamber 14, thereby oxygenating the perfusate.
(104) In the presence of the positive pressure, the oxygenated perfusate is moved from the second portion 18 of the pumping chamber 14 into the bodily tissue T via the adapter 26. For example, the positive pressure can cause the perfusate to move from the pumping chamber 14 through the lumen of the adapter 26 into the vessel of the bodily tissue T. The positive pressure is also configured to help move the perfusate through the bodily tissue T such that the bodily tissue T is perfused with oxygenated perfusate.
(105) After the perfusate is perfused through the bodily tissue T, the perfusate is received in the organ chamber 30. In this manner, the perfusate that has been perfused through the bodily tissue T is combined with perfusate previously disposed in the organ chamber 30. In some embodiments, the volume of perfusate received from the bodily tissue T following perfusion combined with the volume of perfusate previously disposed in the organ chamber 30 exceeds a volume (e.g., a maximum fluid capacity) of the organ chamber 30. A portion of the organ chamber 30 is flexible and expands to accept this excess volume. The valve 12 can then allow oxygen to vent from the first portion 16 of the pumping chamber 14, thus, reducing the pressure in the pumping chamber 14. As the pressure in the pumping chamber 14 drops, the flexible portion of the organ chamber 30 relaxes, and the excess perfusate is moved through the valve 36 into the pumping chamber 14. The cycle of oxygenating perfusate and perfusing the bodily tissue T with the oxygenated perfusate can be repeated as desired.
(106)
(107) The interior of organ containers of the invention may contain a fixed or removable shelf or tray configured to support cooling materials (e.g., frozen gel packs). Such a tray allows the organ to be loaded into the container before the tray is in place and, once the tray is inserted, the tray supports the cooling materials keeping them proximate to the organ for cooling purposes but prevents the materials from contacting the organ which can cause damage thereto. The tray may further serve to locate the organ within the colder bottom portion of the container.
(108) In various embodiments, organ containers may comprise insulation material at least around the organ chamber. Preferably, all sides of the organ chamber are insulated, along with the pumping chamber in embodiments where a pumping chamber is included. Insulation material can comprise an aerogel. When used in conjunction with cooling blocks or packs within the insulated area, containers of the invention can maintain a desired temperature for extended periods of time of 18 hours or more. Aerogel insulation materials may be at least 1 mm, at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, at least 6 mm, at least 7 mm, at least 8 mm, at least 9 mm, at least 10 mm, or at least 15 mm thick in various embodiments. The thickness of the aerogel insulation may vary at different points around the container (e.g., thicker at the top and bottom than the sides).
(109)
(110) Systems of the invention may include a variety of sensors configured to sense and report, for example, temperature of the tissue, temperature of a preservation fluid or perfusate, pressure within the closed air system, pressure within the fluid, or ambient pressure. Displays for the sensors may be disposed on the outer surfaces of the organ transport or may be wirelessly linked to the internal sensors.
(111) In some embodiments, a temperature sensor may include a probe positioned in the transport cavity and attached by a flexible cable to a temperature datalogger. The probe may not be wetted (i.e., the probe would remain outside of any sterile bags or containers) and may be suspended in air by a bracket or support in order to avoid direct contact with any cooling materials. The probe would thereby record and/or report the cavity temperature rather than the lung tissue temperature.
(112) In certain embodiments, the sensor may comprise a mechanical flag that indicates the furthest expansion of the expandable accumulator and can therefore indicate if the accumulator reached maximum expansion presenting the possibility that additional pressure was absorbed by the lung tissue through over-inflation.
(113)
(114)
(115)
(116)
(117)
(118)
(119)
(120)
(121) As one skilled in the art would recognize as necessary or best-suited for the systems and methods of the invention, systems and methods of the invention may include computers that may include one or more of processor (e.g., a central processing unit (CPU), a graphics processing unit (GPU), etc.), computer-readable storage device (e.g., main memory, static memory, etc.), or combinations thereof which communicate with each other via a bus. Computers may include mobile devices (e.g., cell phones), personal computers, and server computers. In various embodiments, computers may be configured to communicate with one another via a network in order to display image series or allow remote storage, viewing, or selection of images of a given series.
(122) A processor may include any suitable processor known in the art, such as the processor sold under the trademark XEON E7 by Intel (Santa Clara, Calif.) or the processor sold under the trademark OPTERON 6200 by AMD (Sunnyvale, Calif.).
(123) Memory preferably includes at least one tangible, non-transitory medium capable of storing: one or more sets of instructions executable to cause the system to perform functions described herein (e.g., software embodying any methodology or function found herein); data (e.g., portions of the tangible medium newly re-arranged to represent real world physical objects of interest accessible as, for example, a picture of an object like a motorcycle); or both. While the computer-readable storage device can in an exemplary embodiment be a single medium, the term computer-readable storage device should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the instructions or data. The term computer-readable storage device shall accordingly be taken to include, without limit, solid-state memories (e.g., subscriber identity module (SIM) card, secure digital card (SD card), micro SD card, or solid-state drive (SSD)), optical and magnetic media, hard drives, disk drives, and any other tangible storage media.
(124) Input/output devices according to the invention may include one or more of a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT) monitor), an alphanumeric input device (e.g., a keyboard), any temperature, pressure, or other sensor described herein, a cursor control device (e.g., a mouse or trackpad), a disk drive unit, a signal generation device (e.g., a speaker), a touchscreen, a button, an accelerometer, a microphone, a cellular radio frequency antenna, a network interface device, which can be, for example, a network interface card (NIC), Wi-Fi card, or cellular modem, or any combination thereof.
(125) One of skill in the art will recognize that any suitable development environment or programming language may be employed to allow the operability described herein for various systems and methods of the invention. For example, systems and methods herein can be implemented using Perl, Python, C++, C#, Java, JavaScript, Visual Basic, Ruby on Rails, Groovy and Grails, or any other suitable tool. For a computer, it may be preferred to use native xCode or Android Java.
EXAMPLES
Example 1Modeling of Lung Pressure Changes During Transport
(126) Lung volume and pressure conditions were modeled during transport without an accumulator, with a spring-based accumulator, and with a weight based accumulator (as described above). Since PV=nRT (ideal gas law) the trapped volume inside the lung will obey pV/T=constant or p.sub.fV.sub.f/T.sub.f=p.sub.oV.sub.o/T.sub.o where o refers to starting and f to final conditions.
(127) P is the atmospheric pressure, absolute. p is the internal pressure, absolute, biased somewhat above P. V is the contained volume (lung, tubing, accumulator) T is the temperature in Kelvin.
(128) For pressure the model defines and uses cmH.sub.2O and atm (the SI unit standard). Pressure measurements are absolute unless otherwise stated.
(129)
Ambient Condition Ranges:
(130) Ambient Pressure (P) can range between the following (note that weather measurements are usually in inHg):
1 atm=29.921 in.sub.HgPatm.sub.min:=25.69 in_Hg=0.859.Math.atm Patm.sub.max=32.06 in_Hg: 1.071.Math.atm
(131) Altitude at recovery should be accounted for. For example, the typical pressure in a city such as Denver, Colo. may be calculated as:
(132)
(133) The range of P.sub.o is from .sup.0.8 to .sup.1.08 atm. Lung temperature (T) can range between the following (assumes that recovery occurs in cold operating rooms and transport is under not as cold conditions):
T.sub.o_min:=2 C.=275.15K and T.sub.o_max=65 F.=291.483K
Travel Conditions:
(134) To model transit conditions, it is assumed that T stays approximately constant. Allowing Tf to rise to 8 C. is conservative. Extremes of pressure will be seen in airplane cabins and is approximated as follows for various aircraft (Cabin Pressure is typically measured in equivalent altitude): Regulatory Maximum=2400 m (p.sub.atmosphere(2400 m)=0.752 atm) Boeing 767=2100 m (p.sub.atmosphere(2100 m)=0.780 atm) (typical of older airliners) Airbus A380=1868 m (p.sub.atmosphere(1868 m)=0.801 atm) Boeing 747400=1572 m (p.sub.atmosphere(1572 m)=0.830 atm) So flight pressures can range from 0.752 up to 0.830 atm.
Range Values for Exploring Solution Space: i=0 . . . 50 (where i is the ambient pressure index); j=0 . . . 2 (where j is the initial conditions index for solutions of multiple cases simultaneously); p.sub.min==0.75 atm and p.sub.max==1.10 atm
(135)
Lung Parameters:
(136) The lung values used herein are taken from literature. The volumes at 40 cmH.sub.2O and above are extrapolated. The resulting interpolated lung pressure-volume model is large: volume is 4.74 liters at 15 cmH2O. The pressure-volume model was scaled to establish a resting volume of 3.5 L at 15 cmH2O.
(137)
(138) The scaled, max-limited Lung Volume formula is then:
(139)
(where p=internal and P=external pressure, absolute)
(140) A graph of the lung curve can be modeled using the following equation:
Plung.sub.min=min(Lung.sub.p)=20.Math.cmH2O
(141)
(142) A graph of the target volume, pressure and target compliance can be created as follows:
(143)
(144) The curve of an ex-vivo lung model, volume vs. pressure is shown in
(145) Accumulator parameters for the model were varied based on the accumulator used as follows:
(146) 1) No Accumulator:
(147)
(this is set by the recovery team, e.g. system is filled with air until accumulator is at the stipulated volume, which may vary based on ambient pressure at time/place of recovery)
(148)
(Higher numbers here represent a weight-loaded design; lower numbers represent a spring-loaded design) P.sub.acmltr=15.Math.cmH2O (This is the nominal accumulator pressure, at Vacmltr.sub.recovery1, e.g., when the piston is at the target volume for the nominal pressure case. It is set by the weight or spring)
(149)
2) Spring-Based Accumulator:
(150) Parameters are same as for no accumulator above aside from the following:
(151)
3) Weight-Based Accumulator:
(152) Parameters are same as for no accumulator above aside from the following
(153)
Initial Conditions:
(154)
(155) The accumulator's behavior was used to determine p.sub.o and V.sub.o, e.g., the initial internal pressure volume at the above P.sub.o and T.sub.o given all other parameters. The accumulator is filled to the target volume, which sets the internal pressure.
(156)
(157) The lung volume was determined by the initial and external pressures as:
Vlung.sub.initial=V.sub.lung(p.sub.o,P.sub.o)=3.5 L
(158) The Contained Volume V.sub.o is the sum of accumulator and lung volumes. This is the initial volume of air inside the system. This mass of air will remain unchanged, so the ideal gas law governs its subsequent behavior (relationship of pressure to volume). V.sub.o can be defined as follows for the various accumulator types:
(159) No Accumulator:
(160)
Spring-Based Accumulator:
(161)
Weight-Based Accumulator:
(162)
(163) The equation for final volume Ve is based on the ideal gas law for contained volume,
(164)
(165)
(166) The adapted equation was used in the solve function below:
p.sub.guess:=1.2.Math.p.sub.o.sub.
(167)
p.sub.guess>P.sub.travel providing a solution of:
ptravel(po,Vo,To,Tf,Ptravel):=Find.sub.(p.sub.
(168) The inputs to this function are the initial conditions together with travel pressure and temperature. The output of this function is the internal pressure.
(169) The solution for a defined range of conditions can then be found:
p.sub.travel.sub.
Vlung.sub.travel.sub.
V.sub.acmltrtravel.sub.
P.sub.lung.sub.
(170)
(171) Initial Conditions:
(172)
Lung Parameters:
Vlung.sub.max=5 L limiting bag/box volume
Accumulator Design Parameters:
(173)
In-Transit Temperature:
T.sub.f=8 C.
Airplane Cabin Pressures: Reguatory Minimum=0.75 atm Older Airplanes==0.78 atm Newer Aiplanes=0.80-0.83 atm
(174) Given the above values,
(175)
(176) As shown in
(177)
(178) Initial Conditions:
(179)
Lung Parameters:
Vlung.sub.max=5 L limiting bag/box volume
Accumulator Design Parameters:
(180)
In-Transit temperature:
T.sub.f=8 C.
Airplane Cabin Pressures: Regulatory Minimum=0.75 atm Older Airplanes=0.78 atm Newer Airplanes=0.80-283 atm
(181) Given the above values,
(182)
(183)
(184) Initial Conditions:
(185)
Lung Parameters:
Vlung.sub.max=5 L limiting bag/box volume
Accumulator Design Parameters
(186)
In-Transit Temperature:
T.sub.f=8 C.
Airplane Cabin Pressures: Regulatory Minimum=0.75 atm Older Airplanes=0.78 atm Newer Airplanes=0.80-283 atm
(187) Given the above values,
(188)
Example 2Accumulator System Testing
(189) Method
(190) Three shippers were used for this test. Each shipper was modified with the addition of a four-way Stopcock (Qosina P/N 88218) and male and female barb fittings to allow the pressure gauge to be attached to the system.
(191) Preconditioning
(192) The three sets of cooling ribbons and pouches were placed inside the Envirotronics chamber and subjected to a forty-eight-hour soak at 20 C. One CX402-T2M Data Logger s/n: 20593104 was placed inside the chamber to record chamber temperatures.
(193) At the same time the cooling ribbons and pouches were placed in the chamber, the three sets of porcine lungs were placed in the CSZ chamber for a forty-eight-hour soak at 6 C. Prior to placement in the chamber, each set of lungs was packaged to simulate use of the device. An Endotracheal Tube (ET tube, Medsource P/N MS-23265) was placed in the trachea and the cuff of the ET tube was inflated and secured with umbilical tape (DeRoyal P/N 30-410). The proximal end of the ET tube was attached to the standard 15 mm connector on the Filtration Assembly per typical device use. As even minor damage to a lung during retrieval can cause leakage of the organ itself, the porcine lungs were only relied upon for mass, form factor, representative handling, and forces within the system during testing. To negate the possibility of study interference from a leaky lung at this juncture, the leak-free volume expected of pristine lungs was represented by a balloon. This was accomplished by making an incision in the trachea closer to the bronchus after insertion of the initial ET tube per typical operation and installing a second ET tube oriented in opposition to the first, again inflating the cuff with water and securing with umbilical tape. This provides a continuous, leak-proof path from the accumulator to the 15 mm connector on the second ET tube, to which a balloon was affixed and then secured with umbilical tape.
(194) Each set of lungs was submerged in water prior to packaging and attached to the accumulator via the quick connect integral to the shipper to check for leaks. The hand bulb was used to fill the accumulators and provide air to the lung setup and balloon. All lung setups were able to be submerged without the detection of bubbles so packaging of the lungs continued. Each lung was then placed in a 3M Steri-Drape Bag (Ref 1003) with 2 L of Phosphate Buffered Saline (PBS). This bag was tied, using the drawstrings integral to the bag, against the first ring on the Filtration Assembly. The bag containing the lung was placed in a second 3M Steri-Drape bag and filled with an additional 2 L of PBS. This bag was tied, using the drawstrings integral to the second bag, against the second ring on the Filtration Assembly. A third 3M Steri-Drape bag was added outside of the second bag and tied to the third ring on the Filtration Assembly via the drawstrings integral to the third bag. Each packaged lung was then placed in the 6 C. chamber. The average mass of the lungs was 1178 g measured with balance 090814.
(195) The purpose of preconditioning during this study was to ensure the payload had the relevant material properties and would behave as would be experienced during operation.
(196) Temperature was recorded per normal operational procedure and for information only.
(197) Altitude and Vibration Test Setup After preconditioning, the packaged porcine lung was placed on the rack within the Shipper. The quick connect on the Filtration Assembly was attached to the corresponding quick connect fitting integral to the Shipper. Each clamp on the Filtration Assembly was ensured to be opened. Each cooling tray was installed in the shipper and the Filtration Assembly was secured to it using umbilical tape. Three cooling ribbons and one pouch (.sup.2500 g) of cooling material was placed on the tray. The Shipper lid was then placed on the Shipper and secured with the integrated latches. The onboard datalogger was started.
(198) Success of this study will be demonstrated by the ability to maintain pressure within the range of 10 to 15 cmH2O (3.7 to 5.9 in H2O) during altitude and vibration testing per ASTM 4169.
(199) Additionally, this study checked the functionality of using the hand bulb to recharge the system.
(200) ASTM 4169 Altitude Test
(201) Each shipper was placed in the altitude chamber and the accumulator was filled to approximately 60% of the accumulator capacity using the hand bulb. The volume in the accumulator was chosen to accommodate air expansion within the system and balloon at altitude. A pressure gauge was connected to the four-way stopcock and was placed such that it could be read during the test. After use of the hand bulb, the clamp integral to the tubing between the hand bulb and pressure gauge was clamped.
(202) Each shipper was subjected to one hour of altitude at 14,000 ft. A pressure measurement was taken prior to test initiation, every fifteen minutes at altitude, and after the conclusion of the test when the shipper was at ambient pressure.
(203) ASTM 4169 Truck and Air Vibration Test
(204) The hand bulb was used to refill the accumulator between altitude and vibration tests to demonstrate accumulator can be recharged during nominal operating conditions through this mechanism. After use of the hand bulb, the clamp integral to the tubing between the hand bulb and pressure gauge was clamped.
(205) The pressure gauge was removed from stopcock and stopcock was switched to an off position to prevent damage to the pressure gauge during vibration testing. The three shippers were placed flat on the vibration table and subjected to thirty minutes of ASTM 4169 Truck Vibration and thirty minutes of ASTM 4169 Air Vibration.
(206) Note: ASTM 4169-09 was appropriate for this testing as 4169-16 requires packaging to be tested in multiple orientations. As this test is meant to evaluate use of the shippers and during a use scenario the shippers will always be accompanied by a doctor, only a single orientation was necessary.
(207) Results
(208) Preconditioning
(209) No visual deformities were found to the samples during Preconditioning testing.
(210) Altitude
(211) No visual deformities or operational problems were found to the shippers before or after Altitude testing.
(212) TABLE-US-00001 Lung #1 Lung #2 Lung #3 Test Time (in H2O) (in H2O) (in H2O) Before test started 5.2 4.5 4.3 15 minutes 5.4 5.8 4.2 30 minutes 4.4 5.0 5.0 45 minutes 4.5 5.0 5.0 1 hour 4.2 4.8 4.2 Ambient after test 4.1 4.4 4.2
Vibration
(213) No visual deformities or operational problems were found to the SherpaPak ALPS shippers before or after both Truck and Air Vibration testing.
(214) TABLE-US-00002 Lung #1 Lung #2 Lung #3 Test Time (in H2O) (in H2O) (in H2O) Before test started 5.2 5.0 5.4 After 30 minutes of Truck 5.2 5.0 5.2 After 30 minutes of Air 5.1 5.2 4.9 Note: After Air Vibration testing only, Lung #2 was not recording a pressure value until the Accumulator was lifted, possibly caused by a pinched tube.
(215) All shipper systems remained within the desired pressure range for both Altitude and Vibration testing per ASTM 4169. Additionally, the hand bulb was able to refill the accumulator between Altitude and Vibration tests to demonstrate that the accumulator can be recharged during nominal operating conditions through this mechanism.
Example 3Accumulator System Benchtop Testing
(216) Setup and Methods
(217) Three sets of shippers were presented for test. To test each Accumulator, the quick connect integral to the Shipper was connected to the corresponding quick connect on the Filtration Assembly. The Filtration Assembly was then connected to an Endotracheal Tube (ET tube, Medsource P/N MS-23265). A balloon was placed around the cuff of the ET tube, the cuff was inflated with water, and the balloon was secured with umbilical tape (DeRoyal P/N 30-410). This setup mimics how the shipper would be set up during normal use with the balloon acting as the lung for this study. Porcine lungs were not used as it was expected that damage during retrieval would cause leaks that would make it difficult to assess performance of the accumulator. Each shipper was modified with the addition of a 4-way Stopcock (Qosina P/N 88218) and male and female barb fittings to allow the pressure gauge to be attached to the system.
(218) To check for air leaks in the test system, the balloon and ET tube were submerged in water and each of the three Accumulators was filled to approximately 75% full volume using the Accumulator Hand Bulb. Each system was able to be submerged without detection of bubbles so set-up continued.
(219) After the accumulator was filled and passed the leak check, each shipper was placed on a flat surface, the tubing between the Accumulator and the hand bulb was clamped, and the test was initiated. The pressure in each accumulator was monitored using a pressure gauge.
(220) Pressure measurements of each accumulator were taken every hour during normal working hours over a twenty-four-hour period. Success criteria for this test is defined as maintenance of pressure between 10 to 15 cmH.sub.2O (3.7 to 5.9 inH.sub.2O) during the full test duration for each of the three systems.
(221) As stated in the Method Section, a pressure range of 10 to 15 cmH.sub.2O (3.7 to 5.9 inH.sub.2O) was acceptable. All three samples remained within the desired pressure range for the full twenty-four-hour bench test.
INCORPORATION BY REFERENCE
(222) References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.
EQUIVALENTS
(223) Various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including references to the scientific and patent literature cited herein. The subject matter herein contains important information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and equivalents thereof.