Gas separation: processes – Degasification of liquid – Plural successive degassing treatments
Reexamination Certificate
2001-03-14
2002-12-31
Smith, Duane S. (Department: 1724)
Gas separation: processes
Degasification of liquid
Plural successive degassing treatments
C095S248000, C095S250000, C095S266000, C141S018000, C141S069000, C206S528000, C210S188000, C222S190000, C604S068000, C604S187000
Reexamination Certificate
active
06500239
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system and multiple methods for removing gas from an aqueous solution, and in particular, embodiments for avoiding subdermal hematomas from the use of a needle-less injector when the system and methods are employed in conjunction with the loading of a needle-less injector ampoule.
BACKGROUND OF THE INVENTION
In an application in which a liquid must be filled into a sealed container, it may be preferable that substantially all gas be removed from the liquid either prior to filling or soon after the container is filled. For example, in filling ampoules with liquid medications for use in a needle-less injector, it may be desirable to de-gas the medication prior to filling the ampoule or, alternatively, for the medication to be de-gassed once the ampoule is filled.
Typically, needle-less medication injections are performed with “permanent gun” instruments, generally referred to as “jet injectors.” These devices use either a compression spring or a compressed inert gas to propel the fluid medication (via a push rod plunger) through a small orifice (an injector nozzle) which rests perpendicular to and against the injection site. The fluid medication is generally accelerated at a high rate to a speed of between about 800 feet per second (fps) and 1,200 fps (approximately 244 and 366 meters per second, respectively). This causes the fluid to pierce through the skin surface without the use of a needle, resulting in the medication being deposited in a flower pattern under the skin surface. This method of medication delivery is referred to as a subcutaneous injection.
Medication delivery via needle-less injector periodically results in the formation of subdermal hematomas, and efforts have been made to reduce the likelihood and severity thereof. In U.S. Pat. No. 6,156,008 issued Dec. 5, 2000, we described an injection site detecting device for avoiding subdermal hematomas from an injection, wherein the detecting device is employed prior to injection to locate a site of low blood flow, relative to the surrounding area. Since it is believed that administering a needle-less injection in a region of lower blood flow corresponds to lower bruising potential, utilization of this device reduces the likelihood of causing a subdermal hematoma from administration of an injection with a needle-less injector.
Subdermal hematomas, tissue damage, and scarring from mechanical force injury may also result from the use of needle-less injectors when pockets of gas are present in the injector ampoule prior to dispensing the medication contained therein. Within the 800 to 1200 fps range, optimal for acceleration of liquid medication through the skin via a needle-less injector, liquid readily penetrates the skin while air does not. Thus, gas pockets accelerated against the skin lead to the formation of a bruise and can be quite painful for the recipient, whereas liquid medication passes into and/or through the skin without discomfort.
In general, the gas pocket is found at the dispensing terminus of the ampoule, which is proximate to the skin, though this can change depending on the orientation of the ampoule during storage. Further, when the cap is removed from the end of a needle-less injector, exposing the dispensing area for application to the skin surface, any gas pocket not already situated at the dispensing end may tend to migrate toward that end, due to the pressure change caused by cap removal. This motion of the gas pocket often forces some liquid from the ampoule, thereby diminishing the volume of liquid that will be injected into the recipient. This renders the dosage level inaccurate, as a nontrivial volume of medication is lost from the injector prior to use.
Gas pockets may be present from the outset, resulting from the improper loading of an ampoule. Filling the ampoule with an insufficient amount of liquid clearly leaves such a pocket. However, overfilling the ampoule and removing any excess to arrive at the desired volume is generally not a practical alternative, either, since it is likely that a small amount of liquid will remain on the outer surface of the ampoule. In the medical context, any such liquid is likely to foster the growth of bacteria, which is unacceptable in a scenario where sterile conditions are imperative. Any ampoule with such bacterial growth must be disposed of, and is therefore wasteful.
Even in a perfectly filled ampoule, where no cognizable gas pockets are present immediately following loading, pockets may still develop over time as the dissolved gases present in the liquid separate out from solution. Dissolved gases are naturally present in liquids as a function of the gases' partial pressures in the local atmosphere. Known to those skilled in the art as Henry's Law, the concentration of a particular gas in solution is proportional to the pressure of that same gas in the air abutting the solution. Thus, dissolved gases are present in the liquids filled into ampoules under normal conditions (i.e., wherein filling is not performed in a vacuum, or the like) in concentrations proportional to their partial pressure in air. These dissolved gases consist mostly of nitrogen and oxygen, along with several trace gases, and are found latent in the solution in amounts related to their partial pressures in the local atmosphere.
The size of gas pockets varies according to the pharmaceutical active in solution, as some actives allow liquid to retain greater amounts of gas than others, but in some instances a pocket may be as large as 20% of the total ampoule volume. This naturally occurring formation of gas pockets is exacerbated when pre-filled ampoules remain unused for substantial periods of time. Again, varying with the type of active in solution, some actives will form substantial gas pockets after only a few days, while others may not form a pocket for a year or more. For certain medicaments, an ampoule may be stored as long as three to five years, and nearly every active will generate a gas pocket in that amount of time.
Increased temperature also affects the separation of gas from solution, prompting gas pockets to form faster and larger. Pharmaceutical actives generally require storage within a certain optimal temperature range in order to prevent the active from breaking down and thus losing efficacy. For example, many proteins suitable for injection will denature at high temperatures. However, optimal temperature ranges for efficacy may not have any correlation with temperature that would avoid a gas pocket from forming in storage. Thus, one may be forced to choose between either preserving drug efficacy or minimizing gas pocket formation.
In the context of injection by more traditional means such as with a preloaded syringe, it is well established that any significant amount of air in such a device will cause pain for the recipient and potentially far more dire consequences if the amount of air is substantial. Gas pockets may develop in these syringes much in the way described above with regard to ampoules of needle-less injectors, as these devices are frequently subject to similar storage conditions and requirements. Those administering such injections can more readily obviate these limitations, however, as air may be evacuated from the liquid-containing chamber of a syringe by partially depressing the plunger while the syringe is inverted immediately prior to administration of an injection. This is generally not possible with a needle-less injector, as the entire volume of a needle-less injector ampoule is evacuated in one step during normal operation. Moreover, liquid that is inadvertently evacuated from the chamber of a syringe along with the undesirable air does not present a sterility concern, since bacteria will not grow in a pharmacologically hazardous amount in the few moments between evacuating such air and administering an injection. Oftentimes some small quantity of air will remain in the syringe chamber, however, resulting in an injection more painful than would have been had the air been remove
Castellano Thomas P.
Ituarte Eloy A.
Penjet Corporation
Smith Duane S.
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