Measuring and testing – Instrument proving or calibrating – Gas or liquid analyzer
Reexamination Certificate
2002-06-03
2004-02-03
Williams, Hezron (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Gas or liquid analyzer
Reexamination Certificate
active
06684680
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the packaging of a probe in a fluid calibrant. More particularly, the invention relates to a cartridge that contains a sensor, a probe and an analyte-containing fluid calibrant, wherein the sensor is responsive to the analyte.
BACKGROUND
Sensors and other devices associated with analyte detection often require calibration in order to ensure their accuracy in quantitating the concentration of analyte. In some instances, one or more calibrants that contain a known amount of analyte are employed, and the devices are calibrated by exposing the device to the one or more calibrants. To ensure that the calibrant conforms to an established standard, the calibrant is generally prepared under strict controls. Strict controls are particularly needed for liquid calibrants containing a solvated gaseous analyte because such calibrants are difficult to prepare. In addition, such calibrants have a relatively short shelf life under ordinary conditions. Accordingly, there is a need for readily made packages of calibrants with a long shelf life, i.e., that are chemically and physically stable over extended time periods.
Typically, liquid calibrants containing solvated gaseous analytes must be prepared under a controlled atmosphere to prevent the analyte concentration from deviating from a standard during preparation. This requires expert labor and expensive extra equipment, and results in uncertainty, as the preparation process may be technically complicated. For example, devices for blood gas analysis or other medical equipment often require a calibrant having a specific hydrogen ion concentration (pH), dissolved oxygen partial pressure (pO
2
) and carbon dioxide partial pressure (pCO
2
). Thus, the calibrant must be prepared or packaged under an atmosphere containing the appropriate analyte gas at a desired partial pressure. In addition, in order to obtain reliable data from the equipment, it is important that the pH, pO
2
, and pCO
2
values of the calibrant be maintained within a specific and very narrow range after packaging and during shipping and storage. Moreover, since many calibrants are used for in vivo or in situ applications, such as with an indwelling arterial catheter as described in U.S. Pat. No. 4,830,013 to Maxwell, or with a paracorporeal system for bedside blood chemistry analysis as described in U.S. Pat. No. 5,976,085 to Kimball et al., they must be biocompatible and prepared under sterile conditions, and the sterility of the fluids must be maintained during shipping and storage.
Glass ampules and other rigid vessels have been employed to contain calibrants, as they typically exhibit sufficient robustness to maintain sterility and avoid degradation of the calibrants packaged therein. However, the use of glass ampules is accompanied by a number of disadvantages. As high temperatures are involved in sealing such ampules, specialized glassmaking equipment is typically required in their manufacture. In use, the calibrant contained in the ampules is accessed by breakage of the ampules. As is the case whenever glass is broken, glass fragments represent a safety concern, and technicians must be properly trained to break the ampules in a controlled manner. Another drawback is that used ampules constitute hazardous waste that requires special disposal procedures.
A number of patents describe the packaging of calibrants in a flexible container. For example, U.S. Pat. No. 3,892,058 to Komatsu et al. describes a process for preparing a flexible sealed package composed of a laminate of flexible sheet materials. The inner layer is composed of a heat-sealable resin, such as a polyamide. The outer layer is composed of a heat-resistant resin, such as a polyester film. Sandwiched between the inner and outer layers is a metal foil. In addition, U.S. Pat. No. 4,116,336 to Sorensen et al. describes the use of a flexible, gastight package to contain a fluid with dissolved O
2
and/or CO
2
. The fluid may be used for calibrating or quality control monitoring of blood gas measuring equipment. The flexible container is a plastic-laminated metal foil, e.g., aluminum. The exterior surface of the metal foil is laminated with a plastic foil, such as a polyester film, to prevent scratching or the like. The inner surface of the metal foil is laminated with a plastic having low gas permeability and good weldability, such as polyvinylidene chloride or polyethylene terephthalate. The inner package is then sealed in an outer pouch that serves as a sterility barrier. The outer pouch may be, for example, a Tyvek®-backed polymeric material that is used as a storage medium for shipping the reference fluid. However, this type of flexible package suffers from a number of deficiencies. When fluids having gases dissolved therein are contained in so-called “gastight” flexible packages, they have a tendency to lose the dissolved gas by slow diffusion through the package, and therefore, have a limited shelf life.
To overcome the aforementioned problem, U.S. Pat. No. 5,690,215 to Kimball et al. describes a device for maintaining the partial pressure of an analyte, i.e., a dissolved gas in a fluid and related methods of use wherein the device comprises a first sealed, gas impermeable pouch containing a calibrant within a second sealed, gas impermeable pouch. A space between the pouches is charged with an atmosphere containing a gas at the same partial pressure as that of the analyte contained in the calibrant. This charged atmosphere prolongs the shelf life of the fluid to a greater degree than would be expected from merely encasing a first pouch within a second pouch.
However, it has been found that flexible pouches suffer from an inherent limitation, i.e., changing the overall shape of the package can alter the volume within the package. As a result, if any undissolved gas is present in such flexible pouches, the gas pressure therein may easily be change depending on external air pressure or by pouch deformation due to ordinary handling. Such pressure changes may result in error-prone calibration procedures. Thus, there is a need for packaged calibrant containing a gaseous analyte that does not suffer from this drawback.
Another problem associated with analyte detection involves probe or sensor contamination. Contamination is particularly problematic when in vivo analyte detection is desired. Even if prepackaged calibrants are sterile, a multiple-use probe or sensor of an analyte detection device adapted for in vivo detection must be sterilized before each use. Unlike laboratory personnel, hospital personnel are typically not trained to perform sterilization procedures. In addition, sterilization is time consuming and requires that the probes be constructed such that they can withstand sterilization conditions. In turn, these limitations increase the cost and lessen the desirability of in vivo analyte detection using multiple-use probes and sensors.
The contamination problem can be solved either by using a sterile disposable probe or a sterile disposable sheath to cover a multiple-use probe with a sterile calibrant. However, when the calibrant is packaged separately from such a disposable sheath or probe, a potential source of calibration error is introduced. Additional precautionary handling measures, for example, must be taken to avoid contaminating the disposable item before use in analyte detection. One such measure includes avoiding exposure of the disposable item to open atmosphere for an extended time period to decrease the possibility of contaminating the disposable item prior to calibration with the calibrant. In addition, separate packaging of the calibrant and the disposable probe or sheath tends to complicate inventory matters, requiring more storage space and an accurate count to ensure that there is no excess of either the calibrant or the sheath or probe.
Cartridges are known in the art that package sensors and calibrants together in a single unit. Typically, such cartridges are typically employed to overcome potential contamination problems. Th
Kimball Victor E.
Pierskalla Irvin T.
Reynolds Brandon W.
Winger Kent R.
Garber Charles D
Oppenheimer Wolff & Donnelly
Optical Sensors, Inc.
Williams Hezron
Wrigley Barbara A.
LandOfFree
Cartridge for packaging a sensor in a fluid calibrant does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cartridge for packaging a sensor in a fluid calibrant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cartridge for packaging a sensor in a fluid calibrant will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3281374