Disposable pouches, including self-sealing pouches, are well known. Also known are sterilizable pouches which are permeable to the sterilizing medium such as steam or ethylene oxide. Usually, the pouch has two webs, one of which may be a transparent thermoplastic material to provide observation of the contents of the pouch and the other of which may be a paper or fiber material having a permeability suitable for use with the particular sterilizing medium employed.
In addition it is known in the medical field to provide pouches having an integrally formed indicator means, usually an impregnated chemical substance on the exterior surface of the pouch. The impregnated substance typically changes color after the pouch has been sterilized.
Indicating inks, such as chemically reactive inks, are also available for use as sterilization indicators. Such ink is available for use with ethylene oxide sterilization and the ink changes color on exposure to sterilization conditions. Typically, the exterior surface of some prior art pouches may be impregnated with such ink to form a sterilization indicator integral with the wall of the pouch.
Although the pouches that have an exterior surface sterilization indicator are available, many medical institutions choose not to rely on the exterior surface sterilization indicator as sole evidence that the inside of the pouch, and the article contained therein, has been properly sterilized. As a result, many medical institutions use one of a number of commercially available separate indicator devices, usually in the form of small strips of material, which can be inserted within the sterilizable pouch next to the article contained therein and which change appearance or color upon sterilization. This provides direct evidence that the interior of the pouch, and hence the article therein, has been properly sterilized.
Such commercially available indicator strips are typically impregnated with a material which is sensitive to, and usually chemically reacts with, the sterilizing medium, in such a manner so as to change appearance (e.g., color) when sufficient sterilization conditions have been achieved. For example, one such strip can be used with steam sterilization in autoclave units and includes a chemical-impregnated structure which turns to a different color when the minimum sterilization conditions of moisture, temperature and time have been achieved.
Though the separate indicator strips can provide adequate indication of the achievement of proper sterilization within the pouches, use of such strips has certain disadvantages. First, individual strips must be separately purchased. Second, adequate supplies of the strips must be maintained. Third, even if an adequate supply of indicator strips is available, the supply of strips must be provided at the location where the sterilizable pouches are used.
It would be desirable to provide a pouch having an indicator for signaling the achievement of sterilization conditions within the pouch and which avoids the shortcomings discussed above. Further, it would be desirable to provide a sterilizable pouch incorporating such an indicating strip in a structure which would be self-sealing to form a contaminant-proof seal.