STERILIZATION METHOD AND APPARATUS

• US 20110076192A1
• Filed: 09/29/2010
• Published: 03/31/2011
• Est. Priority Date: 09/30/2009
• Status: Active Grant

• Current Assignee: Stryker Corporation
• Original Assignee: TSO3 Inc (Stryker Corporation)
• Inventors: DASSIE, Nancy, GAGNE, Marie-Christine, BEDARD, Claudia, VALLIERES, Jean-Martin, DUFRESNE, Sylvie, MARTEL, Cynthia, LEBLOND, Helene, MARTEL, Karine, TREMBLAY, Bruno, ROBITAILLE, Simon
• Granted Patent: US 9,101,679 B2
• Time in Patent Office: Days
• US Class Current: 422/29
• CPC Class Codes: A61L 2/20 Gaseous substances, e.g. vapours
• CPC Class Codes: A61L 2/202 Ozone
• CPC Class Codes: A61L 2/208 Hydrogen peroxide
• CPC Class Codes: A61L 2202/122 Chambers for sterilisation
• CPC Class Codes: A61L 2202/13 Biocide decomposition means, e.g. catalysts, sorbents
• CPC Class Codes: A61L 2202/14 Means for controlling sterilisation processes, data processing, presentation and storage means, e.g. sensors, controllers, programs
• CPC Class Codes: A61L 2202/24 Medical instruments, e.g. endoscopes, catheters, sharps
• CPC Class Codes: B65D 23/001 Supporting means fixed to the container

Abstract

A method of sterilizing an article by sequentially exposing the article to hydrogen peroxide and ozone is disclosed. The article is exposed under vacuum first to an evaporated aqueous solution of hydrogen peroxide and subsequently to an ozone containing gas. The exposure is carried out without reducing the water vapor content of the sterilization atmosphere, the water vapor content being derived from the aqueous solvent of the hydrogen peroxide solution and from the decomposition of the hydrogen peroxide into water and oxygen. The complete sterilization process is carried out while the chamber remains sealed and without removal of any component of the sterilization atmosphere. For this purpose, the chamber is initially evacuated to a first vacuum pressure sufficient to cause evaporation of the aqueous hydrogen peroxide at the temperature of the chamber atmosphere. The chamber is then sealed for the remainder of the sterilization process and during all sterilant injection cycles. Keeping the chamber sealed and maintaining the hydrogen peroxide and its decomposition products in the chamber for the subsequent ozone sterilization step results in a synergistic increase in the sterilization efficiency and allows for the use of much lower sterilant amounts and sterilization cycle times than would be expected from using hydrogen peroxide and ozone in combination.

Claims

1. A method for sterilizing an article in a sealable sterilization chamber, comprising the steps of

a. placing the article into the sterilization chamber,

b. sealing the chamber,

c. applying to the chamber a vacuum of a first pressure,

d. injecting into the sealed chamber a gaseous conditioning agent for forming free radicals,

e. maintaining the chamber sealed for a first exposure period,

f. injecting, after the first exposure period, a sterilant gas for creating or regenerating the free radicals into the sealed chamber,

g. maintaining the chamber sealed for a second exposure period,

h. removing residual sterilant from the chamber at the end of the second exposure period, and

i. removing the sterilized article from the chamber.

2. The method of claim 1, wherein the conditioning agent is hydrogen peroxide, acidic water, carbonated water, peracetic acid, acetic acid, alcohol, ethanol or methanol.

3. The method of claim 2, wherein the sterilant gas is ozone, nitrogen oxide or chlorine dioxide.

4. The method of claim 4, wherein the conditioning agent is hydrogen peroxide and the sterilant gas is ozone.

5. A method for sterilizing an article in a sealable sterilization chamber, comprising the steps of

a. placing the article into the sterilization chamber,

b. sealing the chamber,

c. applying to the chamber a vacuum of a first pressure sufficient to evaporate an aqueous solution of hydrogen peroxide at the temperature of an atmosphere in the chamber,

d. evaporating an aqueous hydrogen peroxide solution into the sealed chamber,

e. terminating the evaporating once a preselected second pressure, higher than the first pressure, is reached in the sealed sterilization chamber,

f. injecting a dry ozone or nitric oxide containing gas into the chamber,

g. maintaining the chamber sealed for a second exposure period,

h. interrupting all removal of any component of the sterilization atmosphere after applying the vacuum and prior to the evaporating step, until an end of the second exposure period;

i. removing residual sterilant from the chamber at the end of the second exposure period, and

j. removing the sterilized article from the chamber.

6. The method of claim 5 including the further step f) of maintaining the chamber sealed for a first exposure period during which hydrogen peroxide gas in the chamber decomposes into free radicals, wherein the dry ozone or nitric oxide containing gas is injected after the first exposure period.

7. The method of claim 5, wherein the gas injected in step g) is ozone.

8. The method of claim 5, wherein the gas injected in step g) is NO.

9. The method of claim 5, wherein the step d) of evaporating the hydrogen peroxide solution includes injecting repeated pulses of hydrogen peroxide solution at a pulse volume of less than 75 μ

L.

10. The method of claim 9, wherein the pulse volume is less than 35 μ

L.

11. The method of claim 10, wherein the pulse volume is about 20 μ

L.

12. The method of claim 7, wherein steps c) to j) are repeated at least once.

13. The method of claim 5, wherein the solution is a 50% hydrogen peroxide solution.

14. The method of claim 8, wherein the first pressure is 1 Torr (1.33 mbar).

15. The method of claim 8, wherein the second pressure is 17-54 Torr.

16. The method of claim 15, wherein the second pressure is 20 Torr.

17. The method of claim 5, wherein an amount ozone in the range of 1-10 mg per liter of sterilization atmosphere is injected in the injecting step.

18. A hydrogen peroxide delivery system for a sterilizer having a hydrogen peroxide injection unit and a housing, comprising

a. a cradle for supporting a hydrogen peroxide solution container in an upright position within the housing,

b. a drainage arrangement connected with the cradle for aspirating the hydrogen peroxide solution from the container, and

c. a delivery arrangement connected with the drainage arrangement for supplying the aspirated hydrogen peroxide solution to the hydrogen peroxide injection unit, the drainage arrangement including a drainage needle connected with the delivery arrangement for penetrating a seal on the container and extending into the hydrogen peroxide solution in the container, and a reciprocatable needle drive for moving the needle from an at rest position, wherein the needle is retracted to allow insertion of a new hydrogen peroxide container into the cradle, to a penetrating position wherein the needle penetrates the seal of the container and extends into the hydrogen peroxide solution in the container, the needle extending all the way to a bottom of the container in the penetrating position.

19. The delivery system of claim 18, wherein the drainage arrangement includes a force sensor for detecting engagement of the needle with the container bottom and terminating needle advance to avoid penetration of the container bottom by the needle.

20. The delivery system of claim 19, wherein the force sensor is incorporated in the needle drive.

21. The delivery system of claim 20, further comprising an ultrasonic sensor for detecting when the hydrogen peroxide liquid in the container drops below a predetermined level.

22. The delivery system of claim 21, wherein the sensor is spring biased against the container, when the container is supported on the stand.

23. A hydrogen peroxide solution container, comprising a hollow body with a top end including a fill and drainage opening, a side wall and a conical bottom, a stand for maintaining the container in an upright position on a flat horizontal surface and a connecting arrangement for connecting the stand to the body, the arrangement including an external recess in the side wall of the body and the stand being cup-shaped and having a radially inwardly extending tab for engagement with the recess to provide a snap fit connection of the stand to the body.

24. The container of claim 23, wherein the recess is a circumferentially extending, continuous groove and the stand includes at least two tabs for engagement of the groove.

25. The container of claim 23, wherein the recess is a circumferentially extending, continuous groove and the tab is a circumferentially extending flange at a top end of the stand for snap fit engagement with the recess.