Remote sterilization monitor

• US 5,745,039 A
• Filed: 02/21/1997
• Issued: 04/28/1998
• Est. Priority Date: 02/21/1997
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Lannigan, Samuel David, Hof, Raymond A., Hof, Craig R., Focarino, Gary
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Lee, Benjamin C.
• Application Number:
  US08/803,740
• Time in Patent Office: 431 Days
• Field of Search: 340/590, 340/572, 340/540, 340/584, 340/825.54, 340/551, 374/160, 116/204, 116/217, 310/313 R, 335/215
• US Class Current: 340/590
• CPC Class Codes: A61L 2/28 Devices for testing the effectiveness or completeness of sterilisation, e.g. indicators which change colour apparatus involving enzymes or microorganisms C12M1/34; methods involving enzymes or microorganisms C12Q1/00
• CPC Class Codes: G01K 3/04 in respect of time

Abstract

A remote sterilization indicator is described. The indicator allows a sterilization cycle to be monitored without the need to visually inspect the indicator.

Claims

1. A remotely detectable steam sterilization process monitor for use with an interrogation mechanism capable of interrogating the monitor by providing a pulsed, excitation magnetic field in an interrogation zone, and capable of detecting an identity signal provided by the monitor;

the monitor comprising;

a strip of magnetostrictive ferromagnetic material adapted to mechanically resonate when interrogated by the interrogation mechanism,

a magnetic material capable of magnetically biasing the strip of magnetostrictive ferromagnetic material to arm the magnetostrictive ferromagnetic material to provide an identity signal such that, after the pulse of the excitation magnetic field of the interrogation mechanism ends, the magnetostrictive material resonates within the magnetic bias provided by the magnetic material in a decaying fashion to thereby provide the identity signal to the interrogation mechanism; and

clamping means for physically holding the magnetostrictive ferromagnetic material such that the magnetostrictive ferromagnetic material is not allowed to resonate when interrogated by the interrogation mechanism;

the clamping means comprising a meltable compound such that, upon exposure of the monitor to predetermined conditions, the meltable compound melts sufficiently to allow the magnetostrictive ferromagnetic material to resonate when interrogated by the interrogation mechanism.

2. A remotely detectable steam sterilization process monitor according to claim 1 including a wicking means for receiving the compound as it melts.

3. A remotely detectable steam sterilization process monitor according to claim 1 including a rate controlling film.

4. A remotely detectable steam sterilization process monitor according to claim 1 including a container constructed from a material suitable for withstanding a sterilization cycle.

5. A remotely detectable steam sterilization process monitor according to claim 1 wherein the clamping means comprises a spring movable between a first position and second position that is spaced from the first position, wherein, in the first position, the spring provides a bias through the meltable compound which physically holds the magnetostrictive ferromagnetic material such that the magnetostrictive ferromagnetic material is not allowed to resonate when interrogated by the interrogation mechanism, and in the second position, the bias of the spring is released sufficiently to allow the magnetostrictive ferromagnetic material to resonate when interrogated by the interrogation mechanism.

6. A remotely detectable steam sterilization process monitor according to claim 1 wherein the clamping means comprises an interference member placing the meltable compound in an interference fit sufficient to physically hold the magnetostrictive ferromagnetic material such that the magnetostrictive ferromagnetic material is not allowed to resonate when interrogated by the interrogation mechanism.

7. A remotely detectable steam sterilization process monitor according to claim 1 including an assembly which includes an organic compound, a wicking means for receiving the organic compound as it melts, and a rate controlling film.

8. A remotely detectable steam sterilization process monitor according to claim 7 wherein the assembly includes indicia.

9. A remotely detectable steam sterilization process monitor according to claim 7 wherein the assembly includes an aluminum backing and the organic compound is situated between the wicking means and the aluminum.

10. A remotely detectable steam sterilization process monitor according to claim 7 wherein the assembly includes an aluminum backing and the wicking means is situated between the compound and the aluminum.

11. A remotely detectable steam sterilization process monitor according to claim 1 including a water absorbing material situated between the strip of magnetostrictive ferromagnetic material and the magnetic material.

12. A remotely detectable steam sterilization process monitor according to claim 11 wherein the water absorbing material comprises paper.

13. A remotely detectable sterilization monitor for use with an interrogation mechanism, the monitor comprising:

creating means for creating a remotely detectable magnetic response, the creating means comprising a magnetic material of high permeability and low coercivity, said creating means having at least two distinct magnetic states, a first state in which a first remotely detectable magnetic response is created upon a first interrogation, and a second state in which a second remotely detectable magnetic response which is different from the first state is created upon a second interrogation, and

clamping and release means for holding the creating means in said first state, said clamping and release means including a spring clamp for holding the creating means in said first state to restrict the creating means from entering the second state, and an organic material which melts upon being heated to a predetermined temperature for changing said creating means from said first to said second state upon melting, wherein the spring clamp is separate and distinct from the magnetic material of high permeability and low coercivity.

14. A remotely detectable sterilization monitor according to claim 13, wherein said creating means comprises a magnetostrictive ferromagnetic material and a magnetizeable material.

15. A remotely detectable sterilization monitor according to claim 13, wherein the organic material comprises a compound selected from the group consisting of 2-chloroacetamide, 2-ethoxybenzamide, benzoic acid, diphenyl succinate, dichlorophenol, dimethyl phenol, benzamide, urea, 1,4 dihydroxybenzophenone, hydroquinone, dioxime, ethylene ester of tuluene sulfonic acid, salicylamide, salicylic acid, and 1,8-octane dicarboxylic acid.

16. A remotely detectable sterilization monitor according to claim 13, wherein said creating means comprises means for changing said first state to said second state upon exposure to a predetermined amount of steam.

17. A remotely detectable sterilization monitor according to claim 13, wherein said creating means includes means for altering pressure from the spring clamp such that the creating means is changed to the second state.

18. A method of monitoring a steam sterilization process using a monitor comprising the steps of:

providing an interrogation mechanism capable of interrogating the monitor and capable of detecting an identity signal provided by the monitor;

providing an interrogation zone;

providing a monitor comprising a strip of magnetostrictive ferromagnetic material adapted to mechanically resonate when interrogated by the interrogation mechanism, a magnetic material capable of magnetically biasing the strip of magnetostrictive ferromagnetic material to arm the magnetostrictive ferromagnetic material to provide the identity signal, and clamping means for physically holding the magnetostrictive ferromagnetic material such that the magnetostrictive ferromagnetic material is not allowed to resonate when interrogated by the interrogation mechanism;

the clamping means comprising a meltable organic compound;

exposing the sterilization monitor to at least a portion of the steam sterilization process to be monitored, such that, after a predetermined exposure to the steam sterilization process to be monitored, the organic compound melts sufficiently to release the clamping means to thereby allow the magnetostrictive ferromagnetic material to resonate when interrogated by the interrogation mechanism;

then interrogating the monitor in the interrogation zone by providing a pulsed, excitation magnetic field at a frequency in the interrogation zone, such that, if the clamping means is released, after the pulse of the excitation magnetic field of the interrogation mechanism ends, the magnetostrictive material resonates within the magnetic bias provided by the magnetic material in a decaying fashion to provide the identity signal to the interrogation mechanism;

detecting the identity signal with the interrogation mechanism; and

indicating to a user whether the identity signal was detected by the interrogation mechanism.

19. A method of monitoring a sterilization process using a remotely detectable sterilization monitor without the need to visually inspect the sterilization monitor, the method comprising the steps of:

providing an interrogation mechanism for interrogating the monitor, the interrogation mechanism including an interrogation zone;

providing a sterilization monitor comprising creating means for creating a remotely detectable magnetic response, the creating means comprising a magnetic material of high permeability and low coercivity, the creating means having at least two distinct magnetic states, a first state in which a first remotely detectable magnetic response is created upon a first interrogation, and a second state in which a second remotely detectable magnetic response which is different from the first state is created upon a second interrogation, and clamping and release means for holding the creating means, said clamping and release means including a spring clamp for holding the creating means to restrict the creating means from entering the second state, and a material which melts upon being subjected to sterilization conditions, the spring clamp being separate and distinct from the magnetic material of high permeability and low coercivity;

exposing the sterilization monitor to at least a portion of the sterilization process to be monitored, such that after a predetermined exposure to the sterilization process to be monitored, the compound melts sufficiently to change the creating means from said first to said second state;

then interrogating the monitor in the interrogation zone;

indicating whether the interrogation mechanism detects the second state of the creating means.