Sterilization Apparatus And Adaptive Control Thereof

Abstract

An apparatus for sterilizing load in a sterilization chamber according to specific characteristics of the load without direct measurement of the load conditions. The apparatus preferably admits sterilant gas into the sterilization chamber under vacuum; during admission of the sterilant gas, the apparatus monitors a sterilant condensation related parameter or data in the sterilization chamber. The apparatus detects the occurrence of condensation and determining a value of the condensation related parameter while detecting condensation and, selects a sterilization cycle among a plurality of predetermined sterilization cycles according to the condensation related data. The apparatus that performs the selected sterilization cycle for sterilizing the load. The condensation related data may be the sterilant dew point, a degree of condensation, or an amount of condensation which may be determined in monitoring the chamber pressure during sterilant gas admission. The sterilization process may be controlled dynamically according to the determined condensation related data.

1 .- 5 . (canceled) 
     
     
         6 . A method for sterilizing a load in a sterilization chamber under vacuum, comprising the steps of:
 admitting a sterilant gas into the sterilization chamber under vacuum;   monitoring a sterilant condensation related parameter in the sterilization chamber;   determining the dew point of the sterilant gas from the sterilant condensation related parameter;   selecting a sterilization cycle according to the dew point; and   performing the selected sterilization cycle for sterilizing the load.   
     
     
         7 . The method of  claim 6 , wherein selecting a sterilization cycle manages the thickness of a layer of condensation and the concentration of sterilant in the layer. 
     
     
         8 . The method of  claim 6 , wherein the dew point is determined from a value determined from the sterilant condensation related parameter and selecting the sterilization cycle further comprises selecting the cycle from a plurality of predetermined sterilization cycles according to the dew point. 
     
     
         9 . The method of  claim 6 , wherein the sterilant condensation related parameter is a load temperature. 
     
     
         10 . The method of  claim 6 , wherein the sterilant condensation related parameter is a thickness of a layer of condensed sterilant on the load. 
     
     
         11 . The method of  claim 6 , wherein the selecting a sterilization cycle comprises determining a predetermined sterilant gas injection end pressure. 
     
     
         12 . The method of  claim 6 , wherein selecting a sterilization cycle comprises determining a final quantity of sterilant gas to inject. 
     
     
         13 . The method of  claim 6 , wherein selecting a sterilization cycle comprises determining the parameters of ventilation to remove condensed sterilant. 
     
     
         14 . The method of  claim 6  further comprising determining sterilant condensation, an absence of sterilant condensation, an onset of sterilant condensation, or a progression of sterilant condensation based on the dew point, then, selecting the sterilization cycle based on the determination. 
     
     
         15 . The method of  claim 6 , wherein the sterilant condensation related parameter is the chamber pressure. 
     
     
         16 . The method of  claim 15  further comprising determining the dewpoint based on the onset or occurrence of condensation, wherein one of the occurrence of condensation and the onset of condensation is detected by monitoring for a change in a rate of pressure increase in the sterilization chamber during admission of the sterilant gas. 
     
     
         17 . The method of  claim 6 , wherein the sterilant condensation related parameter is dependent on a condition of the load. 
     
     
         18 . The method of claim  1 , wherein the sterilant condensation related parameter comprises a ratio of an amount of condensed sterilant gas to a total amount of injected sterilant gas. 
     
     
         19 . The method of  claim 18 , wherein the sterilant gas is provided at a constant rate, the amount of condensed sterilant gas is determined by calculating an area between a theoretical vapor pressure curve of the sterilant gas and an actual vapor pressure curve based on measured chamber atmosphere parameters, the area representing a measure for the quantity of condensed sterilant gas. 
     
     
         20 . The method of  claim 18 , wherein the sterilant gas is hydrogen peroxide gas. 
     
     
         21 . The method of  claim 6 , comprising the further step of evaporating a liquid sterilant to generate the sterilant gas. 
     
     
         22 . The method of  claim 21 , wherein the liquid sterilant is an aqueous sterilant solution and the step of evaporating includes completely evaporating both sterilant and solvent to generate a water vapor and sterilant gas mixture prior to the admitting step, optionally the liquid sterilant is an aqueous solution of hydrogen peroxide and the sterilant gas is hydrogen peroxide gas. 
     
     
         23 . The method of  claim 22 , wherein the sterilant gas is hydrogen peroxide gas. 
     
     
         24 . A system for sterilizing a load in a sterilization chamber under vacuum, comprising
 a sterilization chamber;   a vacuum arrangement for applying a vacuum in the sterilization chamber;   a sterilant injection arrangement for admitting a sterilant gas into the sterilization chamber when under vacuum;   a monitoring arrangement;   a control unit connected to the monitoring unit;   wherein the monitoring arrangement is configured to monitor a sterilant condensation related parameter in the sterilization chamber and configured to determine the dew point of the sterilant gas from the sterilant condensation related parameter; and   wherein the control unit is configured to select a sterilization cycle according to the dew point.   
     
     
         25 . The system of  claim 24 , wherein the sterilant gas is hydrogen peroxide gas.