Recently a client contacted Performance Validation requesting assistance with the cycle validation for a dry goods autoclave, which had failed to achieve sterility. A biological indicator included in the validation demonstrated growth on completion of the autoclave cycle.
On review of the dry goods autoclave cycle, Performance Validation (PV), identified the autoclave used a gravity cycle. With a gravity cycle, steam is gravity fed through the autoclave chamber from the top, pushing the air out of the chamber and through the drain, filling the chamber with steam. Gravity cycles are effective in sterilization of liquid loads. However, in porous loads, air can get trapped in the load and can act as an insulator preventing moist heat from penetrating the load, reducing the efficiency of sterilization.
Being very familiar with the qualification of numerous autoclave systems for many different customers, PV was able to communicate the advantages of using a pre-vacuum cycle. The rationale for using a pre-vacuum cycle is to use a number of vacuum and pressure pulses to fully evacuate air from and then provide consistent and thorough steam penetration into the load. A pre-vacuum cycle can result in reduced sterilization temperature and/or time requirements over a gravity cycle to achieve the same level of sterility within dry goods loads.
A pre-vacuum cycle was incorporated into the dry goods autoclave cycle and an engineering study was performed by PV. This study demonstrated the superior sterilization characteristics of the new cycle, with sterilization temperatures being met at all load locations by the start of the sterilization phase and with final lethality values exceeding specifications at all monitored locations.
PV then wrote a qualification package for the new cycle, conducted the controller reprogramming, and completed qualification execution.
The validation runs on the dry goods autoclave with the addition of the pre-vacuum cycle demonstrated a more consistent and effective sterilization.
Performance Validation offered a solution, the addition of the pre-vacuum cycle that resolved the customers failed sterilization issue. The customer was very pleased with the new cycle’s development and execution by PV. The new cycles were qualified and released to production.
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Principal Validation Engineer
Performance Validation, Inc