by Jen Marlow LM, CPM
With the increasing accessibility of electronic pressure cookers has also come an increase in questions about their viability for sterilization of instruments. In meeting with World Health Organization and United States Food and Drug Administration standards, sterilization in at autoclave at 121°C and 15 PSI for at least 30 minutes is generally recommended. Many out of hospital midwives already successfully use pressure cookers intended for canning, or oven sterilization techniques, so it does not seem like a huge leap to consider using an electronic pressure cooker that needs little more than a button push after being loaded with cleaned and packaged instruments. The simplicity of use is not the only appeal. Most autoclaves are at least 10 times more expensive than a typical electronic pressure cooker.
There are several electronic pressure cookers currently available that reach the necessary pressure and temperature. It is entirely possible to see color change on sterilization package indicators that show these conditions have been achieved. The primary concern, however, is that indicators on packaging only show that those conditions were reached at some point during the sterilization process. To meet sterilization standards, that level of heat and pressure needs to be reached and maintained. Until recently, there hasn’t been any clear evidence as to if any of these pressure cookers are consistently maintaining the necessary pressure and heat for the entire time.
A 2018 study conducted at Dakota State University suggests that, yes, it is possible to substitute an electronic pressure cooker for an autoclave. Their results came with one big caveat though. Only one of the pressure cookers they tested met the criteria they were looking for. A variety of fungal and bacterial cultures were packaged and run through Instant Pot, GoWISE, COSORI, and Gourmia pressure cookers then cultures were incubated for one week before being checked for growth. Most notably, they were tested with Geobacillus stearothermophilus spores, a culture known to be heat resistant and commonly used to test that sterilization devices are functioning as intended. An Instant Pot with a sterilization setting was the only electronic pressure cooker that was able to successfully pass the spore test. The Instant Pot required a sterilization time of 150 minutes or more before the spores were inactivated, but the other pressure cookers tested were unable to inactivate the spores even at 300 minutes of sterilization time.
This longer sterilization time may require some adjustment to practices, but confirmation that use of an Instant Pot is an option opens up another door for out of hospital midwives to utilize lower cost, commercially available equipment without compromising results. If you are unsure of the sterilization results your particular protocol and equipment are producing, easy to use spore testing kits are available through Henry Schein, among other medical equipment retailers in the US.
Jen Marlow LM, CPM is a homebirth midwife and editor for The Birth Mag. She/Her/Hers