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Reading Steam Sterilization Printouts

Updated: Mar 10, 2022

Last week we listed common issues we found in sterile processing departments (SPD) in our round-up report for 2021. This week we would like to focus on reading sterilization printouts. It is surprisingly a common issue found in SPD. Staff in the SPD staff will sign off on a completed sterilization cycle without understanding how to read the critical phases of the sterilization cycle. We will break down what the staff should be reviewing.

Cycle Parameters

The SPD staff must first evaluate if the parameters of the selected sterilization cycle were met. Not all manufacturers place the information in the same locations on the printouts, but the chosen sterilization temperature and exposure time will be on the sterilization printout. Also, the printout will indicate the actual period of time and temperature that the cycle ran. The selected parameters and the actual parameters should correspond.

By reading this sterilization printout, we can tell that the selected cycle was a 4-minute exposure at 270 degrees F with a 1-minute dry time (look at the blue circle at the top of the printout). We can also tell that the sterilization cycle was completed with a maximum temperature of 273.4 F and a minimum temperature of 271.4 F, including a 1:17 minute exhaust period ( look at the blue circle at the bottom of the printout). We can conclude that cycle selected was the cycle completed. However, further investigation needs to be completed to validate the sterilization process.

Sterilization Parameters

Reviewing the documented parameters can evaluate the printout data and correlate it to the documentation summary at the bottom of the printout. There will be variations in cycle types and what you will find in the printout data. For example, gravity cycles like the pictured printout do not indicate vacuum pulses as you will find in pre-vacuum cycles when in the conditioning phase. The attached picture will show vacuum (V) in the exhaust phase. In the attached photo, we can determine that the cycle's conditioning phase (C) began at 12:29:36. We can also specify that the sterilization phase (S) began at 12:31:12 am, ending the conditioning phase, and completed at 12:35:12 am when the exhaust phase (E) began. Completing the math utilizing the starting and ending times shows that the sterilization cycle ran for 4 minutes and correlates to the selected and summarized time frames. Also, by using the beginning time frame for the exhaust phase at 12:35:12 am and the completed time (Z) of 12:36:29 am, we can determine the exhaust period or dry time was for 1 minute and 17 seconds, again correlating to the selected period, although slightly over, and the summarized time. Other parameters to be evaluated are temperature, pressure, and vacuum.

Temperature, Pressure, and Vacuum

First, let's acknowledge that several sterilizer manufacturers who sell sterilizers in the United States have them built overseas. That being said, the typical setup for measuring temperature/pressure in the U.S.A. is PSI (pounds per square inch), but in other areas of the world, the measurement is PSIA (pounds per square inch absolute). The difference in the readout between PSI (G) and PSIA can vary by altitude, but it is 14.7 pounds at sea level. The difference is due to barometric pressure, which again can vary based on altitude. You need to know how your sterilizer's pressure readings are set up. It will be documented on the printout. Essentially, with PSIA, you will need to add back the barometer pressure if you are reviewing a chart for temperature and pressure based on PSI(G). You will need to learn the correlating temperature/pressure readings for your local to ensure the corresponding printout is correct and does not indicate a potential problem. In our example above, the temperature of 273.0-.2 is relative to 29.6 PSIG.

Vacuum is rated in inches of mercury (Hg), and in the conditioning phase, utilizing a pre-vacuum cycle should be at a minimum of around 10 Hg. Read your sterilizer manuals to make sure your sterilizers are functioning correctly.

Each person who reviews and documents sterilization loads must verify that the sterilization parameters were met; not doing so can create the potential for a hospital-acquired infection. The CDC states that 1-25 patients in the U.S. are diagnosed with an HAI. Let's do our part to support and protect our patients.

At Evolved Sterile Processing, our consultants have a greater focus on sterile processing. With our decades of experience, we will help you develop better processes and educational resources for your staff.

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