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12 July 2018

Safer CME processes: learn about the Air Detector

The CME - Material and Sterilization Center - can easily be denominated as the heart of the hospital. The rationale is simple: hospitals are places where there is a cluster of risks to human health, so if the materials that we use are not properly sterilized the patients will be harmed.

When it comes to the sterilization of health products, ABNT NBR ISO 17665-1: 2010 establishes the requirements for the development, validation and routine control of these processes. The standard also addresses a device designed to detect the presence of Non-Condensable Gas (CNG) in a sterilization chamber. What device would this be?

The question may seem strange to you at first. However, although the Brazilian standard already cites this device, in Brazil this was something still unknown until very recently. It was Cisa who changed this scenario. And it's this story that we want to tell you here.

A master's theme, an innovation

Sandoval Barbosa Rodrigues, Research and Development Manager of Cisa, is the name behind the Cisa device we call the Air Detector. The innovation was the result of a master's research, in which the professional studied the effect of non-condensable gases (CNG) in the process of steam sterilization.

For alignment purposes, CNG is defined as those gases which cannot be liquefied by compression, i.e., can not return to liquid in the range of temperature and pressure conditions used during the saturated steam sterilization process. Thus, these gases, mostly oxygen, carbon dioxide and nitrogen (which also compose atmospheric air), can negatively impact the sterilization of materials in the autoclave.

All of this is based on the literature, with EN 285 (2016) specifying the quality of saturated steam. The rule is simple: in the words of Sandoval, "if we don't have quality in saturated steam (which is the sterilizing agent that we use in the sterilization process), we will not have sterilization."

To better understand, according to the standard, for every 100 ml of condensed gas, 3.5 ml (or 3.5%) is the limit defined for CNG. Beyond that, one may be at risk in the sterilization process. This criterion was determined in the standard after experiments of an air detector in 1960.

"The danger related to CNGs has been underestimated," explains Sandoval, who was surprised when, during his research, he found information in the literature that the best chemical and biological indicators on the market don't signal the presence of a CNG content of up to 10 %, while other literatures claimed that 1% could harm sterilization in porous materials or lumens. The research and development manager ignited the red alert and went after the answer to the question:  

How can we detect the presence of CNG in steam autoclaves?

It is important to note that there are several forms of CNG prevention, such as calibration and preventive maintenance of autoclaves, for example. However, if the equipment has an air detector the process becomes safer.

It is worth remembering that, according to ABNT NBR ISO 17665-2 (2013), the differences between the control temperature of the reference point and the theoretical temperature calculated from the chamber pressure may not be adequate to detect the small volumes of air and prevent the penetration of steam. 

Remember the ABNT NBR ISO 17665-1: 2010 normcited in the beginning? It provides for the use of an integrated Autoclave device for air detection that will impair sterilization of materials, right? Well, during the more than a thousand sterilization cycles carried out in Cisa's laboratory, and based on literature calculations, Sandoval developed the Air Detector.

What is the Air Detector?

The Air Detector is a device that operates during the sterilization cycle and which provides assurance that an excess of air (and/or non-condensable gases) does not remain at the end of the air removal phase in amounts that will affect the sterilization process.

As a general rule, autoclaves generally already detect CNG from a certain level. However, Sandoval explains that Cisa's Air Detector detects small volumes of CNG because it calculates the difference in microbial lethality between the main temperature control and the detector that has an impedance to the air removal and vapor penetration defined for the process.

According to parameters established by cycle, residual non-condensable gases from the chamber that may affect sterilization are identified. When this happens, the Air Detector, because it is integrated with the autoclave, automatically cancels the sterilization cycle, that is, it doesn't release the door from the discharge side, thus requiring a restart of the process and making it safer. In addition to this safety, the device promotes productivity and utility savings, as failure is already detected in the sterilization phase. Thus, energy and water that would be consumed until the end of the cycle are saved.

Another important differential of the gas detector is that, unlike the Bowie & Dick test that monitors only the first cycle of the day, the detector monitors each sterilization cycle. This is very important because during the day adverse events can present risks to the sterilization process.

To prove the efficiency of the device, Sandoval says that in addition to the two-year study in Cisa's laboratory, the Air Detector was integrated into the steam autoclave of Hospital Dona Helena, located in Joinville (SC). The hospital became the first in Brazil to have an Autoclave with this system.

Air Detector: testimonial

Suelen Schtiguel Serpa, CME Nurse ofthe Hospital Dona Helena, says that when the CME team understood that any air bubble would be an obstacle to obtaining a 100% sterile material, the center's professionals celebrated the installation of the Air Detector.

According to her, the deployment of the device was smooth. "The Cisa team has always been showing us the results, how it worked and what we could do to improve our processes. The result was perfect," says Suelen.


It is important to note that the Air Detector was designed for sterilizers with a saturated steam sterilization process.



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