Measuring Dew Point in Medical Gases

How to minimize the risk of bacterial contamination

Bacteria and micro-organisms can potentially double in number every four to twenty minutes. If conditions facilitate this accelerated reproduction, it can be a huge risk in a medical setting.

Warm, humid conditions cause these contaminants to thrive if there is a ready source of nutrients, found in carbon, nitrogen, moisture and some minerals. A pH neutral or slightly acidic environment also makes an ideal breeding ground.

This is common knowledge and has prompted the placement of hospital systems and processes that minimize risk. This includes training medical staff in the appropriate sterilization and decontamination measures. 

Nonetheless, no process is 100 % effective in eliminating all bacterial growth: for example, the presence of moisture in a warm compressed gas stream. Because of this, the production of medical gases, either supplied in cylinders or produced on site using gas generation systems, is rigorously controlled. 

Understanding medical gas requirements 

In America, the FDA (Food and Drugs Administration) considers compressed medical gases, including oxygen, nitrogen, carbon dioxide and helium, to be finished pharmaceutical products; their manufacture is regulated under CGMP (current good manufacturing practice). 

Similarly, the European Pharmacopeia specifies a maximum allowable moisture concentration of 67 ppm by volume at -46 °C dew point, while the UK Health Technical Memorandum HTM02 states that all medical gases must be continuously monitored for moisture content or dew point. 

The most common medical gas is breathing air, which generally falls into one of three categories: 

Although the presence of bacteria in the first of these categories – compressed air – is perhaps less of an issue with regard to patient safety, there is still the potential for problems with the equipment: for example, corrosion or other damage, and reduced ability to clean and sterilize effectively. In addition, water vapor could contribute to corrosion or contamination of downstream equipment. 

Medical compressed air and synthetic air present a greater risk to patient safety, as they are used for therapeutic purposes. Much of the focus, however, tends to be on controlling bacterial contamination, either at the point of production or use. For example, respirator and ventilator equipment is generally recognized as a potential source of bacterial contamination and is sterilized accordingly, while, as stated above, compressor systems use advanced-air treatment filters and dryers to remove particulates and water vapor.   

However, it is an often-overlooked fact that problems can also occur in the pipework through which the compressed medical gas travels, especially if pipe joints have been incorrectly constructed or sealed, as these form natural bacteria traps in the presence of even small concentrations of moisture. 

Maintaining optimal quality in medical gas 

Although it is essential to maintain best practice in terms of sterilization and cleaning in each patient area, it is most important to prevent the growth of bacteria in compressed medical and synthetic breathing air systems from the outset. This is where the use of both portable and online dew-point meters and moisture-measurement instruments is critical: the Easidew Advanced Online Hygrometer provides continuous moisture measurement in gas systems, while the MDM300 high-speed portable dew-point hygrometer is a critical instrument for spot checks throughout the medical gas production, distribution and delivery network. 

Michell’s advanced range of instruments for moisture and dew-point measurement in compressed medical gases is extensive and widely used by leading hospitals in England.

To find out more about moisture in medical gases, click here.

Or, view our related blog, Measuring Moisture in Medical Gases, to read about the UK HTM requirements.

With almost 50 years’ experience in the development of innovative precision sensors, we are the application experts in dew-point measurements for all specialized moisture in medical gas applications. If you would like to discuss your requirements, please contact our team today.

Sources:

FDA Medical Gases

FDA CGMP