Qualifying Systems For Medical Service

A frequently asked question involves the qualification requirements for new or upgraded cryogenic and ASME storage vessels for medical service. This article will examine the cleaning, testing and documentation requirements to install a new storage vessel into medical service.

When dealing with FDA, it is important to remember that they view industrial gases and tanks in industrial service as (potentially) contaminated, even if the original source gas used to fill these industrial containers was medical product. This means any container that does not have a documented history or “pedigree” of prior medical use is considered contaminated, and cannot simply be put into medical service without first undergoing a proper qualification process. The historical record in our industry of industrial oxygen and nitrogen containers becoming contaminated through their connection to an industrial process, and then transmitting the contaminant to patients when the unit is returned to medical service, is the basis for FDA's position.

When new tanks are purchased, the manufacturer should be able to provide appropriate documentation as to their qualification activities, and that they certify that particular unit fit for medical service. While documentation of oxygen cleaning is a good start, a proper qualification of a container for medical service should also include, at a minimum, a documented odor test of gas from the container to verify the absence of any odor-containing solvents. Once the unit is installed, I strongly recommend performing the qualification tests specified in NFPA 99 (2005), chapter 5. This includes testing for gas purity, odor and particulate, as well as hydrocarbon and halogenated hydrocarbon difference testing. This testing should be performed before the tank is used to supply the medical fill process, and is the same testing performed on all hospital systems to assure the qualification of the gas delivery systems. These tests must be performed by an individual trained and certified as qualified to the ASSE 6010 standard.

Containers moving over from industrial service, or without a documented medical prior use history, should undergo a “cleaning” process as part of the qualification for medical use. Since it is not feasible to enter cryogenic tanks to clean, inspect and test them, the only practical means of cleaning these types of tanks is by using a pressure purge process. I recommend using a high flow/low flow or pressure pulse procedure with Nitrogen NF. Using industrial nitrogen would not be acceptable. This purge process should sequentially purge all container connections from one end of the unit to the other. For cryogenic bulk tanks, this would also include connections such as gauge lines and vaporizer circuits. You should also purge connections that you do not intend to use. For example, many times tanks have both a bottom draw connection and a dip tube connection. Often only one of these is used, but both should be purged to assure there are no contaminants hiding in a dead leg of the piping.

Once the cleaning process is complete, you will need to perform some testing to verify the process was successful. I recommend firms either perform the NFPA 99 testing referenced earlier in this article, or, if your business has the appropriate analytical capabilities, you can analyze the tank yourself.

This purging and cleaning process should be conducted using written procedures approved by your Quality Control Unit, and all steps of the process must be documented on appropriate forms or other documentation. Once the testing is completed, the results should be reviewed and approved by the QCU prior to using the unit in medical service. If a third party firm performs this purging/cleaning and testing process for you, under FDA requirements it is your responsibility to ascertain that their procedures and processes are adequate, and you remain responsible for the end results of the process.