In the past, breathing gas pathway medical devices were regarded as external communicating devices and evaluated according to the ISO 10993 series of international standards.

This lead to testing that has provided questionable benefits (e.g. implantation testing) and potential hazards may have been missed in the past. ISO TC 121 has released a new set of standards in March 2017, which address the special features of breathing gas pathway medical devices. ISO 18652-1 is comprised of four parts.

These parts are addressing the potential hazards specifically associated with these kind of devices. The first step is the identification of all the potential hazards to patients that are specifically associated with the gas stream coming from the device including particulate matter, volatile organic compounds and leachables in the condensate.

Following the emission testing, the chemical compounds identified must undergo a full toxicological evaluation according to ISO 10993-17. This includes the calculation of the actual dose of the compounds to the patient, considering parameters such as dilution from the amount of gas and the breathing volume of the target population.

Once a dose to the patient is established for each detected compound, an extensive literature search of all available toxicological data and the derivation of allowable daily limits for each compound has to be carried out. In this case it is very important that toxicologists pay attention to available inhalation toxicity data as this is the most relevant endpoint for breathing gas pathways.

Safety and modification factors will be applied to the values of the animal studies in order to establish a safe human dose for each detected chemical compound, by considering also the use of these devices in different subpopulations (e.g. adults, children). Once all the information and data are collected, the potential risk of the breathing gas pathway medical device can be assessed.