To Filter or Not To Filter

The Case for Filtration

The RTube Exhaled Breath Condensate (EBC) Collector is amazingly effective at trapping particles, droplets, and aerosols present in the patient’s exhaled breath.  This is why so many studies rely on the RTube to capture exhaled biomarkers for analysis.

But in some cases, a more discriminating collection protocol is in order.  For example, an occupational health study may seek to isolate endogenously-produced biomarkers from ambient particles such as dust and bacteria inhaled by the study subject during the collections process.  Another example may be a study in which only volatiles and particles smaller than 0.3 microns are of interest.  Yet another application may be as an occupational safety measure for your research team when dealing with study subjects with infectious disease.  Over 90% of research protocols require no filtration at all and simply use the RTube “as is”.  It is for the 10% of protocols where filtration is important that the guidance below applies.

Flexibility is Key

Varied modes of filtration can be accomplished with a simple filter placed in-line in different locations on the RTube device.  Our Box of 25 Inline Filters (Item # 2504) is specifically matched to the RTube and can be used in a number of configurations.  It is a single-use disposable hydrophobic 0.3 micron anti-bacterial mesh filter in a polyethylene housing.  It connects to both 22 mm female and male tapered ports, as well as 15 mm female.  This filter is easily installed onto the RTube by the researcher prior to collection by the study subject.

Filtration Mode 1: Prevent Inhalation of Ambient Particulates

Placing the filter at the inlet of the RTube as shown in the figure captures larger ambient particles such as dust and bacteria and prevents inhalation of these particles by the study subject.  This in turn ensures that any particles captured in the EBC are produced endogenously.  This can be important when attempting to isolate an endogenous response or standardizing the collection protocol to eliminate “pollution” from different collection sites.  It is most effective when combined with nose clips and close supervision to ensure the study subject is always inhaling (and of course exhaling) through the device.

Filtration Mode 2: Capture Only Volatiles and Small Particles

Placing the filter between the mouthpiece assembly and the condensation cartridge traps all particles larger than 0.3 microns.  This may be useful when attempting to preferentially collect particles from the deep lung due to their smaller size.  It also prevents bacterial contamination of the EBC specimen during collection which may be useful for certain sample storage protocols.  Interestingly, these larger particles can be extracted from the filter using methanol as a solvent/carrier and can be analyzed independent of the EBC specimen.

Filtration Mode 3: Protect Research Staff from Infectious Disease

Placing the filter at the outlet of the RTube captures bacteria exhaled by the study subject and prevents staff exposure to a concentrated puff of infectious exhalate in the face.  This is the least common application of the filter, but in certain protocols is provided as a safety and well-being measure for the staff.  Of course, every other aspect of the study subject is still contagious, but staff do seem to appreciate the added measure of protection.

Summary

While most study protocols neither benefit from nor require any filtration, yours may be the exception.  Please feel free to contact us with any questions.  We’ll be glad to review your protocol and make suggestions based on our experience and evidence in published journal articles.  We look forward to working with you!