Advice for ReCIVA Users: Harshman et al. (2019) Characterization of standardized breath sampling for off-line field use
A paper by Harshman et al. (2019) in the Journal of Breath Research performed a detailed study of ReCIVA use looking at a number of factors including background noise and thermal desorption (TD) tube type. This is one of the first studies to do so and we welcome this close investigation of our Breath Biopsy products and the insights it offers.
The paper is positive about the potential of ReCIVA as an improvement on breath collection bags. In their conclusions the authors offer several suggestions based on their experience with ReCIVA, here we discuss their advice and its relevance for other ReCIVA users. Generally, we recommend that you contact us if you’re considering making changes to how you use ReCIVA.
“Collectively, the results demonstrate that the ReCIVA sampler represents a significant step towards standardized exhaled breath sampling for off-line analysis”
The results included in this paper are the product of a single investigative study. Each test uses a sample size of 12 and all the results appear to be based on data from a single ReCIVA unit. Older ReCIVAs like those used in this study, were calibrated specifically to operate with a particular type of sorbet tube (see below), while more recent models enable flow calibration independent of the sorbent tube type.
The results are based on the recovery of isoprene as a chosen example compound in breath. Isoprene was chosen for being particularly high in abundance, having a readily available standard and for being reported on breath in a range of existing publications. However, research suggests that isoprene has a relatively high risk of breakthrough on adsorbent materials at room temperature, and the recommendation is to use a safe sampling volume that minimizes the risk of breakthrough.
Siloxane Emission by Breath Biopsy Masks
Our advice: Breath Biopsy Masks are single use and are now supplied with a coating that reduces emission of background siloxanes, we do not recommend soaking or baking your masks.
Background signals are a persistent issue in all untargeted approaches to breath analysis. Siloxanes emitted by the silicone masks used to interface between ReCIVA and a subjects face are a recognized background signal in Breath Biopsy samples. Harshman et al. test two methods for siloxane reduction - soaking in ethyl alcohol and baking at 200 °C. They report that both methods reduce siloxanes by at least 58% and conclude that baking is preferable as soaking results in increased background alcohol signals.
As the authors note, we have made progressive steps to reduce siloxane emission from our masks. In the past we advised baking to reduce siloxane emission. However, since mid-2018, Breath Biopsy Masks have been supplied with a coating to reduce siloxane signals, this coating offers a more stable and consistent reduction in siloxane levels. Our data suggest that coating reduces total siloxane emissions by orders of magnitude and is stable for at least three weeks. The coating will be damaged by baking, so we now do not advise heating coated masks. Breath Biopsy Masks are recommended for single use only to avoid cross contamination, additional background signals and degradation of sample quality.
ReCIVA Pumps and Airflow Rates
Our advice: The pumps in ReCIVA are calibrated before shipping to provide a standardized air flow through TD tubes, they should not require manual calibration. Manual calibration can cause irreparable damage to ReCIVA components. If you encounter issues, updating your ReCIVA control software may help, alternatively contact us for technical support.
ReCIVA collects air using two pumps to draw air through the TD tubes. There is one pump for the pair of tubes on each side of the device. These pumps are calibrated before shipping to provide airflow through the tubes of 200ml/min. Airflow through TD tubes is an important factor in how efficiently compounds adsorb to the tubes. Although the airflow rate in ReCIVA is higher than is commonly used with bags, it is still within the expected performance range of most TD tubes.
Harshman et al. performed detailed measurements of airflow rates using both Tenax and Tenax/Carbograph 5TD (5TD) tubes. They found differences in flow rates between the two pumps which caused a slight reduction in efficient isoprene capture. The authors were able to improve the situation by updating their ReCIVA control software to a newer version. They also report benefits from manually calibrating the device. The latest ReCIVA models include updated pumps that offer greater reliability and consistency of airflow.
Types of Thermal Desorption Tube
Our advice: ReCIVA is optimized to function with a cartridge containing four Tenax/Carbograph 5TD (5TD) desorption tubes and Breath Biopsy Kits are all supplied with these tubes. However, current ReCIVA models are designed to be compatible with a range of TD tube types. The combination of materials in 5TD tubes offer the capability to collect a wider range of compounds than other common types, such as Tenax alone.
The paper uses both Tenax and 5TD thermal desorption tubes to collect compounds from breath samples using ReCIVA. Tenax is a widely used TD tube option and is suitable for a range of applications, however we favour 5TD particularly for its ability to capture smaller compounds that typically break through Tenax.
If you are considering changing the way you use ReCIVA then we encourage you to contact us to discuss the required adaptations so we can help you to understand the possible effects and support you to get the best possible results.