Impact of thermal desorption tubes on the variability of exhaled breath data.

Due to the overall low abundance of volatile compounds in exhaled breath, it is necessary to preconcentrate the sample prior to traditional thermal desorption (TD) gas chromatography mass spectrometry analysis. While certain aspects of TD tubes, such as volatile storage, have been evaluated, many aspects remain uncharacterized. Two common TD tubes, Tenax TA and Biomonitoring 5TD tubes, were evaluated for background content and flow rate variability. The data illustrate that the Biomonitoring 5TD tubes have the highest number (23) and abundance of background contamination greater than 3x the mean noise when compared to Tenax TA (13) and empty tubes (9). Tentative identifications of the compounds in the background contamination experiment show that greater than 59% (16/27) of the compounds identified have been reported in the breath literature. The data illustrate the TD tube background abundance could account for more than 70% of the chromatographic signal from exhaled breath for these select compounds. Flow rate measurements of 200 Tenax TA and 200 Biomonitoring 5TD tubes show a large range in measured flow rates among the TD tubes (Tenax: 252.9-284.0 ml min-1, 5TD: 220.6-255.1 ml min-1). Finally, TD tubes of each type, Tenax TA and Biomonitoring 5TD, previously established to have high, medium, and low flow rates, show insignificant differences (p> 0.05) among the tubes of different flow rates, using both gas standards and an exhaled breath from a peppermint experiment. Collectively, these results establish overall background compounds attributed to each TD tube type tested. Additionally, while measured flow rate variability is present and plausibly impacts exhaled breath results, the data demonstrate no statistically significant difference was observed between tubes showing high, medium, and low flow rates from two separate sample types.

Detection of Asthma Inhaler Use via Terahertz Spectroscopy.

Inhaled medications are commonplace for administering bronchodilators, anticholinergics, and corticosteroids. While they have a defined legitimate use, they are also used in sporting events as performance-enhancing drugs. These performance enhancers can be acquired via both legal (i.e., at a pharmacy through over-the-counter medications or through a prescription) and illicit (i.e., black market and foreign pharmacies) means, thus making monitoring procurement impossible. While urine tests can detect these pharmacological agents hours after they have been inhaled, there is a significant lag time before they are observed in urine. Direct detection of these inhaled agents is complicated and requires a multiplexed approach due to the sheer number of inhaled pharmacological agents. Therefore, detection of propellants, which carry the drug into the lungs, provides a simpler path forward toward detection of broad pharmacological agents. In this paper, we demonstrate the first use of terahertz spectroscopy (THz) to detect inhaled medications in human subjects. Notably, we were able to detect and quantitate the propellant, HFA-134a, in breath up to 30 min after using an asthma inhaler, enabling the use of a point-of-care device to monitor exhaled breath for the presence of propellants. We also demonstrate via simulations that the same approach can be leveraged to detect and identify next-generation propellants, specifically HFA-152a. As a result, we provide evidence that a single point-of-care THz sensor can detect when individuals have used pressure-mediated dose inhalers (pMDIs) without further modification of the hardware.