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. 2022 Oct 26;12(1):17926.
doi: 10.1038/s41598-022-22581-7.

Advanced setup for safe breath sampling and patient monitoring under highly infectious conditions in the clinical environment

Pritam Sukul  1 , Phillip Trefz  2 , Jochen K Schubert  2 , Wolfram Miekisch  2
Affiliations

Advanced setup for safe breath sampling and patient monitoring under highly infectious conditions in the clinical environment

Pritam Sukul et al. Sci Rep. .

Abstract

Being the proximal matrix, breath offers immediate metabolic outlook of respiratory infections. However, high viral load in exhalations imposes higher transmission risk that needs improved methods for safe and repeatable analysis. Here, we have advanced the state-of-the-art methods for real-time and offline mass-spectrometry based analysis of exhaled volatile organic compounds (VOCs) under SARS-CoV-2 and/or similar respiratory conditions. To reduce infection risk, the general experimental setups for direct and offline breath sampling are modified. Certain mainstream and side-stream viral filters are examined for direct and lab-based applications. Confounders/contributions from filters and optimum operational conditions are assessed. We observed immediate effects of infection safety mandates on breath biomarker profiles. Main-stream filters induced physiological and analytical effects. Side-stream filters caused only systematic analytical effects. Observed substance specific effects partly depended on compound's origin and properties, sampling flow and respiratory rate. For offline samples, storage time, -conditions and -temperature were crucial. Our methods provided repeatable conditions for point-of-care and lab-based breath analysis with low risk of disease transmission. Besides breath VOCs profiling in spontaneously breathing subjects at the screening scenario of COVID-19/similar test centres, our methods and protocols are applicable for moderately/severely ill (even mechanically-ventilated) and highly contagious patients at the intensive care.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Relative differences in exhaled VOCs concentrations (mean over two min) without and with the mainstream (a) and side-stream (b) viral filters. All Y-axis represent protonated VOCs of interest. All X-axis represent experimental conditions. VOCs data were normalised onto the corresponding values from sampling at the steady state of breathing without filters that are placed within red-coloured margins. The steady states are the actual comparison points for physiological and/or analytical effects induced by the filters. Changes in colour represents relative differences in concentrations. Red and blue colour represents relatively high and low values, respectively. (a) Mainstream filters depict both physiological and analytical effects. (b) Side-stream filters depict only analytical effects and repeated measurements (1 and 2) are presented to demonstrate repeatability.
Figure 2
Figure 2
Recovery rates of VOCs concentrations with side-stream syringe filters at two different sampling flow rates. VOCs intensities obtained through measurements without filters represent 100%, VOCs intensities obtained through measurements with syringe filter are presented in % in relation to measurements without filter. VOCs concentration was approximately 100 ppbV. Blue bars represent measurements with a sampling flow rate of 20 sccm (i.e. mL/min), orange bars represent measurements with a sampling flow rate of 50 sccm.
Figure 3
Figure 3
Effects of PTR sampling flow on breath-resolved assignment of expiratory and inspiratory phases via syringe-filters under normal (a) and higher (b) respiratory rates: Here, breath tracker plots are presented under various sampling conditions. In all breath-tracker plots, Y-axis represent signal intensity of acetone (an endogenous and blood-borne VOCs) and all X-axis represent time in s. Red colour represents exhaled alveolar/end-tidal phase and blue colour represents inspiratory (room-air) phase. (a) Sampling flows of 20, 50 and 65 mL/min were applied for sampling under respiratory rate of 10–12 breaths/min. (b) Sampling flow of 65 mL/min was applied for sampling high respiratory rates of 20–30 breaths/min.
Figure 4
Figure 4
Effects of viral filters on side-stream manual sampling with different connection types with and without pre-purging: syringe drawn breath was analysed via PTR-ToF–MS and compared to direct PTR-ToF analysis. Y-axis represents protonated VOCs of interest. X-axis represents experimental conditions. VOCs data from syringe samples were normalised onto the corresponding values without filter. Syringe filters with and without luer-lock were compared. Effect of flushing and not flushing syringes prior to sampling are observed. Changes in colour represents relative changes in concentrations. Red and blue colour represents relatively high and low values, respectively.
Figure 5
Figure 5
Effects of storage time and temperature of glass-syringe samples onto the VOCs concentrations: Y-axis represents protonated VOCs of interest. X-axis represents experimental conditions. VOCs data (from repeated measurements) were normalised onto the corresponding values from the syringe sample i.e. analysed instantly (without storing). Values from direct breath are depicting syringe-filter driven analytical variations. Effects of storage time of 15, 30, 60 and 120 min on VOCs content are presented along with the effects of storage (for transport) temperature (not heated and heated at 37 °C).
Figure 6
Figure 6
General setups for continuous real-time (a) and offline (b) sampling and customised viral filter attachments (c). In compliance to infection safety mandates, general setups for online and offline sampling are optimised. Punctual sampling in glass-syringe and direct continuous real-time sampling in PTR-ToF–MS are adapted via customised viral filter attachments. Combined sampling attachments to conduct simultaneous real-time and offline sampling are also presented.
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