The effect of temperature on exhaled breath condensate collection

Abstract

Exhaled breath condensate (EBC) collection is an innovative method of non-invasively sampling the lung, and can detect a variety of volatile and non-volatile biomarkers, but the disadvantage is the small volume of sample collected. It was hypothesized that a collection system at a lower temperature would increase the volume collected, but may alter the relative concentration of the biomarkers of interest. EBC was collected in a cross-over study using a custom-made collection system, cooled using either wet (4 °C) or dry ice (-20 °C) in randomized order in normal non-smoking volunteers. The volume of the EBC collected per unit time was determined as were conductivity, the concentrations and total amount of protein, hydrogen peroxide, and nitrite/nitrate concentrations. Dry ice was associated with a 79% greater volume of EBC than the wet ice (1387 ± 612 µL; 773 ± 448 µL respectively, p < 0.0001). Conductivity was influenced by the temperature of collection (18.78 ± 6.71 µS cm(-1) for wet ice and 15.32 ± 6.28 µS cm(-1) for dry ice, p = 0.02) as was hydrogen peroxide (1.34 ± 0.88 µg mL(-1) for wet ice and 0.68 ± 0.32 µg mL(-1) for dry ice, p = 0.009) while the concentrations and total values for protein and nitrate/nitrite were not significantly different (p > 0.05). This pilot study suggests that lower collection temperatures facilitate the collection of a larger sample volume. This larger volume is not simply more dilute, with increased water content, nor is there a simple correction factor that can be applied to the EBC biomarkers to correct for the different methods.

Exhaled breath condensate: a comprehensive update

“…Condensation of EBC vapour can be achieved at temperatures of 4 ° C or lower [ 26 ]. The cooling of the exhaled breath vapour has been achieved through various means, including wet ice, wet ice with salt, dry ice, liquid nitrogen, cooling sleeve and electrical refrigerating systems [ 22 , 26 , 27 ].…”

“…The cooling of the exhaled breath vapour has been achieved through various means, including wet ice, wet ice with salt, dry ice, liquid nitrogen, cooling sleeve and electrical refrigerating systems [ 22 , 26 , 27 ]. Depending on the temperature, condensates are collected in either a liquid, solid, or a mixture of both states [ 26 ]. The condensation temperature used can influence biomarkers differently ( Table 2 ).…”

“…Each biomarker has different characteristics, thus researchers should try to optimise the collection conditions when investigating biomarkers that are near the limits of detection. The exact basis of these differences is not well understood, but will related to water solubility, degradation, either spontaneous or by enzyme activity, or to freeze-thawing and oxidation [ 26 ]. It is thus important for condensation temperatures to be reported, to facilitate comparison of data across laboratories.…”

“…4 Glass CMD Healthy subjects, n = 20, p = 0.042 [ 26 ] Nitrate/nitrite (concentration) = − 20 vs. 4 Glass CMD Healthy subjects, n = 20, p = 0.63 [ 26 ] TURBO-DECCS, transportable unit for research on biomarkers obtained from disposable exhaled condensate collection systems; CMD, custom-made device; a more acidic.…”

“…Temperature and humidity of inhaled air [ 66 ], as well as condensation temperatures [ 1 , 65 , 67 ], may influence EBC constituents (due to variable heats of vaporisation and specific heat capacities compared to pure water) such as volume [ 26 ] and pH [ 68 ] but not total protein [ 22 ]. EBC samples should not be left out at room temperature after collection, due to interactions with ambient air with potential formation and degradation of unstable or volatile biomarkers such as leukotrienes, purines, H 2 O 2 and volatile organic compounds (VOC) [ 1 , 52 ].…”