Dilution of Respiratory Solutes in Exhaled Condensates

Abstract

Most exhaled water is produced as gaseous water vapor, which can be collected in cooled condensers. The presence of nonvolatile solutes in these condensates suggests that droplets of respiratory fluid (RF) have also been collected. However, calculation of RF solute concentrations from condensates requires estimation of the dilution of RF droplets by water vapor. We used condensate electrolyte concentrations to calculate the dilution of RF droplets in condensates from 20 normal subjects. The total ionic concentration (conductivity) was 497 plus minus 68 (mean plus minus SEM) muM. Of this, 229 plus minus 43 muM was NH(4)(+), but little NH(4)(+) was collected from subjects with tracheostomies, indicating oral formation. The Na+ concentration in condensate ([Na+](cond)) averaged 242 plus minus 43 muM. Large variations in [Na(+)](cond) correlated well with variations of K+ in condensate ([K+](cond)) and Cl-) in condensate ([Cl-](cond)), and were attributed to differences in respiratory droplet dilution. Dividing condensate values of ([Na+] + [K+] ) by those of plasma indicated that RF represented between 0.01% and 2.00% of condensate volumes. Calculated values for Na+, K+, Cl-, lactate, and protein in RF were [Na+](RF) = 91 +/- 8 mM, [K+](RF) = 60 +/- 11 mM, [Cl-](RF) = 102 +/- 17 mM, [lactate](RF) = 44 +/- 17 mM, and [protein](RF) = 7.63 +/- 1.82 g/dl, respectively.

Exhaled breath condensate: a comprehensive update

“…As warm, fully saturated breath is exhaled from the lungs and comes into contact with the cold EBC collecting apparatus, it condenses into either liquid or ice depending on the cooling temperature. This condensate consists of mainly water ( > 99%) and a small amount of ALF [ 2 ]. This ALF is believed to have been derived from the respiratory surface lining fluids when energy from air turbulence vibrates the respiratory wall, and creates ne bulised droplets.…”

Exhaled Breath Condensate: An Overview

“…Estimates of the dilution of ALF particles in EBC range from 20-fold to 30,000-fold (10). 2000 to 10000 fold seems to be a generally accepted number (11).…”

“…As is common in much of medicine and biomedical science, in terms of a confident dilution marker for EBC there is as yet no gold standard. Within a given study, it seems worthwhile to attempt to standardize against a relevant additional EBC component, such as the conductivity of a lyophilized sample or ion measurements (10,12), total protein, or urea measurement (9). Indeed, in comparison to bronchoalveolar lavage, it may be easier to obtain a reliable dilution indicator for EBC, because unlike BAL, there is no reasonable mechanism by which collection of EBC significantly alters the airway lining fluid (11).…”

Exhaled Breath Condensate as an Alternative Sample for Drug Monitoring

“…However, there are two problems when comparing these reported levels of drugs in EBC: there are very wide variations in the reported levels (e.g., 4.8-29,800 pg/min for methadone [12]) and the different units (i.e., pg/filter, pg/min, mg/l and parts per million by volume) used to express the EBC levels of the analyte which cannot easily be converted for comparison with each other. Variations in analyte concentrations can be partially controlled using normalization by the sum of sodium and potassium concentrations [20] or by measuring the conductivity [21] of the collected EBC samples. Regarding the different units used, a standard and validated collection device and an approved collection procedure should be agreed upon by an expert panel, so that a harmonized unit can be proposed for reporting the levels of analytes in EBC.…”