A simple method for estimating respiratory solute dilution in exhaled breath condensates.

Exhaled breath condensates have been widely used to detect inflammatory mediators in the fluid that covers airway surfaces of patients with inflammatory lung disorders. This approach is much less invasive than bronchoalveolar lavage, but respiratory droplets are markedly diluted by large and variable amounts of water vapor. We estimated the dilution of respiratory droplets by comparing concentrations of nonvolatile, reference indicators (total nonvolatile cations, urea or conductivity) in 18 normal subjects with normal plasma concentrations by assuming similar concentrations in the respiratory fluid and plasma.

Exhaled breath condensates: a potential novel technique for detecting aspiration.

There is an urgent need for diagnostic procedures that can detect aspiration of oral and gastrointestinal (GI) secretions into the respiratory tract. Current approaches are limited by poor sensitivity and specificity. These techniques include (1) adding indicators to feedings; (2) recovery of lipid-filled macrophages in respiratory secretions; (3) measurement of changes in the pH of the upper GI and respiratory tracts; (4) endoscopic visualization of reflux events; and (5) measurement of increased glucose concentrations in respiratory secretions.

Dilution of respiratory solutes in exhaled condensates.

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.