Relationship between exhaled breath condensate volume and measurements of lung volumes

Exhaled breath condensate (EBC) is proving to be a technique which can sample markers of lung inflammation; however, many factors affect the collection process.

We hypothesised that lung volumes--tidal volume, minute volume and total lung capacity (TLC)--would dictate the volume of the EBC sample that could be collected.

First, the volume of EBC collected was measured while measuring the tidal volume and minute volume in normal, asthmatic and chronic obstructive pulmonary disease subjects. Second, the volume of EBC was compared between breathing at tidal volumes and breathing at vital capacity in normal subjects. TLC was measured by plethysmography.

The mean EBC volume was 5.55 +/- 0.50 microl/breath in normal subjects (n = 23), 3.56 +/- 0.33 microl/breath in chronic obstructive pulmonary disease patients (n = 25) and 5.77 +/- 0.50 microl/breath in asthmatic subjects (n = 17). EBC volume was significantly correlated with both tidal volume (Pearson's r = 0.775, p < 0.0005) and minute volume (Pearson's r = 0.425, p < 0.0005), but importantly, EBC volume was not significantly affected by age, gender or disease status. There was a significant difference in EBC volume when tidal breathing was compared with breathing at vital capacity (5.55 +/- 0.50 vs. 20.59 +/- 1.72 microl; p < 0.0001). No significant correlation was found between EBC volume and TLC (21 normal subjects).

These results suggest that tidal and minute volume can predict the amount of EBC that can be expected to be collected. No significant differences in the volume of EBC were seen between normal subjects and those with airway diseases.