The effect of gas standardisation on exhaled breath condensate pH: Fig. 1—

Abstract

We have read with interest the American Thoracic Society/European Respiratory Society Task Force document on exhaled breath condensate (EBC) 1. EBC pH is emerging as a potential biomarker in respiratory disease. Gas standardisation (or de-aeration) of EBC with argon is commonly performed to remove carbon dioxide prior to pH measurement 2–4. It has been argued that CO₂ is unwelcome “noise” in the sample and, although the completeness of CO₂ removal has not been confirmed, gas-standardised EBC pH is stable and provides reproducible measurements 3, 4. However, some authors regard CO₂ as a relevant component of EBC and have measured pH without gas standardisation 5, 6. These variations in methodology make comparison between studies difficult.