Variability of exhaled breath condensate pH in lung transplant recipients.

Background: Measurement of pH in exhaled breath condensate (EBC) may represent a novel method for investigating airway pathology.

Objectives: The aim of this longitudinal study was to assess the variability of EBC pH in stable lung transplant recipients (LTR).

Methods: During routine clinical visits 74 EBC pH measurements were performed in 17 LTR. EBC pH was also measured in 19 healthy volunteers on four separate occasions. EBC pH was determined at standard CO2 partial pressure by a blood gas analyzer.

Results: Mean EBC pH in clinically stable LTR and in controls was similar (6.38 +/- 0.09 vs. 6.44 +/- 0.16; p = nonsignificant). Coefficient of variation for pH in LTR and controls was 2.1 and 2.3%, respectively. The limits of agreement for between-visit variability determined by the Bland-Altman test in LTR and healthy volunteers were also comparable (-0.29 and 0.46 vs. -0.53 and 0.44).

Conclusions: Our data suggest that the variability of EBC pH in stable LTR is relatively small, and it is similar to that in healthy nontransplant subjects.