Exhaled breath condensate pH standardised for CO2 partial pressure

• Published in: The European respiratory journal Vol. 29; no. 3; pp. 496 - 501
• Main Authors: Kullmann, T, Barta, I, Lazar, Z, Szili, B, Barat, E, Valyon, M, Kollai, M, Horvath, I
• Format: Journal Article
• Language: English
• Published: Leeds Eur Respiratory Soc 01.03.2007; Maney
• Subjects: Acid-Base Equilibrium - physiology; Adult; Asthma - physiopathology; Biological and medical sciences; Biomarkers - blood; Breath Tests; Carbon Dioxide - blood; Female; Forced Expiratory Volume - physiology; Humans; Hydrogen-Ion Concentration; Male; Medical sciences; Middle Aged; Partial Pressure; Pneumology; Reference Values; Regression Analysis; Reproducibility of Results; Vital Capacity - physiology; airway inflammation; Expired air; Carbon dioxide; Biological marker; Biology; Inflammation; Airway biology; Breath test; Partial pressure; exhaled breath condensate; pH; exhaled biomarkers; Respiration; Pneumology
• ISSN: 0903-1936; 1399-3003
• DOI: 10.1183/09031936.00084006

Exhaled breath condensate (EBC) pH is considered to reflect the acid-base balance of the airways. Current pH measurements do not take into account the effect of CO2. The aim of the present study was to determine the effect of condensate CO2 partial pressure on pH and to provide a more precise mode of EBC pH determination. Condensate pH and CO2 partial pressure were measured in parallel from 12 healthy volunteers and 12 asthmatics using a blood gas analyser in neat, argon de-aerated and CO2-loaded samples. The regression analysis was used to test the relationship between pH and CO2, and to calculate the pH at a CO2 level of 5.33 kPa (physiological alveolar CO2 partial pressure). Reproducibility of different pH readings was compared using the Bland-Altman test. Condensate CO2 concentration was variable both in neat and argon de-aerated samples. There was a close negative logarithmic relationship between CO2 and pH. Calculation of pH at a CO2 level of 5.33 kPa provided reproducibility approximately six times as good as that of the currently used measurements. Condensate CO2 partial pressure influences pH measurements. Determination of pH at a standard CO2 level provides the most reproducible condensate pH values to date.