Kullmann T, Barta I, Lázár Z, Szili B, Barát E, Valyon M, Kollai M, Horváth I
Dept of Pathophysiology, National Korányi Institute for Tuberculosis and Pulmonology, Budapest, Hungary.
Eur Respir J. 2007 Mar;29(3):496-501. doi: 10.1183/09031936.00084006. Epub 2006 Nov 1.
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.
呼出气体冷凝液（EBC）的pH值被认为可反映气道的酸碱平衡。目前的pH测量未考虑二氧化碳的影响。本研究的目的是确定冷凝液二氧化碳分压对pH值的影响，并提供一种更精确的EBC pH值测定方法。使用血气分析仪对12名健康志愿者和12名哮喘患者的纯净、氩气脱气和加载二氧化碳的样本同时测量冷凝液pH值和二氧化碳分压。采用回归分析来检验pH值与二氧化碳之间的关系，并计算二氧化碳水平为5.33 kPa（生理肺泡二氧化碳分压）时的pH值。使用Bland-Altman检验比较不同pH读数的可重复性。纯净样本和氩气脱气样本中的冷凝液二氧化碳浓度均存在变化。二氧化碳与pH值之间存在紧密的负对数关系。计算二氧化碳水平为5.33 kPa时的pH值，其可重复性约为目前所用测量方法的六倍。冷凝液二氧化碳分压会影响pH测量。在标准二氧化碳水平下测定pH值可提供迄今为止最具可重复性的冷凝液pH值。
