Source: Annual Congress 2002 - Monitoring respiratory parameters in critically ill patients
Disease area: Airway diseases, Respiratory critical care

Abstract

Recently we reported about acidification of exhaled breath condensate (EBC) in mechanically ventilated patients with ARDS/ ALI (Eur. Respir. J. 18 (2001), 480s). Acidification of EBC correlated with markers of pulmonary inflammation as well as with lung injury scores (Murray, PaO2/FiO2). We were therefore investigated whether acidification measured in EBC assumingly reflecting peripheral airway epithelial lining fluid was also apparent when measured in situ using a small pH probe inserted through the working channel of the bronchoscope.
EBC pH was measured in 19 ventilated patients and compared to in situ pH measured during bronchoscopy using a small pH probe (Flexilog Antimon single channel catheter with extern reference; Schwa-Medico, Germany) connected to a Flexilog 2000 pH meter. Bronchial mucosal fluid pH was measured in central (main bronchus) and more peripheral airways (lingula) by ensuring a tight approximation of the mucosal surface and the probe tip.
No correlation of EBC pH and either centrally or peripherally measured in situ pH of bronchial mucosal fluid was observed (r=0.41, p=0.08). In addition, in situ pH was significantly higher than EBC pH (7.04 ±] 0.44 vs. 5.76 ±] 0.29; p<0.0001).
Our results suggest that in situ measurement of bronchial mucosal fluid pH does not reflect EBC pH. Most likely EBC is generated in distant airways and lung parenchyma and may therefore reflect different pathophysiologic mechanisms or different buffer capacity. However it is also possible, that the process of vaporization by itself may favor the lower pH in EBC.

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Citations should be made in the following way:
T. Lange, C. Gessner, S. Hammerschmidt, L. Engelmann, J. Schauer, H. Wirtz (Leipzig, Germany). Comparison of exhaled breath condensate pH with pH measured in situ in patients with ARDS/ ALI. Eur Respir J 2002; 20: Suppl. 38, 618

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