Airway pH affects and is affected by airways diseases It has roles in mucociliary clearance, infection and drug efficacy in human airways, and is altered by air pollution. Accurate measurement of airway pH is difficult in human subjects. Methods include passing a cytology brush through a bronchoscope, collecting airway surface liquid (ASL), and directly measuring the liquid using filter paper and a skin pH meter. We describe a novel method utilizing a gastric pH probe to directly measure airway surface pH.

Bronchoscopy was performed in three subjects. ASL pH in subcarinal airway was measured by two methods 1. As described above. 2. A gastric pH probe was advanced through the working channel and used to measure pH in the same bronchus.  Three samples using each method were obtained from both the right and left lower lobes.

The pH was similar when measured by skin pH meter or gastric pH probe (means 6.6 and 6.8 respectively). There was no significant difference in pH measured by the different methods (p=0.2 by two sample t-Test assuming unequal variance). The avg difference between the measurements was -0.16+/-0.31, 95% confidence interval -0.78-0.46.

We have developed a novel method to measure airway pH and shown that it results in similar values compared to current methods. Measurement by the gastric probe is faster and less prone to contamination by blood. Due to its smaller size pH of more distal airways can be measured.