• bronchoscopy;
  • gastroesophageal reflux disease;
  • lactate dehydrogenase;
  • pulmonary function test


Background and objective:  Many researchers have investigated the pH of exhaled breath condensate but direct measurement of pH in the lung has not been performed in vivo in humans. We hypothesized that the pH measured directly in the lung would differ between healthy subjects and patients with gastroesophageal reflux disease (GERD). We also wished to determine whether an acidic environment in the lung influences pulmonary function and DLCO, and whether microaspiration of gastric contents directly influences non-specific inflammation in the lung.

Methods:  The patients were otherwise healthy individuals who had been newly diagnosed with GERD. The control subjects were mostly volunteers who underwent bronchoscopy for different reasons. For all subjects (n = 63) a medical history was taken, and physical examination, oesophagogastroduodenoscopy, fibre-optic bronchoscopy and pulmonary function testing were performed.

Results:  In patients with GERD the average pH in the lung was 5.13 ± 0.43; this was significantly lower than the pH in the lung of controls 6.08 ± 0.39 (P = 0.001). Patients with GERD had lower FEV1% (P = 0.035), PEF (P = 0.001), FEF50% (P = 0.002) and FEF25% (P = 0.003), while the differences in FVC% and FEF75% were not significant. DLCO (P = 0.003), as well as transfer coefficient of the lung (P = 0.001), was lower in patients with GERD. LDH levels in bronchoalveolar aspirate were higher in the patients with GERD (P = 0.001).

Conclusions:  This study found evidence of cell and tissue injury in the lung, a lowering of pH and higher bronchoalveolar aspirate LDH levels in patients with GERD compared with healthy subjects. These findings suggest that pulmonary function, and especially DLCO, should be evaluated in patients presenting with GERD.