Gastroesophageal reflux disease and pulmonary function: A potential role of the dead space extension

BACKGROUND To evaluate the differences in the existence and size of dead space in patients with and without Gastroesophageal Reflux Disease (GERD and non-GERD) expressed through the size of intrapulmonary shunt (QS/QT). MATERIAL/METHODS The study enrolled 86 subjects - 43 patients referred for endoscopy because of symptoms of GERD (heartburn, acid regurgitation, dysfagia) and 43 healthy subjects with similar anthropometric characteristics without GERD symptoms. Based on endoscopy findings, patients were classified into the erosive reflux disease (ERD) group and non-erosive reflux disease (NERD) group. Spirometry values, single-breath diffusing capacity of the lung for carbon monoxide (DLCO) and intrapulmonary shunt (venous shunt - QS/QT) determined by the oxygen method were measured in all participants. RESULTS Statistically significant differences between GERD and non-GERD groups in FVC (p=0.034), FEV1 (p=0.002), FEV1/FVC (p=0.001), and PEF (p=0.001) were observed. There were no statistically significant differences in FEF 25% (p=0.859), FEF 50% (p=0.850), and FEF 75% (p=0.058). Values of DLCO (p=0.006) and DLCO/VA (p=0.001) were significantly lower and QS/QT was significantly higher (p=0.001) in the GERD group than in the non-GERD group. However, in both groups the average values of DLCO and DLCO/VA expressed as a percentage of predictive values were within normal range, while the value of QS/QT in the GERD group showed pathological (6.0%) mean value (normal value ≤ 5.0%). There were no significant differences in respiratory function test results between patients with ERD and NERD. CONCLUSIONS Our results suggest that microaspiration of stomach contents may cause surfactant damage, development of microatelectasis, and dead space expansion with consequent increase of intrapulmonary (venous) shunt.