A Comparison of Impulse Oscillometry and Spirometry Values in Patients with Gastroesophageal Reflux Disease

BACKGROUND The relationship between gastroesophageal reflux (GERD) and airway diseases is still a matter of debate. Oscillometry is an objective, independent tool for the evaluation of airway resistance. The main purpose of this study is to compare spirometry and oscillometry results before and after treatment by a proton pump inhibitor (PPI) in a group of GERD patients who have no respiratory symptoms. METHODS This study was performed on patients with endoscopically diagnosed reflux esophagitis who had no pulmonary symptoms. Patients received omeprazole 40 mg, twice a day for 12 weeks. Spirometry and oscillometry were performed before and after treatment. Impulse oscillometry (IOS) was performed by a force oscillation instrument. We recorded respiratory resistance at 5 Hz (R5) and 20 Hz (R20), resonant frequency (Fres), and distal capacitive reactance (X5) for each patient. RESULTS Included were 30 patients (17 males; 13 females) whose mean age was 32 years. According to the Los Angeles Classification, 16 patients had grades B or C esophagitis and 14 had grade A. Although all patients had normal spirometry results, 50% had increased airway resistance according to oscillometric findings. After treatment with omeprazole, only 16.3% had abnormal oscillometry results (p=0.004). Spirometry results [forced expiratory volume at the first second (FEV1); forced vital capacity (FVC); FEV1/FVC; and mean forced expiratory flow 25%-75% (FEF 25%-75%)] showed significant further improvement compared to pretreatment normal values (p<0.001 for all). CONCLUSION Abnormal airway resistance may be present in GERD patients even when there is no obvious respiratory symptom. Oscillometry seems to be more sensitive than spirometry in reporting abnormal pulmonary function in patients with GERD.