241 Increased Reflux Severity on Impedance Predicts One-Year Pulmonary Function Decline in Pre-Lung Transplant Patients With Idiopathic Pulmonary Fibrosis

Abstract

Background: Gastroesophageal reflux (GER) has been associated with pulmonary disease in pre-lung transplant patients, especially idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). The mechanism of these associations remains controversial. Microaspiration of refluxate may lead to inflammatory changes and pulmonary fibrosis or airway disease. Worsening pulmonary function may also increase trans-diaphragmatic pressure gradient, magnifying GER. The association between GER and decline in lung function in these patients has not yet been demonstrated. Evaluating the relationship between objective reflux parameters and change in pulmonary function may help clarify pathophysiology and identify targets for treatment. Aim: To investigate the association between objective measures of reflux on multichannel intraluminal impedance and pH study (MII-pH) and change in pulmonary function testing (PFT) parameters over one year, in pre-lung transplant patients with IPF or COPD. Methods: This was a retrospective cohort study of adults with IPF or COPD who underwent pretransplant evaluation with MII-pH, off acid suppression, at a tertiary care center from 6/2010-14. Patients with fundoplication prior to MII-pH were excluded. PFT was performed within 1 month of MII-pH and at 12-month follow-up. Association between baseline reflux measures and change in PFT parameters over one year was evaluated using Student's t-test for continuous variables and Fisher's exact test for binary variables. Results: 57 subjects (mean age=60 yrs, 42% female, 37 IPF vs 20 COPD) met criteria for inclusion. Among IPF patients, abnormal bolus reflux on impedance was associated with a significant decline in forced expiratory volume in 1 second (FEV1) in 1 year (-0.048 L/sec vs +0.24 L/sec, p=0.041), as was increased acid exposure time (-0.195 L/sec vs +0.144 L/sec, p=0.05). Trends toward more severe decline in forced vital capacity (FVC) in 1year for both abnormal bolus reflux (-0.085 L/sec vs +0.25 L/sec, p=0.09) and increased acid exposure time (-0.28 L/sec vs +0.147 L/sec, p=0.10) were also observed. Among COPD patients, trends toward more severe decline in FEV1 in 1 year was noted for increased acid exposure time (-0.27 L/sec vs -0.035 L/sec, p=0.087). No other significant associations between change in PFT and abnormal MII-pH parameters were found (Table 1). Conclusion: Abnormal GER as measured on MII-pH predicts more severe decline in lung function in 1 year on PFT among pre-lung transplant patients with IPF. A similar association between GER and lung function decline was not found in COPD patients. GER may play a more significant role in the pathogenesis of IPF than COPD. Future long-term studies are needed to further characterize the effect of GER on severity and prognosis of pulmonary disorders. Association between measures of reflux severity and worse pulmonary function (FEV1) after 1 year in patients with IPF.