Pulmonary function and gastroesophageal reflux in systemic sclerosis

Objective: To determine the relations among esophageal dysfunction, gastroesophageal reflux, and lung involvement in patients with systemic sclerosis. Design: Retrospective review of esophageal motility, esophageal pH, and pulmonary function data. Setting: University hospital outpatient clinic and community. Patients: 39 consecutively referred patients who were grouped according to the presence or absence of abnormal distal (pH <4.0 for >5% of the 24-hour monitoring period) or proximal (pH <4.0 for >1% of the 24- hour period) gastroesophageal acid reflux. Patients were also grouped according to the presence or absence of distal esophageal peristalsis. Measurements: Esophageal manometry, dual-probe (distal and proximal) esophageal 24-hour pH measurements, and pulmonary function studies (forced vital capacity, forced expiratory volume at 1 second, total lung capacity, and single-breath carbon monoxide diffusing capacity [DL(co)]). Results: The mean total lung capacity (values as percentage predicted) was 87.1% ± 11.2% (SD) for patients with abnormal proximal reflux and 77.8% ± 21.6% for patients with normal proximal reflux (difference, 9.3%; 95% CI, -1.4% to 20.0%). The mean forced vital capacity for these patients was 91.1% ± 12.4% and 85.4% ± 25.6%, respectively (difference, 5.7%; CI, -6.9% to 18.1%). The mean total lung capacity was 83.8% ± 15.4% for patients with abnormal distal reflux and 77.9% ± 22.7% for patients with normal distal reflux (difference, 5.9%; CI, -7.6% to 19.4%). Among potential confounders of pulmonary measures, only smoking was related to decreased pulmonary function (smoking related to decreased DL(co) P < 0.01). Smoking was more common in patients with abnormal distal reflux than in those with normal distal reflux (65% compared with 25%, P = 0.03). After adjusting for smoking, the difference in mean DL(co) between patients with abnormal compared with normal distal reflux was 7.19% (CI, - 8.5% to 22.9%). Conclusion: Important measures of lung volume indicative of interstitial lung disease (total lung capacity, forced vital capacity) do not appear to be related to abnormal gastroesophageal acid reflux in patients with systemic sclerosis.