Background: Respiratory symptoms are present in up to 50% of GERD patients and are the primary or sole symptoms in 20-25%. The well described role of both reflex and reflux mechanisms, coupled with the lack of optimal diagnostic tests, make assessment of the role of GERD in symptom causation a challenge. The aim of this study was to assess the association of gastroesophageal reflux with O2 saturation in patients with and without respiratory symptoms using combined simultaneous ambulatory monitoring systems.
Methods: The study population consisted of 11 patients with symptoms of GERD in which 443 reflux episodes were detected by MII-pH study. Eight patients had primary respiratory symptoms (cough, wheezing, hoarseness), and 3 typical symptoms (heartburn and regurgitation). All patients underwent simultaneously timed 24 hr MII-pH and continuous O2 saturation monitoring via ambulatory reflux and pulse-oximetry monitoring. Reflux events were defined by 24hr esophageal pH and/or impedance and O2 desaturation by one of 3 possible observations; 1) O2 saturation <90%, 2) O2 saturation drop of 7%, and 3) any event 7% below the mean saturation over 24 hours. Proximal reflux was defined by pH <4 20cm above the LES or reflux in proximal 2 impedance channels. A reflux-desaturation association was considered present if O2 desaturation occurred within 30 seconds prior to or 10 minutes after a reflux event.
Results: Three hundred thirty eight reflux events occurred in patients with primary respiratory symptoms and 105 in those with typical GERD symptoms. Nearly 60% of these 443 reflux events were associated with O2 desaturation. Markedly more events were associated with O2 desaturation in patients with respiratory symptoms (68%, 229/338) than in patients with typical reflux symptoms (25%, 26/105, p<0.01). The difference in reflux-desaturation association was even more profound when proximal reflux events were compared, occurring in 76% (130/171) of patients with respiratory symptoms vs 14% (8/56) of those with typical GERD symptoms (p<0.01).
Conclusion: There is a remarkably high prevalence of oxygen desaturation associated with esophageal acidification in patients with primary respiratory symptoms. This novel observation adds to our understanding of the pathogenesis of GERD related respiratory symptoms and, given further study, may prove to be a useful diagnostic test in this difficult group of patients.