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Background: Current diagnostic techniques aimed at establishing gastroesophageal reflux disease (GERD) as the underlying cause in patients presenting with respiratory symptoms are poor. We previously reported preliminary data suggesting that quantifying the association between reflux events and oxygen desaturation may be a useful discriminatory test. The aim of this study was to further refine the proof of principle by assessing whether antireflux surgery normalizes reflux-associated desaturations and to establish normal values.
Methods: Forty seven patients with GERD-related respiratory symptoms, 10 with typical symptoms, and 11 normal subjects underwent simultaneous 24-hour multichannel intraluminal impedance (MII)-pH and pulse-oximetry monitoring. Eight patients returned for post-Nissen studies. Acid reflux episodes were defined as pH<4 5cm (distal) or 20cm (proximal) above LES and non-acid episodes as a drop ≥50% from baseline in impedance 3, 5, 7 or 9cm above LES (distal) and 15 or 17cm above LES (proximal). Oxygen (O2) desaturation events were defined as a drop in O2 saturation <90%, or a decrease ≥6%. Reflux-associated desaturation (RAD) was defined as the first O2 desaturation event occurring within a 5-minute interval following a reflux episode. Values are expressed as median ±IQR.
Results: Patients with typical symptoms had a median of 65, those with respiratory symptoms 64 and normal subjects 26 distal reflux events/24 hours. There was no significant difference in reflux events extending proximally in the 3 groups; 47% (380/804) typical, 45% (1411/3166) respiratory and 41% (114/276) in normal subjects. The number of distal reflux events associated with O2 desaturation was significantly greater in patients with respiratory symptoms 14 (9-20) than those with typical symptoms 5 (1-6; p<0.001) or normal subjects 2 (1-5; p<0.001). This was also true for the number of proximal RADs: 7 (4-13) in patients with respiratory symptoms versus 2 (0-3; p<0.001) with typical symptoms and 1 (0-2; p<0.001) in normals. Repeat study in 8 post-Nissen patients showed marked improvement with RADs approaching those of normal subjects in 6/8; 20 (9-20) distal pre-operative versus 3 (2-5; p=0.05) post-operative; and 12 (2-15) proximal pre-operative versus 2 (0-2) post-operative. Two post-operative patients were found to have recurrent GERD; minimal improvement and/or worsening in the number of RADs were identified in each patient. Using a threshold of 95th %tile of normal subjects, the number of RADs equaled or exceeded normal in 81% (38/47) of patients with respiratory symptoms.
Conclusions: These data provide further proof of principle that measurement of the association between reflux events and oxygen desaturation may be a useful discriminatory test in GERD patients presenting with primary respiratory symptoms, and may predict response to antireflux surgery.