SAN DIEGO – Measuring the number of oxygen desaturations a patient has that are coincident with episodes of esophageal acidity may be an effective new way to identify patients who primarily have respiratory symptoms secondary to gastroesophageal reflux, based on results from a controlled study involving 103 people.
"These data provide further proof of principle that reflux-associated oxygen desaturations are more common in GERD [gastroesophageal reflux disease] patients with respiratory complaints, and may be a useful discriminatory test in GERD patients with primarily respiratory symptoms," Dr. Candice L. Wilshire said at the annual Digestive Disease Week.
"We believe that the desaturations are due to reflux, and we think that if you stop the reflux with surgery you should cure it," said Dr. Wilshire, a thoracic surgeon at the University of Rochester (N.Y.). "We believe that looking at the reflux-associated desaturations could identify patients who have pulmonary symptoms due to reflux, as opposed to primarily pulmonary pathology."
But Dr. Wilshire cautioned that counting a patient’s reflux-associated oxygen desaturations is not ready for routine diagnostic use. "Currently, our indications for [antireflux] surgery have not changed," she said. "At the moment, we use a separate esophageal pH catheter and pulse oximeter, and there are some artifacts," which means that this assessment method is still in development, Dr. Wilshire said in an interview. Further research is needed to "discern what are true desaturations" caused by reflux and "what are artifacts. It would be nice to get some software that can do this for us. I think there are things we could do to make [these assessments] easier and to eliminate some of the artifacts."
Having a reliable way to identify patients who experience frequent oxygen desaturation episodes that are secondary to reflux should refine diagnoses and streamline delivery of appropriate treatment to patients, Dr. Wilshire said. "A subgroup of GERD patients have no gastrointestinal symptoms and just complain of a chronic cough. They get sent to us when they’re far down the road, after seeing pulmonologists." Her new approach for identifying the pulmonary consequences of GERD – by counting episodes of oxygen desaturation – may provide a way to more quickly identify these types of patients, she said.
Her study enrolled 37 GERD patients who primarily had respiratory symptoms (cough, hoarseness, or throat clearing), 26 GERD patients who primarily had gastrointestinal symptoms (such as heartburn or epigastric pain), and 40 controls who were asymptomatic.
All participants underwent 24-hour, ambulatory assessment with a pair of measurement devices: a finger-clip device for measuring oxygen saturation, and a multichannel, intraluminal pH impedance monitor to measure esophageal pH. The researchers tallied an oxygen desaturation episode whenever the subject’s blood oxygen level dropped below 90% or at least 6 percentage points below the person’s baseline level. They tallied acid-reflux episodes as times when esophageal pH registered less than 4, in both proximal and distal sites of the esophagus. They considered reflux-associated oxygen desaturations (RADs) to be desaturations that occurred within 5 minutes of a reflux episode.
The results showed that the controls had a median of 3.0 distal RADs during 24 hours, and the 95th percentile number was 11.0 RADs. In comparison, the patients with GERD and gastrointestinal symptoms had a median of 6.5 RADs, significantly more than the controls; the patients with GERD and pulmonary symptoms had a median of 17.0 RADs, significantly more than both the control group and those with gastrointestinal GERD.
The researchers found a similar pattern for proximal acid-episode RADs. The control group had a median of 1.0 episode during 24 hours, with a 95th percentile level of 7.0 episodes. Patients with gastrointestinal GERD symptoms had a median of 3.0 RADs, significantly more than the controls, whereas those with primarily pulmonary symptoms of GERD had a median of 8.0 RADs, significantly more than the controls and the patients with primarily gastrointestinal symptoms.
The percentage of patients with 11 or more distal RADs – the "elevated" threshold, based on the benchmark established by the controls – was 27% in patients with primarily gastrointestinal symptoms of GERD and 70% in those with primarily pulmonary symptoms of GERD. The percentage with an elevated number of proximal RADs (more than 7) was 19% in the gastrointestinal group and 62% in the pulmonary group, Dr. Wilshire reported.
In addition, RAD numbers substantially declined in the small number of patients in the study who had their symptoms improve by undergoing antireflux surgery and who had their RADs measured before and after surgery.
Dr. Wilshire said that she had no disclosures.