Intraesophageal impedance monitoring: clinical studies

Abstract

Electrical impedance (Z) between two electrodes is the ratio between applied voltage (U) and resulting current (I). In electrical impedance monitoring the resistance to electrical flow in an alternating current circuit is measured. Multichannel esophageal monitoring can be measured by using an intraluminal catheter with multiple, closely spaced pairs of metal rings. Changes in temporal-spatial patterns in impedance are identified at various levels within the esophagus, allowing differentiation between antegrade (swallow) and retrograde (reflux) bolus movement. Esophageal impedance monitoring can be used to assess the clearance of a swallowed bolus (esophageal transit) and to detect gastro-esophageal reflux independent of its acidity. In the first part of the thesis, the value of intraesophageal impedance monitoring as a tool to assess esophageal transit was studied in normal subjects, patients with non-obstructive dysphagia and achalasia patients. In the second part, gastro-esophageal reflux patterns was studied using impedance monitoring in patients with functional dyspepsia, patients with gastro-esophageal reflux disease treated with endoscopic gastroplication as well as in patients with erosive esophagitis and non-erosive reflux disease. Using combined impedance and perfusion manometry, normal esophageal bolus clearance was defined as complete clearance of at least 70% of liquid boluses and at least 60% of viscous boluses. Impedance recording identifies esophageal function abnormalities in non-obstructive dysphagia patients with normal manometry, ineffective esophageal motility and diffuse esophageal spasm. The impedance technique seems to be less suitable for the most severe end of the dysphagia spectrum like achalasia. In achalasia patients, low-baseline impedance levels and air entrapment in the proximal esophagus limit the value of intraluminal impedance monitoring as a test of esophageal emptying. Patients with functional dyspepsia swallow air more frequently than controls and this abnormality is associated with an increased incidence of non-acid gaseous gastro-esophageal reflux. Impedance monitoring can identify the specific effect of endoscopic gastroplication on the different types of reflux episodes with regard to gas-liquid composition and pH, as well as on volume clearance and the proximal extent of the refluxate. Whereas patients with erosive esophagitis have more acid reflux episodes in the supine position than patients with non-erosive reflux disease, both groups have similar non-acid reflux patterns.