Читать книгу The Esophagus - Группа авторов - Страница 242

Measurement of esophageal mucosal impedance with a transnasal catheter can be subject to error due to lack of adequate contact with mucosa, intraluminal fluid, and catheter movement [63]. In addition, it is well known that transnasal catheter‐based testing is associated with significant patient discomfort (nose pain, throat pain, cough, chest discomfort), which can lead to alteration in patients’ daily activities (less likely to be active, more difficulty with swallowing, and more likely to skip meals), leading to variable sensitivity of the reflux testing [64, 65]. Thus, a new balloon MI catheter system was developed to diminish measurement variability by incorporating both radial and axial sensors mounted on a balloon to measure esophageal mucosal integrity. The initial design included four axial columns of 9 impedance channels (total of 36) separated by 90‐degree intervals with length of 10 cm mounted on an inflatable balloon (Figure 9.13) [66]. The most recent modification included reduction to two axial columns of 9 channels (total of 18) separated by 180‐degree intervals on the balloon. The MI balloon is introduced into the esophagus through the mouth under endoscopic guidance with the most distal sensors just above the SCJ. Direct contact of the MI sensors with the esophageal epithelium is obtained by inflating an intra‐esophageal balloon assembly in a controlled fashion using a calibrated inflation device [66]. In an initial study of 23 patients with NERD, 27 patients with functional heartburn, and 19 patients with erosive esophagitis, median mucosal impedance was significantly lower in patients with erosive esophagitis. Further, patients with erosive esophagitis and NERD had significantly lower mucosal impedance compared with those with functional heartburn. Also noteworthy was that mucosal impedance showed a graded increase from the distal to the proximal esophagus in patients with objective evidence of GERD, reflecting greater acid exposure distally. Mucosal impedance also showed good predictive value for identifying patients with GERD, with a sensitivity of 88% and a specificity of 65% when using a threshold of 3200 Ω. Perhaps most importantly, the authors demonstrated that this approach was feasible in clinical practice, noting that it added only 2 min to the procedure time [70].

In EoE, mucosal impedance may also play an important role in the assessment of mucosal integrity [71]. In one study, patients with active and treated EoE demonstrated a significant increase in impedance after treatment (2574 vs. 6618 Ω, P <0.01) corresponding to measurements made on biopsy. These findings suggest that histologic response to therapy in EoE results in mucosal healing and a decrease in trans‐epithelial molecule flux, which is a restoration of mucosal integrity [72]. A recent study confirmed the clinical utility of direct mucosal impedance measurement in the assessment of EoE activity, with an inverse correlation between esophageal eosinophil density, dilated epithelial intercellular spaces, and mucosal impedance. Using a cutoff value of 2300 Ω, mucosal impedance demonstrated a sensitivity of 90% and a specificity of 91% for identifying patients with active EoE [73]. Further studies are needed to determine whether measurement of mucosal impedance in patients with EoE could obviate the need for biopsy to assess disease activity.

In summary, using baseline and direct mucosal impedance to assess diseases that alter mucosal permeability is promising, but further studies are needed before widespread clinical application can be recommended.