Technology Insight

Technology Insight: the role of impedance testing for esophageal disorders

Figure 1. A combined impedance–pH catheter consisting of six impedance channels and two pH sensors

Figure 2. Impedance patterns

(A) Antegrade bolus movement during a swallow. (B) Retrograde movement of a liquid bolus during a reflux event. (C) Retrograde flow of gas resulting in an impedance increase in all channels as seen during a belch. (D) An example of a mixed reflux event, containing both gas and liquid. LES, lower esophageal sphincter.

Figure 3. Combined impedance–pH-metry recordings

(A) An example of an acid reflux event. Retrograde flow of liquid is detected by impedance, and simultaneous pH recording shows a pH drop to below 4. (B) Impedance shows the retrograde movement of a liquid bolus; the esophageal pH remains above 4. LES, lower esophageal sphincter.

Figure 4. An example of a swallow of a viscous bolus as detected by combined impedance–manometry recording

The bolus head advance time (BHAT), bolus transit time (BTT) and bolus presence time (BPT) are indicated in the impedance tracing. LES, lower esophageal sphincter.