Assessment of intraluminal impedance for the detection of pharyngeal bolus flow during swallowing in healthy adults

Abstract

Intraluminal impedance, a nonradiological method for assessing bolus flow within the gut, may be suitable for investigating pharyngeal disorders. This study evaluated an impedance technique for the detection of pharyngeal bolus flow during swallowing. Patterns of pharyngoesophageal pressure and impedance were simultaneously recorded with videofluoroscopy in 10 healthy volunteers during swallowing of liquid, semisolid, and solid boluses. The timing of bolus head and tail passage recorded by fluoroscopy was correlated with the timing of impedance drop and recovery at each recording site. Bolus swallowing produced a drop in impedance from baseline followed by a recovery to at least 50% of baseline. The timing of the pharyngeal and esophageal impedance drop correlated with the timing of the arrival of the bolus head. In the pharynx, the timing of impedance recovery was delayed relative to the timing of clearance of the bolus tail. In contrast, in the upper esophageal sphincter (UES) and proximal esophagus, the timing of impedance recovery correlated well with the timing of clearance of the bolus tail. Impedance-based estimates of pharyngoesophageal bolus clearance time correlated with true pharyngoesophageal bolus clearance time. Patterns of intraluminal impedance recorded in the pharynx during bolus swallowing are therefore more complex than those in the esophagus. During swallowing, mucosal contact between the tongue base and posterior pharyngeal wall prolongs the duration of pharyngeal impedance drop, leading to overestimation of bolus tail timing. Therefore, we conclude that intraluminal impedance measurement does not accurately reflect the bolus transit in the pharynx but does accurately reflect bolus transit across the UES and below.

Esophageal distension during bolus transport: can it be detected by intraluminal impedance recordings?

“…They observed that arrival of the bolus head on the impedance electrodes coincided with the onset of drop in impedance, and nadir impedance corresponds with maximal or peak distension during the passage of bolus. Omari et al also used fluoroscopy to determine changes in impedance and upper esophageal sphincter opening in humans and observed that bolus head arrival correlates with a drop in esophageal impedance (10). Limitation of single plane fluoroscopy is, as was the case in Sifrim (3) and Omari (10) studies, that one can’t quantitate the esophageal CSA in fluoroscopic images.…”

“…Omari et al also used fluoroscopy to determine changes in impedance and upper esophageal sphincter opening in humans and observed that bolus head arrival correlates with a drop in esophageal impedance (10). Limitation of single plane fluoroscopy is, as was the case in Sifrim (3) and Omari (10) studies, that one can’t quantitate the esophageal CSA in fluoroscopic images. Furthermore, detection of bolus head on fluoroscopic images is subjective and may not allow precise determination of the arrival time on to impedance electrodes.…”

Maximum upper esophageal sphincter (UES) admittance: a non‐specific marker of UES dysfunction

“…This determination of luminal cross sectional area [22,23] can allow time and position of nadir impedance to be related to maximal luminal distension. Impedance can thus be used to non-radiologically track the bolus in time and space (as the bolus causes distension as it is propelled), a principle which has led to the development of pharyngoesophageal pressure flow analysis (PFA) [13][14][15][16]. In this context, the nadir impedance value has been shown to relate to UES opening, measured during simultaneous radiology [24].…”

Implementation of High-resolution Manometry in the Clinical Practice of Speech Language Pathology

“…Automated analysis holds the promise of standardizing measures, with algorithms that can maximize use of spatiotemporal data in representing swallowing physiology [21, 30, 31]. The value of impedance data in the pharynx may be greater when combined with manometric measures in composite analysis [29, 32]. Ongoing research is needed to provide the evidence base that can define the role of HRM in swallowing care delivery.…”

“…Saline is utilized as bolus medium to allow for display of impedance, which can indicate the presence of residual saline remaining in the pharynx or esophagus following the swallow. However, the role of impedance measures within the pharynx has remained uncertain as measures have not correlated temporally to represent bolus clearance in a standard manner as utilized and verified at the UES and esophagus [29]. Measured volumes are presented via syringe, with the patient instructed to hold bolus volumes prior to swallowing.…”