Background Postswallow residue is indicative of impaired pharyngeal bolus clearance. The integrated nadir impedance to impedance ratio (iZn/Z) is a novel functional variable that can be derived using automated impedance manometry (AIM). In this study, the postswallow pharyngeal iZn/Z was evaluated as a potential correlated postswallow residue and therefore predictor of ineffective swallowing. Methods Optimal iZn/Z criteria were determine using a database of 50 randomly selected bolus swallows recorded with impedance, manometry, and videofluoroscopy. The iZn/Z was derived for a region of interest (ROI), spanning the mid-point of the pharyngeal stripping wave to the upper esophageal sphincter proximal margin, and from 0.25 to 1.25s after the peak of the pharyngeal stripping wave. Videofluorscopy was scored by four experts using a six-point bolus residue scale (BRS) score. Optimized criteria for iZn/Z were then applied to a much larger database of 225 swallows scored for residue by one expert observer. Key Results Among individual database, swallows iZn/Z was significantly correlated with average expert BRS score (r=0.748, P<0.0001). An iZn/Z of ≥500 was optimally predictive of swallows with residue defined by a BRS score of 4 or more. Within the larger cohort, iZn/Z was higher in dysphagia patient swallows compared with controls [2 (1, 4) vs 1 (1, 3), P<0.005] and swallows with an iZn/Z≥500 had higher bolus residue scores [4 (1, 6) vs 2 (1, 4), P<0.001]. Conclusions & Inferences The AIM derived iZn/Z is an easily determined objective non-radiological marker of clinically relevant postswallow residue and therefore has potential diagnostic relevance as a predictor of ineffective swallowing.
- Bolus residue
- Deglutition and deglutition disorders
- Electric impedance