# The Relationship Between Residue and Aspiration on the Subsequent Swallow: An Application of the Normalized Residue Ratio Scale

Molfenter SM, Steele CM.

Dysphagia. 2013 Mar 5

### Abstract

Postswallow residue is widely considered to be a sign of swallowing impairment and is assumed to pose risk for aspiration on subsequent swallows. We undertook a preliminary retrospective study to investigate the link between postswallow residue and penetration-aspiration on the immediately occurring subsequent clearing swallow (i.e., without introduction of a new bolus). Videofluoroscopy clips for 156 thin-liquid single bolus swallows by patients with neurogenic dysphagia were selected for study because they displayed multiple swallows per bolus. Residue for each subswallow (n = 407) was analyzed using the Normalized Residue Ratio Scale for the valleculae (NRRSv) and piriform sinuses. The association between residue presence at the end of a swallow and penetration-aspiration on the next swallow was examined. Postswallow residue in one or both pharyngeal spaces was significantly associated with impaired swallowing safety on the subsequent clearing swallow for the same bolus. However, when analyzed separately by residue location, only vallecular residue was significantly associated with impaired swallowing safety on the next clearing swallow. The distribution of NRRSv scores by swallowing safety demonstrated an NRRSv cut-point of 0.09, above which there was a 2.07 times greater relative risk of penetration-aspiration. Postswallow vallecular residue, measured using the NRRS, is significantly associated with penetration-aspiration on subsequent clearing swallows. A clinically meaningful cut-point of 0.09 on the NRRSv scale demarcates this risk. Further research with different bolus consistencies is needed.

ACESSE O PERIÓDICO

# Image-based Measurement of Post-Swallow Residue: The Normalized Residue Ratio Scale

Online First™, 22 October 2012

## Abstract

Post-swallow residue is considered a sign of swallowing impairment. Existing methods for capturing post-swallow residue (perceptual and quantitative) have inherent limitations. We employed several different perceptual and quantitative (ratio) methods for measuring post-swallow residue on the same 40 swallows and addressed the following questions: (1) Do perceptual and quantitative methods demonstrate good agreement? (2) What differences in precision are apparent by measurement method (one-dimensional, two-dimensional, and circumscribed area ratios)? (3) Do residue ratios agree strongly with residue area measures that are anatomically normalized? Based on the findings of this series of questions, a new method for capturing residue is proposed: the Normalized Residue Ratio Scale (NRRS). The NRRS is a continuous measurement that incorporates both the ratio of residue relative to the available pharyngeal space and the residue proportionate to the size of the individual. A demonstration of this method is presented to illustrate the added precision of the NRRS measurement in comparison to other approaches for measuring residue severity.