Normative Reference Values for Pharyngeal Volume and Residue During Swallowing in Healthy Adults: Analysis Using 320-Row Area Detector Computed Tomography

This study aimed to establish reference values for quantitative measurements of pharyngeal volume and residue during swallowing in healthy individuals and to examine how these measurements are influenced by age, sex, height, and bolus properties. We performed a retrospective analysis of 288 swallows from 135 healthy Japanese adults (median age, 43 years; height, 163 cm) who underwent Swallowing CT. Test boluses included thin or extremely thick liquids in either 3 mL, 10 mL, or 20 mL amounts. Pharyngeal cavity volume at bolus hold (PVHOLD), unobliterated air and bolus volume at maximum pharyngeal constriction (PVMAX), and pharyngeal volume constriction ratio (PVCR), and post-swallow pharyngeal residue were measured on dynamic 3D-CT images using a semi-automated software. We determined the 2.5th, 50th, 97.5th percentile values to obtain normative reference values for each parameter and made generalized linear regression models to determine how these volume measurements are associated with demographic factors and bolus properties. Normative values (median [97.5th percentile]) across all swallows were PVHOLD 20.9 cm³ [38.6 cm³], PVMAX 0.3 cm³ [2.1 cm³], PVCR 98.8% [2.5th percentile 89.1%], and residue 0 cm³ [0.4 cm³]. Males exhibited larger values than females. PVHOLD significantly increased with height (β = 0.465, p < 0.001) and age (β = 0.068, p = 0.001), while PVMAX and PVCR increased with larger bolus volumes (β = 0.293, p = 0.005) and in thicker consistencies (β = 0.376, p = 0.017). Pharyngeal residue was present in 98/288 (34.0%) of swallows and was significantly associated with increasing bolus volume (adjusted odds ratio [aOR] = 1.865 [95% confidence interval: 1.275–2.727]), age (aOR = 1.025 [1.010–1.040]), thicker bolus (aOR = 1.806 [1.275–2.727]). Each 1 cm² increase in PVMAX was associated with nearly double the odds of residue (aOR = 1.86 [1.202–2.862]). Similarly, each 1% decrease in PVCR corresponded to a 10.6% increase in the odds of residue (aOR = 1.106 [1.015–1.295]). These normative data provide a bases for comparing individuals with or without pharyngeal impairments.