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

Background: Assessment of upper esophageal sphincter (UES) motility is challenging, as functionally, UES relaxation and opening are distinct. We studied novel parameters, UES admittance (inverse of nadir impedance), and 0.2-s integrated relaxation pressure (IRP), in patients with cricopharyngeal bar (CPB) and motor neuron disease (MND), as predictors of UES dysfunction. Methods: Sixty-six healthy subjects (n = 50 controls 20-80 years; n = 16 elderly >80 years), 11 patients with CPB (51-83 years) and 16 with MND (58-91 years) were studied using pharyngeal high-resolution impedance manometry. Subjects received 5 × 5 mL liquid (L) and viscous (V) boluses. Admittance and IRP were compared by age and between groups. A p < 0.05 was considered significant. Key Results: In healthy subjects, admittance was reduced (L: p = 0.005 and V: p = 0.04) and the IRP higher with liquids (p = 0.02) in older age. Admittance was reduced in MND compared to both healthy groups (Young: p < 0.0001 for both, Elderly L: p < 0.0001 and V: p = 0.009) and CPB with liquid (p = 0.001). Only liquid showed a higher IRP in MND patients compared to controls (p = 0.03), but was similar to healthy elderly and CPB patients. Only admittance differentiated younger controls from CPB (L: p = 0.0002 and V: p < 0.0001), with no differences in either parameter between CPB and elderly subjects. Conclusions & Inferences: The effects of aging and pathology were better discriminated by UES maximum admittance, demonstrating greater statistical confidence across bolus consistencies as compared to 0.2-s IRP. Maximum admittance may be a clinically useful determinate of UES dysfunction.