Objective Assessment of Orofacial Muscle Strength: Validation of an Alternative Low-Cost Measurement Device

Objective: Accurate measurement of orofacial muscle strength is essential for phenotyping patients with obstructive sleep apnea (OSA), and particularly those with hypotonic phenotypes. High costs associated with gold standard devices such as the Iowa Oral Performance Instrument (IOPI®) limit their clinical use. This study aims to validate the Sandway® manometer, a low-cost alternative to the IOPI®, by comparing its performance against the IOPI® and the Tongue Digital Spoon (TDS) in both laboratory and clinical settings. Methods: We conducted a two-phase study. In the laboratory phase, pressure readings from the IOPI® and Sandway® devices were compared using standardized force application methods. In the clinical phase, 60 patients with moderate-to-severe untreated OSA underwent orofacial strength evaluation using IOPI®, Sandway®, and TDS devices. Intraclass Correlation Coefficient (ICC), Bland–Altman analysis, and Pearson correlation were used to assess reliability and agreement. Results: The Sandway® showed excellent reliability for anterior tongue and lip strength measures (ICC = 0.978). Bland–Altman plots revealed minimal bias and narrow limits of agreement compared to the IOPI®, indicating strong agreement for both tongue and lip measurements. A high correlation was also observed between Sandway® and TDS results (r = 0.863, p < 0.001), supporting secondary validation. Conclusions: The Sandway® manometer demonstrates high reliability and strong agreement with gold standard instruments, representing a valid, accessible alternative for objective assessment of orofacial muscle strength in clinical practice.