RESUMEN
B-mode ultrasound is a safe noninvasive procedure that has been used to characterize aspects of the oropharyngeal swallow. The submental suprahyoid muscles are often investigated with ultrasound because of their contributions to hyolaryngeal elevation. There are several techniques for positioning the ultrasound transducer in the coronal plane, however, there is limited research on how reliability of measurement of the cross-sectional area (CSA) of the geniohyoid differs across transducer placement technique. This study examined three methods of transducer placement in the coronal plane by two examiners to determine the reliability of measurement of CSA of the geniohyoid muscle. Forty healthy adults participated in the study. Each participant's geniohyoid muscles were imaged using B-mode ultrasound under three transducer placement conditions in the coronal plane by two examiners. Geniohyoid CSA was measured from each ultrasound image. A three-way mixed-methods ANOVA was used to determine whether there were significant differences in geniohyoid CSA among transducer position conditions, trials, and examiners. There were significant differences among the transducer placement conditions, indicating that each condition was measuring a different portion of the muscle. There were no significant differences among repeated trials nor between examiners within each method of transducer placement. All three conditions of transducer placement were reliable at measuring geniohyoid CSA across trials and examiners. This study emphasizes the need for consistency of placement, whichever method is selected. It also highlights the need for researchers to provide a precise description of methods for positioning the transducer so that placement is reproducible.
RESUMEN
Expiratory muscle strength training (EMST) is an exercise program designed to strengthen the muscles of expiration by increasing expiratory load during breathing exercises using either resistive or pressure threshold devices. Previous research has shown that EMST may increase submental suprahyoid muscle activity as measured with surface electromyography. The impact of EMST on submental muscles is of interest to those who treat dysphagia. The purpose of this study was to determine whether the cross-sectional area of the geniohyoid muscle changes as observed with ultrasound during a 5-week EMST program performed at 75% of maximum expiratory strength using the EMST150 device in healthy adults. Ten healthy adults participated in the 5-week program. Maximum expiratory pressure (MEP) and cross-sectional area of the geniohyoid muscle were measured weekly. Geniohyoid cross-sectional area was measured from ultrasound images recorded in the coronal plane. Repeated Measures ANOVA was used to determine whether there were significant changes among the dependent variables over the study period. Both MEP and geniohyoid area increased significantly in response to a 5-week program of EMST. EMST in healthy adults is effective at strengthening the geniohyoid muscle as reflected by significantly increased cross-sectional area measured with B-mode ultrasound. This is the first study to document weekly change in muscle morphology as a result of EMST. Increasing geniohyoid muscle mass and consequent strength through a program of EMST may be beneficial for persons with pharyngeal stage dysphagia resulting from reduced hyolaryngeal elevation, reduced laryngeal closure, or reduced UES opening.