Computerized endopharyngeal myotonometry (CEM): a new method to evaluate the tissue tone of the soft palate in patients with obstructive sleep apnoea syndrome.

Abstract

This study compared the tissue tone of the soft palate in nonsnoring subjects and patients with obstructive sleep apnoea syndrome (OSAS) during wakefulness. Here, tissue tone means the biomechanical property of the tissue which can be characterized by two main parameters: stiffness and elasticity. Tissue tone includes both structural and neural components. A new method to evaluate the tissue tone of the soft palate was used - computerized endopharyngeal myotonometry (CEM). This method records and analyses the response of the soft palate tissues to a brief mechanical impact. The method enabled us to evaluate the most important parameters of tissue tone: stiffness, which is expressed as a frequency; and elasticity, expressed as a logarithmic decrement of the damped oscillation. First, a self-reported questionnaire was completed about the medical history of the subjects. Subjects then underwent a physical examination of the oropharynx and polysomnography with overnight pulse oximetry. The results of the CEM method indicated that patients with OSAS show an increased stiffness of the soft palate tissues (20.3, SD 4.7 Hz) compared with nonsnoring subjects (12.2, SD 1.8 Hz). In patients with sleep apnoea, elasticity is not increased in a similar way to stiffness. Thus, the disproportion between tissue stiffness and elasticity of the soft palate is a measure of the pathological changes in patients with sleep apnoea.