The role of control of peri-pharyngeal muscle tone in the pathogenesis of obstructive sleep apnea (OSA) is obvious: pharyngeal obstruction occurs only during sleep; and pharyngeal collapse occurs in almost all healthy subjects during anesthesia. Better understanding of these control mechanisms may help identifying the central components of the pathogenesis of OSA.

Study plan: Subjects will be studied first during wakefulness, while breathing against external resistors, to evaluate how are the peri-pharyngeal muscles recruited and activated to prevent pharyngeal collapse in the presence of negative intra-pharyngeal pressures. Thereafter, the same parameters will be evaluated during sleep, to assess muscle recruitment during intra-pharyngeal obstruction. The investigaors will record the electromyogram (EMG) of several dilator muscles, as well as the pressures above and below the area of pharyngeal collapse, and airflow.

Inclusion Criteria:

1. subjects that underwent regular sleep studies and found to have either moderate/severe OSA, or no OSA.

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Exclusion Criteria:

1. hemophilia
2. use of anti-coagulants -

adult subjects with and without sleep apnea