TOPICS: Disrupted sleep, daytime somnolence, central sleep apnea, cheyne stokes respiration, CPAP, obstructive sleep apnea, bulky tongue, crowded oropharynx, loud snoring, gasping respiration, weight loss, hypoglossal nerve stimulation, obesity hyperventilation syndrome, PCO2, PO2, A-a gradient, systemic hypertension, pulmonary hypertension, right heart failure, secondary polycythemia