<prompt> Severe obstructive sleep apnea is defined as an apnea-hypopnea index of greater than?10 events hour15 events hour20 events hour30 events hour  <response>: Obstructive sleep apnea hypopnea syndrome quantification and severity scale is graded according to number of apnea hypopnea index events per hour Mild OSAHS 5 -14 events hour Moderate OSAHS 15-29 events hour Severe OSAHS 30 events hour 