Although the majority of the patients receiving dexmedetomidine required rescue sedations with thiamylal , the respiratory disturbance index ( RDI ) defined as the total number of sleep-disordered breathing events divided by the recording time ( @ @ vs. @ @ events/h ; P < @ ) and movement index defined as the number of body movement events per hour ( @ @ vs. @ @ events/h ; P = @ ) were both significantly lower in the dexmedetomidine arm than in the thiamylal arm .