The investigators hypothesize that compared to the use of remifentanil-based MAC protocol, the use of dexmedetomidine-based MAC protocol for EBUS-TBNA will result in a lower incidence of major respiratory and hemodynamic adverse events (bradypnea, apnea, oxygen desaturation, hypotension, hypertension, bradycardia and tachycardia) with equivalent overall procedure conditions.