Significance: Respiratory depression due to oversedation was identified twice as the major factor responsible for claims related to anesthesia. The high prevalence of obstructive sleep apnea combined with more complex procedures done in outpatient settings can increase physical risks to patients and liability cases to anesthesiologists. The main goal of this project is to establish the effect of ketamine in preventing respiratory depression to patients undergoing procedures under sedation. If the investigators confirm the their hypothesis , their findings can be valuable not only to anesthesiologist but also to other specialties ( Emergency medicine, gastroenterologists, cardiologists, radiologists) that frequently performed procedural sedation. The research questions is;does ketamine prevent hypoventilation during deep sedation? The hypotheses is; ketamine will prevent hypoventilation during sedation cases.