Mask ventilation during induction of anesthesia can be improved by administration of neuromuscular blocking agents (NMBAs). NMBAs are usually administered after testing mask ventilation; however, muscle relaxants may improve mask ventilation and they do not alter mask ventilation. Thus, growing evidence suggests to administer muscle relaxants before testing mask ventilation. We will study different dosages of rocuronium; we assume that higher dosages of rocuronium will improve mask ventilation compared with lower dosages.