 The aim of this study is to determine the relation between arterial diameter and flow of carotis interna, brachial artery and radial artery before and after valsalva maneuver. A total of 70 patients in preoperative period will enroll in this study. After a deep inspiration, patients will asked to exhale to a valf system with a flow pressure of 20-40 mmHg and duration of 15 seconds. During valsalva maneuver, the diameter and flow rates of carotis interna, brachial artery and radial artery will measure using ultrasound. All data will be recorded. 