We tested whether positive end-expiratory pressure (PEEP) increases right internal jugular vein (RIJV) cross-sectional area (CSA) in 45 ASA physical status I and II adults. All patients received a standardized IV fluid bolus, induction of general anesthesia, tracheal intubation, and mechanical ventilation. We evaluated the CSA of the RIJV using ultrasound without PEEP (control) and with PEEP (10 cm H(2)O) in the supine, level position. Addition of PEEP increased RIJV CSA 0.42 + or - 0.41 cm(2) (mean + or - SD, median 0.34 cm(2), P < 0.001), which represented a 41% mean increase in CSA.