Pressure experiment using pig arteries. (a) Pressure-test circuit. (b) Experimental schema. Asterisk (*) showing a pig artery: the distal end was closed using a stapler and the proximal end was clamped using Kelly forceps. Arrow showing the pressurized side with a 22-gauge needle in the vessel lumen. Double asterisk (**) showing the measuring instrument (PG208; Nidec Copal Electronics Corp.).