After screening and inclusion, participants will be invited to four trial days at the trial site. On each day participants are required to be fasting for 10 hours (including water, coffee and tobacco). A peripheral venous line is inserted into each antecubital vein. An arterial catheter connected to a pressure transducer is inserted into the radial artery in the wrist. In randomized order, one of the four interventions are performed (see below). A standard 12 lead ECG is placed on the participant as well as a 5 lead ECG connected to a computer.