Strain gauge plethysmography-A small catheter is placed through a needle into an artery at the bend of the arm for measuring blood pressure and drawing blood samples during the study. Pressure cuffs are placed on the wrist and upper arm, and a strain gauge (a rubber band device) is placed around the forearm to measure forearm blood flow. When the cuffs are inflated, blood flows into the arm, stretching the strain gauge at a rate proportional to the flow, and the measurement is recorded.