I have been placing PICC's by ultrasound and with Sherlock for 10 months. I only place 1-4 a month as I work in a small hospital. I have had good success but my measurements are deep a lot and I have to pull back 2-4 cm often. I measure from insertion site to mid clavicle down to third intercostal space. Do any of you that use Sherlock feel like the sound change helps to see where it is at? I do realize that everyones anatomy is different. Is this to be expected or will I get better? What is the expected ratio of perfect to off by 2-4? If we pull back 2-4 we don't usually re-xray as they will still be distal SVC. The radiologist reads them in right atrium or CAJ a lot.