Devices and methods are provided for automatic vascular access. An automatic vessel cannulation device, mechanical or electronic, has a sensor configured to detect a physiologic parameter of a needle tip, and a blunting device advancing member released in response to the sensor. The sensor may measure pressure or any other physiological parameter. A processor is configured to analyze data sent by the sensor and is pre-set to identify parameters unique to arteries, veins, or other body cavities or organs. A method may include comparing a physiologic parameter with pre-determined parameters to deploy a blunting element if the physiologic parameter is within a range of the pre-determined parameters. An expandable sheath may be included. A device can be provided having a motor controlling the cannulation device orientation to scan tissue with the tip of the needle by moving the cannulation device through the ultrasound transducer.
