Methods and apparatus for accessing and monitoring the gastrointestinal tract are disclosed. A positioning apparatus comprises an access device having a length and lumen, a pump in fluid communication with the lumen, and a controller in communication with the pump. The controller is configured to actuate the pump to apply a suction pressure upon a first fluid pulled through the lumen from within a body of a subject when the access device is advanced distally within the body and to apply a pushing pressure upon a second fluid pushed through the lumen for introduction into the body. The controller is configured to determine when the access device is positioned within a predetermined location within the body or when the access device is kinked based upon a flow parameter of the first fluid due to the suction pressure and a flow parameter of the second fluid due to the pushing pressure.