A monitoring catheter (30) that inserts into the patient's esophagus alone or in combination with an existing catheter (84), such as a feeding or aspiration tube. The monitoring catheter (30) includes a pair of EMG electrodes (48, 50) on an exposed surface that contact the patient's esophageal wall to measure the activity of the diaphragm and/or a pair of pressure detecting mechanisms (36, 38) that measure the pressures within the patient at separate locations.