extends approximately 120 u00b0 around the circumference of the catheter 160 the catheters 100 160 as shown in fig7 12 are preferably of a small size to fit easily into the internal jugular vein superior vena cava or other appropriate vessel adjacent to the desired nerve bundle the internal jugular vein is next to the vagal nerve bundle and thus presents an ideal path for the catheter when attempting to stimulate the vagal nerve the human internal jugular vein is about 2 to 6 mm in diameter and tapers over an estimated length of about 15 cm hence the use of a 7f or smaller size catheter is contemplated the electrodes are placed on the catheter in such a way that the amplitude required to stimulate the nerve fibers would have the correct field distribution for an internal jugular vein of about 5 mm diameter and a vagal nerve bundle of about 3 mm in diameter and for an applied current of 10ma with a frequency of 2 20 hz the spacing between the electrodes would need to be about 1 2cm to achieve nerve stimulation this spacing may vary depending on the size of the internal jugular vein and vagal nerve bundle as well as the amount of.