Why is it that my fingers tingle when my arm is propped upwards?

Finger tingle. Sensation is dependent upon nerves, circulation, and acan be affected buy position, temperature and conditions that interfere with nerve transmssion and circulation. When you prop your hand up, you could be compromising the circualtion at your armpit, you coud be interfering with the nerves there, you could be irritation your shoulder you could be pinching a nerve. Or blood vessel at the elbow.