How do patients after prolonged bed rest do exercises to help the cardiovascular system when they are so lightheaded and feel faint when standing?

Lightheadedness: There are several options, first make sure the patient is well hydrated and that may help. Any exercises that promote muscle tone in the lower extremities will help, and this would include riding a stationary bike or leg exercises. Also using compression stockings can help and finally there are meds that can be used to increase tone and raise blood pressure.