Hi, It may be possible, that he may be having a disease of gastro-esophageal reflux. It is a disorder of incompetence of the valve situated between the lower end of esophagus and stomach. This valve normally remains tightly closed to prevent the acids of stomach from going back into the esophagus. If this valve is not functioning properly, then the symptoms of gastro-esophageal reflux may appear, as your father is having. The chances of this reflux with incompetent valve are more, in supine position, as esophagus and stomach are at same level, making it more easy for the stomach contents to leak into the esophagus and hence symptoms of gurgling, nausea and vomiting etc. By the act of vomiting the excessive acid accumulated in the esophagus, is thrown out of body and hence giving relief to symptoms. If the diagnosis can not be made by endoscopy, then further testing by ambulatory acid (Ph ) probe test or esophageal manometry may be needed to confirm the diagnosis. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician