Brief Answer:
Your husband seems to be suffering from GERD.

Detailed Answer:

Thanks for you concern about your husband. You mention that he suffers from nausea while lying down and as a last resort has to sleep in a chair. This happens because of a disease called as GERD.
(Gastro Esophageal Reflux Syndrome). In this condition, a person can easily swallow meals, but once the food has settled into the stomach, it soaks up gastric juices and acids. There is a valve between the esophagus and the stomach called as the cardiac sphincter. When this weakens, the food flows backward into the esophagus along with the acid. This is more pronounced when a person lies down flat (supine) on a horizontal surface. Please take him to a Gastroenterologist who will probably give him omeprazole, pantoprazole or ranitidine tablets, or the like.

I would advise your husband to have a Gastroscopy done too.
Take Care.

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