Hello Neil:
In addition to BillP's excellent reply here is what we have on our web page about the subject:
"If you have a severe case of heartburn every time you dive and it gets worse on ascending to the surface, you probably have pressure-induced GERD (gastroesophageal reflux disease). Remember Boyle's Law--air filled sacs decrease in size as pressure is increased and increase in size as pressure is decreased.
What is happening is that you are swallowing air subconsciously as you try to equalize during the dive. As you do this at depth due to the small up and down movements in the water column, you are putting air into your stomach. As you ascend to the surface, your lower esophageal sphincter is being overwhelmed by the expanding air in your stomach.
This is a very common complaint and it doesn't necessarily mean you have a serious problem--unless you have it while not diving. You might possibly go to your MD and be sure everything is OK---if so you can manage this yourself with several easy maneuvers.
First--don't eat a big meal and then dive.
Second--carry some medication along on the trip that will cut down on acid reflux,i.e., Pepsid, Tagamet or Zantac.
Third, take along a bottle of of antacid tablets and take several before each dive.
Many divers are prone to this problem and find that their greatest problem is on the second dive--usually after eating gas producing dive boat food! It's best to eat less food and try not to wash food down with liquids--during which most air is swallowed.
One other cause of this problem is an alpha blocker medication that causes relaxation of the sphincter (muscle); "Hytrin" or "Cardura", a mild blood pressure drug that's also used for prostate problems can also cause heart burn as well as nasal congestion.
Try these simple tricks and I think your dives will be more pleasant! "
http://www.scuba-doc.com/hrtbrn.htm
In addition to the medications noted above, you might add Viagra as a drug that will relax the cardia (lower esophageal sphincter) - although I can't imagine why you might want to take Viagra before a dive!
Best regards for safe diving!
scubadoc
Diving Medicine Online
http://www.scuba-doc.com/
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