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DEAR DR. ROACH: I'm a scuba diver, and I recently purchased a dry suit that is expectedly tight on my neck. During my first dive with it, I pulled the hood down, and within a few minutes, I immediately felt nauseous before even entering the water. I also briefly felt lightheaded and faint. I removed the hood, loosened the neck a bit, and tried to relax. The feeling somewhat subsided.
I tried again and was able to do a short 25-minute dive. But when I got out, I was immediately nauseated and subsequently vomited. I am usually quite sensitive to motion and take Dramamine when on a boat. But this was a short dive, so I hadn't taken anything. Also, it was completely calm, so motion wasn't the issue. I've also noticed that I get queasy from doing yoga with strong back bends or neck compression.
I'm assuming that this all comes down to vagal nerve compression. Is there anything I can do for this, other than not have anything tight on my neck?
Would Zofran or another medication help? I'd really like to continue cold-water diving, but it seems like all suits (wet or dry) are going to have some amount of neck pressure and cause this reaction.
--A.H.
ANSWER: Your hypothesis of vagal nerve stimulation makes the most sense to me. The vagus nerve has many functions and travels through the neck, where it could be compressed by a tight fit around your neck (like with a dry suit). Stimulation of the vagus nerve can cause nausea and vomiting, and it may be that yoga causes the same reaction as the dry suit.
One other possibility is the stimulation of a nerve system called the carotid sinus, which is located where the carotid artery splits into two. A tight collar can stimulate this nerve system, which causes the heart to slow down. In some people, the heart can slow down so much that it causes lightheadedness and even fainting. Nausea and vomiting are reported with carotid sinus hypersensitivity, so this is also a possibility. Checking your heart rate when you put the suit on would confirm or refute this hypothesis.
I think you're right that the problem is the neck pressure. Although medications -- such as an over-the-counter antihistamine like dimenhydrinate (Dramamine) or the prescription medication ondansetron (Zofran) -- can help reduce symptoms, a different material of suit (neoprene is more forgiving than latex) or an adjustable neckline might make you a lot more comfortable if you're determined to dive.