THE STOMACH/INTESTINE AND PRESSURE
Stomach and intestinal squeeze do not exist. Those organs already do a lot of squeezing to move the food and waste along their tract. Even though the stomach and intestines contain gases, there is no problem with descending and having Boyle's law cause a contraction of the gases causing a squeeze.
What about the ascent? Is there a potential for the stomach and intestines to grow in size creating a barotrauma? It has been written in many texts on diving that if a diver eats gas-forming foods and descends to a reasonable depth, the foods will produce gas at the ambient pressure and that gas would expand upon ascent. Consequently, the stomach and/or the intestines would over-inflate (explode?). The remedy would be to belch or flatulate to relieve the pressure. The latter may condemned by fellow divers.
In the author's entire diving career (since 1954) there has never been a report of anything related to the stomach and/or the intestines causing discomfort either on a descent or ascent. Not one of the hundreds of students, colleagues, and diver acquaintances have ever experienced any expansion of the stomach or intestines upon ascent. Many have burped and flatulated during the post-dive period, but that was mostly due to upbringing and habit!
Throwing up underwater is another matter. This could have serious consequences! Think of the process: There is the uneasy feeling, followed by the super-salivary flow, followed by heaving, and then followed by a shot of stomach contents being projected from the stomach into and out of the mouth. Next, there is an inhalation of air. The process may be repeated.
One of the scuba certification agencies reportedly recommended throwing up into your regulator, removing and replacing it with the alternate air, and then cleaning stomach remains from the primary. If the vomiting continued the process could be repeated. Another agency suggestion was to place the primary regulator mouthpiece next to your mouth and press the purge button. This would envelop the diver's mouth with a massive amount of air. The diver would simply throw up into this air stream. Whew! I'm not sure I would be willing to try either technique!
Fortunately, most divers that experience vomiting on a dive do so at the surface. The majority of cases get sick on the boat, or at the surface. There have been a few instances when divers safely returned to the surface just prior to vomiting. Up until the year 2003 no Deep-Six diver had ever thrown up underwater, nor had there been any other associated divers that have done it. It is quite rare.
The following is an email sent by a Deep-Six diver in March 2003. The incident speaks for itself:
"Brian and I just got back a few days ago from a dive trip to Mexico. We had a great time, but due to storms and current changes the visibility was not great (between 40' -- 50'). I got to see my first shark (a 5' black tip reef shark), and got to experience tossing my breakfast at 85'.
"Here are all the things I did wrong on my 'tossing' dive:
"Since my 'style' of 'tossing' is high-volume, projectile, I removed my regulator in order to 'toss'. I'm sure this was the right thing to do since I believe I otherwise would have blown the regulator out of my mouth. I replaced the regulator in my mouth, gave a hard 'clear' (very difficult to do after nearly fully collapsing my diaphragm), and 'gently' took in a breath (at first plugging the regulator with my tongue and slowly drawing in air). The good news is that I was very calm during the entire experience. I quietly said to my self, 'George said, "You will be OK in nearly every emergency as long as you don't panic'". After dealing with the emergency at 85', I truly felt like a fool as I recounted all the things I did wrong AFTER THE EMERGENCY!
"Although it seems that the natural response to a violent barf projection is to rebound with a gulp of air (or water if at 85'), I carefully calculated that my will to live would allow me to suppress the natural rebound momentarily -- long enough to complete the "clear". I also counted on an adrenaline serge sufficient to execute the hard 'clear' of my regulator. Fortunately I was right on both counts. Again, I know my barfing 'style'. There is absolutely no way that the regulator opening was large enough to handle my volume. Had I kept the regulator firmly in my mouth I probably would have choked on my vomit and/or forced the excess through my nose.
"I remembered PADI's recommended method, but recalled you discussing the alternative I used (either I recalled it or I imagined it). In any case, not only did I survive the experience, but, if ever faced with this emergency again, would readily use this same alternative method. I did have my alternate air out and ready, just in case. I also made sure I was facing down as I gently took air back in. My thoughts were that if I had not sufficiently cleared my regulator, the small amount of water that I took in would rest where gravity placed it -- away from my airway. And, by-the-way, I turned my regulator face up to establish a visible air flow before I did the "clear".
"A few minutes after the experience (and still at 85'), I finally rinsed my mouth with readily available salt water. I truly can't believe I didn't do it sooner -- talk about leaving a bad taste in your mouth.
"During my descent I actually thought back to my training with you. I was fully aware that I was running the risk of being sick underwater. I foolishly had convinced myself that the rough water was the entire culprit and getting into the water was that right thing to do to settle my stomach down. Once under water I realized what could possibly happen, I calmed myself, and did re-runs of the 'tossing' methods you trained me with. Believe it or not, I actually enjoyed the remainder of the dive -- at least until I reached the surface.
"Perhaps the most important thing about the experience is all the things I did wrong, both before and after tossing breakfast. I took a lot of ribbing from a lot of divers for a few days -- 'Hey, are you the guy that was feeding the fish', or 'did your chumming the water attract any fish', or 'were you the guy that...' But, importantly the conversations ultimately ended up being 'turned' by the other divers. They all genuinely wanted to know what the experience was like and they all had a ton of questions. The answers often cost them a beer.
"George, thank you for the great training!!!"