Dive Medicine Myth
Where would the great pastimes be without their myths and legends? After all, it’s the tall tales and exaggerated stories that keep disbelieving eyes wide and doubting ears open for more.
Diving is no different. The myths and misinformation floating around our sport are abundant, partly because divers love to tell stories – the more outlandish the better – and partly because as new information becomes available as technology develops and we learn more about dive medicine, it’s slow to replace the old, “established” information many have long taken as gospel.
Of course, we at DAN hear more than our share of dive medicine myths. The following are actual questions we receive on our Medical Information Line from time to time. The topic list might seem random, but that’s the beauty of myths; you never know when they will surface.
Myth – Diving is a good cardiovascular workout.
If only this were true, we’d all have the excuse we need to hit the water every day! But while diving certainly has physical components, as well as cardiovascular considerations and consequences if we’re not careful, the act of diving itself does not provide the cardiovascular exertion needed to increase and maintain general fitness. At least, it shouldn’t. Most diving guidelines and techniques are designed to minimize the physiological impact of diving, so if you find yourself out of breath underwater, stay calm, breathe as slowly and regularly as you can, and end the dive as soon as it’s safely possible. If your breathing and heart rate do not quickly return to normal after the mitigating factors are removed, seek immediate medical attention.
In the meantime, practice healthy eating and exercise habits – complete with regular cardiovascular activity - to maintain your general fitness level and stay prepared for diving.
Myth – Staying hydrated is a sure-fire way to prevent decompression sickness.
Sorry, but no. Like alcohol consumption and fatigue, dehydration has been suspected of contributing to an increased DCS risk, but depth and time are by far the most important risk factors. Drinking water throughout any day you’re diving is a good practice, and definitely recommended, but there are no magic wards against decompression sickness.
Hydration is still important though, and it’s a cumulative process. Just like dehydration does not happen overnight, hydration does not happen with a single glass of water. Keep it simple – replace fluids as you lose them, especially if you’re sweating because of heat or exercise. Make hydration a regular practice, and make it part of your dive plan. Throughout your dive day, remember to drink early and often, but don’t rely on hydration to protect you from DCS.
Myth – Sports drinks are full of sugar and are a bad source of hydration.
While it is true that some high-energy drinks contain high levels of sugar, sports drinks are designed to keep a person hydrated and in electrolytic balance.
Water is the best fluid you can drink to stay hydrated, but if you prefer the flavor of sports drinks, try to make sure it’s of the low glucose, balanced electrolyte variety.
Myth – Post-dive rashes are caused by sea lice.
Poor sea lice; every time a tropical diver surfaces with an itch, a rash or a blister, sea lice is blamed for the malady. The truth is, sea lice are actually fish parasites and do not affect humans at all.
No, the cause of most “sea bather’s eruptions” is the larvae of jellyfish, specifically the thimble jellyfish (Linuche unguiculata). Found primarily in the waters of Florida and the Caribbean, these critters are just a half a millimeter in length and invisible to the naked eye underwater. They’re able to penetrate swim wear and t-shirts, so if you’re diving in warm, southern waters, be sure you’re well protected with a wetsuit or impermeable dive skin.
Myth – Feeling like you have to pee underwater is due to increasing pressure of deep water.
Actually, the answer is yes and no. It’s not unusual to hear divers discussing urination in wetsuits, and there’s a reason the topic is so common. Most divers, on one dive or another, have felt an increase in bladder pressure while underwater.
However, the increased need to urinate underwater has nothing to do with how deep you go or the increased pressure you experience there. The phenomenon is called immersion diuresis, and it occurs whenever the body is immersed in water, regardless of depth. Because of the immersion, especially in colder water, the blood vessels in the extremities constrict, moving the blood from your extremities. As a result, an increase of blood is sent to the major organs, which is interpreted as a fluid overload by your heart and kidneys. This, in turn, triggers some hormonal changes through which your kidneys regulate urine output. When output of certain hormones change, your kidneys produce urine, and you’ve experienced the rest.
Myth – Menstruating women are sharkbait.
This is one myth that simply won’t be laid to rest. We can only applaud the nature shows that have ingrained in each of us the fact that sharks are attracted to and able to detect even microscopic amounts of blood. However, despite this talent, there are very few reported shark attacks on women, and certainly not enough to show a gender imbalance or physiological reason. The amount of blood lost during a woman’s menstruation cycle is small and lost over several days, and there is no data to support a theory that it puts women at risk underwater. In fact, some studies have shown that many shark species are, in fact, not attracted to menstrual output. So no worries, as the nature shows also teach us, humans remain a much greater threat to them than they do to us, regardless of the time of the month.
Myth – If you get bent once, it’s easier to get bent a second time.
The historical data simply does not support this statement. That being said, this myth requires a closer look. Divers who consistently dive deeper and longer, or who have more repetitive dives and shorter surface intervals are probably at greater risk than their counterparts who choose more conservative profiles. This is an issue of behaviors and dive practices. It is worth mentioning that in some very rare cases individuals may have greater susceptibility to decompression illness for some anatomical or physiological reason, but there is probably no reason to suspect the risk would change because someone has gotten bent.
Myth – DCI symptoms will always resolve on their own if given enough time.
This is the second-most dangerous myth in diving, but sadly, many divers believe that if they just give their symptoms some time and some sleep, the symptoms will resolve. In fact, our experience at DAN is that “divers don’t call DAN because symptoms develop, they call because they won’t go away.”
The truth is that if you experience any symptom associated with decompression illness, the earlier you seek treatment, the better chance you have at maximizing its effectiveness. Call DAN; we’ll be able to offer assistance and advice, and if you do need professional treatment, we’ll help with that, too.
And the most dangerous myth in diving? There’s something shameful about getting DCI. Let’s make it clear - there’s not. It’s a part of diving, and there’s not a diver in the water immune to it.
Myth – Hyperbaric chamber treatments work by squeezing bubbles.
The primary goal of recompressing a diver in a chamber while having them breathe 100 percent oxygen is to hyperoxygenate their tissues. This increases the gradient for off-gassing inert gas (e.g. nitrogen). The oxygen will actually displace the nitrogen from the tissues. Providing a high percentage of oxygen at the surface can achieve this affect to a limited degree in terms of treatment. Breathing high partial pressures of oxygen when in a high-pressure environment maximizes the oxygen therapy.
Myth – It’s important to know the location of the closest chamber when you travel.
Though it’s important to be aware of the medical resources available to you in any area you dive, in terms of hyperbaric chambers, it’s more important to know the DAN Emergency Hotline number than it is to know the location of the nearest chamber. The reason is that DAN maintains an active hyperbaric chamber network, and we know that not all chambers are equipped to treat all injuries, nor are all of them staffed 24 hours a day. So you don’t want to depend on a chamber that may not be available to you in your time of need, whereas DAN is available to you 24 hours a day, every day of the year. So know your surroundings, but keep DAN’s number handy, too; we’ll ensure we get you to the nearest medical facility equipped to help you.
Myth – DAN keeps its members’ medical records on file.
This is absolutely a myth. It’s a fascinating myth, since many divers believe it to be true, even though they’ve never submitted their medical records to us. But let’s set the truth free - DAN does not collect medical records, nor does it maintain medical files on its members.
Myth – DAN will rescue you even if you don’t call, right?
We include this only because we’re flattered that divers believe our talents extend so far as to include psychic abilities. We wish we were psychic, but the truth is, we’re not. We are here for you 24 hours a day, 7 days a week, but if you need our assistance, you will need to give us a call.
Remember that knowledge is power, so the next time you hear a tale too tall to be true, check it out so you’re sure to know fact from fiction.
DAN Emergency Hotline
*This number can be called collect