If there’s one thing you want to avoid when scuba diving it’s decompression sickness

Factors That Increase The Risk Of Decompression Sickness In Scuba Diving

Decompression sickness or ‘The Bends‘ is a potentially fatal affliction that can affect scuba divers, particularly if they don’t follow safe diving practices and procedures.


12 decompression sickness risk factors in scuba diving include: Number and depth of previous dives, age, fitness, exertion, obesity, smoking and other drugs, alcohol consumption, fatigue, dehydration, injuries or birth defects, flying too soon after a dive and being female during the menstrual cycle. Think about your personal circumstances before simply relying on decompression tables or your dive computer.


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12 decompression sickness risk factors in scuba diving

Factors That Increase The Risk Of Decompression Sickness In Scuba Diving include number of dives age and fitness

There are many factors that increase the risk of decompression sickness in scuba diving. This article aims to highlight what these risk factors are and what to do to minimise them for you.

Afterall, you want to be able to safely enjoy this wonderful sport.

Each diving organisation like BSAC, PADI, NAUI and the like have their own scuba diving tables you have to follow when you train with them.

However, most beginner scuba divers will learn the decompression tables of the organisation they train with, only to ditch these tables for a dive computer.

Age, fitness, exertion, obesity, smoking, alcohol consumption, fatigue, dehydration and injuries can all make decompression illness more likely. You should be aware of these factors and take them into account by diving conservatively and not pushing the limits of your chosen decompression computer or table.

British Sub Aqua Club

The biggest dangers divers face when scuba diving is themselves. That means the majority of all the risks associated with scuba diving, land fair and squarely at your feet.

You may want to squirm at this point, you may not want that responsibility.

Making scuba diving safe

But this is a good thing. It means that you are in control. If you are in control of the scuba diving risk factors and you follow my 107 top tips for beginner scuba divers, you'll make scuba diving safe.

Also, if you look after the following decompression sickness risk factors, you'll reduce your risks even further.

The Divers Alert Network comments that around 1,000 US scuba divers are affected by decompression illness each year. Don't be one of those this year or next year, or ever.

Recreational divers should dive conservatively, whether they are using dive tables or computers. Experienced divers often select a table depth (versus actual depth) of 10 feet (3 meters) deeper than called for by standard procedure.

Diver's Alert Network

BSAC list the majority of these decompression sickness risk factors in their safe diving guide. But in my article, I go into more detail with a few added risk factors. Although before that let me explain what causes decompression sickness in scuba divers.

What causes decompression sickness in scuba divers

The cause of decompression sickness, which is also called the bends, is from nitrogen bubbles forming in the bloodstream and tissues of the body.

These nitrogen bubbles form if you ascend too quickly from deep water after a dive. Or decompression sickness occurs if you fail to carry out decompression stops at the appropriate depth and for the correct time on your ascent.

The reason why bubbles form is because the pressure of the surrounding water decreases as you ascend. If this pressure falls too quickly (i.e due to a fast ascent or an ascent without the required decompression stops), the dissolved nitrogen is released too quickly and forms potentially deadly bubbles.

If however you ascend at the correct ascent rate and carry out the correct decompression stops, the nitrogen is released slowly enough that these nitrogen bubbles don’t form.

So here is my list of 12 decompression sickness risk factors and in each case how to avoid the risk:

#1 Decompression Sickness Risk Factor - Number and depth of recent previous dives

Risk Factor #1 For Decompression Sickness - Number and depth of recent previous dives

If you are using BSAC tables, BSAC recommends you should not conduct more than three dives in one day, and that if you are diving deeper than 30m you should take a 24-hour break after diving for four consecutive days.

British Sub Aqua Club

If you use BSAC diving tables, they recommend you shouldn’t dive more than three scuba dives in one day. BSAC also recommend that if you are diving deeper than 30 metres (100 feet), you should take a 24-hour break after diving for four consecutive days.

The message in this is to be careful with the number of dives you do each day and when you're diving deeper, give your body a rest. This will allow your tissues to properly decompress and release the built-up nitrogen.

Liveaboard diving presents the opportunity to do more dives per day

The time when this may present a problem is on a liveaboard dive trip. On a liveaboard trip you have the opportunity to dive many more times per day.

On some liveaboard trips, including liveaboard trips to Socorro Island to see manta rays, they allow up to four dives per day.

The choice of how many dives you do each day. Plus the depth of the dives you do is entirely your choice.

However, on trips like the one to Socorro Island or a liveaboard to the Cocos Islands and Mergui Archipelago involves 'remote scuba diving.' This means that should anything go wrong, you’re a long way from land and a hospital. But more importantly, a long distance from a recompression chamber or hyperbaric chamber.

Although, one of the liveaboards that visits Socorro Island has a recompression chamber on board. But that's not to say you want to put it through its paces.

How to avoid decompression sickness risk factor #1

Therefore in order to avoid the first decompression risk factor, be careful about how many dives you do each day. Also, consider taking a ‘scuba diving break’ to help reduce the nitrogen build-up.

If you are diving from a liveaboard, take time out to read a book or review your photos and videos.

#2 Decompression Sickness Risk Factor - Age and being older than 30

Unfortunately, age gets to us all. It's a well known fact that as you get older, your body no longer responds quite how it did when you were younger. If you exercise for example, it takes longer to recover from exercise as you get older. But exercise in itself gets harder too once you’re the wrong side of 30!

What this all boils down to is, as you age your body becomes less efficient at its automatic processes. Your bodily tissues get tired more quickly. Your tissues are also less likely to decompress as quickly as they did when you were younger.

How to avoid decompression sickness risk factor #2

If you are the wrong side of 30, 40 or 50, you are better to take a little bit more time with your ascent rate. Plus reduce your bottom times for no stop dives. Be conservative.

You may also wish to use nitrox when you dive too. Nitrox diving increases the percentage of oxygen in your air.

But in itself, an increased amount of oxygen in your air tank will limit your dive depth. But then in my opinion that's not a bad thing as you age.

Also, if you don’t do it already, make sure you do a three minute safety stop on every dive at between 5-6 metres (16-20 feet).

#3 Decompression Sickness Risk Factor - Low cardiovascular fitness

Whilst scuba diving doesn't require you to be ultra fit, you would benefit by being fitter than not.

Scuba diving itself is a calorie burner. Diving can burn up to 600 calories per hour. But to get the most out of scuba diving, I suggest you look after yourself out of the water too.

The fitter your body, the better it will be at releasing the built-up nitrogen in your tissues. The converse is; the less fit you are, the slower your tissues will be at releasing the nitrogen, as you decompress on your ascent from your dive.

Being fit will also help you with your air consumption too. This in turn will give you more time underwater on each dive, as your air will last longer.

How to avoid decompression sickness risk factor #3

If you consider yourself to be unfit, you may either wish to get fit (which is the preferred option. See below for an idea to get fit). Or take your 'unfitness' into account when planning your dive time and dive ascent.

You want your body to be efficient at nitrogen releasing. You don't want an increased risk of getting decompression sickness, but a reduced risk instead.

One possible solution for you to get fit for scuba diving includes:

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#4 Decompression Sickness Risk Factor - Over exertion

Risk Factor #4 For Decompression Sickness - Over exertion

Scuba diving is supposed to be effortless. When you immerse yourself and dive underwater, you become weightless. You want to use as little energy as possible, conserve your air for as long as possible and not exert yourself too much.

That being said, there are times when you may exert yourself more times than others when scuba diving. An example of this is swimming against a current. When you are scuba diving in a current or what's known as drift diving, you are supposed to go with the current.

However, there may be times you have to swim against the current. If this is the case you will be exerting yourself much more than normal.

This will not only mean you use up more of your air, but it may have an impact on the amount of nitrogen you build-up in your body too.

That means, you must be more careful with your dive time and decompression time or stops, which includes carrying out a safety stop, when you've exerted yourself more than normal.

How to avoid decompression sickness risk factor #4

The best way to avoid the risks associated with over exertion when scuba diving, is to take everything slowly and calmly.

If you are in a current, where possible and when circumstances allow, always go with the current. Don’t attempt to swim against the current.

If however during the course of your dive you have over exerted yourself for whatever reason, to avoid the possibility of getting decompression sickness on your ascent, take extra time to ascend.

But be careful with your air supply, because during your over exertion you will have consumed much more of you air than usual. This will mean you need to make sure you have enough air left to ascend and to carry out your decompression stops, where applicable, and your safety stop.

#5 Decompression Sickness Risk Factor - Obesity and a high percentage of body fat

#5 Decompression Sickness Risk Factor - Obesity and a high percentage of body fat

If you suffer from obesity and you are over weight, this may have an impact on the amount of time it takes to decompress on your diving ascent.

If you have an obese body it makes sense that you have more body tissues than the average person. This may have an impact on the amount of nitrogen you adsorb and on how long it takes to release it from your body.

I therefore suggest you are more careful than the average scuba diver when you plan your ascent rate and dive times. Be more conservative with your approach.

How to avoid decompression sickness risk factor #5

If you don’t want to limit your dive times or make allowances on your ascent rates and so on, you could alternatively consider losing some of your weight.

One possible solution to lose weight is using this Workout Finishers course:

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#6 Decompression Sickness Risk Factor - Smoking and tobacco or other drugs

Risk Factor #6 For Decompression Sickness - Smoking and tobacco or other drugs

I don't want this article to come across as a 'bash the scuba diving smokers' type of article. But I do want to highlight the potential added risk you take by combining scuba diving and smoking.

I would also include in this category the use of other recreational drugs. It probably goes without saying that the use of drugs cannot be good for you when scuba diving. But I will focus more on smoking and tobacco for this article.

Smoking has many effects on your body, as detailed by the UK's NHS's smoking health problems.

The health problems directly associated with scuba diving in this article include reducing the efficiency of your circulation, damage to your heart and damage to your lungs.

All of these factors will affect how efficient your body will be at releasing and expelling nitrogen in your bodily tissues.

How to avoid decompression sickness risk factor #6

To avoid the risks of scuba diving if you’re a smoker, you therefore need to be more mindful of the types, depths and lengths of your dives.

Although, a better solution would be to quit smoking alltogether. Combine this with getting fit and you're good to go!

I know I said that this article wasn't about bashing you if you are a smoker. But I didn't say it wasn't going to be about encouraging you to quit smoking. I mean well!

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#7 Decompression Sickness Risk Factor - Alcohol consumption

Risk Factor #7 For Decompression Sickness - Alcohol consumption

When it comes to alcohol, I'd say everything in moderation. There's nothing that says you can't drink alcohol before you scuba dive. But I was always taught to keep my drinking to a minimum the night before I was going scuba diving.

I'd suggest you don't get completely paralytic or stone drunk the night before you are going to scuba dive. I'd say this is particularly more important if you intend to dive deeper than 20 plus metres (66 plus feet).

The deeper you go, the greater the risks of decompression sickness. This not only includes your body's ability to release the nitrogen from your body as you decompress, but it also includes having a clear mind.

If you are suffering from a hangover from the night before, you are putting yourself and your dive buddy at more risk.

More Reading: Diving Buddy Check Acronym or Mnemonic (Why Scuba Buddy Checking Is Important)

How to avoid decompression sickness risk factor #7

Be a safe diver and limit your alcohol intake the night before you scuba dive. If however, you find you have had a skin-full, you would be better off postponing your dive and/or limiting the depth you go on that day.

#8 For Decompression Sickness Risk Factor - Fatigue, sickness or lack of sleep

Risk Factor #8 For Decompression Sickness - Fatigue, sickness or lack of sleep

One of the factors that BSAC include in their list of things that make decompression illness more likely is fatigue. This would include the lack of sleep and sickness.

How to avoid decompression sickness risk factor #8

Before your next day’s diving, it's a good idea to get a good night's sleep. Make sure you are not overly tired, also that you are free from major sickness.

Diving when your body is rested and free from sickness will not only improve your body's ability to decompress, but it will help you to not make mistakes when scuba diving too.

#9 Decompression Sickness Risk Factor - Dehydration

Risk Factor #9 For Decompression Sickness - Dehydration

Most diving organisations and dive companies will always encourage you to keep hydrated when scuba diving.

If your body and your bodily tissues are well hydrated they will perform better.

I'm no scientist. Nor am I a doctor. But it makes complete sense that in order for your cells to work efficiently, they need to be fully hydrated.

How to avoid decompression sickness risk factor #10

The easiest way to avoid any risks associated with dehydration, I recommend you drink plenty before and after each dive. This will ensure you maintain a good level of hydration.

#10 Decompression Sickness Risk Factor - Injuries or birth defects

Scuba divers with an abnormal hole or opening in the heart from a birth defect are at a high risk of developing serious symptoms from decompression illness than those without any abnormalities.

I've been witness to this at one of my old BSAC diving clubs.

In fact two members of my old club discovered they had a hole in the heart (or congenital heart disease), as a result of being affected by decompression illness.

In both cases the decompression illness was a minor skin bend. But never the less it was decompression sickness. It's better to discover the defect with minor decompression sickness, than to have a serious problem from depth.

How to avoid decompression sickness risk factor #10

If you are worried you may have a birth defect, it’s very simple to be checked for a congenital heart defect.

Go to your doctor and ask them to put you in for a check. If it turns out you have a 'hole in the heart,' this is a simple procedure to correct. Which will make things safer for you to scuba dive.

#11 Decompression Sickness Risk Factor - Flying too soon after diving

Risk Factor #11 For Decompression Sickness - Flying too soon after diving

There are a few accidents involving decompression sickness (DCS) where scuba divers fly too soon after diving.

It is recommended you don't fly for at least 24 hours after diving. If you use a dive computer, this will normally tell you when it's save to fly after your last dive.

However, even if this is clear before 24 hours is up, I recommend you are cautious and wait the full 24 hours.

The reason why it’s not recommend to fly with 24 hours is that higher up in the earths atmosphere, the atmospheric pressure reduces. Most aircraft fly at over 9,000 metres (30,000 feet) or more.

At this height, which is roughly the height of Everest, the pressure drops by about 30 percent. That means if you’ve just scuba dived and you still have nitrogen in your body, you could get the bends.

More Reading: How long should you wait to fly after diving? (What’s safe?)

How to avoid decompression sickness risk factor #11

If you know you going to be flying, never dive on the day of the flight. Plus, always do your last dive on the day before at least 24 hours before the flight is due to take off on the following day.

More Reading: What should you not do after scuba diving (11 must NOT do’s after diving)

#12 Decompression Sickness Risk Factor - Being female and the menstrual cycle

Decompression sickness in women and a possible relationship with the menstrual cycle is worth taking note of if you are a woman scuba diver.

Women are increasingly participating in recreational scuba diving these days. There are also more professional roles of women in the fields of aviation, space, and diving.

As a result of this and a limited amount of research, evidence does exists that there may be a relationship between altitude decompression sickness (DCS) and the menstrual cycle.

How to avoid decompression sickness risk factor #12

Whilst there are limited diving studies to support these findings, I suggest that if you are a female diver and you are in your menstrual cycle at the time of scuba diving, you take more care and be more cautious in your approach to decompressing.

A final thought on the risks associated with decompression illness

Finally, as you'll note, I've looked at each of these decompression sickness risk factors in isolation.

However, in real life this is never the case.

Be very aware and extremely careful if you are able to tick a number of the above 'decompression sickness-risk-boxes' when it comes to planning your bottom time, dive ascent, decompression and stop times.

For example, if you are an older diver, who has put on extra weight, this means you are not at your peak fitness. If you combine that with being a smoker who's had a skin-full of alcohol the night before, combined with a late night, so you're now also fatigued. Having drunk loads of alcohol you are also potentially dehydrated.

Whilst this example is an extreme case, it's a possible situation and creates a high risk scenario for decompression sickness.

What I really want you to do is to think carefully about the things you do around scuba diving.

And always, always do a safety stop on each and every dive at 5-6 metres (16-20 feet) for three minutes.

I hope you enjoyed this article about the 12 decompression sickness risk factors in scuba diving

I’d love to hear from you. Tell us about your adventures of diving and snorkeling, in the comments below. Please also share your photos. Either from your underwater cameras or videos from your waterproof Gopro’s!

If this article hasn’t answered all of your questions. If you have more questions either about snorkeling or types of scuba diving (or specifically about 12 decompression sickness risk factors in scuba diving), please comment below with your questions.

There will also be many more articles about scuba diving (and snorkeling) for you to read and learn about these fabulous sports.

Have fun and be safe!

More Reading: How do I get a dive buddy? (5 easy ways to find a dive buddy)


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