Vacationists who travel by plane right after diving may possess enough residual nitrogen that is responsible in causing bends. To prevent decompression sickness, divers can follow a series suggestions that would relieve them of residual nitrogen intake.
Your success at remaining bends free when flying after diving depends on a number of critical factors: your preparation for diving, how you dive, how much bottom time you accumulate and how long you wait before flying. Some of these factors are obvious but others are more subtle – things you might not think of unless someone mentioned them.
The reason your body needs to be “clean” of residual nitrogen is because the passenger cabins of most commercial airliners are only pressurized to 8,000 feet – not sea level. This little known fact is not critical to most passengers but extremely important to divers who have been underwater within three days prior to aircraft departure.
A cabin pressure of 8,000 feet is considerably less than atmospheric pressure at sea level. It is the equivalent of being 1.5 miles high, at the top of a mountain. You might be okay on the ground but painfully bent at this reduced pressure.
The risk of flying after diving has been further compounded by the change in the way recreational divers dive. Back in the 1960s and 1970s traveling sport divers made one dive per day, possibly two. Today, vacationing divers are making multiple dives on multiple days. Hardcore enthusiasts, especially on liveaboards, are making five dives per day for a week.
Multi dives/multi days can significantly increase the risk of bends, even if you stay within the limits of the dive tables or computers. This type of diving builds up long term residual nitrogen in the body, making you a borderline risk for flying after your diving is finished. However, by following the 21 hints listed here, you can substantially reduce the risk of bends occurring during your flight home.
21 Helpful Hints
1 Drink plenty of liquids: Make a special effort to drink plenty of water prior to the start of your diving activity, during the day (at surface intervals) and afterward. Dehydration thickens the blood and reduces the body’s ability to offgas nitrogen – thus contributing to the possible cause of bends.
Be careful to choose liquids that do not contribute to dehydration. Water is the best. Lemonade, fruit juices and other non-alcoholic drinks are fine. Coffee, beer and other alcoholic beverages are not good, as they contribute to dehydration.
2 Eliminate or reduce alcohol intake: Alcohol causes dehydration by voiding the body’s liquids through the bladder. The best medical advice is to abstain from alcohol during the entire dive trip (few people ever do). If you wish to drink (in the evenings for social reasons) restrict your alcohol intake to one or two beers, glasses of wine or mild mixed drinks. Drink more water between alcoholic beverages in order to offset dehydration.
3 Get plenty of rest: Fatigue is another contributing factor in decompression sickness. Fatigue causes body systems to slow or shut down completely, thus preventing the proper rate of offgassing. You can reduce this risk by getting a full night’s sleep before the beginning of any dive day. Also, take short naps during your surface intervals to regain strength and restore energy.
4 Avoid undue physical exertion: Strenuous exercise such as weight lifting has been known to cause muscle soreness and contribute to the onset of decompression sickness. Avoid strenuous exercise before diving. If you have been sitting behind a desk for the last six months, don’t volunteer to help load all the tanks onboard the dive boat.
Avoid strenuous exercise during your dive. For example, don’t try to move a heavy anchor to a better location if you are not used to doing this kind of work. Abnormal physical exertion can accelerate nitrogen uptake.
Avoid abnormal physical exertion after your dive. Don’t volunteer to haul up the anchor or unload the tanks if you don’t normally do this type of work. Post dive strenuous exercise can cause muscle soreness and possibly contribute to decompression sickness.
5 Cancel your dive if feeling ill: Abort your dive if you feel ill or unwell. The onset of a cold or the flu greatly reduces your body’s ability to handle the offgassing of nitrogen at the proper rate. If you feel ill, get plenty of rest and drink lots of fluids – but don’t dive.
6 Make the first dive the deepest: If you are planning to make multiple dives during the day, plan your first dive to be the deepest. Each dive thereafter should be at a lesser depth. For example, you might start with a dive to 100 feet. The second dive should be shallower, say 80 feet. The third dive should be even shallower, perhaps 60 feet.
7 Avoid pushing the tables or computer to the limit: Do not stay U/W until you have reached the maximum limit of your dive tables or computer. Instead, allow a five minute safety margin. For example, you make a dive to 80 feet. Your dive computer indicates you can stay for a maximum limit of 31 minutes and still be within the no decompression profile. Instead, begin your ascent at 26 minutes, thus allowing yourself a safety margin of five minutes. Never allow yourself to get anywhere close to the maximum limit.
8 Plan the deepest level for the first part of your dive: Make the deepest part of your dive at the beginning – gradually ascending to lesser depths. For example, you might begin a wall dive by descending the face of the drop-off to 100 feet. You might spend 5 or 10 minutes at the 100 foot level, then move up to 80 feet for a few minutes, then 60 feet and so on. Your dive profile should be a gradual curve or staircase from deep to shallow depths.
9 Ascend very slowly: Your ascent from the bottom to the surface should be made at a very slow, measured speed. This is one of the most difficult diving skills, yet one of the most important to master. Few divers realize how fast they are traveling during ascent and most exceed the recommended rate of ascent. In one study, divers were clocked at ascent rates of 120 to 180 feet per minute, when they felt certain that they were ascending at the prescribed 60 feet per minute.
A good way to control your ascent rate is to come up the anchorline very slowly, one hand in front of the other – pausing every 10 feet to check the elapsed time. Ascending a distance of 60 feet should take one to two minutes, to be safe.
Another good way to control your ascent is to purchase a dive computer that has a built-in rate of ascent alarm or rate of ascent indicator. Keep an eye on the computer display during your ascent, so you can immediately stop if the computer indicates an ascent rate violation.
10 Make safety decompression stops at 25 and 15 feet: Make a habit of doing safety decompression stops for 3 to 5 minutes at depths of 25 and 15 feet – even though you are diving well within the no decompression limits. A depth of 15 feet is preferable to 10 feet because there is less danger of floating upward in heavy seas or strong currents as the boat swings on its anchorline.
Make your safety decompression stops progressively longer during a day of multiple dives. For example, you might take a 3 minute safety decompression stop at 15 feet at the end of the first dive of the day. You might extend this decompression stop to 5 minutes for the second dive. By the third dive, you may wish to make a 3 minute stop at 25 feet and a 5 minute stop at 15. These safety stops greatly decrease the risk of bends and provide an opportunity to take a short rest before climbing up the dive boat ladder.
By now, you might be wondering what all these tricks and techniques have to do with flying home at the end of the vacation week. Everything you do during the week has a bearing on the residual nitrogen in your body at the end of the trip. Studies of bends accidents indicate the initial contributing cause can occur several days prior to the actual hit. The precautions you take during the week will help to reduce the risk when it is time to fly home.
11 Cease diving for 24 hours after a profile violation: Should you experience a dive profile violation, such as exceeding your no decompression bottom time limit or making a rapid ascent because you are out of air, stop diving for at least 24 hours after the violation. Dive profile violations are often those little safety slips that can cause micro bubbles in your body’s system. If you keep diving, the bubbles may grow until you experience a full blown case of the bends.
By discontinuing your diving for 24 hours, you allow your body to dissipate the micro bubbles and eliminate excess nitrogen gas buildup. It is a small price to pay for avoiding the bends.
12 Limit repetitive deep dives to 3 per day: If you are planning to make 4, 5 or 6 dives per day (often done on liveaboards), limit your repetitive deep dives to 3 or fewer per day. By deep dives, we mean dives from 80 to 130 feet.
There is now evidence that indicates repeated or continuous deep diving can result in decompression sickness, even though the diver stays within the no decompression limits. The repetitive dive tables and dive computer formulas are not designed for continuous deep diving.
13 Allow a minimum one hour surface interval between dives: Plan a minimum of one hour surface interval time between repetitive dives, even though the tables or computer indicates you can go in sooner. This technique is particularly important if you are making long shallow dives or many dives in one day. If you wish to be extra safe, allow a 1.5 hour surface interval between dives.
The extended surface interval accomplishes two things. It provides sufficient time for your body to offgas nitrogen that has been absorbed over long periods of submersion as well as allowing your body to rest and regenerate energy.
14 Allow a minimum 12 hour surface interval between dive days: Allow a minimum of 12 hours between the end of one day’s diving and the beginning of the next day’s diving. For example, if you finish your Tuesday night dive at 9:00 pm, do not plan to go into the water until at least 9:00 am on Wednesday morning.
A diver’s body requires a full 12 hours to offgas and dissipate residual nitrogen so it does not significantly contribute to the next day of diving. Any shorter surface interval will cause the body to begin loading up on excess nitrogen. By the end of the week, this excess could become a problem.
15 Taper off diving on the last day: If you have been diving hard and steady for four or five days, begin to taper off toward the end of your trip. The more dives you make, the more conservative your diving should become.
As you approach the last day or two of your trip, begin cutting back on your bottom time. Make your dive profiles more conservative and spend more time at the safety decompression stops. If you have been making four or five dives per day, cut back to two or three on the last day. Spend more time washing and packing your gear for the return trip home. ln other words, relax and enjoy.
16 Wait 12 hours before flying after normal diving: There has been a lot of controversy over the amount of time you should wait before flying after diving. Some medical researchers felt 12 hours was a sufficient surface interval, while others felt 24 hours would be best to eliminate all risk. The current consensus among most diving doctors is that divers should wait at least 12 hours before flying after normal recreational diving. Normal diving is defined as having less than two hours of total bottom time.
17 Wait 24 hours before flying after strenuous diving: If your diving week has been strenuous because of strong currents, chilly conditions (causing shivering) or hard work underwater, you should wait at least 24 hours before flying. Strenuous exertion underwater or lowered body core temperature can result in a much higher level of residual nitrogen. Give your body the time necessary to offgas and restore the energy you need for the flight home.
18 Wait 48 hours before flying after decompression diving: If you have experienced any decompression diving (by accident or intent), you should wait at least 48 hours before flying. Decompression diving definitely loads the body with excess residual nitrogen and you will need time to dissipate it.
If you have even the slightest suspicion or vaguest symptoms of decompression sickness, see a doctor before boarding your flight home. If there is no doctor available, do the next best thing – wait at least 48 hours before flying.
19 Get plenty of rest prior to flying: A week of multi dive/multi day diving can be exhausting. Toward the end, you may begin to experience “deep fatigue” – sort of a constant weariness. The only cure for this kind of fatigue is plenty of rest.
You should plan on resting before you board your flight home – not while you are on the plane. Flying is fatiguing in itself, mainly because you cannot lie completely horizontal. You will need to get a good night’s sleep prior to the flight home. Don’t stay up late to party on the last night or try to cram in three days worth of sightseeing on the last day.
20 Avoid alcohol during the flight: As we indicated earlier, alcohol and diving do not mix very well. Alcohol is a depressant that slows down the body’s functions and causes dehydration. Since you are continuing your decompression while flying, it is wise to refrain from drinking alcoholic beverages or reduce your intake to a minimum.
21 Continue drinking plenty of liquids during the flight: You should continue to combat the problem of dehydration while you are flying home. Your body loses a considerable amount of fluid during flight, owing to the super dry air circulating in the passenger cabin. Drink at least one glass of water per hour during the flight, to replace the lost fluid.
While there is no guarantee that by following all these hints you will never be bent, your risk will be greatly reduced. There are no hard and fast rules in the diving game, because every person’s physiology is different and the variance can be tremendous. The best advice is to use common sense. If you are an older diver (over 40), overweight or out of shape, be more conservative than the techniques recommended here.
The most important piece of advice is don’t push it. It is senseless to push the dive tables, push the dive computer or push yourself beyond your physical limits. Remember, diving is supposed to be fun.
- Drink plenty of liquids
- Eliminate or reduce alcohol intake
- Get plenty of rest
- Avoid undue physical exertion
- Cancel your dive if feeling ill
- Make the first dive the deepest
- Avoid pushing the tables or computer to the limit
- Plan the deepest level for the first part of your dive
- Ascend very slowly
- Make safety decompression stops at 25 and 15 feet
- Cease diving for 24 hours after a profile violation
- Limit repetitive deep dives to 3 per day
- Allow a minimum one hour surface interval between dives
- Allow a minimum 12 hour surface interval between dive days
- Taper off diving on the last day
- Wait 12 hours before flying after normal diving
- Wait 24 hours before flying after strenuous diving
- Wait 48 hours before flying after decompression diving
- Get plenty of rest prior to flying
- Avoid alcohol during the flight
- Continue drinking plenty of liquids during the flight