Head Cases

By Samuel Shelanski, M.D.

How to treat the most common types of diver headaches.

QUESTION: My wife and I are real bottom hogs. We always stay within safe limits using both the tables and a dive computer. Nevertheless, after two or three days of intensive resort diving, I suffer from headaches. Somewhere I have seen a reference to carbon dioxide headaches. Can you tell me why I suffer major headaches while engaging in rather intensive diving?

Peter G. Smith
via e-mail

QUESTION: I seem to get headaches when I dive deeper than about 80 feet. This started last summer and continued through my recent Cozumel vacation. Aspirin clears up the headache between dives, but it usually returns on the next dive. Can't be mask squeeze, as I'm constantly clearing water from my mask. These aren't blinding, debilitating headaches but are more generalized with some nausea (no vomiting yet). Not very comfortable, any suggestions?

Bill Anderson
Ottawa, Ontario

ANSWER: Diving can trigger a headache in several different ways: neck and back strain from improperly adjusted or too-heavy gear, dehydration, sun glare, masks that are too tight, aspiration of salt water, and the mental strain of calculating repetitive dive tables. Some of the other diving-related causes deserve more detailed discussion. They are:

Type: Carbon dioxide toxicity headache
Symptoms: Dull, throbbing head pain after diving
Cause: Carbon dioxide buildup in the body due to hypoventilation
Remedy: Breathe properly: slow, deep breaths. Do not skip-breathe to conserve air.

Carbon dioxide headaches are probably the most common type of headaches to afflict divers. They are caused by an increase in the amount of CO2 in the body. This in turn stimulates special receptors in the blood vessels of the brain, and results in an increase in the blood flow to the brain, causing headaches.

While an increase in CO2 can result from a contaminated tank of air, it most frequently stems from hypoventilation. Hypoventilation occurs when too little air circulates through the lungs to "flush" the system, allowing waste gases to build up. Imagine a long hallway with lots of small rooms off of it. Even if the air in the hall circulates, the air in the rooms can become stagnant. Hypoventilation can be brought about in two ways:

Not taking large enough breaths. This occurs intentionally when a diver mistakenly believes taking smaller breaths will conserve air. There can also be some mechanical limitation, such as a tight wetsuit or jacket-style BC, that prevents the diver from fully expanding his lungs. In either case, there will be areas of the lung where there is no gas exchange with each breath, and where high levels of CO2 from the blood will accumulate.

Not breathing often enough. This is also usually done consciously in order to conserve air. In this case, there is air circulating through the alveoli, or "rooms," where gas exchange occurs. But the abnormal time between breaths allows CO2 buildup with an associated rise in blood levels.

Carbon dioxide headaches are characteristically throbbing in nature, and do not respond to analgesics or migraine medications. The most effective preventive measure is to make sure you're taking slow, deep breaths. This will help reduce the buildup of carbon dioxide and help you relax as well, leading to reduced air consumption.

Type: Tension headache
Symptoms: Pain in the back of neck and head
Cause: Muscular tension
Remedy: Experience, diving within your capabilities

Particularly in newer divers, or in divers encountering new diving conditions, anxiety can lead to a tension headache. These headaches are due to muscular stress, usually in the neck and back of the head, but also can result from a clenched jaw. Divers generally stop getting these headaches as they become more comfortable in their diving environment and learn to relax.

Type: Sinus headache
Symptoms: Forehead or face pain on ascent or descent
Cause: Inability to equalize pressure in the sinuses
Remedy: Long-acting decongestants, slower descents and ascents

On ascent or descent, changes in pressure can cause pain in the sinuses, which can be interpreted as a headache when there is some problem with equalizing. Most commonly, this affects the frontal sinuses on descent, and is felt as pain across the forehead and will frequently improve on ascent.

Contributing factors include inflammation in the nose and sinuses, often caused by allergies or a cold. For this reason, you shouldn't dive while sick. If you have allergies, you should discuss with your doctor which medications will help you, while avoiding drugs that may be sedating.

Type: Migraine headache
Symptoms: Severe headaches with nausea
Cause: Various causes
Remedy: Avoiding whatever triggers the headache

In general, people who suffer severe migraines really shouldn't dive. Any of the factors associated with diving that contribute to headaches can precipitate a migraine. A diver who gets a severe migraine headache while diving is at increased risk of accident or injury from the effects of the headache - which include an inability to think clearly, psychological stress, vertigo and vomiting.

Some migraine sufferers can dive safely if they are able to identify a specific stressor, such as cold, that causes their attacks, and taking the necessary measures to avoid that trigger. Migraine sufferers must be very careful about any medications that they take while diving. Many drugs used to treat migraines contain codeine or barbiturates which are sedating and increase the risk of nitrogen narcosis.

Type: DCS headache
Symptoms: Headache with neurological deficit
Cause: Type II DCS, arterial gas embolism
Remedy: Hyperbaric oxygen therapy

If your dive buddy starts to complain of a headache after diving and reports other symptoms of decompression sickness - including pain in a joint or limb, itching, skin rash, localized swelling, nausea or vomiting, dizziness, ringing in the ears and extreme exhaustion - don't review the list of possible causes of headaches. Get to the nearest phone and call DAN (919-684-8111). A headache, along with neurological deficit, can be symptomatic of arterial gas embolism or Type II decompression sickness. Even if it turns out that the headache is not diving-related, anyone with these symptoms should seek medical care immediately.

The Diagnosis

To answer Mr. Ellermeier's and Mr. Anderson's questions, it is always difficult to make a diagnosis based upon a brief description. There are so many questions that I would like to ask. For example, where is the headache localized? Do you have a history of headaches?

However, Mr. Ellermeier, since your headaches come on after two or three days of diving, I suspect that they are most likely due to the cumulative effects of fatigue and muscle strain that build up over the days. I suggest that you make sure that you are as fit as possible for diving, and if this does not help, then try taking a break with a nondiving day in the middle of your dive trips.

Mr. Anderson, your situation is a little different. The fact that your headaches come on at a certain depth is unusual. The accompanying nausea is suggestive of a migraine, but this isn't definitive. Is it possible that you're anxious about diving beyond these depths, and that this is manifesting itself as a tension-related headache? I know several divers who dislike diving beyond depths from which they feel they could make a free ascent if necessary. The anticipation of getting another headache could be enough to result in a self-fulfilling prophecy.

Finally, common things frequently present themselves in uncommon ways. Eighty to 90 feet may be the depth at which the ambient pressure, combined with your breathing pattern, results in an elevated carbon dioxide level. It would be odd for this to happen on every dive, but it could happen.

Try to relax, and make sure that you are taking deep breaths when you dive. If this still doesn't help, then you may be one of those divers who gets headaches that we can't explain.

Even if you could eliminate all the possible causes listed, some divers are still going to get headaches. A certain number of these may have absolutely nothing to do with diving, while some undoubtedly do. As we learn more about the effects of diving on the body, we may be able to add more causes of headaches to the above list, as well as ways to avoid them.

Questions for Dr. Shelanski should be addressed to RSD, Dive Medicine, 6600 Abercorn St., Suite 208, Savannah, GA 31405; e-mail RSDmgzn@aol.com.