Diseases & Conditions Posts Archive

Decompression Illness

Decompression illness, or DCI, is associated with a reduction in the ambient pressure surrounding the body. DCI encompasses two diseases, decompression sickness (DCS) and arterial gas embolism (AGE). DCS results from bubbles in body tissues causing local damage. AGE occurs when bubbles enter arterial circulation, traveling through the arteries and potentially causing tissue damage by blocking blood flow at the small vessel level.

Who Gets Decompression Illness?

Decompression illness affects scuba divers, aviators, astronauts and compressed-air workers. The main risk factor for DCI is a reduction in ambient pressure, but other risk factors will increase the likelihood of DCI occurring. The known risk factors for divers are deep or long dives, cold water, heavy exercise at depth, and rapid ascents.

Rapid ascents contribute significantly to the risk of AGE. Other factors that may increase DCI risk but lack conclusive evidence of association are obesity, dehydration, heavy exercise immediately after surfacing, and pulmonary disease. We don’t yet fully understand possible individual risk factors. Some divers get DCI more frequently than others despite following the same dive profile.

Almost any dive profile can result in DCI, no matter how safe it seems. The risk factors, both known and unknown, can influence the probability of DCI in many ways. Evaluation of a diver for possible decompression illness is done on a case-by-case basis. The diver’s signs, symptoms and dive profiles are all considered when making a diagnosis.

Decompression Sickness

DCS (also called the bends or caisson disease) results from inadequate decompression following exposure to increased pressure. In some cases, it is mild and not an immediate threat. In other cases, a serious injury occurs. The sooner the treatment of an injury begins, the better the chance for a full recovery.

During a dive, the body tissues absorb nitrogen (and/or other inert gases) from the breathing gas in proportion to the surrounding pressure. As long as the diver remains at pressure, the gas presents no problem. If the pressure is reduced too quickly, the nitrogen may come out of solution and form bubbles in the tissues and bloodstream. Bubbles may occur as a result of violating prescribed limits, but it can also happen even when following accepted guidelines.

Bubbles forming in or near joints are the presumed cause of joint pain (the bends). With high levels of bubbles, complex reactions can take place in the body. The spinal cord and brain are usually affected, causing numbness, paralysis, impaired coordination and disorders of higher cerebral function. If large numbers of bubbles enter the venous bloodstream, congestive symptoms in the lung, and eventually circulatory shock, can occur.

Arterial Gas Embolism

If a diver ascends without exhaling, air trapped in the lungs expands and may rupture lung tissue. This injury, called pulmonary barotrauma, involves release of gas bubbles into the arterial circulation. Circulation distributes them to body tissues in proportion to the blood flow. Since the brain receives the highest proportion of blood flow, it is the main organ in which bubbles may interrupt circulation if they become lodged in small arteries.

This circulation interruption is AGE, considered the more serious form of DCI. The diver may have made a panicked ascent or held their breath during ascent. However, AGE can occur even if the ascent was completely normal. Pulmonary diseases such as obstructive lung disease may increase the risk of AGE.

A diver may surface unconscious and remain so or lose consciousness within 10 minutes of surfacing. These cases are true medical emergencies and require rapid evacuation to a treatment facility.

AGE may involve minor symptoms of neurological dysfunction, such as sensations of tingling or numbness, weakness without obvious paralysis, or complaints of difficulty in thinking but no apparent confusion. In these cases, there is time for a more thorough evaluation by a diving medical specialist to rule out other causes.

Like DCS, mild symptoms may appear to be due to causes other than diving, which can delay treatment. Symptoms may resolve spontaneously, and the diver may not seek treatment. The consequences of this are similar to untreated DCS. Residual brain damage may occur, making it more likely there will be residual symptoms after a future AGE — even after treating the later instance.

Manifestations

DCS

The most common manifestations of DCS are joint pain and numbness or tingling. The next most common are muscular weakness and inability to empty a full bladder. Severe DCS is easy to identify because the signs and symptoms are apparent. However, most DCS manifests subtly with a minor joint ache or paresthesia (an abnormal burning or tingling sensation) in an extremity.

Signs and Symptoms

DCS

Unusual fatigue
Skin itch
Pain in joints or arm, leg or torso muscles
Dizziness or vertigo
Ringing in the ears
Numbness, tingling and/or paralysis
Shortness of breath
A blotchy rash
Muscle weakness or paralysis
Difficulty urinating
Confusion, personality changes or bizarre behavior
Amnesia
Tremors
Staggering
Coughing up bloody, frothy sputum
Unconsciousness or collapse

Note: Signs and symptoms usually appear within 15 minutes or up to 12 hours after surfacing. In severe cases, symptoms may appear before surfacing or immediately afterward. Delayed onset of symptoms is rare but can happen, especially if air travel follows diving. In many cases, these symptoms are ascribed to another cause such as overexertion, heavy lifting or even a tight wetsuit. Sometimes these symptoms remain mild and resolve by themselves, but they may increase in severity until it is obvious that something is wrong and help is needed.

AGE

Dizziness
Visual blurring
Areas of decreased sensation
Chest pain
Disorientation
Bloody froth from mouth or nose
Paralysis or weakness
Convulsions
Unconsciousness
Cessation of breathing
Death

Preventing Decompression Illness

DCS

Recreational divers should dive conservatively, whether they are using dive tables or computers. Experienced divers sometimes select a table depth (rather than actual depth) of 10 feet (3 meters) deeper than called for by standard procedure. This practice is recommended for all divers, especially when diving in cold water or under strenuous conditions. Divers should be cautious about approaching no-decompression limits, especially when diving deeper than 100 feet (30 meters).

Avoiding the risk factors described above will decrease the risk of DCS. Flying or other exposure to altitude too soon after diving can also increase the risk of decompression sickness as explained in Flying After Diving.

AGE

Always relax and breathe normally during ascent. Lung conditions such as asthma, infections, cysts, tumors, scar tissue from surgery, or obstructive lung disease may predispose a diver to AGE. If you have any of these conditions, consult a physician with experience in diving medicine before you dive.

Treatment

The treatment for decompression illness is recompression. Early management of AGE and DCS is the same. It is essential that a diver with AGE or severe DCS to be stabilized at the nearest medical facility before being transported to a chamber.

Early oxygen first aid is essential and may reduce symptoms, but this should not change the treatment plan. Symptoms of AGE and severe DCS often resolve after breathing oxygen from a cylinder, but they may reappear later. Always contact DAN or a physician trained in dive medicine in cases of suspected decompression illness — even if the signs and symptoms appear resolved.

Delays in seeking treatment elevate the risk of residual symptoms. Over time the initially reversible damage may become permanent. After a delay of 24 hours or more, treatment may be less effective, and symptoms may not respond. Even if there has been a delay, consult a diving medical specialist before making any conclusions about possible treatment effectiveness.

After Treatment

There may be residual symptoms after treatment. Soreness in and around an affected joint is common and usually resolves in a few hours. If the DCI was severe, there could be significant residual neurological dysfunction. Follow-up treatments, along with physical therapy, can help. The usual outcome is eventual complete relief from all symptoms with prompt treatment.

With severe DCS, you may have a permanent residual effect such as bladder dysfunction, sexual dysfunction or muscular weakness, to name a few.

In some cases of neurological DCS, there may be permanent damage to the spinal cord, which may or may not cause symptoms. However, this type of injury may decrease the likelihood of recovery from a subsequent bout of DCS.

Untreated joint pain that subsides could cause small areas of bone damage (osteonecrosis). If this happens through repeated instances of DCS, there may be enough damage to cause the bone to become brittle, or for joints to collapse or become arthritic.

Responding to DCI

Determine the Urgency of the Injury

Make an initial evaluation at the dive site. You can suspect decompression illness if you notice any of the signs or symptoms listed above within 24 hours of surfacing from a dive. While waiting for professional medical care or evacuation, take as detailed a history as possible and try to evaluate and record the diver’s neurological status. Base your response on one of these three categories depending upon the symptoms: emergency, urgent or timely.

If necessary, you can administer first aid within the scope of your training, as described below.

Emergency

Symptoms are severe and appear within an hour or so of surfacing. The diver may lose consciousness. Symptoms might progress, and the diver is obviously ill. The diver may be profoundly dizzy or have trouble breathing. Neurological symptoms may manifest as altered consciousness, abnormal gait or weakness.

If necessary (e.g., if the diver isn’t breathing and has no pulse), begin CPR and take immediate action to have the diver evacuated. Check for foreign bodies in the airway. If they need ventilatory or cardiac resuscitation, the injured diver should be lying on their back. Vomiting in this position is dangerous; if it happens, turn the diver to the side until the airway is clear and resuscitation can resume in the supine position. While awaiting evacuation, take as detailed a history as possible and try to evaluate and record the diver’s neurological status.

Use supplemental oxygen while administering breaths to increase the percentage of oxygen breathed by the injured diver. Even if CPR is successful and the diver regains consciousness, continue administering 100 percent oxygen until the diver arrives at a medical facility and health care professionals assume care.

Urgent

The only noticeable symptom is severe pain that is unchanging or has progressed slowly over a few hours. The diver does not appear to be in distress except for the pain, and the neurological signs and symptoms are not evident without a careful history and examination.

Administer 100 percent oxygen and give fluids by mouth. Do not attempt to treat the pain with analgesics until advised to do so by medical personnel. Continue providing oxygen until arrival at the medical treatment facility.

Timely

Symptoms are either not visible or have progressed slowly for several days. The main signs or symptoms are vague complaints of pain or an abnormal sensation, which could indicate something other than DCI. Obtain as complete a diving history as possible and do a neurological evaluation. Then go to the nearest medical facility for evaluation.

Get the Dive History

If possible, obtain and document the following information for all suspected cases of decompression illness:

All dives (depth, time, ascent rates, surface intervals, breathing gases) for 48 hours preceding the injury. Also note problems or symptoms at any time before, during or after the dive.
Symptom onset times and progression after surfacing from the last dive
All first aid measures (including times and method of emergency oxygen delivery) and their effect on symptoms
Results of an on-site neurological examination
All joint or other musculoskeletal pain including location, intensity and changes with movement or weight-bearing maneuvers
Description and distribution of any rashes
Any traumatic injuries before, during or after the dive.

On-Site Neurological Examination

Information regarding the injured diver’s neurological status will be useful to medical personnel. Examination of an injured diver’s central nervous system soon after an accident may be valuable to the treating physician.

The exam is easy to learn, and individuals with no medical experience can perform it. Do as much of the examination as possible, but do not let it interfere with prompt evacuation to a medical treatment facility. (Find the instructions at On-Site Neurological Examination.)

Medical Evaluation

Call local EMS to get the diver to the nearest medical facility.

Returning to Diving after DCI

For recreational divers, whose livelihood is something other diving, a conservative approach will help minimize the chance that a diving injury will recur.

After pain-only DCI without neurological symptoms, you can consider a return to diving after a minimum of two weeks.
With minor neurological symptoms, consider returning after six weeks.
If you had severe neurological symptoms or have any residual symptoms, you should not return to diving.

You should always consult with a physician before returning to diving. Even if symptoms were not severe and they resolved completely, if you have had multiple instances of decompression illness, you must make special considerations. If you are getting DCI when other divers who dive the same profile are not, you may have elevated susceptibility. In these cases, consult a dive medicine specialist to determine if you can safely resume diving.

Ed Thalmann, M.D.

Flying After Diving

When flying after diving, the ascent to altitude increases the risk of decompression sickness (DCS) because of the additional reduction in atmospheric pressure. The higher the altitude, the greater the risk.

Cruising cabin pressure in commercial aircraft is usually maintained at a constant value regardless of the actual altitude of the flight. The equivalent effective cabin altitude generally ranges from 6,000 to 8,000 feet, though it varies somewhat with aircraft type. The maximum value is 8,000 feet, which equates to about 0.75 atmospheres absolute (ATA).

DAN-Funded Research at Duke University Medical Center

Because there was little human experimental data that was relevant to commercial flying after recreational diving, DAN funded a series of trials at the Duke University Center for Hyperbaric Medicine and Environmental Physiology. From 1992 to 1999, dry, resting volunteers tested nine single and repetitive dive profiles that were near the recreational diving no-decompression limits. The divers then had 4-hour simulated flights at 8,000 feet (2,438 meters).

In 802 trials, there were 40 DCS incidents during or after flight. For single no-stop dives to 60 fsw (18 msw) or deeper, there were no cases of DCS with surface intervals of 11 hours or longer. For repetitive, no-stop dives, DCS occurred with surface intervals shorter than 17 hours.

The 2002 DAN Flying After Recreational Diving Workshop

In 2002, DAN hosted a one-day workshop to review what was known about flying after diving and discuss the need for new flying-after-diving (FAD) guidelines in recreational diving. Representatives from the recreational diving industry and experts from other diving communities had two goals:

To review the guidelines and experimental data developed since the first flying-after-diving workshop in 1989
To achieve a consensus for new flying-after-recreational-diving guidelines

The previous consensus was to wait 12 hours after a single no-stop dive, 24 hours after multiday repetitive dives and 48 hours after dives that required decompression stops. In response to some participants viewing this consensus as too conservative, DAN proposed a simpler 24-hour wait after all recreational diving. Objections to DAN’s proposal were that DCS risks of FAD were too low to warrant such a long delay.

The Consensus Process

The workshop participants endeavored to reach consensus concerning:

Whether flying-after-diving guidelines were necessary for recreational diving
Whether the current guidelines were adequate
What the longest-duration guideline might be
If shorter guidelines were appropriate for short dives

The participants determined that guidelines were needed, and the available evidence demonstrated that existing guidelines were inadequate. After some debate, the participants agreed that unless they could rely on dive computers, written guidelines for recreational diving should be simple and unambiguous, without the need for reference to tables as the U.S. Navy procedures required. They considered three groups of divers:

Uncertified people who took part in an introductory scuba experience
Certified divers who made an unlimited number of no-decompression air or nitrox dives over multiple days
Technical divers who made decompression dives or used helium breathing mixes

Provisional Flying-After-Diving Guidelines

The following recommendations for recreational divers represent the consensus reached by attendees at the 2002 Flying After Recreational Diving Workshop. The attendees created the recommendations based on earlier published work and experimental trials. They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of DCS.

The recommendations should reduce the DCS risk associated with flying after diving but do not guarantee avoidance of DCS. Preflight surface intervals longer than the recommendations will further reduce DCS risk.

Dives Within No-Decompression Limits

For a single no-decompression dive, the recommendation is a minimum preflight surface interval of 12 hours.
For multiple dives per day or multiple days of diving, the recommendation is a minimum preflight surface interval of 18 hours.

Dives Requiring Decompression Stops

There is little experimental or published evidence on which to base a recommendation for decompression dives. A preflight surface interval substantially longer than 18 hours appears prudent.

Flying with DCS Symptoms

The workshop attendees reviewed recent FAD trials and available field data regarding flying after diving and flying with DCS symptoms and identified potentially important differences between field and chamber studies. Diving in the field involved immersion, exercise and multiple days of diving, while the chamber trials occurred on a single day with dry, resting divers. The chamber trials may not have adequately simulated flying after diving.

It is more common for divers to fly with DCS symptoms than to develop symptoms during or after a flight. Flying with symptoms may be a greater health problem than symptoms that arise during or after a flight. Divers should seek medical advice and avoid flying if they note signs or symptoms that may indicate DCS.

Limitations

The workshop proceedings stressed that because the experimental trials described in the workshop used a dry hyperbaric chamber with resting volunteers, the guidelines might need to be longer for divers who were immersed and exercising.

The participants determined that the effects of exercise and immersion on preflight surface intervals would need an experimental study. Additional studies have occurred and results are awaiting publication.

Additional Resources

Download the complete Flying After Recreational Diving Workshop proceedings in our Publication Library.

Anxiety: Is It a Contraindication to Diving?

Anxiety is a mental health condition that refers to an overwhelming sense of apprehension or fearfulness. Marked by physiological signs, anxiety can produce both psychological and physical symptoms.

Anxiety can cause uncertainty about the nature and reality of threats as well as self-doubt about one’s capacity to deal with situations. Physical symptoms of anxiety can vary widely, from the damp palms and quickened heartbeat associated with mild apprehension to the crippling, paralyzed feelings of a full-blown panic attack or phobic reaction.

Symptoms

Symptoms of anxiety can vary from person to person, situation to situation, and even day to day. Signs include:

Dilated pupils
Increased heart rate and blood pressure
Constricted peripheral blood vessels
Blood flow diverted to the skeletal muscles
Rapid breathing
Increased perspiration

Some people who suffer from anxiety can experience severe panic attacks or debilitating physical symptoms. These may include:

Shortness of breath
Palpitations
Chest pain
Dizziness or vertigo
Hot or cold flashes

Implications in Diving

The ocean can be a major stressor for some people. As stress increases, a diver’s ability to recognize and respond properly diminishes.⁴ In a demanding situation it is critical that a diver be able to recognize and break out of the escalating cycle of stress before it reaches the level of panic. Divers may exhibit some specific symptoms and behaviors, including:

Rapid breathing or hyperventilation
Muscle tension
“White knuckle” grip
“Wild-eyed” look or avoiding eye contact
Irritability or distractibility
“Escape to the surface” behavior
Stalling, e.g., taking too long to don equipment or enter the water
Imaginary equipment or ear problems
Being overly talkative or becoming withdrawn
Contact maintenance, e.g., clutching the swim ladder or anchor line

Dive professionals are taught to recognize signs and symptoms of stress, both in themselves and in students and new divers. In many cases, identifying and removing a particular stressor can help alleviate anxieties. However, there will be instances in which recreational divers remain apprehensive, and the reason(s) may not be readily apparent. Depending on divers’ motivations for continuing to dive and their willingness to work toward a resolution of their anxieties, there are psychological techniques that can be useful in overcoming these problems. Mild anxiety does not have to be a contraindication to recreational diving. Dive professionals learn to intervene before that stress becomes excessive and results in exhaustion, panic or a dive accident or fatality.

Common Stressors in Diving Include:

Time pressure — Dive tables limit the time that can be spent at various depths. Planning and staying within no-decompression limits provides a significant source of stress, especially when accompanied by task-loading.
Task-loading — This involves doing or managing too many things at once. An example is a scuba diver attempting to hold a light and camera while navigating in an overhead environment. It is easy to focus on one task to the exclusion of others when that task is complicated or particularly demanding. This is known as perceptual narrowing.
Pushing limits — Diving beyond physical limitations or pushing oneself too hard, either physically or mentally.
Environmental conditions — These include unfamiliar dive sites, currents and surface conditions and diving in cold water, reduced visibility or at night.
Lack of readiness — Too little preparation or training for a particular dive can be a major stressor.
Equipment considerations — Diving with new or unfamiliar equipment, or diving with equipment (a drysuit, for example) in which one is insufficiently experienced or trained.
Diving for the wrong reason — This includes peer pressure, diving beyond safe limits “just for the thrill,” diving when you are uncomfortable or ill (seasick or hungover), diving because a friend is diving, diving to save face or diving due to fear of being left out.

Practice and additional training can help reduce anxiety. Instructors sometimes overlook the importance of patience and repeated practice in making students comfortable in the open water. Some students will need additional time and practice or require one-on-one instruction in particular areas. It should be emphasized that it is always acceptable to sit out a dive for any reason.

Medical Conditions

Certain medical conditions can produce feelings of anxiety: anemia, mitral valve prolapse (a cardiac condition), premenstrual symptoms, menopausal symptoms, diabetes, hypoglycemia (an abnormally low level of blood glucose), thyroid and parathyroid disorders, asthma and some systemic infections.⁵ Along with other stressors, one or more of these could amount to a potent and dangerous combination.

Overcoming Anxiety

There are ways to treat and overcome anxiety. Work with your health care provider to see what options are available. Treatment may include medication or working with a licensed professional or a combination of the two. An understanding of the mechanisms of anxiety help you understand how possible treatments and techniques might work.

John R. Yarbrough, Ph.D.

References

1 Barlow, David H. (1988). Anxiety and its Disorders: The Nature and Treatment of Anxiety and Panic. New York: Guilford Press.

2 Professional Association of Diving Instructors. (1999). The PADI Divemaster Manual. Rancho Santa Margarita, CA: PADI.

3 Smith (1979) as discussed in Gilliam, Bret. (1995). Deep Diving: An Advanced Guide to Physiology, Procedures and Systems. San Diego: Watersport Publishing.

4 Hardy, William, Jr. (1997). Psychiatric Physician Assistant Protocol: A Handbook for Mid-Level Psychiatric Practitioners. Tyler, TX: William Hardy, MS, PA-C.

5 DuPont, Robert L. (1987). Phobia: A Comprehensive Summary of Modern Treatments. NY: Brunner-Mazel.

6 Gilliam, Bret. (1995). Deep Diving: An Advanced Guide to Physiology, Procedures and Systems. San Diego: Watersport Publishing.

7 Maultsby, Maxie C., Jr. (1984). Rational Behavior Therapy. Englewood Cliffs, NJ: Prentice-Hall.

Hypertension

Hypertension (high blood pressure) is a common medical condition among the general population and divers.

Blood pressure is a measure of the force with which blood pushes outward on the arterial walls. A blood pressure reading is a ratio. The first number (systolic pressure) is measured when your heart is beating. The second is the diastolic pressure, taken when your heart is resting between beats. Blood pressure numbers are in millimeters of mercury (mmHg). A typical reading is 120/80 mmHg (“120 over 80”). What constitutes hypertension varies slightly from country to country and from reference to reference.

Epidemiology

About one-third of U.S. adults have hypertension.
69% of those who have a first heart attack, 77% of those who have a first stroke and 74% of those with chronic heart failure have hypertension. It is also a risk factor for kidney disease.
348,000 deaths in the U.S. in 2009 had hypertension as either a primary or contributing cause.
Only 47% of people with hypertension have the condition under control.
30% of American adults have prehypertension.

Sources: U.S. Centers for Disease Control and Prevention; and American Heart Association

Symptoms

Most people don’t have obvious symptoms and therefore don’t know they have hypertension. Some know they have it but don’t manage it because they feel fine.

Symptomatic people commonly have headaches, particularly at the back of the head. Headaches are common enough that people can underestimate them as a symptom. Spontaneous nosebleeds and shortness of breath are more concerning but don’t tend to occur until blood pressure has reached life-threatening levels.

Management

Mild hypertension can often be controlled with diet and exercise. In some cases medication may be necessary to keep blood pressure within acceptable limits. Many classes of drugs are used to treat hypertension, and they have varying side effects. Some individuals change medications after one is (or becomes) ineffective. Others might need more than one drug at a time to keep their blood pressure under control.

Antihypertensive drugs, known as beta-blockers, may cause a decrease in maximum exercise tolerance and have some effect on the airways. These side effects typically pose no problem for the average diver.
Another class of antihypertensives, known as angiotensin-converting enzyme (ACE) inhibitors, may be preferred for divers. A persistent dry cough is a possible side effect of ACE inhibitors.
Calcium channel blockers are another choice. A potential side effect of these drugs is becoming lightheaded when standing up.
Diuretics (drugs that promote the production of urine) are frequently used to treat hypertension. Their use requires careful attention to maintaining adequate hydration and monitoring electrolyte levels in the blood.

Complications

High blood pressure can affect your health in several ways. A person with hypertension faces short- and long-term complications. One of the main reasons why doctors pay so much attention to hypertension is because it is a silent killer.

Short-term complications generally result from extremely high blood pressure. The most significant is the risk of a stroke due to the rupture of a blood vessel in the brain.
Long-term detrimental effects are more common, including:
- Coronary artery disease (angina)
- Congestive heart failure
- Atrial fibrillation
- Chronic kidney disease
- Stroke
- Loss of vision

Implications in Diving

For the Diver

With controlled blood pressure and no evidence of damage to major organs, the main concerns regarding fitness to dive are the side effects of the medication(s) used. Most antihypertensive drugs are compatible with diving as long as side effects are minimal and your performance in the water is not significantly compromised.
If you have a history of hypertension, have a doctor monitor possible associated damage to the heart and kidneys.
Have regular physical examinations, including screening for long-term consequences of hypertension such as coronary artery disease.

For the Dive Operator

Controlled hypertension is not a contraindication for diving but is one of several cardiovascular risk factors.
Medications for blood pressure control may have side effects such as dehydration, dizziness, chronic cough or decreased exercise capacity. These side effects can be a contraindication to diving and need to be addressed by a physician.
Divers with hypertension should be under a physician’s care and be able to tell you their condition is under control and without complications.
Older, obese or clearly out of shape divers are at increased risk of cardiovascular emergencies and may need further medical evaluation before diving.

For the Physician

Ensure that divers with hypertension can tolerate high exertion for at least five to 10 minutes should it be required. Environmental conditions may change, or an emergency may arise in which the diver needs to exert themself to avoid a life-threatening risk.
Elevated levels of catecholamines may cause additional stress on a heart that is already undergoing an increased preload and afterload due to immersion. A more conservative criterion for further testing is justified for divers.
Cardiac arrest in the water has even worse outcomes than out-of-hospital events, so closer screening and evaluation for unacceptable risks are justified.
When adding or changing a medication regimen, allow several weeks to monitor side effects. Do not have patients discontinue antihypertensive medication before diving.

High-Pressure Ophthalmology

Our eyes normally exist in a world where the pressure around them is the result of the combined weight of all of the gases in the earth’s atmosphere. Diving exposes the eyes to increased pressure. While most of the time this has little or no negative effects on the diver, increased eye pressure in scuba diving can result in ocular decompression sickness or other problems.

In regard to personal eye health and diving, here are some common questions with corresponding answers:

What are the best contact lenses to wear underwater?

Divers who wish to wear contact lenses while diving should ask their ophthalmologists or optometrists to prescribe “soft” contact lenses. “Hard” lenses or rigid gas-permeable lenses, the other two commonly prescribed types of lenses, have been found to sometimes cause symptoms of eye pain and blurred vision during and after dives, in which the diver accumulates a significant inert gas load. These symptoms occur as a result of gas bubbles forming between the cornea and the contact lens.

Can individuals who have had cataract surgery dive?

Yes. Most cataract surgeons now use surgical incisions designed to provide maximum post-operative wound strength. The recommended waiting time prior to returning to diving depends on exactly what type of incision was made. Ask your surgeon for recommendations for your particular type of surgery.

Is it dangerous to dive if you have glaucoma?

Glaucoma is a disease in which increased pressure inside the eye is associated with damage to the optic nerve and loss of vision. Because of this, physicians have voiced concern about the possibility that a hyperbaric environment might therefore cause increased damage to the eye. Although this would seem to be a logical conclusion, diving thus far has not been shown to be a problem for glaucoma patients. This is most likely because the damage associated with glaucoma is a factor of the difference between the pressure inside the eye and the surrounding pressure, rather than simply the absolute magnitude of the pressure inside the eye.

There are two important considerations for glaucoma patients who wish to dive. Some of the medications used to lower the pressure in the eyes of glaucoma patients may have adverse effects while diving. Timolol, for example, may result in a decrease in heart rate that could theoretically place a small percentage of divers at higher risk for loss of consciousness underwater; acetazolamide (diamox) may cause tingling sensations of the hands and feet that could be mistaken for symptoms of decompression sickness. These and other ocular medications are discussed in detail in the article mentioned in the introduction.

Certain types of glaucoma surgery (collectively called glaucoma filtering procedures) create a communication between the anterior chamber of the eye and the subconjunctival space to help lower the pressure in the eye. Facemask barotrauma may have an adverse effect on the functioning of the filter and result in a need for additional surgery or further damage to the eye from the glaucoma.

Individuals who have had glaucoma surgery or who are taking glaucoma medications should check with their ophthalmologist before diving.

Is it possible to get ocular (eye) decompression sickness?

Ocular decompression sickness (DCS) is a relatively uncommon event, but one which does occur and it is very important that divers be aware of this possible presentation of DCS. Symptoms may include:

Loss of vision
Blurred vision
Diplopia (double vision)
Blind spots in your field of vision
Pain around the eye
Nystagmus (abnormal eye movements)

The presence of any of these symptoms following a dive should be evaluated as soon as possible by a physician knowledgeable about diving injuries, or the diver should call DAN.

What eye conditions would preclude someone from diving?

Gas in the eye (may be present after vitreoretinal surgery). Diving with gas in the eye may result in vision-threatening intraocular barotrauma due to the pressures of the surrounding water column.
Hollow orbital implants. The presence of a hollow orbital implant after an eye has been surgically removed because of injury or disease may preclude diving. The increased pressures encountered while diving may cause a hollow orbital implant to collapse, resulting in cosmetic problems and a need for further surgery to replace the damaged implant. Many ocular plastic surgeons are now using implants made of hydroxyapatite, a porous material which is not a contraindication for diving.
Acute eye disorders. Any acute eye disorder which produces significant pain, light sensitivity, double vision, or decreased vision is a contraindication to diving. These symptoms may be produced by a number of ocular infectious, traumatic, or inflammatory conditions. In general, it’s best to wait until the underlying acute condition has resolved and there are no distracting or disabling ocular symptoms to contend with before returning to diving.
Recent eye surgery. After eye surgery, avoid diving prior to completion of the recommended convalescent period for your particular type of surgery.
Inadequate vision. There is a detailed discussion of visual acuity and diving in the article entitled “Diving and Hyperbaric Ophthalmology” mentioned in the introduction.Deciding on your own visual acuity is primarily a judgment call, with few relevant scientific studies available to help resolve the issue. The approach taken in the article was to use statutory visual standards established for another hazardous activity — driving a car, for example — whose visual requirements are more demanding than diving. The recommendation made was that if you see well enough to qualify for a driver’s license and operate a motor vehicle safely, then you should be able to see well enough to dive. If a prospective diver has visual acuity which is poor enough to preclude them from being allowed to drive, then the fitness-to-dive decision needs to be individualized with the assistance of an eye physician and dive instructor.
Decreased vision. If your vision is impaired from previous episodes of decompression sickness (DCS) or arterial gas embolism, don’t risk further injury.
Some types of glaucoma surgery.

Is it safe to dive after radial keratotomy?

Radial keratotomy (RK) is a surgical procedure designed to cure myopia (nearsightedness). In this operation, the surgeon makes a small number of radially-oriented incisions in the cornea of the eye. These incisions cause a decrease in the strength of the cornea and may increase the risk of serious injury if the eye is subjected to subsequent trauma, including barotrauma such as a facemask squeeze. Despite this theoretical risk, there have been no reports of which I am aware involving a traumatic rupture of the cornea resulting from diving after RK.

Divers who have had this procedure should wait at least three months after the surgery before returning to diving and should be careful to avoid a facemask squeeze — it’s important to avoid imposing the “Boyle’s Law Stress Test” on these corneal incisions.

If you are a diver and considering having this procedure done, I would recommend that you also ask your eye surgeon to discuss the potential advantages of photorefractive keratectomy, the alternative refractive surgical procedure discussed below.

Is it safe to dive after having had the new laser refractive surgery (photorefractive keratectomy)?

Yes. This procedure uses laser reshaping of the cornea instead of incisions to treat myopia. This method results in no decrease in the structural integrity of the cornea and no risk of corneal rupture as a result of facemask squeeze. It should be safe to dive approximately two weeks after this surgery. Discuss your plans with your physician and have a final evaluation before you dive.

I just came up from a dive and noticed that my vision is now blurry. What conditions could cause this symptom?

Possible causes of blurred vision after diving include:

Contact lenses which become tightly adherent to the eye during a dive
Displaced contact lens
Corneal irritation from mask anti-fog solutions
Ultraviolet or “sunburn” damage to the cornea
Corneal irritation resulting from bubbles under hard or rigid gas-permeable contact lenses
Use of transdermal scopolamine to prevent motion sickness
Decompression sickness
Arterial gas embolism

If you are a contact lens wearer, first ensure that the lens is still in place and then instill some lubricant eye drops. If this is successful in restoring your vision to normal, then it is not necessary to seek medical attention. If you are not a contact lens wearer or these actions are unsuccessful, then you should have your symptoms evaluated by a physician knowledgeable about diving injuries. For a list of dive physicians in your area, call DAN.

I just came up from a dive and one of my eyes has a bright red spot on it. What could cause this? Do I need to see an eye doctor?

The most common cause of a red spot on the eye after a dive is a subconjunctival hemorrhage. This is a collection of blood over the sclera (white part) of the eye. It is usually caused by a mild mask squeeze and does not require any treatment. A more severe squeeze could result in other injuries to the eye, however, so it is a good idea to see your eye doctor just in case. It is absolutely essential to see your eye doctor if you have eye pain, double vision, blind spots in your field of vision, or decreased vision after a dive or if you have a history of eye surgery in the past.

I am undergoing hyperbaric oxygen treatments and have noticed that my vision is slowly getting worse. Why is this happening?

Hyperbaric oxygen (HBO) therapy may cause a change in the way that the lens of the eye refracts light. This change occurs slowly and is usually not noticed until after a week or two of treatment. If the HBO therapy continues to that point or beyond, the patient may experience a slow myopic (nearsighted) change. This slow change typically continues as long as the HBO treatments continue. It is usually reversible after the treatments are finished, although there have been some reports in which this reversal did not occur or was incomplete.

A Final Word

Most of the restrictions to diving mentioned above do not apply to hyperbaric oxygen (HBO) therapy. According to Diving and Hyperbaric Ophthalmology: hyperbaric exposures in a dry chamber “do not entail immersion of the eye or the possibility of facemask barotrauma. Only the presence of intraocular gas or hollow orbital implants remains as possible ocular contraindications to diving in these patients.”

Frank K. Butler Jr., M.D.

Mask Squeeze (Facial Barotrauma)

Overview

Mask squeeze (mask barotrauma or facial barotrauma) results from a failure to equalize the air space created between your mask and face. In most cases this is a relatively benign injury. It tends to be more common in new divers. Blockages of nose — such as congestion or nose clips — will interfere with mask equalization.

Mechanisms of Injury

As with your sinuses and ears, you must also equalize the air space in your mask as you descend. Failure to equalize by adding air to the space in the mask (by exhaling through your nose), can create unequal pressure between the air space in the mask and the vascular pressure within the blood vessels of the face. The pressure difference can result in various degrees of facial barotrauma, which is an injury to the soft tissues of the face contained within the mask. Imagine your face in a suction cup.