คลังเก็บ: Diseases & Conditions Posts

Information regarding an injured diver’s neurological status will be useful to medical personnel not only for deciding the initial course of treatment but also in the effectiveness of treatment. Examination of an injured diver’s central nervous system soon after an accident may provide valuable information to the physician responsible for their treatment. The examination may help diagnose decompression illness, which can have neurological components. The On-Site Neurological Exam is easy to learn and can be done by individuals with no medical experience. Perform as much of the examination as possible, but do not let it interfere with evacuation to a medical treatment facility.

Perform the following steps in order, and record the time and results.

1. Orientation

• Does the diver know their own name and age?
• Does the diver know the present location?
• Does the diver know what time, day and year it is?

Note: Even though a diver appears alert, the answers to these questions may reveal confusion. Do not omit them.

2. Eyes

• Have the diver count the number of fingers you display, using two or three different numbers.
• Check each eye separately and then together.
• Have the diver identify a distant object.
• Tell the diver to hold head still, or you gently hold it still, while placing your other hand about 18 inches (0.5 meters) in front of their face. Ask the diver to follow your hand. Now move your hand up and down, then side to side. The diver’s eyes should follow your hand and should not jerk to one side and return.
• Check that the pupils are equal in size.

3. Face

• Ask the diver to purse their lips. Look carefully to see that both sides of the face have the same expression.
• Ask the diver to grit their teeth. Feel the jaw muscles to confirm that they are contracted equally.
• Instruct the diver to close the eyes while you lightly touch your fingertips across the forehead and face to be sure sensation is present and the same everywhere.

4. Hearing

• Hearing can be evaluated by holding your hand about 2 feet (0.6 meters) from the diver’s ear and rubbing your thumb and finger together.
• Check both ears moving your hand closer until the diver hears it.
• Check several times and compare with your own hearing.

Note: If the surroundings are noisy, the test is difficult to evaluate. Ask bystanders to be quiet and to turn off unneeded machinery.

5. Swallowing Reflex

• Instruct the diver to swallow while you watch the “Adam’s apple” to be sure it moves up and down.

6. Tongue

• Instruct the diver to stick out their tongue. It should come out straight in the middle of the mouth without deviating to either side.

7. Muscle Strength

• Instruct the diver to shrug shoulders while you bear down on them to observe for equal muscle strength.
• Check diver’s arms by bringing the elbows up level with the shoulders, hands level with the arms and touching the chest. Instruct the diver to resist while you pull the arms away, push them back, up and down. The strength should be approximately equal in both arms in each direction.
• Check leg strength by having the diver lie flat and raise and lower the legs while you resist the movement.

8. Sensory Perception

• Check on both sides by touching lightly as was done on the face. Start at the top of the body and compare sides while moving downwards to cover the entire body.

Note: The diver’s eyes should be closed during this procedure. The diver should confirm the sensation in each area before you move to another area.

9. Balance and Coordination

Note: Be prepared to protect the diver from injury when performing this test.

• First, have the diver walk heel to toe along a straight line while looking straight ahead.
• Have the diver walk both forward and backward for 10 feet or so. Note whether movements are smooth and if they can maintain balance without having to look down or hold onto something.
• Next, have the diver stand up with feet together and close eyes and hold the arms straight out in front — with the palms up. The diver should be able to maintain balance if the platform is stable. Your arms should be around, but not touching, the diver. Be prepared to catch the diver who starts to fall.
• Check coordination by having the diver move an index finger back and forth rapidly between the diver’s nose and your finger held approximately 18 inches/0.5 meters from the diver’s face. The diver should be able to do this, even if you move your finger to different positions.
• Have the diver lie down and instruct them to slide the heel of one foot down the shin of the other leg, while keeping their eyes closed. The diver should be able to move their foot smoothly along the shin, without jagged, side-to-side movements.
• Check these tests on both right and left sides and observe carefully for unusual clumsiness on either side.

Important Notes

Ed Thalmann, M.D.

Asthma is a disease characterized by narrowing of the breathing tubes (bronchi) in response to a variety of stimuli. The response can be variable, and a person can have a sudden worsening in lung function called an “attack.” An asthma attack can be triggered by pollen and other so-called allergens, cold air, irritants in the atmosphere, a cold or the flu. The topic of asthma and diving has long been controversial in the recreational diving community. Historically, divers with asthma were excluded from diving.

Epidemiology

• 1 in 13 Americans have asthma.
• More than 25 million Americans have asthma, which translates to 7.7% of adults and 8.4% of children.
• Asthma is more common in adult women then adult men.
• 10 Americans die from asthma each day.

Sources: U.S. Centers for Disease Control and Prevention; and Asthma and Allergy Foundation of America

Symptoms

The bronchial narrowing that occurs with asthma has two effects. One is a decrease in the amount of air that can be moved in and out of the lungs. This can reduce exercise capacity — especially for a diver, who already has reduced breathing capacity due to the resistance of the breathing apparatus and increased internal resistance due to higher breathing gas density at depth. Secondly, narrowed airways could cause trapping of gas in the lungs during ascent. If trapped gas expands faster than it can be exhaled through the narrowed airways, lung rupture may result, potentially causing arterial gas embolism or pneumothorax (collapsed lung). People with asthma who dive are at risk not only from gas-trapping but also from reduced exercise capability. While it is often easy to stop, rest and catch one’s breath while exercising on land, this may not be possible underwater.

The South Pacific Underwater Medical Society (SPUMS) has stated that diving may precipitate an asthma attack. People with asthma are at risk of shortness of breath, panic and drowning during diving activities, including while on the surface.

Management

There are four kinds of asthma, and the treatment is based on the diagnosis.

• Mild Intermittent Asthma: Symptoms occur less than once a week and are associated with less than a 20 percent decrease in peak flow (the maximum rate of air flow during exhalation). This type of asthma involves brief increases in the severity of symptoms (called exacerbation) that last a few hours to a few days. Nocturnal symptoms occur less than twice per month, and between acute attacks the patient should be asymptomatic with normal lung function. Treatment includes the use of short-acting bronchodilators on an as-needed basis.
• Mild Persistent Asthma: Peak flow should be near normal (with less than 20 percent variation), but symptoms occur more than once weekly. Exacerbation affects sleep, with nighttime symptoms often appearing more than twice per month. Treatment involves use of short-acting bronchodilators during the day and long-acting bronchodilators at night.
• Moderate Persistent Asthma: Symptoms, which may include coughing, can occur daily and often interfere with activities or sleep. People with moderate persistent asthma may require a short-acting bronchodilator. Peak flow is generally between 60 and 80 percent of normal. Ironically, many patients with these symptoms do not believe they have asthma. Coughing with exercise or at night is a notable symptom and a likely indicator of this type of asthma. Daily medication, usually inhaled steroids, is required; short- acting bronchodilators may be needed for acute episodes.
• Severe Persistent Asthma: People with this type of asthma have continual symptoms and peak flows of 60 percent of normal or less. Increases in symptom severity occur frequently, limiting physical activity, and nocturnal symptoms occur frequently. Regular use of long-acting bronchodilators and oral steroids is required as is use of short-acting bronchodilators during acute episodes.

If the treatment regimen can return the pulmonary function test results to normal, especially following exercise, people with asthma may be able to safely dive (and perform the strenuous exercise that may be required during diving).

Complications

The treatment of asthma is relevant in determining its severity and the associated risk of diving. According to discussions among experts at the Undersea and Hyperbaric Medical Society (UHMS), divers who have mild intermittent asthma, mild persistent asthma or moderate persistent asthma, may be allowed to dive, provided their asthma is well controlled.

Implications in Diving

Diabetes is a disease in which the body is unable to produce or effectively respond to insulin, a hormone the body needs in order to use glucose (sugar) in the blood. Healthy individuals maintain plasma glucose in a narrow range of 70 to 110 milligrams per deciliter (mg/dL) of blood. People with diabetes can experience dramatic fluctuations in plasma glucose. The primary concern is that low levels of blood glucose (hypoglycemia) can make you lose consciousness. Long-term elevation of blood glucose (hyperglycemia) can result in circulatory problems and compromised vision.

The inability to produce insulin is known as Type 1 diabetes, or insulin-requiring diabetes mellitus (IRDM). The inadequate production of insulin or the insensitivity of the body’s cells to insulin is known as Type 2 diabetes, or mature onset diabetes. Individuals with diabetes, particularly IRDM, have faced exclusion from activities during which a sudden loss of consciousness might pose a significant risk, such as scuba diving.

DAN Study on Plasma Glucose Levels and Recreational Diving

DAN researchers measured the plasma glucose response to recreational diving in adults with IRDM compared to a control group of divers without diabetes. The divers with IRDM had at least moderately controlled diabetes, no secondary complications and no hospitalizations for blood glucose irregularities in the previous 12 months; furthermore they understood the relationship between plasma glucose and exercise.

Most of the dives were from commercial liveaboard dive boats or day boats in subtropical or tropical waters. The divers’ blood glucose had to be above 80 mg/dL before each dive. Divers used commercially available portable monitors to measure plasma glucose by finger stick. Values were recorded several times before and after the dives.

Results

The variability in plasma glucose levels was higher in the IRDM group than in the control group. Neither group had symptoms or complications related to hypoglycemia during dives or immediately postdive, despite some low levels of plasma glucose. The IRDM divers took extra glucose before nearly half of the dives. Postdive plasma glucose fell below 70 mg/dL after 7 percent of the IRDM group dives (the lowest being 41 mg/dL) and after 1 percent of the control group dives (the lowest being 56 mg/dL).

Although IRDM divers did not report symptomatic hypoglycemia immediately before, during or immediately after diving, there were instances unrelated to diving. Symptoms included nausea, anxiety, shaking, feeling cold and headaches. In several cases, these symptoms were enough to wake the diver in the middle of the night. Moderate levels of asymptomatic hyperglycemia (greater than 300 mg/dL) were present on 67 occasions predive and 17 occasions postdive.

Conclusions

• Plasma glucose level changes in the IRDM divers ranged from a rise of 283 mg/dL to a fall of 370 mg/dL. The magnitude of change was frequently surprising to the divers, who had experience in diabetes management. People with less stable IRDM and those who regularly maintained very tight control may have an increased risk of hypoglycemia.
• High plasma glucose may increase susceptibility to decompression sickness or worsen neurological decompression illness.¹ Simply elevating glucose levels to reduce the risk of hypoglycemia occurring during a dive may not be completely harmless.
• Despite occasional instances of plasma glucose levels in the 40 to 50 mg/dL range, the lack of symptoms associated with hypoglycemia in this study could be due to a failure to recognize or report symptoms. Divers noted and corrected equivalent low blood glucose levels they experienced at other times of the day.
• Signs and symptoms associated with hypo- or hyperglycemia can be due to other medical conditions, such as hypothermia, nausea from seasickness and possibly decompression illness.
• All of the dives monitored were recreational, with minimally or modestly stressful conditions in tropical or subtropical waters. The additional stress associated with additional or more complex equipment, more severe water conditions, more extreme dive profiles, or emergencies could produce more dramatic fluctuations in plasma glucose.
• This study had adult subjects only. Children may be at higher risk due to increased distractibility, less experience in regulating plasma glucose and a physiological predisposition to greater variability in plasma glucose levels during exercise.²

Diabetes and Diving Safely

• Symptoms of severe hypoglycemia include seizure and loss of consciousness, which are likely to be fatal if experienced underwater.
• There are no reliable ways to take a rest while diving as there are when exercising on land. Conditions may change rapidly and turn a relaxed dive in benign conditions into a physically demanding situation.
• Management of serious illnesses is more difficult in remote areas.
• The dive buddy standard assumes that both individuals can provide adequate and rapid support for a partner. If a preexisting medical condition impairs one of the pair, this assumption may not be accurate.
• Diabetes can be progressive, and such progression may increase risk while diving.

For more information, see Guidelines for Diabetes and Recreational Diving.

Neal W. Pollock, Ph.D., Donna M. Uguccioni, M.S., Guy de L Dear, M.B., FRCA

References

1. Moon RE. Fluid resuscitation, plasma glucose and body temperature control. In: Moon RE, ed. Report of the Decompression Illness Adjunctive Therapy Committee of the Undersea and Hyperbaric Medical Society; 2003; Duke University, Durham NC: Undersea and Hyperbaric Medical Society; 2003: 119-128.

2. American Diabetes Association. Diabetes Mellitus and Exercise. Diabetes Care 2002; 25(90001):S64-8.

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

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.

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).

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.

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

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:

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.

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.

Manifestations

You will likely feel a suction effect over the affected area. The negative pressure over the soft tissues beneath the mask (upper cheeks, nose, lower forehead, eyelids and eyeballs) will cause engorgement of the blood vessels. The result ranges from mild discomfort to pain. After it is resolved by properly equalizing the mask or ascending to the surface, you may show some swelling in the affected area and red, brown, or purple spots (petechiae), particularly on your eyelids.

In some cases, subconjunctival petechiae or hemorrhage (blood from burst vessels) appears in the white of the eye. Visual disturbances are rare, but they are a sign of a more severe compromise and require immediate medical evaluation.

During the healing process, blood will change color from the initial bright red to a darker red, then greenish, then yellowish before the eye returns to its standard white color. This healing is a natural process that corresponds with how your body metabolizes the blood.

Treatment

Unless you are experiencing eye pain or visual problems, there is no treatment for facial barotrauma except time. Because it is essentially a bruise, your body will eventually reabsorb the blood.

If you have eye pain or visual disturbances such as blurred vision or loss of part of the visual field, or feel blood that has accumulated/layered (hyphema) in colored part of your eye (iris), see your physician or an eye specialist immediately. These symptoms are infrequent in mask squeeze. With routine healing, and depending on the extent of the injury, the symptoms of mask squeeze can take up to two weeks or more to resolve. You will probably look worse than you’d like before it gets better. Your body needs to reabsorb the blood and fluid. These are gravity-dependent, meaning they will spread downward on your face.

Who Gets Mask Squeeze?

It is most common in new divers. They tend to be overwhelmed by all the skills they need to remember, such as buoyancy control and equalization of their ears and sinuses, while adjusting to an unfamiliar environment. Experienced divers are not immune to mask squeeze. They tend to get it when they are concentrating on a new activity or focusing on a task that diverts their attention from clearing their mask. Changing to a new mask or a low-volume mask may also lead to mask squeeze because the diver may not be accustomed to when to add air. Poor-fitting masks or other factors, such as facial hair, may lead to problems with equalizing. 

Prevention

The solution to preventing mask squeeze is to remember to keep your nasal passageways open during descent by blowing small amounts of air through your nose every time you equalize your ears. By exhaling through your nose and using a properly fitted mask, you will minimize the risk of facial barotrauma. A mask should fit comfortably against your face. You should be able to achieve an appropriate seal by gently placing the mask on your face and inhaling through your nose.

The mask should seal to your face and not fall off even without the mask strap in place. It is not unusual for a small amount of leakage to occur while diving, especially if you have facial hair. Exhaling through your nose and tilting your face towards the surface while cracking the lower seal of the mask will generally remove any unwanted water from your mask. This technique will also keep the air space between the mask and your face adequately

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Implications in Diving

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Fitness to Dive

Do not dive until recommended by your physician. Assess why the problem occurred and address each factor. Consider contacting a dive instructor to address preventing future injuries.

Middle-ear barotrauma (ear squeeze) is the most common dive injury. It occurs when pressure in the air space of the middle ear is not equalized to the ambient pressure. It can cause a ruptured eardrum and can happen either while diving or flying.

Anatomy and Functions of the Ear

The human ear has three distinct sections:

• External ear: This includes the ear itself and the ear canal to the eardrum.
• Middle ear: This is an air-filled cavity between the eardrum and the inner ear. It has three components: the middle-ear cavity, the three ear bones (ossicles) and the mastoid process.
• Inner ear: The inner ear is a sensory organ. It is part of the central nervous system, and it has two functions:
  • Auditory: The cochlea turns soundwaves into electrical impulses for the brain.
  • Balance, orientation and acceleration: The canals provide some of our control of balance and position and help detect acceleration.

Mechanisms of Injury

The air pressure in the tympanic cavity — an air-filled space in the middle ear — must be equalized with the pressure of the surrounding environment. The Eustachian tube connects the throat with the tympanic cavity and provides passage for gas when pressure equalization is needed. This equalization normally occurs with little or no effort. Various maneuvers, such as swallowing or yawning, can facilitate the process.

An obstruction in the Eustachian tube can lead to an inability to achieve equalization, particularly during descent, when the pressure changes quickly. If the pressure in the tympanic cavity is lower than the pressure of the surrounding tissue, this imbalance results in negative pressure (a relative vacuum) in the middle-ear space. It causes tissue to swell, the eardrum to bulge inward, leakage of fluid and bleeding of ruptured vessels. At a certain point an active attempt to equalize will be futile, and a forceful Valsalva maneuver may injure the inner ear. Eventually the eardrum may rupture; this is likely to bring relief from the pain associated with MEBT, but it is an outcome to avoid if possible.

Often the injury is serious enough that it causes rupture of the eardrum, tympanic membrane rupture or inner ear barotrauma.

Factors that can contribute to the development of MEBT include the common cold, allergies or inflammation — conditions that can cause swelling and may block the Eustachian tubes. Poor equalization techniques or too rapid descent may also contribute to the development of MEBT.

Manifestations

Divers who cannot equalize middle-ear pressure during descent will first feel discomfort in their ears (clogged or stuffed ears) that may progress to severe pain. Further descent only intensifies the ear pain, which is soon followed by a serous fluid buildup and bleeding in the middle ear. With further descent, the eardrum may rupture, providing pain relief; this rupture may cause vertigo and hearing loss. Exposure of the normally sterile middle ear to infection from a mixture of pathogens from the non-sterile contents of the ear canal and surrounding water may result in a middle-ear infection.

Signs and Symptoms

• A feeling of clogged or stuffed ears
• Ear discomfort or pain
• Pain increases with descent during diving
• Fluid buildup and bleeding
• Eardrum rupture, leading to vertigo and hearing loss

Prevention

• Do not dive when congested.
• Refrain from diving when feeling popping or crackling in your ears, or if you have a feeling of fullness in your ears after diving.
• Learn and use proper equalization techniques.

First Aid

• Use a nasal decongestant spray or drops. This might reduce the swelling of the mucous membranes, which may help to open the Eustachian tubes and drain the fluid from the middle ear.
• Do not put any drops in your ear canal. If the tympanic membrane is ruptured, this might make things worse.
• Seek professional medical evaluation. Any doctor should be able to help, regardless of any dive medicine knowledge or training.

Implications for Diving

Fitness to dive

Do not dive until swelling and inflammation have resolved, and you can adequately equalize, preferably under otoscopic evaluation. Assess why the problem occurred (lack of training, allergy, etc.) and address each factor. If you are unable to equalize, then you may consider ENT consultation. The inability to equalize properly is disqualifying.

Note: Do not dive with earplugs, as this may cause external-ear barotrauma.

If you want to dive, you need to be ready. Readiness entails medical, psychological and physical fitness, appropriate knowledge and adequate physical skills. If you exercise regularly at an intensity that keeps your heart rate above 70 percent of maximum or so for more than 90 minutes per week, it is a good bet that you are physically fit enough to dive recreationally under a variety of conditions. Just diving, however, will likely not be enough to constitute regular exercise. In addition, exercise conducted during or close to diving has implications for safety. By following the right recommendations and protocols, you can ensure strength and safety for diving all year long.

Physical Fitness for Diving

Divers need to have sufficient strength and aerobic capacity reserves to meet both the normal and reasonable exceptional demands of diving in their chosen environment.⁷ Physical fitness is maintained when the intensity and frequency of exercise are sufficient to protect the body’s capacity — the array of biochemical and physiological capacities that determine a fitness limit. Physical fitness is improved when the exercise load exceeds the body’s current capacity and a training effect is established. Most training programs rely on progressive overload — the incremental increase in training intensity to continue the drive to adapt at a pace that can be tolerated. Exceeding the threshold for maintenance or improvement of fitness, as desired, makes for an effective workout.

While a diver’s physical strength can be tested by carrying tanks and related gear, the duration of the effort is typically too short to constitute an effective workout. The aerobic demands of most well-planned dives are even less likely to reach the intensity to protect even a moderate aerobic capacity. Ultimately, the diver has to do something outside of normal diving to maintain or improve their fitness level.

There are additional fitness issues directly relevant to diving physiology. While the data are incomplete, physical fitness has been associated with fewer post-decompression bubbles in humans.^2,8 While bubbles are not equated with decompression sickness, it is accepted that lower bubble counts indicate a reduced degree of decompression stress. Experiencing less decompression stress on any dive is definitely a good thing. Animal models have also demonstrated a lower incidence and reduced severity of decompression sickness (DCS) for trained versus untrained subjects.^1,10 Ultimately, it may be clear that sound physical fitness is desirable for decompression safety as well as for physical competence, which is the ability to meet the physical demands of a situation.

Timing Exercise and Diving

Just as important as a regular exercise regimen is the timing of such as it relates to diving. Scheduling outside physical fitness activities can be problematic when someone dives frequently. While part of this is simply a time management problem, there are other considerations. Conducting intense physical exercise too close to diving activity can be problematic for more fundamental reasons.

Bubble formation, while noted earlier as not equivalent to or a guarantee of DCS, can indicate an increased risk for it. Intense physical activity — generally with substantial muscular forces and joint loading, or the application of forces on joints — is believed to transiently increase micronuclei activity, the presumed agent of bubble formation. Intense physical activity too close to diving may therefore be problematic. Physical activity after diving may also stimulate additional bubble formation, possibly through a combination of increased microicronuclei activity and increased joint forces.

Interestingly, some preliminary work has shown that an intense bout of exercise conducted 24 hours prior to diving may reduce bubble presence in humans,³ possibly by inhibiting micronuclei activity. This potentially protective effect was not seen with exercise conducted closer to dive time. While this effect needs to be validated, the preliminary findings may support a simple rule of thumb for scheduling exercise. To reduce the risk, it is a good idea to avoid intense exercise 24 hours before and after diving.

The near-dive window will be best for low-intensity activities. Those who participate in cross-training activities may find it easiest to accommodate this schedule. For those who are more singleminded, diving may fit well into training rest days for those who put the priority on exercise, while training may fit best into diving rest days for those who put the priority on diving. Overall, lower training intensities will likely be more appropriate for the latter group, but accommodations can be reached.

Timing of Exercise During Diving

Physical activity during the dive also has a direct impact on decompression safety.^4,5,6,9 Exercise during the compression and bottom phase increases inert gas uptake, effectively increasing the subsequent decompression obligation of any exposure. It is important to remember that dive tables and computers estimate inert gas uptake, they never know reality. However, light exercise during the decompression phase (including safety or decompression stops) increases inert gas elimination and reduces risk. The caveat regarding exercise during decompression is that more is not always better. Too much or too intense exercise during the decompression phase can stimulate bubble formation, thus inhibiting inert gas elimination and increasing decompression risk.

Final Recommendations

We do not yet have sufficient data to quantify the difference between beneficial and potentially harmful exercise. Understanding the various issues and applying common sense offer the best protection. Most important is that moderate time-depth profiles are your best defense. Exercise considerations provide only a secondary defense. In terms of the secondary defense, though, the compression and bottom phases are best associated with the lightest exercise possible. Ascent and stop phases are best associated with mild, low-intensity exercise. Exercise that is aggressive and/or stimulates substantial joint-loading is almost always undesirable at any point near or during a dive.

The post-dive period is a good time to take it easy. Both decompression safety and mental health can be helped by an extended period of relaxation between the end of the dive and the start of equipment shifting and/or racing on to the next activity.

Physical fitness — including both strength and aerobic capacity — is important for divers both for physical safety and decompression safety. Regular exercise training is best scheduled to separate intense exercise and diving. Intense physical training should be avoided 24 hours on either side of diving activity. Any exercise within 24 hours of diving should involve the lowest possible joint forces.

Neal Pollock, Ph.D.

References

1. Broome JR, McNamee GA, Dutka AJ. “Physical conditioning reduces the incidence of neurological DCI in pigs.” Undersea Hyperb Med. 1994; 21(suppl): 69.

2. Carturan D, Boussuges A, Burnet H, Fondarai J, Gardette B. “Circulating venous bubbles in recreational diving: relationships with age, weight, maximal oxygen uptake and body fat percentage.” Int J Sports Med. 1999; 20(6): 410-414.

3. Dujic Z, Duplancic D, Marinovic-Terzic I, Bakovic D, Ivancev V, Valic Z, Eterovic D, Petri NM, Wisloff U, Brubakk AO. “Aerobic exercise before diving reduces venous gas bubble formation in humans.” J Physiol. 2004; 555(3): 637-642.

4. Jankowski LW, Nishi RY, Eaton DJ, Griffin AP. “Exercise during decompression reduces the amount of venous gas emboli.” Undersea Hyperb Med. 1997; 24(2): 59-65.

5. Jankowski LW, Tikuisis P, Nishi RY. “Exercise effects during diving and decompression on postdive venous gas emboli.” Aviat Space Environ Med. 2004; 75(6): 489-495.

6. Jauchem JR. “Effects of exercise on the incidence of decompression sickness: a review of pertinent literature and current concepts.” Int Arch Occup Environ Health. 1988; 60(5): 313-319.

7. Pollock NW. “Aerobic fitness and underwater diving.” Diving Hyperb Med. 2007; 37(3): 118-124.

8. Powell MR. “Exercise and physical fitness decrease gas phase formation during hypobaric decompression.” Undersea Biomed Res. 1991; 18(suppl): 61.

9. Van der Aue OE, Kellar RJ, Brinton ES. “The effect of exercise during decompression from increased barometric pressures on the incidence of decompression sickness in man.” US Navy Experimental Diving Unit Research Report No. 8-49, 1949.

10. Wisloff U, Brubakk AO. “Aerobic endurance training reduces bubble formation and increases survival in rat exposed to hyperbaric pressure.”