Diving Medicine: Questions Physicians Often Ask, Part 1

Recreational diving continues to increase in popularity; as many as 15 million Americans are certified scuba divers. Although a few serious and possibly life-threatening conditions require recompression treatment, most diving injuries are uncomplicated and can be managed by the primary care physician. In this article, we address the questions most often asked about fitness and safety issues. In a future article, we will review the principal medical problems associated with sport diving.

1How does sport diving differ from other types of diving?

Sport diving is recreational breath-hold or scuba diving that does not involve pure oxygen breathing, switching of different gases during diving, and/or planned decompression stops. Recreational diving is usually limited to depths of less than 120 ft and the time a single tank of gas will allow the diver to stay under water, which varies from about an hour near the surface to less than 15 minutes at depths of 100 ft. Many factors-including body size, activity level, experience, and size and fill pressure of the tank-determine how long a diver is able to remain underwater. A 40-hour training program usually suffices to qualify a sport diver for scuba diving.

Technical or commercial divers may dive to depths of 500 ft or more, and hours or even days may be required for a safe ascent. These divers use special equipment to increase the duration and/or depth of their dives and may need to complete 1000 or more hours of training before becoming fully certified.

2What are the fitness requirements for diving?

All sport diving requires good physical and mental health. The prospective diver should be able to swim several hundred yards comfortably in open water without swimming aids. Typically, applicants for scuba diving training programs in the United States are required to complete a medical questionnaire. This usually includes queries about a history of such conditions as heart disease, asthma, seizures, diabetes, serious injury, episodes of dizziness, and chronic cough. Positive responses warrant a focused medical examination and clearance by a physician. If a diver is older than 40 years, we recommend an ECG with exercise stress testing, especially if the diver does not exercise regularly, smokes, and/or has a family history of cardiovascular disease.

For snorkeling and breath-hold diving, minimal, if any, medical screening is necessary. If your pa-tient is interested in this type of diving, evaluate him or her for conditions that might affect physical performance, stamina, and alertness.

The physical examination is an appropriate time to offer pointers on diving safety. Technologic advances in diving equipment that have greatly enhanced safety are described in the Box.

When conducted appropriately, diving has minimal side effects and risks. There are caveats, however. Ordinarily, sport diving does not promote aerobic conditioning or muscle building. This is because properly executed dives place minimal demands on the body. Neutral buoyancy, slow drifting with a current, and positive pressure ventilation from the regulator place fewer energy demands on the body than being at rest on land. However, good physical conditioning is essential for safe diving. In such emergency situations as swimming against currents, extricating oneself from entanglements, and passing through surf zones, enormous efforts may be required. Unless he is physically fit, the diver may be subject to near-drowning, myocardial infarction (MI), and/or death.

3What are the relative and absolute contraindications to sport diving?

Precautions. A history of recurrent ear, nose, sinus, or throat infections is not a contraindication to scuba diving if the infections are controlled and if the diver is able to equilibrate pressures in the middle ear spaces. Teach patients with recurrent ear and sinus infections how to use vasoconstrictors at the first signs of middle ear and sinus congestion.

Cardiac arrhythmias may be precipitated by the stresses of exertion, breath-holding, the diving reflex, and cold water in persons with a history of heart disease. We recommend that such persons-especially those who have a history of heart block or are prone to tachyarrhythmia-avoid diving. Mild to moderate overweight is not a contraindication to snorkeling or breath-hold diving.

Asthma is a risk factor for air trapping during ascent, a condition that can lead to arterial gas embolism. Most experts agree that patients with a history of asthma who are asymptomatic, are not taking maintenance medications, and have no exercise-induced abnormality on pulmonary function studies can be allowed to dive.¹ Diving is contraindicated in persons with severe asthma who require maintenance medication and in those who are symptomatic much of the time. Obtain a chest film if there is a history of pulmonary disease.

Relative contraindications. These include diabetes, obesity, behavior problems (including immaturity, rebelliousness, defiance, and inability to follow directions), phobias, neuropathies, myelopathies, hearing loss, a history of heart disease, and residual effects of musculoskeletal injuries. Verification of fitness, stamina, and insight about his condition are essential before a patient can be cleared for sport scuba diving. Encourage those who are cleared to dive in settings that minimize exertional stresses, such as diving from a boat in warm, clear, calm waters. Give advice about injury avoidance, and emphasize strict adherence to diving safety practices and selection of a competent dive partner who is aware of the diver's limitations.

Absolute contraindications to both breath-hold and scuba diving include any cardiovascular condition that requires medication in order to maintain cardiac function; pulmonary conditions associated with markedly abnormal pulmonary function testing results or air trapping (eg, emphysematous blebs); psychotic disorders; Ménière disease; morbid obesity; markedly symptomatic Raynaud phenomenon; coagulopathies; and the inability to equilibrate pressure in the middle ear spaces and sinuses. Most patients with these conditions elect not to dive.

A history of epilepsy is considered by most authorities to be an absolute contraindication. The stresses of diving-especially the breathing of oxygen at increased partial pressure-can lead to seizures and loss of consciousness underwater, which invariably results in near-drowning or drowning.

4Which problems are typically associated with each phase of the dive-and which are most likely to be seen in office practice?

A dive can be divided into 4 phases, according to when a problem is most likely to occur (Table).

Surface problems include panic, which can lead to exhaustion, cardiac arrest, and drowning; blackouts, which may result in near-drowning or drowning; injuries from contact with the marine environment; exposure problems, such as hypothermia and sunburn; sprains and strains; fatigue; and seasickness. These problems, which may occur at other phases of the dive, usually happen near or on the surface before or after the dive. They may also be associated with swimming and snorkeling.

Descent problems include "squeezes" (local differences in pressure), which may lead to pulmonary or otic barotrauma or sinus injury. Pulmonary barotrauma of descent is one of the rarest conditions in diving. It is associated with deep breath-hold dives in which the pressure associated with descent reduces the vital capacity below the residual volume. This causes leakage of fluid from the alveolar capillaries into the alveoli, which results in dyspnea and other conditions associated with ventilation-perfusion inequalities in the lungs.

Signs of otic barotrauma include pain, vertigo, and hearing loss. Local squeezes can occur in "artificial" cavities, such as the space created by a face mask, and cause local hemorrhage and tissue damage.

Bottom problems are usually associated with long, deep dives and/or with special devices, such as rebreather and surface-supplied equipment. Associated disorders include anoxia, nitrogen narcosis, oxygen toxicity, carbon dioxide toxicity, and carbon monoxide poisoning.

Significant ascent and postdive problems include extra-alveolar air syndromes (frequently referred to as pulmonary barotrauma of ascent), such as subcutaneous emphysema, pneumothorax, and arterial gas embolism; decompression sickness (including the onset of joint pains during ascent); and alternobaric vertigo (a type of ear squeeze).

Nonurgent ascent problems include the delayed onset of joint pains, rashes, fatigue, subcutaneous emphysema, and vertigo. Symptoms-such as joint pains ("the bends")-that suggest decompression sickness warrant referral for hyperbaric oxygen recompression treatment. Vertigo, which may be caused by a round window rupture, necessitates otolaryngologic consultation.

The primary care physician is likely to be the first medical contact a diver seeks for surface and descent problems. Most bottom problems are self-limited and resolve with ascent or termination of the dive. (A possible exception is carbon monoxide poisoning, for which "washout" of the residual carbon monoxide with hyperbaric oxygen is generally recommended.) Technical divers (those most susceptible to bottom problems) usually have prearranged medical support systems.

5Are there special issues of concern for women divers?

About a third of scuba divers and dive instructors are women. After appropriate training, women can reach the same level of performance as men. Although physiologic, anatomic, and psychological differences between the sexes are relatively minor, they can assume greater importance under water. The female body contains more fat tissue and less muscle. This offers an advantage for cold water tolerance but may increase the risk of decompression sickness.² Women's smaller size enables them to make more efficient use of their gas supplies. However, women generally have less strength and stamina than men. This could mean the difference between life and death in such situations as swimming against strong currents or freeing oneself from entanglements.

The ratio of female to male scuba diving deaths is 1:10.³ This difference may be explained by diving habits rather than anatomic or physiologic differences: women tend to select less dangerous diving environments than men.

Premenstrual and menstrual periods are characterized by specific changes in women's physiology that may or may not be associated with psychological changes. They can produce symptoms that affect physical performance and psychological responses. Women divers must decide whether they want to dive during these times. The psychological diversion of the aquatic environment, the buoyancy effects of water, and the relaxation that a well-conducted dive offers may outweigh all but the most severe premenstrual and/or menstrual symptoms. Menstrual blood loss is almost never severe enough to cause hemodynamic changes.

There is no evidence that diving during menstruation increases the likelihood of a shark attack. In fact, female divers who dive during menstruation experience a much lower incidence of shark attacks than male divers,³ perhaps because hemolyzed blood associated with menstruation acts as a shark deterrent.

Some women may wonder whether oral contraceptives or hormone replacement therapy affect diving. A significant side effect of oral contraceptives is the propensity for blood clotting, which increases the risk of deep venous thrombosis, pulmonary embolism, cerebrovascular accidents, and MI. However, there is no evidence that oral contraceptives increase the risk of decompression sickness or other diving-related problems. Although hormone replacement therapy may reproduce some of the physiologic effects of menstruation and oral contraceptives, there are no data on how this therapy affects women divers.

Most authorities do not recommend scuba diving during pregnancy because of the unknown effects of increased partial pressures of nitrogen on the fetus and the increased propensity for nitrogen deposition in the fetal-maternal lipid tissues. This may make the fetus more susceptible than the mother to the harmful effects of bubbling phenomena. In addition, if the pregnant diver requires hyperbaric oxygen recompression treatment for decompression sickness, the increased partial pressures of oxygen may have teratogenic effects; this phenomenon has been observed in animal studies. Snorkeling is acceptable during pregnancy.

6Is diving a safe activity for children and older persons?

With proper supervision, children should be able to participate in snorkeling and breath-hold diving as soon as they can use fins, mask, and snorkel comfortably-usually at the age of 6 years or older.

We recommend that children be at least 13 or 14 years old before they scuba dive. The potential for damage to growth centers of the bones exists because of gas bubbling in the venous sinusoids and the associated sluggish blood flow. Theoretically, this would be a preferential environment for inert gas bubbling to develop.

Moreover, most diving equipment is designed for larger persons. Finally, a level of maturity and the ability to make decisions analogous to those that are required for driving an automobile are essential for safe diving.

There are no specific upper age limits for scuba diving. Older persons should base their decisions to dive on physiologic rather than chronologic age. Because most older persons have less muscle strength, stamina, and cardiovascular reserve, it is best that they dive "conservatively." n

References:

REFERENCES:

1. Neuman TS, Bove AA, O'Connor RD, Kelsen SG. Asthma and diving. Ann Allergy. 1994;73:344-350.

2. Robertson AG. Decompression sickness risk in women. Undersea Biomed Res. 1992;19:216-217.

3. Edmonds C, Lowry C, Pennefather J, Walker R. Diving and Subaquatic Medicine. 3rd ed. Flagstaff, Ariz: Best Publishing; 2002.

FOR MORE INFORMATION:

m Bennett PB, Elliot DH, eds. The Physiology and Medicine of Diving. 4th ed. Philadelphia: WB Saunders Company; 1993.

m Dierker RL, Strauss MB. Treating swimmer's ear. US Pharmacist. 1990;15:72-74.

m Joiner JT, ed. NOAA Diving Manual: Diving for Science and Technology. 4th ed. Washington, DC: US Dept of Commerce, National Oceanic and Atmospheric Administration; 2001.

m Moon RE, Camporesi EM, Kisslo JA. Patent foramen ovale and decompression sickness in divers. Lancet. 1989;1:513-514.

m Strauss MB, Aksenov IV. Diving Science. Essential Physiology and Medicine for Divers. Champaign, Ill: Human Kinetics; 2004.

m Strauss MB, Borer RC Jr. Diving medicine: contemporary topics and their controversies. Am J Emerg Med. 2001;19:232-238.

m Strauss MB, Orris WL. Injuries to divers by marine animals: a simplified approach to recognition and management. Mil Med. 1974;139:129-130.

m US Navy Diving Manual. NAVSEA 09994-LP-001-9110. Flagstaff, Ariz: Best Publishing; 1993.