A Guide to Avoiding Lung Expansion Injuries

Like decompression sickness, one can never completely eliminate the risk of a lung expansion injry. But you can reduce your chances of injury. Here's how:

Ascend Slowly. Even if your're breathing normally, a rapid ascent rate could lead to a lung overpressure injury through gas trapping.
Use a high-quality regulator and have it serviced regularly. It's believed by some that excessive inhalation effort may cause edema (fluid damage) to tissues surrounding the alveoli, thus reducing the size and impeding flow into and out of the airway.
Avoid diving too soon after a chest cold or respiratory infection. This means that no matter how good you feel, no diving if you are coughing up mucus, or if your breathing produces any abnormal noise or resistance. To reduce the tendency for mucus obstruction after a chest cold, drink plenty of water before diving.
Running out of air is the major cause of lung expansion problems, so practice good air management techniques. Have enough air to make the dive you're planning - plus some reserve. And monitor your own and your buddy's gauges frequently.
Never exceed an ascent rate of 30 feet (9m) per minute, and try to go even slower as you approach the surface.
Dont smoke, and if you do, stop. Smoking causes the buildup of mucus, which can obstruct airways.

Asthma and Diving

Fred Bove, MD, PhD

Because of the changes in medical practice, new medications, a better understanding of the spectrum of asthma, and the growing awareness that many divers have some form of asthma and are diving safely, the Undersea and Hyperbaric Medical Society held a workshop on diving with asthma in June of 1995. The proceedings and conclusions of the workshop have now been published, and they provide important new guidelines for managing the individual with asthma who wants to dive.

Several surveys have shown that 4-7% of active divers in the United States have asthma. Data collected by the Divers Alert Network has also shown that diving accidents are mot markedly increased in individuals with asthma. The DAN data on asthma suggested that active asthmatics (someone who is short of breath and actively wheezing) may have a small increase in diving accident risk (either decompression sickness-DCS or arterial gas embolism-AGE), but the increase is small and does not reach statistical significance. The only conclusion which can be drawn from the information is that there may be a slight increase in risk for a diver who has active asthma.

Both the DAN data and the data from a British sport diving survey failed to show a risk for pulmonary barotrauma in asthmatics. Indeed when reviewing the few cases of asthmatics who died while diving, it was apparent that failure to swim to safety on the surface was a major problem with these individuals.

The new guidelines take into account the need to have normal exercise capacity when diving. The consensus was that lung function must be normal before an asthmatic can undertake diving. If treatment results in normal lung function, the risk of a problem is eliminated, and the individual can dive. The workshop provides information on the measurements needed to determine that lung function is normal.

Obviously the asthmatic who is acutely ill, with difficulty breathing, wheezing, cough, or fever should not dive. The acute illness must be resolved and breathing function restored to normal before considering diving. Full recovery however would allow return to diving, again based on evidence that the breathing test is normal. Individuals who have permanent lung damage from long standing asthma, with chronic emphysema should not dive. It is also important to avoid smoking tobacco if you are asthmatic, as the smoke will sometimes aggravate the asthma.


Fred Bove, MD, PhD

Although diving for diabetics using insulin has been considered dangerous, recent analysis of diabetic divers indicates that some diabetics can dive safely. Two major issues raise concern in diabetic divers. The first is that hypoglycemia (low blood sugar) might result in loss of consciousness or poor judgment in the water. As a result the diabetic diver must have good control of his or her blood sugar, a good understanding of the relationship between exercise and blood sugar levels, and be able to recognize and treat the early signs of low blood sugar. The second concern is the increased incidence of heart disease in people who have had diabetes for many years and the risks they face of heart attacks while diving.

There are many diabetics who are not dependent on Insulin. These individuals may be able to control their diabetes by diet alone, or with use of an oral medication which helps to control blood sugar. In the case of diet or oral medication control of diabetes, there is no risk of hypoglycemia, and the diver will not be at risk for a serious underwater accident. Diabetics who are dependent on Insulin also represent a spectrum of illness, one end of which will not interfere with diving or increase risk enough to exclude diving. It is clear that diabetics who have lost the ability to develop a normal defense reaction against hypoglycemia are at high risk for hypoglycemia when diving. Loss of this safety system usually occurs in long standing diabetes. The portable machines to test blood sugar from a single drop of blood, and newer Insulin preparations make management of diabetes simpler for the active young person interested in sports of any kind. The new methods for testing and regulating blood sugar can be used at the dive site to be certain that risk of hypoglycemia is eliminated. A proper physical examination, and exercise testing when indicated can reduce the risk for a heart problem while diving.

Advances in medicine have allowed a diabetic to avoid risk when diving. These new techniques coupled with a careful medical examination will provide the basis for some insulin dependent diabetics to dive.


Fred Bove, M.D., PhD.

There are several parts of the ear, each of which has a unique set of diving related disorders. The external ear includes the ear itself, and the external canal leading to the ear drum. The ear drum separates the external from the middle and inner ear.


The ear structure can be injured by trauma. Feeding fish underwater sometimes invites a nip on the ear by a dissatisfied "customer." Occasionally, a fish bite becomes severe enough to require treatment.

Swimmer's Ear

External canal infections, sometimes called "swimmer's ear", occur when water accumulates in the external ear canal, and remains long enough to allow bacteria and fungus to grow. Prevention of external infections is best done by using Otic Domeboro solution. A few drops in each ear before and after water exposure are adequate.


The middle ear includes the chamber situated behind the ear drum, which contains the small bones of the ear that transmit sound to the hearing organ. Connected into the middle ear is the Eustachian tube from the throat which is necessary for pressure equalization, and the mastoid cells which are spaces in the bone of the skull. The middle ear is easily injured by barotrauma (squeeze), and is susceptible to infection. The diagram shows the structures of the ear.

Ear Squeeze

Ear squeeze with injury to the ear drum, is the most common diving related illness. To avoid ear squeeze, be sure there is no congestion in your nose or throat when you dive. Begin clearing your ears on the surface before you descend, and continue to clear every foot or two as you go down. Waiting for ear pain to occur before you try to equalize is a bad habit. Usually you cannot clear the blocked ear at this stage.

Besides causing direct injury to the ear drum, middle ear squeeze produces swelling of the lining of the middle ear and Eustachian tube. Often fluid will persist in the middle ear until the swelling has subsided and normal Eustachian tube function returns. When a squeeze occurs, there is some damage to the ear drum. If the damage is severe, and ear problems persist for several days after diving, medical attention should be sought. Most middle ear squeeze can be successfully treated with medication, but you should not return to diving until the ear is completely clear.


The inner ear consists of the hearing(Auditory) and balance (Vestibular) organs, and their nerve connections to the brain. The inner ear is connected to the spinal fluid space, and when injured, can allow infection to spread into the brain. The inner ear is separated from the middle ear by the round and oval windows. Injuries to the middle ear include round window rupture, inner ear decompression sickness and vestibular decompression sickness. Scroll up to see a diagram of the ear.

Round window rupture

A more serious barotrauma injury related to diving is rupture of the round window (RWR). You can cause RWR by forcefully trying to equalize during descent. By doing a Valsalva maneuver to equalize, you raise the pressure in the inner ear above ambient pressure. If the Eustachian tube is blocked, the middle ear pressure will be below ambient, and the large pressure difference can blow out the round window. When the round window tears, fluid from the inner ear leaks into the middle ear. When fluid is lost, hearing is lost, Vertigo occurs, and hissing or buzzing is heard constantly. The tear in the RW can heal itself, but often surgery is needed to correct the problem

Inner ear Decompression Sickness (DCS)

Rarely DCS can occur in the inner ear and cause permanent hearing loss or permanent abnormalities in balance. This injury is characterized by sudden total hearing loss in one ear following a dive. Inner ear DCS usually occurs in commercial divers after deep saturation diving. One case of suspected inner ear DCS was recounted in a sport diver, but considering the larger number of sport divers and the questionable diagnosis, there should be no concern for inner ear DCS in sport diving. If other symptoms, such as hearing loss, vertigo, dizziness, or loud roaring or ringing noises are present, you should seek prompt consultation with an ENT specialist.


You should learn the various ways to clear your ears. If you still have trouble after using the correct method of clearing, have an ear, nose and throat exam by a doctor who knows diving medicine. Protection of your ears during diving requires careful attention to the health of your nose and throat, and to your techniques of descent and ascent.