Diagnoses: Pulmonary bleb

Can I safely dive after being diagnosed with a pulmonary bleb? I am healthy and fit with no history of pneumothorax.

The responsibility for the decision of whether to dive is generally left up to the individual and his or her physician. This decision, however, should be based on a medical evaluation and awareness of the risks involved in scuba diving.

Your best resource is a physician, preferably a pulmonologist, trained in dive medicine. A physician without the relevant experience may be thinking in terms of above-water activities and may not recognize the inherent dangers of breathing compressed gas at increased atmospheric pressure. A physician familiar with dive medicine would not likely give medical clearance to an individual diagnosed with a pulmonary bleb, which is a small blister or pocket of air trapped between the lung and the outer surface of the lung (visceral pleura). These spots are weaker than the normal lining of the lung and can occasionally break and cause air to leak from the lung into the chest cavity. A person who has pleural blebs usually has more than one, and all blebs are prone to leak at some time.

At depth there is normally a reduction in breathing capacity and an increase in breathing resistance caused by the higher gas density. At 33 feet, the maximum breathing capacity of the average scuba diver is only 70 percent of the surface value, and at 100 feet it is only 50 percent. The pressures on the lung caused by diving are likely to stimulate a bleb to rupture and leak air into the chest cavity. When this happens, the result is a spontaneous pneumothorax (collapsed lung). The lung collapse can occur without provocation or warning. Above water, pneumothorax is often associated with exercising, straining while lifting or performing some other physical task, but many times the affected individual is doing nothing out of the ordinary.

Since barotrauma can occur with hyperinflation of lung tissue, a diver's lungs must be able to tolerate rapid changes in volume and pressure. Any weakness in lung structure or architecture may be predisposed to rupture from even slight overinflation in an otherwise healthy person. Pulmonary barotrauma, which can lead to rupture of the lung air sacs (alveoli), usually happens toward the end of a dive, even a shallow one. Escaping gas can enter one of four places: the subcutaneous tissues of the neck and chest wall; the area around the heart, causing pneumomediastinum (mediastinal emphysema); the pleural space between the lung and chest wall, causing pneumothorax; or the bloodstream, causing arterial gas embolism (AGE).

Please remember that most divers and dive-boat personnel are not trained to provide first aid to a diver with pneumothorax. While generally manageable above water, a spontaneous pneumothorax in the diving environment is likely to be fatal.

If you would like to be referred to a physician trained in dive medicine, call +1-919-684-2948 or email medic@dan.org.
— Frances Smith, EMT-P, DMT