Pulmonary barotrauma generally occurs at the end of a dive, when trapped gas causes alveoli (air sacs in the lungs) to expand during ascent and ultimately rupture if normal exhalation is impaired by breath-holding or a lung problem.
Gas from a ruptured lung can leak into one or more of four places:
- The area around the heart (pneumomediastinum, also known as mediastinal emphysema)
- The pleural space between the lungs and chest wall (pneumothorax)
- The bloodstream (arterial gas embolism [AGE])
- Under the skin around the upper chest and neck (subcutaneous emphysema)
The risk of pulmonary barotrauma is greater in people who have blebs in their lungs. Blebs are abnormal, balloonlike air-sacs most often caused by inflammation, which destroys the thin walls that separate alveoli.
Although these are common in smokers, they have also been found in non-smokers. Blebs empty air slowly because of their thin, non-elastic wall. On exhalation during ascent, pressure can build, causing rupture.
People with blebs are also at risk of spontaneous pneumothorax (collapsed lung). Those with a history of spontaneous pneumothorax are automatically disqualified from diving, because of the high risk of pulmonary barotrauma.
There is a consensus among diving doctors that, despite the appearance of normal lungs via testing or imaging, someone with a history of spontaneous pneumothorax should not dive under any circumstances.
Rick’s pulmonary barotrauma manifested as pneumomediastinum, the principal symptom of which is a substernal ache, or chest tightness.
This is likely to be what Rick was feeling before his third dive. Occasionally a diver might experience sharp pain in the shoulders, back or neck that may be aggravated by deep breathing, swallowing, movement of the neck or trunk, coughing or lying flat.
Voice changes, such as the Donald Duck voice that results from breathing helium, are also common.
The crackling sensation Rick described under the skin around his neck is known as subcutaneous crepitation (grating or rattling). The air was trapped under the skin when it escaped from the chest cavity and into the soft tissues of the neck.
Breath-holding, rapid ascent and certain lung diseases can cause pulmonary barotrauma, the risk of which is increased by lung diseases such as asthma (if not optimally medicated) because of the risk of bronchospasm and/or obstruction of air passages.
Lung scarring or inflammation caused by sarcoidosis or interstitial fibrosis prevents proper gas exchange and increases risk of pulmonary barotrauma.
In addition, people who have previously experienced a spontaneous pneumothorax or pneumomediastinum are at increased risk. Generally, anyone with lung conditions that might increase the risk of pulmonary barotrauma is advised to avoid scuba-diving.
For those with underlying lung diseases, risk of pulmonary barotrauma increases with rapid ascents, especially conducted close to the surface, where the relative pressure changes are greatest.
Diving doctors recommend that anyone who has experienced pulmonary barotrauma be properly evaluated before returning to diving. Unfortunately, Rick didn’t recognise his symptoms during the training dives a year earlier as subcutaneous emphysema, so went on diving without talking to a doctor.
Fortunately for him, he recognised his symptoms after the second occurrence and was properly treated. He has since returned to diving after two successful operations to correct the blebs.