Scuba divers, who breathe compressed gas, are exposed to the risks of pulmonary barotrauma. According to Boyle’s law, at a constant temperature, the volume of a gas is inversely proportional to its pressure. Thus, the gas-containing cavities of the body are at risk of barotrauma. During descent, gas-containing cavities in which the pressure cannot be equalized may suffer from “squeeze” barotrauma, ie, the middle ear, sinuses, etc.1
At depth, tidal volume and vital capacity are very much the same as in normobaric conditions, but the same volumes contain larger amounts of gas due to its being compressed. According to Boyle’s law, the gas will expand on ascent and may cause lung expansion and barotrauma if not vented. Divers are therefore taught to exhale continuously during their ascent. If the diver holds his breath while making his ascent, or if he has regional gas trapping, the lung may over distend to the point of rupture. The consequences of this may be pneumothorax, pneumomediastinum, subcutaneous emphysema, pulmonary tissue damage, gas embolism, or in rare cases pneumopericardium.1–2
In pneumomediastinum, after alveolar rupture gas escapes into the interstitial tissues, causing cervical and mediastinal emphysema. The free gas might reach the larynx, causing discomfort, dysphagia or voice alterations.3–
Alteration of the voice has been reported as hoarseness, a high pitched voice, or rhinolalia.4–5
These changes in the voice have been attributed to “submucosal emphysema” of the upper airways or recurrent laryngeal nerve damage.1
Braverman et al5
suggest that hyponasality due to narrowing of the nasopharyngeal passage by air spreading into the retronasopharynx may account for the rhinolalia.