According to Henry’s Law, if the temperature is constant, the amount of gas that dissolves into liquid is directly proportional to the partial pressure of that gas. ĭCS (also called “the bends”) happens when divers ascend too quickly and do not take proper “decompression stops.” Dissolved inert gas (nitrogen) comes out of solution and forms bubbles in the blood and tissues (most commonly in the spine, nerves, joints, and skin). This “block and lock” scenario leads to no change in middle ear pressure because of the blockage but increases the perilymph pressure in the cochlea and leads to rupture of the round or oval window. The most common scenario is when the Eustachian tube is blocked, and a person performs an “explosive” Valsalva maneuver. This may result in a labyrinthine fistula or perilymph leakage. Middle ear barotrauma may rarely be associated with inner ear barotrauma when there is a sudden pressure differential between the inner ear and the middle ear, leading to round or oval window rupture. In the ear, this can lead to transudate or bleeding into the middle ear and trauma to the tympanic membrane. If there are gas pockets from dental surgery, a loose crown, or bacterial degradation. There are several theories as to the etiology. It occurs more commonly during ascent when flying but can occur during descent. This leads to a failure to equalize pressure. Sinus or middle ear barotrauma (also known as “squeeze” injuries) can occur when a diver has sinus or nasal congestion or a nasal polyp that blocks the openings to the sinuses or the Eustachian tubes. Even a small amount of air (0.5 mL) can be fatal, especially if it reaches the cerebral or coronary vasculature. Some physiological effects of gas bubbles include protein denaturation, leukocyte activation, and endothelial damage which lead to microvascular leak and edema, hemorrhage, infarct, and cell death. Gas bubbles in the systemic vasculature usually lodge in small vessels, producing ischemia distal to the blockage and local activation of the inflammatory cascade. AGE happens when lung tissue tears and gas bubbles enter the systemic circulation. This can cause pneumothorax, pneumomediastinum, subcutaneous emphysema, or AGE. Divers who hold their breath as they ascend (or those with obstructive airway diseases such as asthma or chronic obstructive pulmonary disease ) can suffer an overexpansion injury and alveolar rupture. The lung volume is cut in half while the pressure doubles when a diver reaches a depth of 10 meters. Boyle’s law can explain pulmonary barotrauma and AGE. According to Boyle’s Law, if the temperature is constant, the volume of a gas varies inversely with pressure. In the example of an undersea diver, the ambient pressure increases by 1 atm for every 10 meters (33 feet) of depth. However, the areas of the body that are air-filled (lungs, sinuses, middle ear, gas in bowels, and cavities in teeth) are the structures affected by barotrauma. Usually, these structures are usually connected to the outside world to allow for free air exchange, but if they are blocked the high-pressure air will push on tissues surrounding the low-pressure area and this can cause tissue damage when the pressure gradient exceeds the tensile strength of the tissues involved. The human body is mostly comprised of water, which is minimally compressible, thus pressure changes do not typically directly affect these portions of the body.
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