Ralph is taking SCUBA diving classes and is confused as to why he should not hold his breath under water while ascending–his instructor told him he must exhale continuously. What would you tell him?
What will be an ideal response?
When breathing the compressed air from a SCUBA tank, the lungs are virtually completely inflated. Problems would arise if he held his breath and began to ascend. On ascending, the decrease in pressure would cause the gas in his lungs to expand (Boyle's law). Since the lungs are already fully inflated, this would cause over-inflation and possible rupturing of the lung. If this occurred, air would leak from the lungs into the pleural cavity, resulting in a pneumothorax and a collapsed lung.
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