What is a potential effect of ascending too quickly without proper ventilation?

Ascending too quickly without proper ventilation can lead to a serious condition known as an air embolism. This occurs when nitrogen or other gases dissolved in the tissues and blood form bubbles during rapid ascent. If a diver ascends too quickly, pressure decreases rapidly, potentially causing these bubbles to expand and escape into the bloodstream. If these bubbles travel through the bloodstream and obstruct a blood vessel, it can result in blockage, which may affect various organs and potentially lead to life-threatening complications.

In contrast, while barotrauma, decompression sickness, and hypoxia are also related to diving and changes in pressure, they involve different processes. Barotrauma refers to tissue injury due to pressure changes and can occur without a rapid ascent if there is improper equalization. Decompression sickness, often referred to as "the bends," involves the formation of nitrogen bubbles in the body due to too rapid a reduction in pressure after being at depth but differs from the direct vascular obstruction seen in an air embolism. Lastly, hypoxia refers to inadequate oxygen levels in the body, which can occur for various reasons but is not specifically a direct result of rapid ascent without proper ventilation. Hence, the focus on air embolism highlights the specific risk associated with rapid ascents from depth.