Why is central nervous system oxygen toxicity a significant concern for decompression divers?

Central nervous system oxygen toxicity (CNS toxicity) is a critical concern for decompression divers due to its potential to induce lethal convulsions, which can indeed lead to drowning. During a dive, particularly at depths greater than 1.4 ATA (atmospheres absolute), the partial pressure of oxygen increases significantly. This elevated level of oxygen can affect the central nervous system, resulting in symptoms that can escalate quickly, including seizures. These seizures can occur without warning and can incapacitate a diver, leading to a loss of control and the inability to return to the surface safely.

Understanding the severe implications of CNS toxicity is crucial for divers, as it dictates deep diving limits and the use of oxygen-enriched gas mixtures. The other options, while they mention symptoms like headaches, fatigue, or restricted breathing, do not capture the acute and life-threatening nature of the risk associated with CNS toxicity. The primary focus for divers is not just on discomfort but rather on the potential for immediate and dangerous situations that can arise if CNS toxicity is not appropriately managed. Thus, the most critical consequence highlighted is the risk of convulsions, emphasizing the importance of monitoring oxygen exposure during dives.