A diver experiencing headache, confusion, nausea, and bright red lips may be suffering from which condition?

The symptoms of headache, confusion, nausea, and bright red lips align with carbon monoxide poisoning, making this the correct choice. Carbon monoxide is a colorless, odorless gas that can result from incomplete combustion of fuels. In a diving context, it might be encountered in poorly ventilated environments where combustion engines are present.

When carbon monoxide is inhaled, it binds to hemoglobin in red blood cells more effectively than oxygen does, leading to reduced oxygen transport throughout the body. This condition results in the characteristic bright red lips due to the presence of carboxyhemoglobin, which gives the blood a distinctive color, and the other symptoms can be attributed to inadequate oxygen reaching the brain and organs.

Decompression sickness, heat stroke, and deep vein thrombosis present different symptom profiles. Decompression sickness primarily involves joint pain and other issues related to nitrogen bubbles in tissues after rapid ascent. Heat stroke typically includes high body temperature, altered mental state, and skin changes, while deep vein thrombosis is characterized by swelling and pain in a limb, rather than systemic symptoms like confusion and respiratory involvement.