If surface oxygen is not effective after 30 minutes, what should be done next?

Administering in-water recompression is the appropriate next step if surface oxygen has not been effective after 30 minutes. This procedure is crucial in treating decompression sickness or preventing further deterioration of the diver’s condition. If surface oxygen does not alleviate symptoms, it indicates that the gas embolism or the decompression sickness may require more aggressive intervention to facilitate the evacuation of nitrogen from the bloodstream.

In-water recompression allows for a controlled environment where the diver can be subjected to higher ambient pressures, which helps minimize gas bubbles and aids in the absorption of inert gas. This treatment can significantly improve blood oxygen levels and decrease the likelihood of serious complications.

The other response options are not advisable in this situation. Waiting indefinitely for symptoms to resolve could lead to exacerbate the diver's condition without intervention. Transporting without treatment risks worsening the situation, and opting to administer air instead of oxygen would not address the need for high flow oxygen in the presence of potential gas embolism. Therefore, beginning in-water recompression is a critical and effective response to ensure the safety and health of the diver.