Which substance can make the effects of gas narcosis shallower?

Decongestants can help alleviate the effects of gas narcosis by minimizing the impact of respiratory issues that may arise due to pressure changes during a dive. When divers experience narcosis, it is often associated with the buildup of carbon dioxide (CO2) and other gases in the body. Decongestants work by reducing nasal congestion and improving airflow, which may enhance a diver's ability to breathe more efficiently. By potentially improving ventilation and gas exchange, divers may experience a reduction in the subjective feeling of narcosis.

In contrast, caffeine typically has stimulant effects, which do not specifically address or mitigate the causes of gas narcosis. Vitamin supplements and antibiotics do not have any direct role in managing narcosis; they are intended for different health-related concerns and do not influence the physiological processes impacted by pressure and gas absorption in diving scenarios.