Your patient is fully submerged in freezing water. She is losing body heat through which mechanism?

The correct answer is conduction. When a person is submerged in freezing water, heat is transferred directly from the body to the cold water surrounding it. This process occurs because the water is at a lower temperature than the body, allowing for a transfer of thermal energy. Conductive heat loss is particularly significant in this scenario because water is an excellent conductor of heat compared to air; it draws heat away from the body much more effectively.

In contrast, evaporation involves the loss of heat as moisture on the skin turns to vapor, which is not the primary mechanism at play when someone is submerged in water. Radiation describes the loss of heat in the form of infrared rays, which is less effective in water since the surrounding medium is significantly colder than the body. Finally, convection involves the movement of fluid (like water or air) around the body; while it can also contribute to heat loss, in the case of full submersion, conduction is the dominant mechanism leading to rapid heat loss.