Heat Loss Mechanism in Cold Water Immersion
When a baby with high temperature is placed in cold water, the primary mechanism of heat loss is conduction (Answer B). 1
Mechanism of Conduction
Conduction is the passive transfer of heat from the body into surrounding liquid in direct contact with the skin along a temperature gradient. 1 This occurs when two objects of different temperatures are in direct physical contact, with heat energy transferring from the warmer object (the baby's body) to the cooler object (the cold water). 1
Why Cold Water Immersion Works Through Conduction
Direct skin-to-water contact creates the most efficient thermal gradient for heat transfer in immersion cooling, distinguishing it from other cooling methods. 1
Immersion in iced or cold water is the most widely used conventional cooling technique for hyperthermia, specifically because conduction provides rapid heat transfer rates. 1
The cooling rate achieved through cold water immersion (0.14-0.20°C/min) is significantly faster than evaporative methods (0.03°C/min) or passive cooling (0.04°C/min). 1
Comparison with Other Heat Loss Mechanisms
Evaporation (Answer A)
- Evaporation requires water to change from liquid to gas phase on the skin surface, which does not occur when the body is submerged in water. 1, 2
- Evaporative cooling is relevant for methods like misting and fanning, not immersion. 1
Convection (Answer C)
- Convection involves heat transfer during mass movement of gas or liquid around the body, but is a secondary mechanism in immersion. 1
- While water circulation may contribute minimally, the dominant mechanism remains direct conductive heat transfer. 1
Radiation (Answer D)
- Radiation involves electromagnetic wave transfer without direct contact, which is blocked when the body is surrounded by water. 1
- Radiation accounts for 10-50 kcal/h in air but is negligible during water immersion. 1
Clinical Evidence for Conduction-Based Cooling
Seven studies specifically identified cold water immersion as a conduction-based cooling method in systematic reviews of heat stroke treatment. 1
Ice water immersion (1-5°C) achieved cooling rates of 0.20°C/min, making it the fastest cooling modality available. 1
The 2025 Society of Critical Care Medicine guidelines recommend cold water immersion as the preferred cooling method specifically because conductive heat transfer is most efficient. 1
Important Clinical Caveat
While conduction is the answer to this physics question, clinicians should note that cold water immersion in very young infants requires careful monitoring due to their high surface area-to-body weight ratio and risk of overcooling. 3, 4 The principle remains conduction, but application requires clinical judgment regarding water temperature and duration.