Hand cold pressor test induces thermogenesis in upper thoracic regions as measured by skin surface infrared thermography

BackgroundCold exposure may cause health problems and impaired productivity in outdoor or cold-temperature workers. The cold pressor test (CPT) is a laboratory procedure that measures cardiovascular and thermoregulatory responses to acute cold exposure such as metabolic activity in brown adipose tissue. How the body responds to acute cold exposure of a hand is not completely understood. We tested the hypothesis that the upper thorax produces heat during a single hand-CPT, which restores warmth to the cold-expose appendage. ObjectivesThe objective was to measure skin temperature changes in the upper thoracic regions and the cold-exposed appendage during a CPT. The secondary objective was to determine if cardiovascular or psychological responses during CPT accounted for skin temperature changes. Methods50 healthy participants immersed their right hand up to wrist level in 4 {degrees}C water for three minutes. Surface skin temperatures were imaged by infrared thermography at baseline, during CPT, and in the recovery phase. Sublingual oral temperature and water bath temperature were recorded throughout the test. Cardiovascular responses were monitored by continuous finger pulse-wave plethysmography. Peak pain and peak stress were reported by the participants on a Likert scale. ResultsCPT increased the systolic blood pressure (+22 mmHg, p < 0.001), diastolic blood pressure (+15 mmHg, p < 0.001) and heart rate (+7 beats per minute, p = 0.024). During CPT, skin temperature increased on thoracic regions including mediastinal (+0.5{degrees}C, p < 0.021), sternal (+0.5{degrees}C, p < 0.002), right supraclavicular (+0.3{degrees}C, p < 0.042) and left supraclavicular (+0.3{degrees}C, p < 0.016) regions. During CPT, the hand was cooler on ventral (-14.6{degrees}C p < 0.001) and dorsal (-15.2{degrees}C p < 0.001) sides, and warmed up during recovery. The ventral forearm, dorsal forearm, antecubital fossa, and adjacent medial epicondyle region were significantly cooler throughout the recovery time. The oral temperature did not change during CPT. There were no correlations between the change in mediastinal skin temperature and the sex of the participant, or changes in cardiovascular parameters, peak pain, or peak stress values. ConclusionsLocalized hand cooling caused a rapid warming of the thorax, dissipation of cold in the forearm, and rewarming of the hand during recovery. Thermoregulation was not dependant on pain, stress, sex, or cardiovascular changes between participants. By understanding thermoregulation, better approaches can be developed to mitigate the negative impacts of cold exposure.