Human physiological adaptations to acute cold exposure

1. Human physiological adaptations
to acute cold exposure
David Barton
October 2, 2014
University of Pittsburgh School of Medicine

2. Outline
• Thermal homeostasis
• Behavioral adaptations
• Physiological adaptations

3. General adaptation syndrome

4. How low is too low?
Brooks et al., 2005

5. Temp Regulation
Hammel et al., 1959
Sleep at 5 °C
“Although certain
features of this
sleeping chamber
were objectionable
to the natives it
proved to be
entirely adequate
for maintaining a
suitable cold
exposure.”

6. Balance of heat gain/loss
Brooks et al., 2005
Radiative heat loss
Respiration
Insensible water loss
Urination

8. Normal Thermoregulation
Pozos and Danzl, 2002

9. Types of adaptations
• Behavioral
• Physiological

10. Behavioral adaptations
• Prevent physiological adaptation from needing to occur (usually)
Clothing
FireShelter
Insulative air pocket

11. Physiological adaptations
• Insulative
• Metabolic

12. Insulative adaptation
• Cutaneous vasoconstriction
• Skin fold thickness
• Fat/muscle insulation

13. Thompson-Torgerson et al., 2007
Tloc, local skin temperature.
Skinbloodflow
Cutaneous vasoconstriction

14. Infrared scan of the palmar hand surface. Blue, 43° C (109.4° F); red, 68° C
(154.4° F). A, At room temperature. B, After 5 minutes in a cold room, with evidence of
vasoconstriction.
Auerbach, Wilderness Medicine

15. Cui et al., 2005
Skin suit with 34 or 16 °C water
Cardiac output (CO) = Stroke volume + Heart rate
Wagner and Horvath, 1985

16. Cold-induced diuresis
Budd and Warhaft, 1966
Segar and Moore, 1968
*Renal blood flow decreases 50%
at 27-30 °C

17. Cold-induced cutaneous vasoconstriction is mediated by Rho
kinase in vivo in human skin
Tloc, local skin temperature.
Skinbloodflow
Thompson-Torgerson et al., 2007

18. Effect of cooling (to 28°C) on Rho activity in human cultured dermal arteriolar VSM cells.
Bailey et al., 2004

19. Hunting reflex

20. Physiological adaptations
• Insulative
• Metabolic

21. Metabolic adaptation
• Shivering (and pre-shivering) response
• Non-shivering thermogenesis

22. Metabolic adaptation
• Shivering (and pre-shivering) response
• Non-shivering thermogenesis

23. Budd and Warhaft, 1966
Exposure to 10°C
Petajam and Williams, 1972
Shivering response

24. Shivering yields heat production
Madden et al., 2013
Shivering is mediated by
α2-adrenoreceptors

25. Metabolic adaptation
• Shivering (and pre-shivering) response
• Non-shivering thermogenesis

26. Young et al., 1986
Increased metabolic rate
90 min at 5°C

27. How does norepinephrine cause this?
Golozoubova et al., 2006
Cannon, 2011

28. Brown-Adipose-Tissue Activity as Assessed by PET–CT with 18
F-FDG.
van Marken Lichtenbelt WD et al. N Engl J Med 2009;360:1500-1508.

29. Metabolic energy sources
• From fats
• Also from usual sources:
▫ Carbohydrates, especially glycogen stores
▫ Protein
• Can cause hypoglycemia  decompensation
Havel and Goldfien, 1959

30. Special considerations
• Some groups cannot adapt as well
▫ Age extremes
▫ Disease states
▫ Alcohol/drugs
• Risk factors for death from accidental
hypothermia: ethanol use, homelessness,
psychiatric disease, and older age
CDC, 2005

31. Mareedu et al., 2008

32. Mareedu et al., 2008

33. References
Brooks GA, Fahey TD, and Baldwin KM. Exercise physiology: human bioenergetics and its applications. New York: McGraw-Hill,
2005.
Budd GM, and Warhaft N. Body temperature, shivering, blood pressure and heart rate during a standard cold stress in Australia and
Antarctica. J Physiol 186: 216-232, 1966.
Cannon B, and Nedergaard J. Nonshivering thermogenesis and its adequate measurement in metabolic studies. J Exp Biol 214: 242-253,
2011.
Centers for Disease Control and Prevention. Hypothermia-related deaths-United States, 2003-2004. MMWR 54:173, 2005.
Cui J, Durand S, Levine BD, and Crandall CG. Effect of skin surface cooling on central venous pressure during orthostatic challenge.
Am J Physiol Heart Circ Physiol 289: H2429-2433, 2005.
Golozoubova V, Cannon B, and Nedergaard J. UCP1 is essential for adaptive adrenergic nonshivering thermogenesis. Am J Physiol
Endocrinol Metab 291: E350-357, 2006.
Hammel HT, Elsner RW, Le Messurier DH, Andersen HT, and Milan FA. Thermal and metabolic responses of the Australian
aborigine exposed to moderate cold in summer. Journal of Applied Physiology 14: 605-615, 1959.
Hillier AP. Thyroxine deiodination during cold exposure in the rat. J Physiol 197: 135-147, 1968.
Lewis T. Observations upon the reactions of the vessels of the human skin to cold. Heart 15: 177-208, 1930.
Madden CJ, Tupone D, Cano G, and Morrison SF. alpha2 Adrenergic Receptor-Mediated Inhibition of Thermogenesis. J Neurosci 33:
2017-2028, 2013.
Mareedu RK, Grandhe NP, Gangineni S, Quinn DL. Classic EKG changes of hypothermia. Clin Med Res 6:107-8, 2008.
Petajan JH, and Williams DD. Behavior of single motor units during pre-shivering tone and shivering tremor. Am J Phys Med 51: 16-22,
1972.
Pozos RS, and Danzl DF. Human physiological responses to cold stress and hypothermia. In: Medical Aspects of Harsh Environments,
Volume 1, edited by Pandoff KB, and Burr RE. Washington, DC: Office of the Surgeon General, U.S. Army, 2002.
Segar WE, and Moore WW. The regulation of antidiuretic hormone release in man: I. Effects of change in position and ambient
temperature on blood ADH levels. J Clin Invest 47: 2143-2151, 1968.
Thompson-Torgerson CS, Holowatz LA, Flavahan NA, and Kenney WL. Cold-induced cutaneous vasoconstriction is mediated by
Rho kinase in vivo in human skin. Am J Physiol Heart Circ Physiol 292: H1700-1705, 2007.
Wagner JA, and Horvath SM. Cardiovascular reactions to cold exposures differ with age and gender. J Appl Physiol 58: 187-192, 1985.
Young AJ, Muza SR, Sawka MN, Gonzalez RR, and Pandolf KB. Human thermoregulatory responses to cold air are altered by
repeated cold water immersion. J Appl Physiol 60: 1542-1548, 1986.

34. Questions?