The influence of aging and diabetes on heat transfer characteristics of the skin to a rapidly applied heat source.
BACKGROUND
Numerous studies have examined the blood flow of the skin at rest and in response to sustained heat and shown that, in older people and people with diabetes, the skin blood flow response to heat is diminished compared to younger people. It is not sustained heat, however, that usually causes burns; it is a more rapid application of heat.


METHODS
Ten younger subjects, 10 older subjects, and 10 subjects with diabetes were examined before and after applying a water-filled thermode to the skin above the quadriceps muscle to observe the changes in skin temperature and skin blood flow and the ability of the skin to absorb heat after a 2-min heat exposure with water at 44°C.


RESULTS
Skin temperature rose from 31.2°C at rest to 38.3°C after 2 min of heat application in all subjects (P > 0.05 between groups). The calories required in the younger group of subjects was 2.26 times the calories required in the older group of subjects for the same change in skin temperature and 13.8 times the calories needed to increase skin temperature in the subjects with diabetes. Furthermore, the blood flow at rest was lower in people with diabetes than older subjects and both groups less than that seen in younger subjects. The blood flow response to heat was slower in the subjects with diabetes compared to the older subjects and much slower than that seen in the younger subjects.


CONCLUSIONS
Reduced skin blood flow of older and subjects with diabetes, decreased thickness of the dermal layer, and increased subcutaneous fat, as well as damage to transient receptor potential vanilloid 1 receptors, may account for some of the differences between the groups.
Department of Physical Therapy, Loma Linda University, Loma Linda, CA 92350, USA. jpetrofsky@llu.edu
Jerrold
J
Petrofsky
Haneul
H
Lee
Moxi
M
Trivedi
Akshay N
AN
Hudlikar
Chia-hao
CH
Yang
Neha
N
Goraksh
Faris
F
Alshammari
Mitali
M
Mohanan
Janhavi
J
Soni
Brindha
B
Agilan
Nikhila
N
Pai
Tirupathi
T
Chindam
Vengatesh
V
Murugesan
Jong Eun
JE
Yim
Vahishta
V
Katrak
D000367:Age Factors; D001783:Blood Flow Velocity / Q000502:physiology; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D012867:Skin / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012881:Skin Temperature / Q000502:physiology*; D018608:Ultrasonography, Doppler