title: The influence of environmental temperature on the response of the skin to local pressure: the impact of aging and diabetes.
abstract: BACKGROUND
  To protect against ischemia, pressure-induced vasodilation (PIV) causes an increase in skin blood flow. Endothelial dysfunction, which is commonly found in older patients and those with diabetes, and global temperatures can affect the resting blood flow in skin, which may reduce the blood flow during and after the application of local pressure. The present study investigated the PIV of the skin with exposure to three global temperatures in younger and older populations and those with diabetes.
  
  
  METHODS
  Older subjects (n = 15, mean age 64.2 +/- 14.0 years), subjects with diabetes (n = 15, mean age 62 +/- 5.9 years, mean duration 13.2 +/- 9.1 years), or younger subjects (n = 15, mean age 25.7 +/- 2.9 years) participated. An infrared laser Dopler flow meter was used to measure skin blood flow on the bottom of the foot, lower back, and hand during and after applications of pressure at 7.5, 15, 30, 45, and 60 kPa at 16 degrees C, 24 degrees C, and 32 degrees C global temperatures.
  
  
  RESULTS
  The resting blood flow for all subjects was significantly lower in the 16 degrees C environment (P < 0.05). Blood flow in the group with diabetes was significantly lower at rest, during the application of all pressure, and after the release of pressure in all global temperatures (P < 0.05). The younger group showed a significant increase in blood flow after every pressure application, except 7.5 kPa, in all global conditions (P < 0.001). Older subjects and patients with diabetes did not have a significant reactive hyperemia, especially in the 16 degrees C environment.
  
  
  CONCLUSIONS
  The protective mechanism of PIV is severely reduced in older populations and those with diabetes, especially in colder environments where skin blood flow is already diminished.
authors.affiliation: Department of Physical Therapy, School of Allied Health Professions, Loma Linda University, Loma Linda, California 92350, USA.
authors.forename: Katie
authors.initials: K
authors.lastname: McLellan
authors.forename: Jerrold S
authors.initials: JS
authors.lastname: Petrofsky
authors.forename: Grenith
authors.initials: G
authors.lastname: Zimmerman
authors.forename: Everett
authors.initials: E
authors.lastname: Lohman
authors.forename: Michelle
authors.initials: M
authors.lastname: Prowse
authors.forename: Ernie
authors.initials: E
authors.lastname: Schwab
authors.forename: Scott
authors.initials: S
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology*; D003920:Diabetes Mellitus / Q000503:physiopathology*; D004777:Environment; D005260:Female; D005528:Foot / Q000098:blood supply; D006801:Humans; D007259:Infrared Rays; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D008875:Middle Aged; D011312:Pressure; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000503:physiopathology; D013696:Temperature; D014664:Vasodilation