title: Cold-induced vasoconstriction may persist long after cooling ends: an evaluation of multiple cryotherapy units.
abstract: OBJECTIVE
  Localized cooling is widely used in treating soft tissue injuries by modulating swelling, pain, and inflammation. One of the primary outcomes of localized cooling is vasoconstriction within the underlying skin. It is thought that in some instances, cryotherapy may be causative of tissue necrosis and neuropathy via cold-induced ischaemia leading to nonfreezing cold injury (NFCI). The purpose of this study is to quantify the magnitude and persistence of vasoconstriction associated with cryotherapy.
  
  
  METHODS
  Data are presented from testing with four different FDA approved cryotherapy devices. Blood perfusion and skin temperature were measured at multiple anatomical sites during baseline, active cooling, and passive rewarming periods.
  
  
  RESULTS
  Local cutaneous blood perfusion was depressed in response to cooling the skin surface with all devices, including the DonJoy (DJO, p = 2.6 × 10(-8)), Polar Care 300 (PC300, p = 1.1 × 10(-3)), Polar Care 500 Lite (PC500L, p = 0.010), and DeRoyal T505 (DR505, p = 0.016). During the rewarming period, parasitic heat gain from the underlying tissues and the environment resulted in increased temperatures of the skin and pad for all devices, but blood perfusion did not change significantly, DJO (n.s.), PC300 (n.s.), PC500L (n.s.), and DR505 (n.s.).
  
  
  CONCLUSIONS
  The results demonstrate that cryotherapy can create a deep state of vasoconstriction in the local area of treatment. In the absence of independent stimulation, the condition of reduced blood flow persists long after cooling is stopped and local temperatures have rewarmed towards the normal range, indicating that the maintenance of vasoconstriction is not directly dependent on the continuing existence of a cold state. The depressed blood flow may dispose tissue to NFCI.
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA.
authors.forename: Sepideh
authors.initials: S
authors.lastname: Khoshnevis
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Craik
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Diller
mesh_terms: D000328:Adult; D017679:Cryotherapy / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D005260:Female; D006801:Humans; D007717:Knee; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D014661:Vasoconstriction