Cold-induced vasoconstriction may persist long after cooling ends: an evaluation of multiple cryotherapy units

Abstract

Purpose: 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.

Conflict of interest statement

Conflict of interest A patent application has been submitted by Dr. Khoshnevis and Dr. Diller to the United States Patent and Trademark Office under the title Improved Cryotherapy Devices and Methods to Limit Ischaemic Injury Side Effects. Ownership rights to this patent reside with The University of Texas System. Dr. Diller has served as an expert witness for both plaintiff and defendant counsel since 2000 in numerous legal cases regarding the safety and design of existing cryotherapy devices.

Figures

Fig. 1

a Placement of instrumentation consisting of thermocouples (T), heat flux gauge (HFG), and LDF2 probes (P) to the ventral aspect of the right knee. Heat flux data are not reported in this paper. b Same location after application of a single thermal insulation layer (ACE bandage wrap) with no elastic stretching. c After application of a PC300 cooling pad over the insulation layer

Fig. 2

Data for a trial with a BREG Polar Care 300 cryotherapy unit applied to the knee, consisting of 30 min of baseline data, followed by 60 min of active cooling, and 84 min of passive rewarming. a Temperature histories measured at two locations on the skin surface under the cooling pad (red and green) and on the surface of the pad (blue). b Perfusion histories at the two sites in the skin under the cooling pad

Fig. 3

Mean and standard errors of perfusion values from the a PC300 and b DJO cryotherapy devices during 90 and 95 min of rewarming, respectively. The overlap among the error bars shows that there is no overall significant change in perfusion during rewarming