Effect of the Forearm Tissue Temperature on the Cold Induced Vasodilation

Recent work suggests an influence of the mean body skin (Tsk) and deep body temperatures (Tb) on coldinduced vasodilatation (CIVD). For example, minimum finger temperature (Tfi,min)was lower, and the maximum finger temperature (Tfi,max) was greater during CIVD when Tb was elevated, and the onset time of the CIVD response was reduced at higher Tsk. Question remain, though, about the influence of forearm tissue temperature on CIVD at a given Tsk and Tb. On two different occasions, eleven healthy male subjects pre-conditioned their forearm tissue at two different water temperatures (Tw), 20 and 38°C, until steady state forearm muscle temperature was achieved. After the conditioning period (129 ± 15 and 85 ± 15 min for 20 and 38°C, respectively), the fingers of the conditioned forearm were immersed in a 5°C water bath for 30 min. During finger immersion, Tsk and Tb were similar at each forearm skin temperature (Tsk = 34.3 ± 0.6°C, Tb = 36.8 ± 0.2°C), but temperature 3cm deep into the forearm’s flexor digitorum profundus muscle differed significantly, averaging 23.6 ± 1.7°C when Tw was 20oC and 36.7 ± 0.6°C when Tw was 38°C. Arterial blood temperature in the radial artery measured at the wrist averaged 28.2 ± 2.5 and 35.6 ± 0.9°C for the 20 and 38°C conditions, respectively (p < 0.05). The two forearm conditions caused significant differences in all the CIVD parameters during the 30 min immersion in 5°C water. During the 38oC condition, the onset time for the CIVD was faster and the average, maximal and minimal Tfi were higher than during the 20oC condition. We concluded that a low forearm tissue temperature impedes the CIVD response despite normal Tsk and Tb, possibly by decreasing the temperature of the arterial blood to the fingers. 1.0 INTRODUCTION Cold-induced vasodilation (CIVD) is a local cold vascular phenomenon likely caused by a decrease in the release of neurotransmitters from the local sympathetic nerves innerving the arterio-venous anastomoses (AVAs). This cold paralysis of the smooth muscle cells of the AVAs is responsible for the opening of the lumen of the arterioles and the subsequent increase of blood flow and the observed increase in tissue temperature of the digits. The presence of this physiological reaction has a practical implication for people exposed to cold environments. Wilson and Goldman [1] observed that CIVD prevented freezing in fingers exposed to subzero ambient temperatures. Investigators thus believe that CIVD plays a substantial role in reducing the risk of local cold injuries [2], and may be beneficial for improving dexterity and tactile sensitivity during exposure to cold [3]. Many factors have been shown to influence the CIVD responses to cold. Daanen recently provided an extensive review on the topic [3]. One factor that is of particular relevance to this study is the effect of Ducharme, M.B.; Sessler, D.I.; Doufas, A.; Greif, R. (2005) Effect of the Forearm Tissue Temperature on the Cold Induced Vasodilation. In Prevention of Cold Injuries (pp. 14-1 – 14-8). Meeting Proceedings RTO-MP-HFM-126, Paper 14. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 01 MAY 2005 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Effect of the Forearm Tissue Temperature on the Cold Induced Vasodilation 5a. CONTRACT NUMBER