Relation between finger cold-induced vasodilation and rewarming speed after cold exposure

ACSM Expert Consensus Statement: Injury Prevention and Exercise Performance during Cold-Weather Exercise

ABSTRACT

Cold injury can result from exercising at low temperatures and can impair exercise performance or cause lifelong debility or death. This consensus statement provides up-to-date information on the pathogenesis, nature, impacts, prevention, and treatment of the most common cold injuries.

Heat acclimation enhances the cold-induced vasodilation response

Purpose

It has been reported that the cold-induced vasodilation (CIVD) response can be trained using either regular local cold stimulation or exercise training. The present study investigated whether repeated exposure to environmental stressors, known to improve aerobic performance (heat and/or hypoxia), could also provide benefit to the CIVD response.

Methods

Forty male participants undertook three 10-day acclimation protocols including daily exercise training: heat acclimation (HeA; daily exercise training at an ambient temperature, T_a = 35 °C), combined heat and hypoxic acclimation (HeA/HypA; daily exercise training at T_a = 35 °C, while confined to a simulated altitude of ~ 4000 m) and exercise training in normoxic thermoneutral conditions (NorEx; no environmental stressors). To observe potential effects of the local acclimation on the CIVD response, participants additionally immersed their hand in warm water (35 °C) daily during the HeA/HypA and NorEx. Before and after the acclimation protocols, participants completed hand immersions in cold water (8 °C) for 30 min, followed by 15-min recovery phases. The temperature was measured in each finger.

Results

Following the HeA protocol, the average temperature of all five fingers was higher during immersion (from 13.9 ± 2.4 to 15.5 ± 2.5 °C; p = 0.04) and recovery (from 22.2 ± 4.0 to 25.9 ± 4.9 °C; p = 0.02). The HeA/HypA and NorEx protocols did not enhance the CIVD response.

Conclusion

Whole-body heat acclimation increased the finger vasodilatory response during cold-water immersion, and enhanced the rewarming rate of the hand, thus potentially contributing to improved local cold tolerance. Daily hand immersion in warm water for 10 days during HeA/Hyp and NorEx, did not contribute to any changes in the CIVD response.

Research progress in the pathogenic mechanisms and imaging of severe frostbite

PURPOSE

This article reviews the pathological mechanisms and progress of imaging of severe frostbite to assist in the search for targets for clinical diagnosis and treatment of severe frostbite. This review also aims to provide strong evidence for clinical diagnosis and treatment of deep frostbite.

METHODS

The review was based on the summary and analysis of the existing literature, and explored the pathological mechanism of deep frostbite and the advantages and disadvantages of imaging diagnostic methods.

RESULTS

According to the depth of tissue involvement, frostbite is divided into 4 levels. Severe frostbite includes Grade 3 and Grade 4 frostbite. Clinical performance evaluation and imaging diagnostic research have always been the mainstream of severe frostbite diagnosis. Imaging methods focus on vascular patency and tissue vitality. This article introduces angiography, SETCT/CT and MRA, and we summarize the advantages and disadvantages of these imaging methods. We recommend corresponding imaging modalities according to the state of frostbite patients.

CONCLUSIONS

Imaging examination, especially angiography and bone scans, provide useful information for determining the diagnosis and prognosis of severe frostbite. In order to obtain a good clinical prognosis, clinicians should first perform SPECT/CT. MRA does not burden the patient's body, but the balance between cost and benefit must be considered. Angiography provides a good feedback on the changes in blood vessel status before and after treatment, which is helpful for discovering the response of limbs to treatment.

Dynamics of Matrix Metalloproteinases in Local Cold Injury

The relevance of cold injury is due to its high specific weight in the structure of injuries, complexities of complex therapy, and unsatisfactory results of treatment. It is known that in the pathogenesis of local cold injury, the leading role belongs to endothelial dysfunction, which secretes a huge amount of biologically active substances, including matrix metalloproteinases.Aim: to determine the dynamics of the content of matrix metalloproteinases of the second subfamily (MMP-2, MMP-9) in the serum of patients with local cold injury.Materials and methods. The study included 80 patients (60 men, 20 women) with frostbite of the III–IV degree of the foot to the level of the lower third of the leg in the late reactive period and the period of granulation and epithelization.Results. In the late reactive period in patients with cryopreservation, the level of MMP-2 was 3.4 times higher relative to the control (p = 0.011), on day 30 MMP-2 values did not differ from the control parameters (p = 0.103). The level of collagenase B (MMP-9) in patients with local cold injury on day 5 was 14.5 times higher than the control parameters (p = 0.002), on day 30 – 12.5 times higher compared to the control group (p = 0.000094).Conclusion. During the analysis of the data obtained, we can think about the dual nature of collagenases during the processes of inflammation. In a situation of distress, collagenases prevent endothelial dysfunction by eliminating the cellular structures of the endothelium to ensure adequate metabolism in tissues. Their importance as markers of failure of adequate flow of reparative processes is not excluded.

Finger cold-induced vasodilation test does not predict subsequent cold injuries: A lesson from the 2018 Canadian Forces Exercise

A cold-induced vasodilation (CIVD) test was administered to 113 Canadian Armed Forces (CAF) soldiers (age 25.6 ± 6 yrs) during pre-deployment to a Canadian Arctic training exercise. The incidence and rates/types of subsequent peripheral cold injuries, as well as the relationship of CIVD responses against other hypothesized/reported risk factors (smoking, gender, age, ethnicity and prior cold injury), were analyzed. Although there was a wide range of CIVD RIF (resistance index to frostbite) scores (mean = 5.0 ± 1.5), there were no systematic relationships between RIF and injury type/location and rate, and the other risk factors analyzed. The absence of physiological links to cold injury occurrence suggests that in a military cold deployment setting, other factors are in play, which might include clothing, training, leadership and doctrine. These factors should be examined in future work.