Modeling and simulation of an invasive mild hypothermic blood cooling system

Abstract: Nowadays, mild hypothermia is widely used in the fields of post-cardiac arrest resuscitation, stroke, cerebral hemorrhage, large-scale cerebral infarction, and craniocerebral injury. In this paper, a locally mixed sub-low temperature device is designed, and the cold and hot water mixing experiment is used to simulate the human blood transfer process. To set a foundation for the optimization of the heat transfer system, the static characteristics are analyzed by building the mathematic model and setting up the experimental station. In addition, the affection of several key structure parameters is researched. Through experimental and simulation studies, it can be concluded that, firstly, the mathematical model proved to be effective. Secondly, the results of simulation experiments show that 14.52 °C refrigeration can reduce the original temperature of 33.42 °C to 32.02 °C, and the temperature of refrigerated blood rises to 18.64 °C, and the average error is about 0.3 °C. Thirdly, as the thermal conductivity of the vascular sheath increases, the efficiency of the heat exchange system also increases significantly. Finally, as the input cold blood flow rate increases, the mass increases and the temperature of the mixed blood temperature decreases. It provides a research basis for subsequent research on local fixed-point sub-low temperature control technology

Helpful to Live Healthier? Intermittent Hypoxic/Ischemic Training Benefits Vascular Homeostasis and Lipid Metabolism with Activating SIRT1 Pathways in Overweight/Obese Individuals

Introduction: The present study aimed to investigate whether and how normobaric intermittent hypoxic training (IHT) or remote ischemic preconditioning (RIPC) plus normoxic training (RNT) has a synergistic protective effect on lipid metabolism and vascular function compared with normoxic training (NT) in overweight or obese adults. Methods: A total of 37 overweight or obese adults (36.03 ± 10.48 years) were randomly assigned to 3 groups: NT group (exercise intervention in normoxia), IHT group (exercise intervention in normobaric hypoxic chamber), and RNT group (exercise intervention in normoxia + RIPC twice daily). All participants carried out the same 1-h exercise intervention for a total of 4 weeks, 5 days per week. Physical fitness parameters were evaluated at pre- and postexercise intervention. Results: After training, all three groups had a significantly decreased body mass index (p < 0.05). The IHT group had reduced body fat percentage, visceral fat mass (p < 0.05), blood pressure (p < 0.01), left ankle-brachial index (ABI), maximal heart rate (HRmax) (p < 0.05), expression of peroxisome proliferator-activated receptor-γ (PPARγ) (p < 0.01) and increased expression of SIRT1 (p < 0.05), VEGF (p < 0.01). The RNT group had lowered waist-to-hip ratio, visceral fat mass, blood pressure (p < 0.05), and HRmax (p < 0.01). Conclusion: IHT could effectively reduce visceral fat mass and improve vascular elasticity in overweight or obese individuals than pure NT with the activation of SIRT1-related pathways. And RNT also produced similar benefits on body composition and vascular function, which were weaker than those of IHT but stronger than NT. Given the convenience and economy of RNT, both intermittent hypoxic and ischemic training have the potential to be successful health promotion strategies for the overweight/obese population

Clinical practice guidelines of remote ischemic conditioning for the management of cerebrovascular diseases

Remote ischemic conditioning (RIC) using transient limb ischemia and reperfusion has been shown in small clinical studies to reduce myocardial injury and infarction in cardiac patients, although larger clinical outcome studies have been neutral. Experimental and emerging clinical studies have also reported beneficial effects of limb RIC in a number of different settings of cerebrovascular disease including stroke (ischemic and hemorrhagic), carotid artery stenosis, intracranial artery stenosis, aneurysms, small vessel disease, and vascular cognitive impairment. Although limb RIC has many advantages, in that it is non-invasive, easy to administer, relatively innocuous, cost-effective, has few or no contraindications, and may be deployed under various circumstances (e.g., home, ambulance, and hospital), several questions remain regarding its clinical application for cerebrovascular disease. Therefore, in this document, we aim to provide practicing clinicians with a coherent synthesis of the latest scientific evidence, and we propose several recommendations to help facilitate the clinical application of limb RIC for the management of cerebrovascular disease

Stem cell therapies in age-related neurodegenerative diseases and stroke

Aging, a complex process associated with various structural, functional and metabolic changes in the brain, is an important risk factor for neurodegenerative diseases and stroke. These diseases share similar neuropathological changes, such as the formation of misfolded proteins, oxidative stress, loss of neurons and synapses, dysfunction of the neurovascular unit (NVU), reduction of self-repair capacity, and motor and/or cognitive deficiencies. In addition to gray matter dysfunction, the plasticity and repair capacity of white matter also decrease with aging and contribute to neurodegenerative diseases. Aging not only renders patients more susceptible to these disorders, but also attenuates their self-repair capabilities. In addition, low drug responsiveness and intolerable side effects are major challenges in the prevention and treatment of senile diseases. Thus, stem cell therapies—characterized by cellular plasticity and the ability to self-renew—may be a promising strategy for aging-related brain disorders. Here, we review the common pathophysiological changes, treatments, and the promises and limitations of stem cell therapies in age-related neurodegenerative diseases and stroke

Effect of Gd on microstructure and corrosion behavior of Mg-xGd-1Er-1Zn-0.6Zr alloys

The Mg-xGd-1Er-1Zn-0.6Zr alloys with Gd contents of 7%(mass fraction), 9% and 11% were prepared by gravity casting method.The microstructure of the alloys was studied by means of optical microscope, scanning electron microscope and X-ray diffractometer.The corrosion behavior of the alloys were evaluated by means of open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy measurements in 3.5%NaCl solution.The results show that when Gd content increases from 7% to 11%, the peak time of open circuit potential decreases from 1609 s to 851 s, the charge transfer resistance decreases from 588.50 Ω to 31.9 Ω, the corrosion current density increases from 2.21×10-5 A/cm2 to 3.97×10-5 A/cm2, indicating that the corrosion resistance of the alloys decreases with the increase of Gd content.It is attributed to the combined operation of the micro-galvanic corrosion effect as well as corrosion barrier effect of second phase.When the Gd content increases from 7% to 11%, the volume fraction of (Mg, Zn)3(Gd, Er) phase increases from 1.9% to 5.2%, and changes from discontinuous distribution to semi-continuous distribution along grain boundaries, the volume fraction of the lamellar-shape LPSO phase increases from 11.7% to 26.7% and penetrates into grains.The increase in the volume fraction of the (Mg, Zn)3(Gd, Er) phase and the lamellar-shape LPSO phase results in the decrease of corrosion resistance, however, a large number of fine lamellar-shape LPSO phases is able to prevent the corrosion from spreading and slow down the growth of corrosion rate of the alloy with 11%Gd content in 8-24 h