Effect of Geometry and Blood Flow in Cooling of Upper Leg

2013 ◽  
Author(s):  
M. Kalra ◽  
M. Bahrami ◽  
C. J. Sparrey
Keyword(s):  
Thermal Response ◽  
Tissue Perfusion ◽  
Neurological Damage ◽  
Surface Cooling ◽  
Perfusion Rate ◽  
Human Comfort ◽  
Metabolic Heat ◽  
Metabolic Heat Generation ◽  
Systemic Hypothermia

Systemic hypothermia has been shown to reduce neurological damage in post-cardiac arrest patients. Reducing a patient’s core temperature to 33°C over a period of 24 to 48 hours has been shown to reduce long-term neurological damage by 16% and mortality by 14% [1]. Hypothermia is frequently induced by surface cooling, either with medical devices that circulate coolant in a pad, or ice packs. However, there is a lack of knowledge about the thermal response of tissue to localized cooling. Current thermal models are designed for determining human comfort and have not been evaluated for the targeted low temperatures required for inducing hypothermia. Metabolic heat generation and tissue perfusion rate can significantly change under low temperature, which in turn affects the overall heat flux and cooling rates.

scholarly journals WALANT–Epinephrine injection may lead to short term, reversible episodes of critical oxygen saturation in the fingertips

2021 ◽  
Vol 141 (3) ◽  
pp. 527-533
Author(s):  
P. Moog ◽  
M. Dozan ◽  
J. Betzl ◽  
I. Sukhova ◽  
H. Kükrek ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Substantial Reduction ◽  
Tissue Perfusion ◽  
Critical Levels ◽  
Short Term ◽  
Doppler Flowmetry ◽  
Epinephrine Injection ◽  
Venous Oxygen Saturation

Abstract Introduction Although the WALANT technique’s long-term safeness has been demonstrated in many studies, there are only few data investigating its short-term effects on tissue perfusion and oxygen levels. It was hypothesized that, temporarily, critical levels of tissue perfusion may occur. Methods Seventeen patients, who were scheduled for different procedures in WALANT technique, were injected with 5–7 ml of 1% Articain containing 1:200,000 epinephrine at the finger base. Capillary-venous oxygen saturation, hemoglobin volume in the capillaries, and relative blood flow in the fingertips were recorded once per second by white light spectrometry and laser Doppler flowmetry before, during and after injection for an average of 32 min. Results Clinically, no persistent tissue malperfusion was observed, and there were no postoperative complications. Capillary-venous oxygen saturation was reduced by ≥ 30% in seven patients. Critical levels of oxygen saturation were detected in four patients during 13 intervals, each lasting for 132.5 s on average. Oxygen saturation returned to noncritical values in all patients by the end of the observation period. Blood flow in the fingertips was reduced by more than 30% in nine patients, but no critical levels were observed, as with the hemoglobin. Three patients demonstrated a reactive increase in blood flow of more than 30% after injection. Conclusions Injection of tumescent local anesthesia containing epinephrine into finger base may temporarily cause a substantial reduction in blood flow and lead to critical levels of oxygen saturation in the fingertips. However, this was fully reversible within minutes and does not cause long-term complications.

scholarly journals Field Test and Numerical Simulation on the Long-Term Thermal Response of PHC Energy Pile in Layered Foundation

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3873
Author(s):  
Guozhu Zhang ◽  
Ziming Cao ◽  
Yiping Liu ◽  
Jiawei Chen
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchange ◽  
Temperature Variation ◽  
Thermal Response ◽  
Ground Temperature ◽  
Short Term ◽  
Energy Pile ◽  
Backfill Soil ◽  
Short And Long Term

Investigation on the long-term thermal response of precast high-strength concrete (PHC) energy pile is relatively rare. This paper combines field experiments and numerical simulations to investigate the long-term thermal properties of a PHC energy pile in a layered foundation. The major findings obtained from the experimental and numerical studies are as follows: First, the thermophysical ground properties gradually produce an influence on the long-term temperature variation. For the soil layers with relatively higher thermal conductivity, the ground temperature near to the energy pile presents a slowly increasing trend, and the ground temperature response at a longer distance from the center of the PHC pile appears to be delayed. Second, the short- and long-term thermal performance of the PHC energy pile can be enhanced by increasing the thermal conductivity of backfill soil. When the thermal conductivities of backfill soil in the PHC pile increase from 1 to 4 W/(m K), the heat exchange amounts of energy pile can be enhanced by approximately 30%, 79%, 105%, and 122% at 1 day and 20%, 47%, 59%, and 66% at 90 days compared with the backfill water used in the site. However, the influence of specific heat capacity of the backfill soil in the PHC pile on the short-term or long-term thermal response can be ignored. Furthermore, the variation of the initial ground temperature is also an important factor to affect the short-and-long-term heat transfer capacity and ground temperature variation. Finally, the thermal conductivity of the ground has a significant effect on the long-term thermal response compared with the short-term condition, and the heat exchange rates rise by about 5% and 9% at 1 day and 21% and 37% at 90 days as the thermal conductivities of the ground increase by 0.5 and 1 W/(m K), respectively.

scholarly journals Exploring and Quantifying River Thermal Response to Heatwaves

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1098 ◽  
Author(s):  
Sebastiano Piccolroaz ◽  
Marco Toffolon ◽  
Christopher Robinson ◽  
Annunziato Siviglia
Keyword(s):  
Water Temperature ◽  
River Water ◽  
Thermal Response ◽  
Hydrological Regime ◽  
Management Policy ◽  
Extreme Weather Events ◽  
Thermal Dynamics ◽  
Depth Analysis ◽  
River Water Temperature

Most of the existing literature on river water temperature focuseds on river thermal sensitivity to long-term trends of climate variables, whereas how river water temperature responds to extreme weather events, such as heatwaves, still requires in-depth analysis. Research in this direction is particularly relevant in that heatwaves are expected to increase in intensity, frequency, and duration in the coming decades, with likely consequences on river thermal regimes and ecology. In this study we analyzed the long-term temperature and streamflow series of 19 Swiss rivers with different hydrological regime (regulated, low-land, and snow-fed), and characterized how concurrent changes in air temperature and streamflow concurred to affect their thermal dynamics. We focused on quantifying the thermal response to the three most significant heatwave events that occurred in Central Europe since 1950 (July–August 2003, July 2006, and July 2015). We found that the thermal response of the analyzed rivers contrasted strongly depending on the river hydrological regime, confirming the behavior observed under typical weather conditions. Low-land rivers were extremely sensitive to heatwaves. In sharp contrast, high-altitude snow-fed rivers and regulated rivers receiving cold water from higher altitude hydropower reservoirs or diversions showed a damped thermal response. The results presented in this study suggest that water resource managers should be aware of the multiple consequences of heatwave events on river water temperature and incorporate expected thermal responses in adaptive management policy. In this respect, additional efforts and dedicated studies are required to deepen our knowledge on how extreme heatwave events can affect river ecosystems.

scholarly journals Novel Insights into the Pathogenesis and Prevention of Intradialytic Hypotension

2018 ◽  
Vol 45 (1-3) ◽  
pp. 230-235 ◽  
Author(s):  
Frank M. van der Sande ◽  
Marijke J.  Dekker ◽  
Karel M.L. Leunissen ◽  
Jeroen P. Kooman
Keyword(s):  
Tissue Perfusion ◽  
Organ Damage ◽  
Adverse Outcomes ◽  
Fine Tuning ◽  
Great Promise ◽  
Intradialytic Hypotension ◽  
Related Factors ◽  
Thermally Induced ◽  
Discontinuous Nature

Background: Intradialytic hypotension (IDH) is a common complication of haemodialysis (HD) and associated with adverse outcomes, especially when a nadir definition (systolic blood pressure <90 mm Hg) is used. The pathogenesis of IDH is directly linked to the discontinuous nature of the HD treatment, in combination with patient-related factors such as age, diabetes mellitus and cardiac failure. Summary: Although the decline in blood volume due to removal of fluid by ultrafiltration is the prime mover, thermally induced reflex vasodilation compromises the haemodynamic response to hypovolemia. Recent studies have stressed the relevance of changes in tissue perfusion during HD, which may translate in long-term organ damage. Monitoring changes in tissue perfusion, for which emerging evidence becomes available, appears to have great promise in the fine-tuning of the dialysis procedure. Key Messages: While it is unlikely that IDH can be completely prevented, reduction in inter-dialytic weight gain, prevention of an increase in core temperature by adjusting the dialysate temperature and more frequent or prolonged dialysis treatment remain cornerstones in providing a more comfortable and safe treatment.

Analiza obrazu klinicznego niedokrwistości z niedoboru witaminy B12 u dzieci

2019 ◽  
Vol 23 (1) ◽  
Author(s):  
Aleksandra Pankiewicz ◽  
Anna Adamowicz-Salach ◽  
Marek W. Karwacki ◽  
Katarzyna Pawelec ◽  
Katarzyna Albrecht ◽  
...  
Keyword(s):  
Vitamin B12 ◽  
Metabolic Pathways ◽  
Essential Role ◽  
Vitamin B12 Deficiency ◽  
Neurological Damage ◽  
Laboratory Findings ◽  
Delay In Diagnosis ◽  
B12 Deficiency ◽  
Late Manifestation

Diagnosis of vitamin B12 deficiency could be difficult due to various and rather unspecific symptoms and often late manifestation in hematological findings. B12 has a crucial role as cofactor of many metabolic pathways and has essential role in many processes such as DNA synthesis, neuron myelination and gluconeogenesis. Blood smear has a huge role in early diagnosis and should be performed. B12 deficiency is not very common, however could be underestimated especially in developing countries. In children main cause of deficiency is exclusively breastfeeding by vitamin B12 depleted mothers. Consequences of low intake in children are more severe than in adults, because of lower liver storage. Early detection and treatment is very important, because long term deficiency could result in persistent neurological damage. Coexistence iron or folate deficiencies could result delay in diagnosis. In this article different manifestation and laboratory findings in group of children with B12 deficiency is described.

Evolution of the thermal state of permafrost under climate warming in Central Yakutia

The Holocene ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 1401-1410 ◽  
Author(s):  
Stepan P Varlamov ◽  
Yuri B Skachkov ◽  
Pavel N Skryabin
Keyword(s):  
Heat Exchange ◽  
Active Layer ◽  
Climate Warming ◽  
Thermal State ◽  
Thermal Response ◽  
Snow Accumulation ◽  
Climatic Fluctuations ◽  
Exchange Layer ◽  
Central Yakutia

The relevance of the problem under review is explained by the need to study the thermal response of permafrost to the modern climate change. Evolution of the thermal state of grounds has been studied with a view to evaluate the effects of modern climate warming on permafrost in Central Yakutia. The leading method to study this problem is the arrangement and performance of long-term monitoring observations of the permafrost thermal state that enable quantitative evaluation of the thermal response of upper permafrost layers to climatic fluctuations of recent decades. The analysis of long-term records from weather stations in the region has clearly revealed one of the highest increasing trends in the mean annual air temperature in northern Russia. Quantitative relationships in the long-term variability of ground thermal parameters, such as ground temperature at the bottom of the active layer, at the bottom of the annual heat exchange layer, and active thaw depth, have been established. The thermal state dynamics of the annual heat exchange layer under climate warming indicates that both warm and cold permafrost are thermally stable. Short-term variability of the snow accumulation regime is the main factor controlling the thermal state of the ground in permafrost landscapes. The active-layer thickness is characterized by low interannual variability and exhibits little response to climate warming, with no statistically meaningful increasing or decreasing trend. The results of ground thermal monitoring can be extended to similar landscapes in the region, providing a reliable basis for predicting heat transfer in natural landscapes.

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