Experimental Study on Effective Placement of PCM Packets in Cooling Vest to Improve Performance in Warm Environment

2017 ◽  
Author(s):  
Mariam Itani ◽  
Nesreen Ghaddar ◽  
Kamel Ghali ◽  
Beatrice Khater ◽  
Djamel Ouahrani ◽  
...  
Keyword(s):  
Heat Stress ◽  
Perceived Exertion ◽  
Human Subjects ◽  
Whole Body ◽  
Local Cooling ◽  
Coverage Area ◽  
Local Skin ◽  
Gradual Improvement ◽  
Body Cooling ◽  
Skin Temperatures

Global warming has increased the risk of heat stress of outdoor workers and one measure against heat stress is wearing passive personal cooling clothing. Passive body cooling systems, including phase change material (PCM) cooling vests, are considered as an effective solution to improve the working endurance of outdoor active workers. The objective of this study is to assess the effective placement of PCM packets in the cooling vest by examining the local and overall sensation and comfort when: (i) only the frontal segment of the human torso is covered (ii) only the back segment of the human torso is covered and (iii) both segments are covered. The PCM cooling vest is worn by human subjects performing cycling at about 3 Mets and for 30 minutes in a climatic chamber maintained at 28 °C and 60 % relative humidity. The used PCM melting temperature is 28 °C with a coverage area of 642 cm2 and total weight of the vest of 1.19 kg including 8 PCM packets (87.5 grams each). The physiological/thermal responses such as body core and mean skin temperatures, heart rate, and skin wittedness are monitored during the experiments while exercising and wearing the vest. In particular, the frontal and back torso skin temperatures are examined after being subjected to local cooling compared to the case when no PCM packets cover the torso segment. Moreover, subjective votes of thermal comfort, whole body and torso thermal sensations, skin and clothing wetness sensation and perceived exertion are recorded throughout the experiment. The experiment was repeated on five male subjects to ensure robustness of the obtained results. It was found that the core temperature changed slightly when wearing the vest, however the local skin temperature of the back and front torso segments decreased by about 5 °C and 3 °C at the end of the exercise, respectively. Gradual improvement in comfort that reaches a stable level when the PCM starts melting till the end of the exercise was also noticed.

The Effect of Pressure on Skin Temperature Measurements for a Disk Sensor

1979 ◽  
Vol 101 (4) ◽  
pp. 261-266 ◽  
Author(s):  
S. D. Mahanty ◽  
R. B. Roemer
Keyword(s):  
Skin Temperature ◽  
Human Subjects ◽  
Reactive Hyperemia ◽  
Circular Disk ◽  
Temperature Measurements ◽  
Whole Body ◽  
Local Pressure ◽  
Local Skin ◽  
Local Skin Temperature ◽  
Skin Temperatures

In order to determine the effect of application pressure on the accuracy of skin temperature measurements for area contact sensors, low values of pressure (2-20 mm Hg) were applied to the mid-thigh and to the lateral aspect of the trochanter of human subjects using a thin, circular disk with a thermistor mounted in the base. From measurements of the local skin temperatures, it was determined that a pressure of 2 mm Hg is adequate to measure the skin temperature accurately. Applying larger pressure results in higher local skin temperatures with the thighs showing larger temperature increases than the trochanters. The results of a finite difference analysis indicate that the increases in skin temperature at higher pressures can be accounted for by the physical phenomena associated with the penetration of the sensor into the tissue. After the release of pressure, the local skin temperature immediately decreased for all subjects indicating little or no reactive hyperemia was occurring. A method of compensating for the changes in local skin temperature which are due to whole body transient thermal effects was also developed. Use of this method allows the effects of the local pressure application to be separated from the transient environmental effects.

scholarly journals The nitric oxide dependence of cutaneous microvascular function to independent and combined hypoxic cold exposure

2020 ◽  
Vol 129 (4) ◽  
pp. 947-956
Author(s):  
Josh T. Arnold ◽  
Alex B. Lloyd ◽  
Stephen J. Bailey ◽  
Tomomi Fujimoto ◽  
Ryoko Matsutake ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Nitrite Reduction ◽  
Whole Body ◽  
Local Cooling ◽  
Cutaneous Reflex ◽  
Body Cooling ◽  
Whole Body Cooling ◽  
Oxide Removal ◽  
Oxide Synthase

When separated from local cooling, whole body cooling elicited cutaneous reflex vasoconstriction via mechanisms independent of nitric oxide removal. Hypoxia elicited cutaneous vasodilatation via mechanisms mediated primarily by nitric oxide synthase, rather than xanthine oxidase-mediated nitrite reduction. Cold-induced vasoconstriction was blunted by the opposing effect of hypoxic vasodilatation, whereas the underpinning mechanisms did not interrelate in the absence of local cooling. Full vasoconstriction was restored with nitric oxide synthase inhibition.

scholarly journals Endothelial nitric oxide synthase control mechanisms in the cutaneous vasculature of humans in vivo

2008 ◽  
Vol 295 (1) ◽  
pp. H123-H129 ◽  
Author(s):  
Dean L. Kellogg ◽  
Joan L. Zhao ◽  
Yubo Wu
Keyword(s):  
Nitric Oxide ◽  
Heat Stress ◽  
Local Heating ◽  
Ringer Solution ◽  
Whole Body ◽  
Control Mechanisms ◽  
Local Skin ◽  
Doppler Flowmetry ◽  
Whole Body Heat Stress ◽  
Body Heat

Nitric oxide (NO) participates in locally mediated vasodilation induced by increased local skin temperature (Tloc) and in sympathetically mediated vasodilation during whole body heat stress. We hypothesized that endothelial NOS (eNOS) participates in the former, but not the latter, response. We tested this hypothesis by examining the effects of the eNOS antagonist NG-amino-l-arginine (l-NAA) on skin blood flow (SkBF) responses to increased Tloc and whole body heat stress. Microdialysis probes were inserted into forearm skin for drug delivery. One microdialysis site was perfused with l-NAA in Ringer solution and a second site with Ringer solution alone. SkBF [laser-Doppler flowmetry (LDF)] and blood pressure [mean arterial pressure (MAP)] were monitored, and cutaneous vascular conductance (CVC) was calculated (CVC = LDF ÷ MAP). In protocol 1, Tloc was controlled with LDF/local heating units. Tloc initially was held at 34°C and then increased to 41.5°C. In protocol 2, after a normothermic period, whole body heat stress was induced (water-perfused suits). At the end of both protocols, 58 mM sodium nitroprusside was perfused at both microdialysis sites to cause maximal vasodilation for data normalization. In protocol 1, CVC at 34°C Tloc did not differ between l-NAA-treated and untreated sites ( P > 0.05). Local skin warming to 41.5°C Tloc increased CVC at both sites. This response was attenuated at l-NAA-treated sites ( P < 0.05). In protocol 2, during normothermia, CVC did not differ between l-NAA-treated and untreated sites ( P > 0.05). During heat stress, CVC rose to similar levels at l-NAA-treated and untreated sites ( P > 0.05). We conclude that eNOS is predominantly responsible for NO generation in skin during responses to increased Tloc, but not during reflex responses to whole body heat stress.

scholarly journals Cutaneous vascular and sudomotor responses in human skin grafts

2010 ◽  
Vol 109 (5) ◽  
pp. 1524-1530 ◽  
Author(s):  
Craig G. Crandall ◽  
Scott L. Davis
Keyword(s):  
Heat Stress ◽  
Heat Dissipation ◽  
Skin Grafting ◽  
Whole Body ◽  
Sweat Glands ◽  
Skin Grafts ◽  
Local Cooling ◽  
Doppler Flowmetry ◽  
Graft Area ◽  
The Individual

Each year millions of individuals sustain burns. Within the US 40,000–70,000 individuals are hospitalized for burn-related injuries, some of which are quite severe, requiring skin grafting. The grafting procedure disrupts neural and vascular connections between the host site and the graft, both of which are necessary for that region of skin to contribute to temperature regulation. With the use of relatively modern techniques such as laser-Doppler flowmetry and intradermal microdialysis, a wealth of information has become available regarding the consequences of skin grafting on heat dissipation and heat conservation mechanisms. The prevailing data suggest that cutaneous vasodilator capacity to an indirect heat stress (i.e., heating the individual but not the evaluated graft area) and a local heating stimulus (i.e., directly heating the graft area) is impaired in grafted skin. These impairments persist for ≥4 yr following the grafting procedures and are perhaps permanent. The capacity for grafted skin to vasodilate to an endothelial-dependent vasodilator is likewise impaired, whereas its capacity to vasodilate to an endothelial-independent vasodilator is generally preserved. Sweating responsiveness is minimal to nonexistent in grafted skin to both a whole body heat stress and local administration of the primary neurotransmitter responsible for stimulating sweat glands (i.e., acetylcholine). Likewise, there is no evidence that this absence of sweat gland responsiveness improves as the graft matures. In contrast to the heating stimuli, cutaneous vasoconstrictor responses to both indirect whole body cooling (i.e., exposing the individual to a cold stress but not at the evaluated graft area) and direct local cooling (i.e., directly cooling the graft area) are preserved in grafted skin as early as 5–9 mo postgrafting. If uninjured skin does not compensate for impaired heat dissipation of grafted skin, individuals having skin grafts encompassing significant fractions of their body surface area will be at a greater risk for a hyperthermic-related injury. Conversely, the prevailing data suggest that such individuals will not be at a greater risk of hypothermia upon exposure to cold environmental conditions.

Control of skin blood flow by whole body and local skin cooling in exercising humans

1996 ◽  
Vol 270 (1) ◽  
pp. H208-H215 ◽  
Author(s):  
P. E. Pergola ◽  
J. M. Johnson ◽  
D. L. Kellogg ◽  
W. A. Kosiba
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Threshold Level ◽  
Tissue Temperature ◽  
Whole Body ◽  
Internal Temperature ◽  
Local Cooling ◽  
Local Skin ◽  
Doppler Flowmetry ◽  
Rate Of Increase

We examined the independent roles of whole body skin temperature (Tsk) and tissue temperature (local temperature, Tloc) in the control of skin blood flow (SBF) during cooling and the roles of the vasoconstrictor (VC) and active vasodilator (AVD) systems in mediating these effects. SBF was monitored by laser-Doppler flowmetry (LDF) at untreated sites and sites with local VC blockade by pretreatment with bretylium (BT). Seven subjects underwent four sessions of moderate bicycle exercise (20-30 min duration) at neutral Tsk and Tloc (34 degrees C), neutral Tsk and cool Tloc (27 degrees C), low Tsk (28 degrees C) and neutral Tloc, and low Tsk and Tloc. Cutaneous vascular conductance (CVC; LDF/mean arterial pressure) was expressed relative to the maximum. Cool Tsk increased the threshold level of internal temperature at which CVC began to rise equally at BT-treated and untreated sites (P < 0.05). The rate of increase in CVC relative to internal temperature was reduced by local cooling. BT pretreatment partially reversed this effect (P < 0.05). Thus a cool environment results in reflex inhibition of the onset of AVD activity by cool Tsk and a reduced rate of increase in CVC due, in part, to norepinephrine release stimulated by cool Tloc.

Local skin injury as a complication of whole body cooling for perinatal asphyxia

2012 ◽  
Vol 98 (2) ◽  
pp. F150-F151 ◽  
Author(s):  
Gamze Demirel ◽  
Istemi Han Celik ◽  
Fuat Emre Canpolat ◽  
Serife Suna Oguz ◽  
Omer Erdeve ◽  
...  
Keyword(s):  
Perinatal Asphyxia ◽  
Whole Body ◽  
Skin Injury ◽  
Local Skin ◽  
Body Cooling ◽  
Whole Body Cooling

scholarly journals Antagonism of soluble guanylyl cyclase attenuates cutaneous vasodilation during whole body heat stress and local warming in humans

2011 ◽  
Vol 110 (5) ◽  
pp. 1406-1413 ◽  
Author(s):  
Dean L. Kellogg ◽  
Joan L. Zhao ◽  
Yubo Wu ◽  
John M. Johnson
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Guanylyl Cyclase ◽  
Soluble Guanylyl Cyclase ◽  
Whole Body ◽  
Local Skin ◽  
Cutaneous Vasodilation ◽  
Local Skin Temperature ◽  
Whole Body Heat Stress ◽  
Body Heat

We hypothesized that nitric oxide activation of soluble guanylyl cyclase (sGC) participates in cutaneous vasodilation during whole body heat stress and local skin warming. We examined the effects of the sGC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on reflex skin blood flow responses to whole body heat stress and on nonreflex responses to increased local skin temperature. Blood flow was monitored by laser-Doppler flowmetry, and blood pressure by Finapres to calculate cutaneous vascular conductance (CVC). Intradermal microdialysis was used to treat one site with 1 mM ODQ in 2% DMSO and Ringer, a second site with 2% DMSO in Ringer, and a third site received Ringer. In protocol 1, after a period of normothermia, whole body heat stress was induced. In protocol 2, local heating units warmed local skin temperature from 34 to 41°C to cause local vasodilation. In protocol 1, in normothermia, CVC did not differ among sites [ODQ, 15 ± 3% maximum CVC (CVCmax); DMSO, 14 ± 3% CVCmax; Ringer, 17 ± 6% CVCmax; P > 0.05]. During heat stress, ODQ attenuated CVC increases (ODQ, 54 ± 4% CVCmax; DMSO, 64 ± 4% CVCmax; Ringer, 63 ± 4% CVCmax; P < 0.05, ODQ vs. DMSO or Ringer). In protocol 2, at 34°C local temperature, CVC did not differ among sites (ODQ, 17 ± 2% CVCmax; DMSO, 18 ± 4% CVCmax; Ringer, 18 ± 3% CVCmax; P > 0.05). ODQ attenuated CVC increases at 41°C local temperature (ODQ, 54 ± 5% CVCmax; DMSO, 86 ± 4% CVCmax; Ringer, 90 ± 2% CVCmax; P < 0.05 ODQ vs. DMSO or Ringer). sGC participates in neurogenic active vasodilation during heat stress and in the local response to direct skin warming.

The role of baseline in the cutaneous vasoconstrictor responses during combined local and whole body cooling in humans

2007 ◽  
Vol 293 (5) ◽  
pp. H3187-H3192 ◽  
Author(s):  
Gary J. Hodges ◽  
Wojciech A. Kosiba ◽  
Kun Zhao ◽  
Guy E. Alvarez ◽  
John M. Johnson
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Local Heating ◽  
Laser Doppler ◽  
Whole Body ◽  
Local Cooling ◽  
Doppler Flowmetry ◽  
Vasoconstrictor Response ◽  
Body Cooling ◽  
Whole Body Cooling

Previous work showed that local cooling (LC) attenuates the vasoconstrictor response to whole body cooling (WBC). We tested the extent to which this attenuation was due to the decreased baseline skin blood flow following LC. In eight subjects, skin blood flow was assessed using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was expressed as LDF divided by blood pressure. Subjects were dressed in water-perfused suits to control WBC. Four forearm sites were prepared with microdialysis fibers, local heating/cooling probe holders, and laser-Doppler probes. Three sites were locally cooled from 34 to 28°C, reducing CVC to 45.9 ± 3.9, 42 ± 3.9, and 44.5 ± 4.8% of baseline ( P < 0.05 vs. baseline; P > 0.05 among sites). At two sites, CVC was restored to precooling baseline levels with sodium nitroprusside (SNP) or isoproterenol (Iso), increasing CVC to 106.4 ± 12.4 and 98.9 ± 10.1% of baseline, respectively ( P > 0.05 vs. precooling). Whole body skin temperature, apart from the area of blood flow measurement, was reduced from 34 to 31°C. Relative to the original baseline, CVC decreased ( P < 0.05) by 44.9 ± 2.8 (control), 11.3 ± 2.4 (LC only), 29 ± 3.7 (SNP), and 45.8 ± 8.7% (Iso). The reductions at LC only and SNP sites were less than at control or Iso sites ( P < 0.05); the responses at those latter sites were not different ( P > 0.05), suggesting that the baseline change in CVC with LC is important in the attenuation of reflex vasoconstrictor responses to WBC.

scholarly journals The involvement of heating rate and vasoconstrictor nerves in the cutaneous vasodilator response to skin warming

2009 ◽  
Vol 296 (1) ◽  
pp. H51-H56 ◽  
Author(s):  
Gary J. Hodges ◽  
Wojciech A. Kosiba ◽  
Kun Zhao ◽  
John M. Johnson
Keyword(s):  
Sympathetic Nerve ◽  
Transmitter Release ◽  
Whole Body ◽  
Local Skin ◽  
Axon Reflex ◽  
Sympathetic Function ◽  
Cutaneous Vascular Conductance ◽  
Skin Temperatures ◽  
Adrenergic Terminals ◽  
Adrenergic Effects

Slow local skin heating (LH) causes vasodilator responses, some of which are dependent on sympathetic nerve function. It is not known, however, how the rate of LH affects either the sympathetic or the nonadrenergic components of the responses to LH and whether the adrenergic effects of LH depend on tonic sympathetic activity or whether LH stimulates transmitter release. In part 1, cutaneous vascular conductance (CVC) responses to slow and fast LH (+0.1° and +2°C/min) from 34° to 40°C were compared both at control sites and at sites pretreated with bretylium tosylate (BT; blocks transmitter release from adrenergic terminals). We confirmed, as previously found, the axon reflex (AR) response to slow LH to be blocked by BT ( P < 0.05). Pretreatment with BT reduced the AR only with fast LH. BT inhibited the peak vasodilation achieved with both rates of LH ( P < 0.05). Longer-term LH was associated with a slow fall in CVC, the classical “die away” phenomenon, at untreated sites ( P < 0.05) but not at BT-pretreated sites. Thus the LH-stimulated AR is only partially dependent on intact sympathetic function, and the “die away” phenomenon is dependent on such function. In part 2, we tested whether the conditions in part 1 (whole body and local skin temperatures of 34°C) completely suppressed sympathetic nerve activity. The infusion of BT by microdialysis did not change the CVC ( P > 0.05), suggesting the absence of tonic activity in those conditions and therefore that the adrenergic components of the responses in part 1 are via the stimulation of the transmitter release by LH.

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