scholarly journals Skin blood flow measurements during heat stress: technical and analytical considerations

2020 ◽  
Vol 318 (1) ◽  
pp. R57-R69 ◽  
Author(s):  
Georgia K. Chaseling ◽  
Craig G. Crandall ◽  
Daniel Gagnon
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Research Question ◽  
The Body ◽  
Control Mechanisms ◽  
Vascular Control ◽  
Subsequent Increase ◽  
Flow Measurements ◽  
Doppler Flowmetry

During heat stress, the skin vasculature can greatly increase conductance secondary to vasodilation. The subsequent increase in skin blood flow allows for convective heat transfer from the core to the skin and between the skin surface and the surrounding environment. Measurement of skin blood flow, therefore, provides valuable information regarding heat exchange between the body and the environment. In addition, assessment of skin blood flow can be used to study vascular control mechanisms. Most often, skin blood flow is measured by venous occlusion plethysmography, Doppler ultrasound, laser-Doppler flowmetry, and, more recently, optical coherence tomography. However, important delimitations to each of these methods, which may be dependent on the research question, must be considered when responses from these approaches are interpreted. In this brief review, we discuss these methods of skin blood flow measurement and highlight potential sources of error and limitations. We also provide recommendations to guide the interpretation of skin blood flow data.

scholarly journals Nonuniform, age-related decrements in regional sweating and skin blood flow

2013 ◽  
Vol 305 (8) ◽  
pp. R877-R885 ◽  
Author(s):  
Caroline J. Smith ◽  
Lacy M. Alexander ◽  
W. Larry Kenney
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Heat Exposure ◽  
The Body ◽  
Whole Body ◽  
Older Individuals ◽  
Doppler Flowmetry ◽  
Age Related ◽  
Thermoregulatory Function ◽  
Aged Subjects

Aging is associated with attenuated thermoregulatory function that varies regionally over the body. Decrements in vasodilation and sweating are well documented with age, yet limited data are available concerning the regional relation between these responses. We aimed to examine age-related alterations in the relation between regional sweating (RSR) and skin blood flow (SkBF) to thermal and pharmacological stimuli. Four microdialysis fibers were inserted in the ventral forearm, abdomen, thigh, and lower back of eight healthy aged subjects (64 ± 7 yr) and nine young (23 ± 3 yr) during 1) ACh dose response (1 × 10−7 to 0.1 M, mean skin temperature 34°C) and 2) passive whole body heating to Δ1°C rise in oral temperature (Tor). RSR and SkBF were measured over each microdialysis membrane using ventilated capsules and laser-Doppler flowmetry. Maximal SkBF was measured at the end of both protocols (50 mM SNP). Regional sweating thresholds and RSR were attenuated in aged vs. young at all sites ( P < 0.0001) during whole body heating. Vasodilation thresholds were similar between groups ( P > 0.05). Attenuated SkBF were observed at the arm and back in the aged, representing 56 and 82% of those in the young at these sites, respectively (0.5 ΔTor). During ACh perfusion, SkBF ( P = 0.137) and RSR were similar between groups ( P = 0.326). Together these findings suggest regional age-related decrements in heat-activated sweat gland function but not cholinergic sensitivity. Functional consequences of such thermoregulatory impairment include the compromised ability of older individuals to defend core temperature during heat exposure and a subsequently greater susceptibility to heat-related illness and injury.

Recent Advances in Cochlear Blood Flow Measurements

1988 ◽  
Vol 97 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Jonathon S. Sillman ◽  
Michael J. Larouere ◽  
Alfred L. Nuttall ◽  
Merle Lawrence ◽  
Josef M. Miller
Keyword(s):  
Blood Flow ◽  
Hearing Loss ◽  
Inner Ear ◽  
Laser Doppler ◽  
Control Mechanisms ◽  
Clinical Value ◽  
Cochlear Blood Flow ◽  
Flow Measurements ◽  
Local Flow ◽  
Doppler Flowmetry

Changes in blood flow to the inner ear have been thought to influence or underlie a number of cochlear diseases, including some forms of noise-induced hearing loss, sudden hearing loss, and Meniere's disease. Recently, important advances have been made in two technologies for the study of cochlear blood flow. The first is in the area of vital microscopic studies of cochlear microcirculation, and the second is based on the introduction of laser technology in the form of laser Doppler flowmetry. In this report, measurements are given of changes in cochlear circulation caused by carbon dioxide breathing, intravenous phenylephrine injection, systemic hemodilution, positive end expiratory pressure, and direct electrical stimulation of the cochlea. From these changes, we observe that cochlear blood circulation responds to systemic blood pressure alterations and is subject to local flow control mechanisms. Linearity and speed of response of the laser Doppler instrumentation also are shown. These advances show promise for contributing to our knowledge of control mechanisms of inner ear blood flow and for revealing the influence of various pharmacologic agents of potential clinical value.

Thermoregulatory reflexes and cutaneous active vasodilation during heat stress in hypertensive humans

1998 ◽  
Vol 85 (1) ◽  
pp. 175-180 ◽  
Author(s):  
D. L. Kellogg ◽  
S. R. Morris ◽  
S. B. Rodriguez ◽  
Y. Liu ◽  
M. Grossmann ◽  
...  
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Forearm Blood Flow ◽  
Venous Occlusion ◽  
Vascular Conductance ◽  
Doppler Flowmetry ◽  
Forearm Vascular Conductance ◽  
Normotensive Subjects ◽  
Cutaneous Vascular Conductance

During dynamic exercise in the heat, increases in skin blood flow are attenuated in hypertensive subjects when compared with normotensive subjects. We studied responses to passive heat stress (water-perfused suits) in eight hypertensive and eight normotensive subjects. Forearm blood flow was measured by venous-occlusion plethysmography, mean arterial pressure (MAP) was measured by Finapres, and forearm vascular conductance (FVC) was calculated. Bretylium tosylate (BT) iontophoresis was used to block active vasoconstriction in a small area of skin. Skin blood flow was indexed by laser-Doppler flowmetry at BT-treated and untreated sites, and cutaneous vascular conductance was calculated. In normothermia, FVC was lower in hypertensive than in normotensive subjects ( P < 0.01). During heat stress, FVC rose to similar levels in both groups ( P > 0.80); concurrent cutaneous vascular conductance increases were unaffected by BT treatment ( P > 0.60). MAP was greater in hypertensive than in normotensive subjects during normothermia ( P < 0.05, hypertensive vs. normotensive subjects). During hyperthermia, MAP fell in hypertensive subjects but showed no statistically significant change in normotensive subjects ( P < 0.05, hypertensive vs. normotensive subjects). The internal temperature at which vasodilation began did not differ between groups ( P> 0.80). FVC is reduced during normothermia in unmedicated hypertensive subjects; however, they respond to passive heat stress in a fashion no different from normotensive subjects.

scholarly journals Diurnal variation in cutaneous vasodilator and vasoconstrictor systems during heat stress

2001 ◽  
Vol 281 (2) ◽  
pp. R591-R595 ◽  
Author(s):  
Ken Aoki ◽  
Dan P. Stephens ◽  
John M. Johnson
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Diurnal Variation ◽  
Skin Blood Flow ◽  
Whole Body ◽  
Noninvasive Blood Pressure ◽  
Vascular Conductance ◽  
Doppler Flowmetry ◽  
Cutaneous Vasodilation ◽  
Cutaneous Vascular Conductance

It is not clear whether the diurnal variation in the cutaneous circulatory response to heat stress is via the noradrenergic vasoconstrictor system or the nonadrenergic active vasodilator system. We conducted whole body heating experiments in eight male subjects at 0630 (AM) and 1630 (PM). Skin blood flow was monitored by laser-Doppler flowmetry at control sites and at sites pretreated with bretylium (BT) to block noradrenergic vasoconstriction. Noninvasive blood pressure was used to calculate cutaneous vascular conductance. The sublingual temperature (Tor) threshold for cutaneous vasodilation was significantly higher in PM at control and at BT-treated sites (both P < 0.01), suggesting the diurnal shift in threshold depends on the active vasodilator system. The slope of cutaneous vascular conductance as a percentage of its maximum with respect to Tor was significantly lower in AM at control sites only. Also, in the AM, the slope at control sites was significantly lower than that at BT-treated sites ( P < 0.05), suggesting that the diurnal change in the sensitivity of cutaneous vasodilation depends on vasoconstrictor system function. Overall, the diurnal variation in the reflex control of skin blood flow during heat stress involves both vasoconstrictor and active vasodilator systems.

Influence of female reproductive hormones on local thermal control of skin blood flow

1999 ◽  
Vol 87 (5) ◽  
pp. 1719-1723 ◽  
Author(s):  
Nisha Charkoudian ◽  
Dan P. Stephens ◽  
Kenna C. Pirkle ◽  
Wojciech A. Kosiba ◽  
John M. Johnson
Keyword(s):  
Blood Flow ◽  
Skin Blood Flow ◽  
Thermal Control ◽  
Reproductive Hormones ◽  
Whole Body ◽  
Vascular Control ◽  
Local Cooling ◽  
Doppler Flowmetry ◽  
Vasodilator Response ◽  
Local Warming

Progesterone and estrogen modify thermoregulatory control such that, when both steroids are elevated, body temperature increases and the reflex thermoregulatory control of cutaneous vasodilation is shifted to higher internal temperatures. We hypothesized that the influence of these hormones would also include effects on local thermal control of skin blood flow. Experiments were conducted in women in high-hormone (HH) and low-hormone (LH) phases of oral contraceptive use. Skin blood flow was measured by laser-Doppler flowmetry, and local temperature (Tloc) was controlled over 12 cm2 around the sites of blood flow measurement. Tloc was held at 32°C for 10–15 min and was then decreased at one site from 32 to 20°C in a ramp over 20 min. Next, Tloc was increased from 32 to 42°C in a ramp over 15 min at a separate site. Finally, Tloc at both sites was held at 42°C for 30 min to elicit maximum vasodilation; data for cutaneous vascular conductance (CVC) are expressed relative to that maximum. Whole body skin temperature (Tsk) was held at 34°C throughout each study to minimize reflex effects from differences in Tsk between experiments. Baseline CVC did not differ between phases [8.18 ± 1.38 (LH) vs. 8.41 ± 1.31% of maximum (HH); P > 0.05]. The vasodilator response to local warming was augmented in HH ( P < 0.05, ANOVA). For example, at Tloc of 40–42°C, CVC averaged 76.41 ± 3.08% of maximum in HH and 67.71 ± 4.43% of maximum in LH ( P < 0.01 LH vs. HH). The vasoconstrictor response to local cooling was unaffected by phase ( P > 0.05). These findings indicate that modifications in cutaneous vascular control by female steroid hormones include enhancement of the vasodilator response to local warming and are consistent with reports of the influence of estrogen to enhance nitric oxide-dependent vasodilator responses.

Plasma hyperosmolality elevates the internal temperature threshold for active thermoregulatory vasodilation during heat stress in humans

2009 ◽  
Vol 297 (6) ◽  
pp. R1706-R1712 ◽  
Author(s):  
Manabu Shibasaki ◽  
Ken Aoki ◽  
Keiko Morimoto ◽  
John M. Johnson ◽  
Akira Takamata
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Skin Blood Flow ◽  
Isotonic Saline ◽  
Plasma Osmolality ◽  
Saline Infusion ◽  
Temperature Threshold ◽  
Internal Temperature ◽  
Doppler Flowmetry ◽  
Cutaneous Vasodilation

Plasma hyperosmolality delays the response in skin blood flow to heat stress by elevating the internal temperature threshold for cutaneous vasodilation. This elevation could be because of a delayed onset of cutaneous active vasodilation and/or to persistent cutaneous active vasoconstriction. Seven healthy men were infused with either hypertonic (3% NaCl) or isotonic (0.9% NaCl) saline and passively heated by immersing their lower legs in 42°C water for 60 min (room temperature, 28°C; relative humidity, 40%). Skin blood flow was monitored via laser-Doppler flowmetry at sites pretreated with bretylium tosylate (BT) to block sympathetic vasoconstriction selectively and at adjacent control sites. Plasma osmolality was increased by ∼13 mosmol/kgH2O following hypertonic saline infusion and was unchanged following isotonic saline infusion. The esophageal temperature (Tes) threshold for cutaneous vasodilation at untreated sites was significantly elevated in the hyperosmotic state (37.73 ± 0.11°C) relative to the isosmotic state (36.63 ± 0.12°C, P < 0.001). A similar elevation of the Tes threshold for cutaneous vasodilation was observed between osmotic conditions at the BT-treated sites (37.74 ± 0.18 vs. 36.67 ± 0.07°C, P < 0.001) as well as sweating. These results suggest that the hyperosmotically induced elevation of the internal temperature threshold for cutaneous vasodilation is due primarily to an elevation in the internal temperature threshold for the onset of active vasodilation, and not to an enhancement of vasoconstrictor activity.

scholarly journals Methodological assessment of skin and limb blood flows in the human forearm during thermal and baroreceptor provocations

2010 ◽  
Vol 109 (3) ◽  
pp. 895-900 ◽  
Author(s):  
R. Matthew Brothers ◽  
Jonathan E. Wingo ◽  
Kimberly A. Hubing ◽  
Craig G. Crandall
Keyword(s):  
Blood Flow ◽  
Heat Stress ◽  
Doppler Ultrasound ◽  
Skin Blood Flow ◽  
Skin Surface ◽  
Laser Doppler ◽  
Whole Body ◽  
Surface Cooling ◽  
Doppler Flowmetry ◽  
Human Forearm

Skin blood flow responses in the human forearm, assessed by three commonly used technologies—single-point laser-Doppler flowmetry, integrated laser-Doppler flowmetry, and laser-Doppler imaging—were compared in eight subjects during normothermic baseline, acute skin-surface cooling, and whole body heat stress (Δ internal temperature = 1.0 ± 0.2°C; P < 0.001). In addition, while normothermic and heat stressed, subjects were exposed to 30-mmHg lower-body negative pressure (LBNP). Skin blood flow was normalized to the maximum value obtained at each site during local heating to 42°C for at least 30 min. Furthermore, comparisons of forearm blood flow (FBF) measures obtained using venous occlusion plethysmography and Doppler ultrasound were made during the aforementioned perturbations. Relative to normothermic baseline, skin blood flow decreased during normothermia + LBNP ( P < 0.05) and skin-surface cooling ( P < 0.01) and increased during whole body heating ( P < 0.001). Subsequent LBNP during whole body heating significantly decreased skin blood flow relative to control heat stress ( P < 0.05). Importantly, for each of the aforementioned conditions, skin blood flow was similar between the three measurement devices (main effect of device: P > 0.05 for all conditions). Similarly, no differences were identified across all perturbations between FBF measures using plethysmography and Doppler ultrasound ( P > 0.05 for all perturbations). These data indicate that when normalized to maximum, assessment of skin blood flow in response to vasoconstrictor and dilator perturbations are similar regardless of methodology. Likewise, FBF responses to these perturbations are similar between two commonly used methodologies of limb blood flow assessment.

scholarly journals Independent and combined impact of hypoxia and acute inorganic nitrate ingestion on thermoregulatory responses to the cold

2021 ◽  
Vol 121 (4) ◽  
pp. 1207-1218
Author(s):  
Josh T. Arnold ◽  
Stephen J. Bailey ◽  
Simon G. Hodder ◽  
Naoto Fujii ◽  
Alex B. Lloyd
Keyword(s):  
Blood Flow ◽  
Cooling Rate ◽  
Skin Blood Flow ◽  
Rectal Temperature ◽  
Onset Time ◽  
Rate Of Change ◽  
Vascular Control ◽  
Delta Change ◽  
Core Cooling ◽  
The Impact

Abstract Purpose This study assessed the impact of normobaric hypoxia and acute nitrate ingestion on shivering thermogenesis, cutaneous vascular control, and thermometrics in response to cold stress. Method Eleven male volunteers underwent passive cooling at 10 °C air temperature across four conditions: (1) normoxia with placebo ingestion, (2) hypoxia (0.130 FiO2) with placebo ingestion, (3) normoxia with 13 mmol nitrate ingestion, and (4) hypoxia with nitrate ingestion. Physiological metrics were assessed as a rate of change over 45 min to determine heat loss, and at the point of shivering onset to determine the thermogenic thermoeffector threshold. Result Independently, hypoxia expedited shivering onset time (p = 0.05) due to a faster cooling rate as opposed to a change in central thermoeffector thresholds. Specifically, compared to normoxia, hypoxia increased skin blood flow (p = 0.02), leading to an increased core-cooling rate (p = 0.04) and delta change in rectal temperature (p = 0.03) over 45 min, yet the same rectal temperature at shivering onset (p = 0.9). Independently, nitrate ingestion delayed shivering onset time (p = 0.01), mediated by a change in central thermoeffector thresholds, independent of changes in peripheral heat exchange. Specifically, compared to placebo ingestion, no difference was observed in skin blood flow (p = 0.5), core-cooling rate (p = 0.5), or delta change in rectal temperature (p = 0.7) over 45 min, while nitrate reduced rectal temperature at shivering onset (p = 0.04). No interaction was observed between hypoxia and nitrate ingestion. Conclusion These data improve our understanding of how hypoxia and nitric oxide modulate cold thermoregulation.

Using reactive hyperemia to investigate the effect of cupping sizes of cupping therapy on skin blood flow responses

2021 ◽  
pp. 1-7
Author(s):  
Xiangfeng He ◽  
Xueyan Zhang ◽  
Fuyuan Liao ◽  
Li He ◽  
Xin Xu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Laser Doppler Flowmetry ◽  
Skin Blood Flow ◽  
Repeated Measures ◽  
Recovery Time ◽  
Reactive Hyperemia ◽  
Cupping Therapy ◽  
Doppler Flowmetry ◽  
Healthy Participants ◽  
Hyperemic Response

BACKGROUND: Various cupping sizes of cupping therapy have been used in managing musculoskeletal conditions; however, the effect of cupping sizes on skin blood flow (SBF) responses is largely unknown. OBJECTIVE: The objective of this study was to compare the effect of three cupping sizes of cupping therapy on SBF responses. METHODS: Laser Doppler flowmetry (LDF) was used to measure SBF on the triceps in 12 healthy participants in this repeated measures study. Three cup sizes (35, 40 and 45 mm in diameter) were blinded to the participants and were tested at -300 mmHg for 5 minutes. Reactive hyperemic response to cupping therapy was expressed as a ratio of baseline SBF. RESULTS: All three sizes of cupping cups resulted in a significant increase in peak SBF (p< 0.001). Peak SBF of the 45 mm cup (9.41 ± 1.32 times) was significantly higher than the 35 mm cup (5.62 ± 1.42 times, p< 0.05). Total SBF of the 45 mm cup ((24.33 ± 8.72) × 103 times) was significantly higher than the 35 mm cup ((8.05 ± 1.63) × 103 times, p< 0.05). Recovery time of the 45 mm cup (287.46 ± 39.54 seconds) was significantly longer than the 35 mm cup (180.12 ± 1.42 seconds, p< 0.05). CONCLUSIONS: Our results show that all three cup sizes can significantly increase SBF. The 45 mm cup is more effective in increasing SBF compared to the 35 mm cup.

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