Permeation of inert gases through human skin: modeling the effect of skin blood flow

1989 ◽  
Vol 67 (4) ◽  
pp. 1670-1686 ◽  
Author(s):  
J. M. Whang ◽  
J. A. Quinn ◽  
D. J. Graves ◽  
G. R. Neufeld
Keyword(s):  
Blood Flow ◽  
Human Skin ◽  
Series Resistance ◽  
Inert Gases ◽  
Analytic Method ◽  
Total Flow ◽  
Single Measurement ◽  
Flow Rates ◽  
Skin Perfusion ◽  
Different Gases

We present an analytic method for determining the effects of skin perfusion--vasculature and flow rates--on the flux of inert gases through human skin. We systematically specify the underlying blood flow and examine the resulting fluxes of several gases, allowing for the appropriate tissue resistances. For physiological flows, the stratum corneum has an effect equivalent to a series resistance. Helium flux at low total flow depends primarily on subdermal perfusion, but at higher flow, middermal and subpapillary effects become important. The fluxes of less permeable gases, such as argon and xenon, depend on middermal and subpapillary flow at lower total flows. From any single measurement of gas flux, it is difficult to establish an unambiguous value for the underlying blood flow, but the simultaneous measurement of different gases narrows the range of plausible conditions.

Nutritive blood flow affects microdialysis O/I ratio for [14C]ethanol and3H2O in perfused rat hindlimb

2001 ◽  
Vol 281 (6) ◽  
pp. H2731-H2737 ◽  
Author(s):  
John M. B. Newman ◽  
Carla A. Di Maria ◽  
Stephen Rattigan ◽  
Michael G. Clark
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Flow Rate ◽  
Perfusion Pressure ◽  
Total Flow ◽  
Flow Rates ◽  
Perfusion Flow ◽  
Pressure Oxygen ◽  
Saline Vehicle ◽  
Perfusion Flow Rate

Changes in the microdialysis outflow-to-inflow (O/I) ratio for [14C]ethanol and3H2O were determined in the perfused rat hindlimb after increases and decreases in nutritive flow mediated by the vasoconstrictors norepinephrine (NE) and serotonin (5-HT), respectively. Microdialysis probes (containing 10 mM [14C]ethanol and 3H2O pumped at 1 or 2 μl/min) were inserted through the calf of the rat. Hindlimb perfusion flow rate was varied from 6 to 56 ml · min−1 · 100 g−1 in the presence of NE, 5-HT, or saline vehicle. The O/I ratios for both tracers were determined at each perfusion flow rate, as was perfusion pressure, oxygen uptake (a surrogate indicator of nutritive flow), and lactate release. Both tracers showed a decreased O/I ratio as hindlimb perfusion flow was increased, with [14C]ethanol being higher than 3H2O. NE decreased the O/I ratio compared with vehicle, and 5-HT increased it for both tracers and both microdialysis flow rates. We conclude that the microdialysis O/I ratio, while able to detect changes in total flow, is also sensitive to changes in nutritive and nonnutritive flow, where the latter still extracts tracer, but less than the former.

MEASUREMENT OF BLOOD FLOW WITH FREELY DIFFUSIBLE INDICATORS AS INERT GASES, ANTIPYRINE, LABELLED WATER AND RUBIDIUM

1972 ◽  
Vol 68 (2_Supplb) ◽  
pp. S95-S111 ◽  
Author(s):  
Niels A. Lassen ◽  
Ole Andrée Larsen
Keyword(s):  
Blood Flow ◽  
Flow Measurement ◽  
Capillary Wall ◽  
Inert Gases ◽  
Tissue Blood Flow ◽  
Blood Flow Measurement

ABSTRACT Indicators which freely cross the capillary wall can be used for measurement of tissue blood flow in many different ways. Basically one can distinguish two categories of methods, viz. the ones where the indicator enters the tissue via the inflowing blood and the ones where the indicator is deposited locally in the tissue. The most important methods are briefly described with special emphasis on the theory of blood flow measurement.

scholarly journals Hallucal thenar index: A new index to detect peripheral arterial disease using laser speckle flowgraphy

Vascular ◽  
2020 ◽  
pp. 170853812093893
Author(s):  
Kazuhiro Tsunekawa ◽  
Fumio Nagai ◽  
Tamon Kato ◽  
Ikkei Takashimizu ◽  
Daisuke Yanagisawa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Peripheral Arterial Disease ◽  
Operating Characteristic ◽  
Ankle Brachial Index ◽  
Arterial Disease ◽  
Laser Speckle ◽  
Laser Speckle Flowgraphy ◽  
Skin Perfusion ◽  
Peripheral Arterial ◽  
Cutaneous Blood

Objectives Laser speckle flowgraphy is a technology using reflected scattered light for visualization of blood distribution, which can be used to measure relative velocity of blood flow easily without contact with the skin within a short time. It was hypothesized that laser speckle flowgraphy may be able to identify foot ischemia. This study was performed to determine whether laser speckle flowgraphy could distinguish between subjects with and without peripheral arterial disease. Materials and methods All subjects were classified based on clinical observations using the Rutherford classification: non-peripheral arterial disease, class 0; peripheral arterial disease group, class 2–5. Rutherford class 6 was one of the exclusion criteria. Laser speckle flowgraphy measured the beat strength of skin perfusion as an indicator of average dynamic cutaneous blood flow change synchronized with the heartbeat. The beat strength of skin perfusion indicates the strength of the heartbeat on the skin, and the heartbeat strength calculator in laser speckle flowgraphy uses the blood flow data to perform a Fourier transform to convert the temporal changes in blood flow to a power spectrum. A total of 33 subjects with peripheral arterial disease and 40 subjects without peripheral arterial disease at a single center were prospectively examined. Laser speckle flowgraphy was used to measure hallucal and thenar cutaneous blood flow, and the measurements were repeated three times. The hallucal and thenar index was defined as the ratio of beat strength of skin perfusion value on hallux/beat strength of skin perfusion value on ipsilateral thenar eminence. The Mann–Whitney U-test was used to compare the median values of hallucal and thenar index and ankle brachial index between the two groups. A receiver operating characteristic curve for hallucal and thenar index of beat strength of skin perfusion was plotted, and a cutoff point was set. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index was explored in all subjects, the hemodialysis group, and the non-hemodialysis (non-hemodialysis) group. Results The median value of the hallucal and thenar index of beat strength of skin perfusion was significantly different between subjects with and without peripheral arterial disease (0.27 vs. 0.87, respectively; P <  0.001). The median value of ankle brachial index was significantly different between subjects with and without peripheral arterial disease (0.8 vs. 1.1, respectively; P <  0.001). Based on the receiver operating characteristic of hallucal and thenar index, the cutoff was 0.4416 and the sensitivity, specificity, positive predictive value, and negative predictive value were 68.7%, 95%, 91.7%, and 77.6%, respectively. The correlation coefficients of all subjects, the hemodialysis group, and the non-hemodialysis group were 0.486, 0.102, and 0.743, respectively. Conclusions Laser speckle flowgraphy is a noninvasive, rapid, and widely applicable method. Laser speckle flowgraphy using hallucal and thenar index would be helpful to determine the differences between subjects with and without peripheral arterial disease. The correlation between hallucal and thenar index of beat strength of skin perfusion and ankle brachial index indicated that this index was especially useful in the non-hemodialysis group.

scholarly journals Laser Doppler blood flowmeter as a useful instrument for the early detection of lower extremity peripheral arterial disease in hemodialysis patients: an observational study

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Takeo Ishii ◽  
Shizuka Takabe ◽  
Yuki Yanagawa ◽  
Yuko Ohshima ◽  
Yasuhiro Kagawa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Peripheral Arterial Disease ◽  
Early Stage ◽  
Arterial Disease ◽  
Hemodialysis Patients ◽  
Laser Doppler ◽  
Doppler Flowmetry ◽  
Skin Perfusion ◽  
Dorsal Area ◽  
Peripheral Arterial

Abstract Background A simpler method for detecting atherosclerosis obliterans is required in the clinical setting. Laser Doppler flowmetry (LDF) is easy to perform and can accurately detect deterioration in skin perfusion. We performed LDF for hemodialysis patients to determine the correlations between blood flow in the lower limbs and peripheral arterial disease (PAD). Methods This retrospective study included 128 hemodialysis patients. Patients were categorized into the non-PAD group (n = 106) and PAD group (n = 22), 14 early stage PAD patients were included in the PAD group. We conducted LDF for the plantar area and dorsal area of the foot and examined skin perfusion pressure (SPP) during dialysis. Results SPP-Dorsal Area values were 82.1 ± 22.0 mmHg in the non-PAD, and 59.1 ± 20.3 mmHg in PAD group, respectively (p < 0.05). The LDF-Plantar blood flow (Qb) values were 32.7 ± 15.5 mL/min in non-PAD group and 21.5 ± 11.3 mL/min in PAD group (p < 0.001). A total of 21 non-PAD patients underwent LDF before and during dialysis. The LDF-Plantar-Qb values were 36.5 ± 17.6 mL/min before dialysis and 29.6 ± 17.7 mL/min after dialysis (p < 0.05). We adjusted SPP and LDF for PAD using logistic regression, SPP-Dorsal-Area and LDF-P were significantly correlated with PAD (p < 0.05). The receiver-operating characteristic curve analysis indicated cut-off values of 20.0 mL/min for LDF-Plantar-Qb during dialysis. Conclusion LDF is a simple technique for sensitive detection of early-stage PAD. This assessment will help physicians identify early-stage PAD, including Fontaine stage II in clinical practice, thereby allowing prompt treatment.

787The influence of age, gender, site and sun exposure on human skin thickness, blood flow and content

1996 ◽  
Vol 40 ◽  
pp. S200 ◽  
Author(s):  
P. Simonen ◽  
C. Hamilton ◽  
P. O'Brien ◽  
J. Denham
Keyword(s):  
Blood Flow ◽  
Human Skin ◽  
Sun Exposure ◽  
Skin Thickness

scholarly journals The creeping motion of liquid drops through a circular tube of comparable diameter

1975 ◽  
Vol 71 (2) ◽  
pp. 361-383 ◽  
Author(s):  
B. P. Ho ◽  
L. G. Leal
Keyword(s):  
Pressure Drop ◽  
Circular Tube ◽  
Total Flow ◽  
Flow Rates ◽  
Liquid Drops ◽  
Neutrally Buoyant ◽  
Creeping Motion

The creeping motion through a circular tube of neutrally buoyant Newtonian drops which have an undeformed radius comparable to that of the tube was studied experimentally. Both a Newtonian and a viscoelastic suspending fluid were used in order to determine the influence of viscoelasticity. The extra pressure drop owing to the presence of the suspended drops, the shape and velocity of the drops, and the streamlines of the flow are reported for various viscosity ratios, total flow rates and drop sizes.

Control of bat wing capillary pressure and blood flow during reduced perfusion pressure

1988 ◽  
Vol 255 (5) ◽  
pp. H1114-H1129 ◽  
Author(s):  
M. J. Davis
Keyword(s):  
Blood Flow ◽  
Capillary Pressure ◽  
Perfusion Pressure ◽  
Arterial System ◽  
Total Flow ◽  
Capillary Recruitment ◽  
Null System ◽  
Arteriolar Resistance ◽  
Sampling Procedures ◽  
Bat Wing

Regulation of blood flow depends on changes in the sum of arterial (Ra) and venous (Rv) resistances, whereas regulation of capillary pressure (Pc) depends on the ratio of Rv to Ra. If the myogenic response of the arterial system (i.e., delta Ra) is the primary mechanism for controlling pressure and flow when perfusion pressure is lowered, then Pc and total flow should be regulated to the same degree under these conditions. This hypothesis was tested by making direct measurements of Pc and flow in skin and skeletal muscle in the wings of unanesthetized bats. The box method was used to reduce perfusion pressure to the wing. Pressures were measured with a servo-null system; flows were computed from measurements of vascular diameters and red cell velocities using intravital microscopy. All branching orders of arterioles dilated significantly during decreases in box pressure (Pb). For 0 less than Pb less than or equal to -30 mmHg, total flow (1st-order arteriolar flow) remained nearly constant, whereas Pc was "regulated" only approximately 60%. These results cannot be explained by changes in arteriolar resistance alone and suggest that changes in Rv may be important. The possible consequences of flow redistribution, capillary recruitment, and micropressure sampling procedures are discussed in relationship to local regulation of capillary pressure and flow.

Patterns of gas flow in the upper bronchial tree

1959 ◽  
Vol 14 (5) ◽  
pp. 753-759 ◽  
Author(s):  
J. B. West ◽  
P. Hugh-Jones
Keyword(s):  
Gas Flow ◽  
Lower Lobe ◽  
Bronchial Tree ◽  
High Flow ◽  
Human Beings ◽  
Lobe Bronchus ◽  
Flow Rates ◽  
Expiratory Flow ◽  
Different Gases ◽  
Expiratory Flow Rates

Patterns of gas flow in the upper bronchial tree have been studied by observing the flow of dye and different gases through a lung cast, and by measurements made on open-chested dogs and on human beings at bronchoscopy. Flow is completely laminar throughout the bronchial tree at low expiratory flow rates (up to 10 l/min.) and completely turbulent, proximal to the segmental bronchi, at high flow rates (80 l/min.). Both at low and high expiratory flow rates, gas from segmental bronchi was not uniformly mixed in the lobar or main bronchi which they supplied. The composition of a catheter sample in these airways would therefore not be representative of the alveolar gas in the corresponding lobe or lung unless the alveolar gas in all areas distal to the sampling tube was homogeneous. Penetration of the left upper lobe bronchus by gas from the lower lobe was demonstrated in the model and a normal subject at bronchoscopy. Submitted on September 3, 1958

The Effect of Hematocrit on the Clearance of Small Molecules during Hemodialysis

1983 ◽  
Vol 6 (3) ◽  
pp. 127-130 ◽  
Author(s):  
C. Woffindin ◽  
N.A. Hoenich ◽  
D.N.S. Kerr
Keyword(s):  
Blood Flow ◽  
Regression Analysis ◽  
Small Molecules ◽  
Flat Plate ◽  
Flow Rate ◽  
Distribution Curve ◽  
Blood Flow Rate ◽  
Hollow Fibre ◽  
Urea Clearance ◽  
Flow Rates

Data collected during the evaluation of a series of hemodialysers were analysed to see the effect of hematocrit on the clearance of urea and creatinine. All evaluations were performed on patients with a range of hematocrits with a mean close to 20%. The urea clearance of those in the upper half of the distribution curve (mean hematocrit 29.4%) was not significantly different from that of patients in the lower half of the distribution curve (mean hematocrit 16.9%) whether the clearance was studied at high or low blood flow rates and with hollow fibre or flat plate disposable hemodialysers. Likewise, there was no correlation between hematocrit and urea clearance by regression analysis. In contrast, the clearance of creatinine was affected by hematocrit being greater at lower hematocrit values. This difference was independent of blood flow rate and dialyser type and was confirmed by regression analysis.

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