Forearm Plethysmography in Normotensive and Hypertensive Pregnant Women
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Forearm plethysmography affords a simple noninvasive method of studying dynamic changes in the microcirculation. This technic was used to study the peripheral circulation of normotensive nongravid women and normotensive and untreated hypertensive pregnant women during the third trimester. The variables of forearm blood flow, vascular resistance, venous capacitance, and capillary filtration coefficient were measured in the resting state and during and after exercise. The pregnant women demonstrated an increase in forearm blood flow over the nonpregnant women. As expected, vascular resistance was higher in the hypertensive pregnant patients than in normotensive pregnant women. The possible predictive value of these findings is discussed.Keywords:
Plethysmograph
Peripheral resistance
Photoplethysmogram
Peripheral resistance
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In the course of plethysmographic studies on the peripheral vascular responses of hypertensive patients, it was noted that in about 50% of the cases the resting blood flow in the forearm was much greater than that in subjects with normal blood pressure. Such findings differ from those presented previously by Prinzmetal and Wilson using a similar method, and from those obtained by Pickering, who utilized Stewart's calorimetric procedure. These investigators found that the average blood flow reading for the forearm in a series of hypertensive subjects was no greater than that in a normal group, and on the basis of these observations, together with some confirmatory studies, they concluded that the increased vascular resistance in hypertension is generalized throughout the systemic circulation rather than confined to the splanchnic area. Pickering subsequently pointed out, as did also Stead and Kunkel, that in the light of Grant and Pearson's work, the data included in the two investigations represented not only arterial inflow to the forearm, but also venous return from the hand. It is well known that blood flow through the hand can be affected by a variety of stimuli, and hence readings obtained under such conditions cannot be considered representative of peripheral blood flow generally. Further, as Prinzmetal and Wilson indicated, the opposite conclusion to the one presented by them, namely that the hypertonus is limited to the splanchnic region, could have been drawn if an increase in blood flow had been found in the forearm of hypertensive subjects of the magnitude of 1.5 times the normal figure, i.e., approximately 2.65 cc per min. per 100 cc of limb volume instead of 1.7 cc.
Plethysmograph
Splanchnic Circulation
Essential hypertension
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Forearm plethysmography affords a simple noninvasive method of studying dynamic changes in the microcirculation. This technic was used to study the peripheral circulation of normotensive nongravid women and normotensive and untreated hypertensive pregnant women during the third trimester. The variables of forearm blood flow, vascular resistance, venous capacitance, and capillary filtration coefficient were measured in the resting state and during and after exercise. The pregnant women demonstrated an increase in forearm blood flow over the nonpregnant women. As expected, vascular resistance was higher in the hypertensive pregnant patients than in normotensive pregnant women. The possible predictive value of these findings is discussed.
Plethysmograph
Peripheral resistance
Photoplethysmogram
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Occlusion plethysmography is an important method for assessment of the status of the cardiovascular system, which provides valuable information concerning arterial and venous blood flow, including mechanisms of their regulation. All up-to-date systems estimate change of the limb's volume during occlusion by contact-type sensors. The objective of the research is demonstration of feasibility of the novel approach to measuring the blood flow during venous occlusion by using imaging photoplethysmography (PPG). Twenty healthy individuals participated in the experiment. We used four synchronized video cameras to record all-around view of the forearm illuminated by the green light. After the recording, the PPG waveform was calculated in more than 4000 non-overlapping Regions of Interest (ROI). In the most of the ROIs, the waveform shape was typical for classical plethysmography with the distinctive linear growth of the signal. Speed of the signal change was the same along the forearm but it varied along the forearm's circumference. These findings allows us to hypothesize that the PPG waveform is the direct consequence of the forearm blood flow. Therefore, the novel technique could be applied to the same medical examinations as the classical plethysmography, but it is more advantageous because of non-contact nature and easiness in implementation.
Photoplethysmogram
Plethysmograph
SIGNAL (programming language)
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Sixty one non diabetic, asymptomatic patients with untreated primary hypertension and 122 age and sex matched non diabetic controls have been investigated in the peripheral circulation of the lower limbs by digital pulse plethysmography. The inclination time of the ascending ramp has been chosen as index of arterial wall elasticity. Inclination time was prolonged in the hypertensive group as compared to the control one (123 +/- 29 vs 107 +/- 13 msec; p less than .001). In addition, by using a cut-off point of 120 msec (X +/- 1SD of controls) 23/61 hypertensives and 26/122 controls presented an inclination time above this value (p less than .05 by chi square test). Since no other difference was observed in the main cardiovascular risk factors, we conclude that high blood pressure may produce early structural lesions of the vessel wall.
Plethysmograph
Peripheral resistance
Essential hypertension
Photoplethysmogram
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To elucidate the mechanisms determining peripheral vascular resistance in arterial hypertension the circulation in the leg was studied by venous occlusion plethysmography in 41 hypertensive patients and 11 normotensive controls. It was found that vascular resistance in the leg both at rest and during maximal vasodilatation were within the normal limits in labile and mild hypertension, but it was significantly raised in established, malignant and refractory hypertension. The increased Rmin strongly suggests structurally narrowed lumina, but not enhanced vasoconstriction of the neurohumoral origin. Moreover, vascular smooth muscle activity at rest was not increased in absolute values in hypertensive patients though it may be considered as inappropriately "high" in relation to the altered vascular design. It was concluded, that at least in the vascular bed of the leg a rise in peripheral resistance is caused by structural changes of the resistance vessels along with unchanged contractile activity of the vascular smooth muscles.
Plethysmograph
Peripheral resistance
Rest (music)
Essential hypertension
Vascular occlusion
Pathophysiology of hypertension
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Calf muscle
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Peripheral resistance
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To assess femoston effects on the cardiovascular system in postmenopause.Cardiovascular effects of femoston were studied in 20 postmenopausal women with menopausal syndrome. 70% patients had arterial hypertension. Cardiovascular system was examined before the treatment and after three treatment months using 24-h monitoring of arterial pressure, echocardiography, photoplethysmography, conjunctival biomicroscopy, central hemodynamics tests.In the course of femoston treatment menopausal manifestations relieved, arterial pressure was lowering. 3-month treatment has improved parameters of central and peripheral hemodynamics: total peripheral vascular resistance significantly fell, stroke and minute blood volumes, cardiac indexrose, tissue blood flow and microcirculation improved.Femoston produces positive changes in cardiovascular system, vascular tone, microcirculation and arterial pressure.
Photoplethysmogram
Peripheral resistance
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Twenty patient with severe atherosclerotic affection of the lower limbs, but without any symptoms of involvement of their upper extremities, and twenty healthy controls were examined. The investigation included measurement of arterial blood flow and resistance in the left forearm at rest and after a three-minute circulatory arrest, using a strain-gauge venous occlusion plethysmograph. Comparison of the results obtained in each group showed statistically significant differences in haemodynamic parameters such as maximal blood flow, resting resistance, and minimal resistance which suggested the presence of vascular changes also in the upper extremities. Arterial resistance proved to be a more sensitive indicator of circulatory disorder than blood flow.
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