Forearm Cutaneous Blood Flow Research Articles

Vascular and Microvascular Endothelial Function in Heart Failure With Preserved Ejection Fraction

BackgroundAssessment of vascular endothelial function lacks consistency, and microvascular endothelial function has been only partly assessed in heart failure with preserved ejection fraction (HFpEF). MethodsThe study population consisted of 90 patients: 45 had well documented HFpEF, and 45 had hypertension and no history or evidence of heart failure. Patients with hypertension but no heart failure were matched with HFpEF patients for age, sex, and diabetes. They served as control subjects. All patients underwent 2-dimensional Doppler echocardiography and vascular function measurements, including assessment of arterial wave reflections and arterial stiffness, brachial artery flow-mediated dilation (FMD), and forearm cutaneous blood flow with the use of a laser Doppler flow probe at rest and after release of arterial occlusion for 5 minutes. ResultsBrachial artery FMD was lower in HFpEF than in control subjects (median (IQR) 3.6 (0.4-7.4) vs 7.2 (3.2-17.2)%, P = .001). Forearm cutaneous blood flow at rest was similar in HFpEF and control subjects (P = .68). After release of arterial occlusion, forearm cutaneous peak blood flow was lower in HFpEF than in control subjects (P = .03). Estimated aortic systolic and mean blood pressures were similar in HFpEF and control subjects, whereas pulse pressure and pressure augmentation were greater in HFPEF than in control subjects (both P < .05). ConclusionCompared with hypertensive control subjects, patients with HFpEF had a depressed endothelial function in the forearm vasculature and microvasculature.

Maximal cutaneous blood flow is not affected by endurance training: implications for physiological interpretation of cutaneous blood flow

Cutaneous blood flow can be altered by non‐sympathetic influences such as hydration level, acclimatization, and training level. It is currently unknown what effect these factors have on maximal cutaneous blood flow. The purpose of this study was to investigate the effect of endurance training on maximal cutaneous blood flow. Fifteen healthy sedentary subjects (age, 25±1 years) had maximal cutaneous blood flow measured before and after eight weeks of endurance training or eight weeks of sedentary control. Arterial blood pressure (Finometer), brachial blood flow (Doppler ultrasound), and forearm cutaneous vascular conductance (laser Doppler flowmetry; flux/mean arterial pressure) were measured for 5 min at room temperature (22±1ºC). The arm was then heated for 30 min followed by an additional 30 min of measurements. A water perfused tube‐lined sleeve was used to heat the forearm skin to 41±1ºC. Exercise training increased VO2peak by 19.3%. Brachial blood flow and cutaneous vascular conductance increased with heating. Training did not alter brachial blood flow at rest (47±11 ml/min before training and 41±6 ml/min after training) or during maximal heating (217±28 ml/min before training and 217±28 ml/min after training). Training did not alter cutaneous vascular conductance at rest (0.010±0.003 ml/min/mmHg before training and 0.010±0.002 ml/min/mmHg after training) or during maximal heating (0.047±0.007 ml/min/mmHg before training and 0.051±0.009 ml/min/mmHg after training). These results suggest that endurance training does not alter maximal forearm cutaneous blood flow in humans.Research supported by NIH DC006459, HL077670, &amp; M01RR10732

Transdermal estrogen replacement therapy and vasomotor response.

Previous studies have shown that acute administration of estrogen improves endothelial function in postmenopausal women, but there has been little investigation of the chronic effects of transdermal estrogen replacement therapy. The present study assessed the effect of transdermal estrogen replacement therapy (0.025 mg / day for 4 weeks, the normally applied dosage in Japan) on flow-mediated endothelium-dependent vasodilation of the brachial artery (B-mode ultrasound) and forearm cutaneous blood flow (laser Doppler flowmetry), and plasma hormonal and lipid levels in 12 normolipidemic postmenopausal women. Neither resting vascular diameter, flow-mediated vasodilation, nor time to peak vasodilation, showed significant changes after the estrogen therapy. In contrast, resting forearm cutaneous blood flow decreased significantly after the estrogen therapy. The time to the peak reactive hyperemia in the forearm skin was slightly shortened, and the % change in reactive hyperemia decreased slightly after the therapy. These findings seemed to reflect the inhibition of hot-flush symptoms associated with vasomotor abnormalities in cutaneous tissue. The lack of improvement in flow-mediated vasodilation of the brachial artery despite the inhibitory effect on cutaneous vasomotor abnormalities may be related to the low plasma estradiol concentration obtained with the present transdermal therapy (42.4+/-15.2 pg / ml), a finding which supports the estrogen threshold hypothesis in hormone replacement therapy.

Post-exercise thermal homeostasis as a function of changes in pre-exercise core temperature.

We have previously reported that, following continuous exercise, a prolonged elevated plateau of esophageal temperature (Tes) was directly related to the Tes at the time of cutaneous vasodilation (Thdil) during exercise. In order to investigate the hypothesis that the factors which result in an increase of the post-exercise Thdil and define the post-exercise Tes elevation are related to pre-exercise Tes, nine healthy, young [24.0 (1.9) years], non-training males rested at 29 degrees C, 50% humidity for > 1 h (control). They then completed three successive cycles of 15 min treadmill running at 70% maximal oxygen consumption (VO2max) followed by 30 min rest. Esophageal, rectal (Tre) and skin (Tsk) temperatures and forearm cutaneous blood flow were recorded at 5-s intervals throughout. Laser-Doppler flowmetry of forearm skin blood flow was used to identify the Thdil during exercise. Pre-exercise Tes was 36.74 (0.25) degrees C and post-exercise Tes fell to stable and significant (P < 0.05) elevations above pre-exercise values at 37.22 (0.27) degrees C, 37.37 (0.27) degrees C and 37.48 (0.26) degrees C following each successive work bout respectively. Correspondingly, Thdil during each work bout rose in proportion to, and was not different than, the post-exercise Tes in the following recovery [37.20(0.23) degrees C, 37.41 (0.24) degrees C and 37.58 (0.24) degrees C]. Although the increases were less with each successive exercise bout, the differences between each exercise bout, in terms of post-exercise Tes and Thdil values, were significant (P < 0.05). These results reinforce our previous observations of elevations in Thdil and post-exercise Tes after a single exercise bout and lead to the tentative conclusions that (1) pre-exercise Tes has a direct influence on Thdil and post-exercise Tes, and (2) the exercise-induced increase of Thdil persists into recovery, influencing post-exercise thermal recovery.

Effects of the Berlin Heart Biventricular Assist Device on Microvascular Responses in Pre-transplant Patients

Microcirculatory forearm cutaneous blood flow was monitored continuously and noninvasively by laser doppler flow-metry (LDF) in 15 patients treated with the Berlin Heart biventricular assist device system (BVAD) for end-stage heart failure under stable hemodynamic states (BVAD pts, n = 10) and norepinephrine therapy (BVAD nor pts, n = 5). Ten healthy human subjects served as controls (C). Cutaneous blood flow was measured before, during, and after external brachial artery occlusion to evaluate the post-occlusive reactive hyperemia (PORH) as a standardized response. To examine microvascular responses to macrohemodynamic changes, the cardiac output (CO) was decreased by a 20% reduction in BVAD pump rate. No significant differences in baseline LDF measurements (in millivolts) were observed among the three groups (C, 470.7 mV +/- 177.3; BVAD pts, 328.0 mV +/- 122.7; BVAD nor pts, 360.0 mV +/- 160.0). After cuff pressure release (1 min later), a significant (p < 0.004) three-fold to four-fold blood flow increase (PORH) occurred in each group (C, 1113.6 mV +/- 469.2; BVAD pts, 813.0 mV +/- 190.1; BVAD nor pts, 498.0 mV +/- 191.8). The difference in PORH between the BVAD pts and BVAD nor pts was significant (p < 0.01), and the time to peak PORH values was different (p < 0.05) among the three groups (C, 22.2 s +/- 10.7; BVAD pts, 11.3 s +/- 12.5; BVAD nor pts, 7.0 s +/- 5.8). A markedly delayed return to baseline occurred in the BVAD pts. The 20% reduction in BVAD pump rate decreased CO significantly (p < 0.05) and increased (p < 0.01) systemic vascular resistance (SVR).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of kwashiorkor malnutrition on measured capillary filtration rate in forearm.

This study investigated the effects of kwashiorkor malnutrition on blood tissue fluid exchange by measuring the rate of capillary filtration (CFR) in response to a 60-mmHg increment in venous pressure in the forearms of 1- to 3-yr-old native African children within the Transkei Homeland. They were divided into the following subject groups: kwashiorkor patients (K); kwashiorkor patients who were at various stages of recovery (RK); marasmus patients (M); patients with edema of nonkwashiorkor origin (E); and control children (C). Measurements of CFR were significantly lower in the K subjects compared with any of the other groups (P less than 0.05), whereas, the RK, M, E, and C subjects were not significantly different from each other. This latter finding indicates that the lower CFR of the K patients is reversible and is not due to malnutrition or edema per se. Measurements of forearm cutaneous blood flow by laser Doppler flowmetry (LDF) in C and K subjects showed only a slightly lower value for the K patients (P greater than 0.20), and there was no relationship between CFR and LDF for either group (r = 0.073). These results suggest that the lower CFR of the K patients is not secondary to peripheral vasoconstriction.

Periodic cutaneous blood flow during aldehyde-provoked hyperemia

Forearm cutaneous blood flow was monitored continuously by laser Doppler velocimetry in 12 normal human subjects before and after a 5-min topical challenge with 5 M propionaldehyde. The aldehyde challenge routinely provoked an increase in cutaneous blood flow. During the recovery phase from peak stimulated blood flow to a lower, stable, resting level of flow, the cutaneous blood flow exhibited rhythmic oscillatory activity. Three stages of oscillatory vasomotion were defined to characterize changes: the first 5 min after onset (I), the 5-min span bracketing the temporal midpoint (II), and the final 5 min (III). The average period, wave height, and erythrocyte flux decreased during these three stages of oscillatory vasomotion. These changes and the temporal characteristics of onset and disappearance of oscillatory vasomotion suggest an origin of the oscillations in the slow wave activity of vascular smooth muscle.

Exercise thermoregulation after prolonged wakefulness.

The effect of 33 h of wakefulness on the control of forearm cutaneous blood flow and forearm sweating during exercise was studied in three men and three women. Subjects exercised for 30 min at 60% peak O2 consumption while seated behind a cycle ergometer (Ta = 35 degrees C, Pw = 1.0 kPa). We measured esophageal temperature (Tes), mean skin temperature, and arm sweating continuously and forearm blood flow (FBF) as an index of skin blood flow, twice each minute by venous occlusion plethysmography. During steady-state exercise, Tes was unchanged by sleep loss. The sensitivity of FBF to Tes was depressed an average of 30% (P less than 0.05) after 33 h of wakefulness with a slight decrease (-0.15 degrees C, P less than 0.05) in the core temperature threshold for vasodilatory onset. Sleep loss did not alter the Tes at which the onset of sweating occurred; however, sensitivity of arm sweating to Tes tended to be lower but was not significant. Arm skin temperature was not different between control and sleep loss experiments. Reflex cutaneous vasodilation during exercise appeared to be reduced by both central and local factors after 33 h of wakefulness.

Periodic cutaneous blood flow during postocclusive reactive hyperemia.

Forearm cutaneous blood flow was monitored continuously by laser Doppler velocimetry in 10 normal human subjects before, during, and after external brachial artery occlusion for 6 min duration. During the reactive hyperemic response, the cutaneous blood flow exhibited rhythmic oscillatory activity. The amplitude of the oscillations was maximum 30 s postocclusion. Thereafter, the amplitude of the oscillations declined until cutaneous blood flow returned to control values. The mean (+/- SEM) period for the oscillations was 9.26 +/- 0.30 s. Bilateral forearm sites were examined simultaneously in eight studies and demonstrated a progressive loss of synchronicity. Nine additional studies were performed in which two forearm sites only 1.8 cm apart demonstrated a progressive loss of synchronicity resulting from different periodicities of microcirculatory flow patterns. These oscillations in cutaneous blood flow, which occur during postocclusive reactive hyperemia as a normal physiological phenomenon, are not synchronous in adjacent areas of skin. The data suggest an origin of the oscillations in the cutaneous vasculature that is either unrelated to sympathetic vasoconstrictor influences or is due to nonuniform cutaneous sympathetic excitation.