Peak Forearm Blood Flow Research Articles

Trial‐to‐Trial and Day‐to‐Day Variability in Forearm Blood Flow During Reactive Hyperemia

Reactive hyperemia (RH) following the release of a brief limb occlusion is commonly used to assess resistance vessel function. The purpose of this study was to examine the impact of repeated trials on the within subject day‐to‐day variability of forearm blood flow during RH. Ten young, healthy, non‐smoking subjects (6 female, 4 male) were examined in the fasted state. Brachial artery diameter and blood velocity were assessed with Echo and Doppler ultrasound, respectively. Subjects visited the lab twice and performed four RH trials each visit. The RH protocol was performed on the left arm and included 5 minutes of forearm cuff occlusion at a pressure of 250 mmHg, followed by release. Within subjects trial‐to‐trial and day‐to‐day variability was assessed by the coefficient of variation (CV = (Standard Deviation/Mean) x 100). The Day‐to‐day CV was calculated using 1) Trial 1 from each day and 2) a 4‐Trial average. Peak forearm blood flow did not differ significantly between trials or days (p > 0.05). Within subject trial‐to‐trial variability was consistent between visits (CV, 9.39 ± 7.78% and 10.1 ± 3.19%; p = 0.737). The within subject day‐to‐day CV determined from the first trial on each day was not significantly different from the CV determined from the four trial average (CV, 14.9± 15.1% and 12.0± 9.62%; p = 0.240). In conclusion, averaging over repeated trials on each visit did not significantly reduce the day‐to‐day variability in peak reactive hyperemia blood flow.

The effect of ageing and indomethacin on forearm reactive hyperaemia in healthy adults

We have previously shown that non-selective cyclo-oxygenase inhibition, via indomethacin, unfavourably increased central blood pressure in older adults, with little effect in young adults. In addition, the vasoactive prostaglandins have been shown to contribute to both peripheral vasodilator responses and large artery function; however, there is little information available in older adults and conflicting reports in young adults on the extent to which resistance vessel function is influenced by indomethacin. Thus, we tested the hypothesis that cyclo-oxygenase inhibition using indomethacin would attenuate forearm vascular conductance during reactive hyperaemia in older adults compared with young adults. Forearm blood flow responses to 5 min of forearm ischaemia were measured in 26 healthy adults (13 young, 25 ± 5 years old; and 13 older, 65 ± 6 years old), using venous occlusion plethysmography before and after indomethacin. Baseline forearm blood flow and vascular conductance were not different between groups during either trial, and there were no age-related differences prior to cyclo-oxygenase inhibition. Peak forearm vascular conductance and blood flow were similar between groups before indomethacin, but lower in older adults after indomethacin compared with young adults (27 ± 4 versus 41 ± 4 ml (100 ml)(-1) min(-1) (100 mmHg)(-1), P = 0.02; and 23 ± 3 versus 33 ± 3 ml (100 ml)(-1) min(-1), P = 0.02, respectively). These results, in conjunction with our previous findings in large arteries, suggest that ageing alters the effect of cyclo-oxygenase inhibition on vascular responses, and specifically, the resistance vessel responses underlying reactive hyperaemia.

A fish-based diet intervention improves endothelial function in postmenopausal women with type 2 diabetes mellitus: A randomized crossover trial

ObjectiveThe beneficial effects of fish and n-3 polyunsaturated fatty acids (PUFAs) consumption on atherosclerosis have been reported in numerous epidemiological studies. However, to the best of our knowledge, the effects of a fish-based diet intervention on endothelial function have not been investigated. Therefore, we studied these effects in postmenopausal women with type 2 diabetes mellitus (T2DM). Materials/MethodsTwenty-three postmenopausal women with T2DM were assigned to two four-week periods of either a fish-based diet (n-3 PUFAs≧3.0g/day) or a control diet in a randomized crossover design. Endothelial function was measured with reactive hyperemia using strain-gauge plethysmography and compared with the serum levels of fatty acids and their metabolites. Endothelial function was determined with peak forearm blood flow (Peak), duration of reactive hyperemia (Duration) and flow debt repayment (FDR). ResultsA fish-based dietary intervention improved Peak by 63.7%, Duration by 27.9% and FDR by 70.7%, compared to the control diet. Serum n-3 PUFA levels increased after the fish-based diet period and decreased after the control diet, compared with the baseline (1.49 vs. 0.97 vs. 1.19mmol/l, p<0.0001). There was no correlation between serum n-3 PUFA levels and endothelial function. An increased ratio of epoxyeicosatrienoic acid/dihydroxyeicosatrienoic acid was observed after a fish-based diet intervention, possibly due to the inhibition of the activity of soluble epoxide hydrolase. ConclusionsA fish-based dietary intervention improves endothelial function in postmenopausal women with T2DM. Dissociation between the serum n-3 PUFA concentration and endothelial function suggests that the other factors may contribute to this phenomenon.

Arterial stiffness and blood flow adaptations following eight weeks of resistance exercise training in young and older women

Resistance training is recommended for all adults of both sexes. The arterial stiffness and limb blood flow responses to resistance training in young and older women have not been well-studied. The purpose of this study was to examine arterial stiffness and blood flow adaptations to high-intensity resistance exercise training in young and older women. Young (aged 18–25) and older (aged 50–64) women performed full-body high-intensity resistance exercise three times per week for eight weeks. The following measurements were performed twice prior to training and once following training: carotid to femoral and femoral to tibialis posterior pulse wave velocity (PWV), blood pressure, heart rate, resting forearm blood flow and forearm reactive hyperemia. Data was analyzed by ANOVAs with alpha set at 0.05. Correlations were also examined between changes in arterial stiffness and baseline arterial stiffness values. Older subjects had higher carotid–femoral PWV than younger subjects. No significant effects were found for femoral-tibialis posterior PWV or for resting forearm blood flow. Changes in carotid–femoral and femoral-tibialis posterior PWV correlated significantly with their respective baseline values. Older subjects increased peak forearm blood flow while young subjects showed no change. Total hyperemia increased significantly in both groups. In conclusion, in both young and older women, eight weeks of high-intensity resistance training appeared to improve microvascular forearm function while not changing carotid–femoral or femoral-tibialis posterior arterial stiffness. However, a large degree of individual variation was found and arterial stiffness adaptations appeared positively related to the initial stiffness values.

Low dose of green tea catechins improves endothelial function and vascular smooth muscle cell reactivity in obese women

BACKGROUND: The high prevalence of obesity in the world is associated with several health problems, with endothelial dysfunction figuring as a frequent feature. We investigated whether low dose consumption of green tea extract (catechins,< 200 mg/day) could modify endothelial function, lipid profile, fasting glucose and insulin, post load plasma glucose, inflammatory/oxidative stress biomarkers and blood pressure in obese women. METHODS: Sixteen obese women with body mass index (BMI) between 30 and 40 Kg/m2, mean age 38 [33-40] years, consumed 600 ml green tea (3 × 200 ml) per day, containing 153.3 mg of catechins and 72.5 mg of caffeine, during three months. Endothelial function was evaluated through venous occlusion plethysmography by increment of peak forearm blood flow (FBF), after 5 min ischemia, during the reactive hyperemia response/baseline FBF. Endothelium-independent vasodilation was analyzed through peak FBF after 0.4 mg sublingual nitroglycerin/baseline FBF. RESULTS: After 3 months, this consumption of green tea reduced BMI from 34.02 to 33.13, and diastolic blood pressure by 4 mmHg. The reactive hyperemia response/baseline FBF improved by 27%, and the endothelium-independent vasodilation by 12%. The blood biochemical profile, where all parameters were within the normal range, remained unaltered. CONCLUSIONS: A low dose of green tea ameliorated the endothelial dysfunction present in obesity, indicating that its consumption should be encouraged in these patients, because endothelial dysfunction is an early marker of atherosclerosis.

Dietary carbohydrate restriction improves insulin sensitivity, blood pressure, microvascular function, and cellular adhesion markers in individuals taking statins

Statins positively impact plasma low-density lipoprotein cholesterol, inflammation and vascular endothelial function (VEF). Carbohydrate restricted diets (CRD) improve atherogenic dyslipidemia, and similar to statins, have been shown to favorably affect markers of inflammation and VEF. No studies have examined whether a CRD provides additional benefit beyond that achieved by habitual statin use. We hypothesized that a CRD (<50 g carbohydrate/d) for 6 weeks would improve lipid profiles and insulin sensitivity, reduce blood pressure, decrease cellular adhesion and inflammatory biomarkers, and augment VEF (flow-mediated dilation and forearm blood flow) in statin users. Participants (n = 21; 59.3 ± 9.3 y, 29.5 ± 3.0 kg/m2) decreased total caloric intake by approximately 415 kcal at 6 weeks (P < .001). Daily nutrient intakes at baseline (46/36/17% carb/fat/pro) and averaged across the intervention (11/58/28% carb/fat/pro) demonstrated dietary compliance, with carbohydrate intake at baseline nearly 5-fold greater than during the intervention (P < .001). Compared to baseline, both systolic and diastolic blood pressure decreased after 3 and 6 weeks (P < .01). Peak forearm blood flow, but not flow-mediated dilation, increased at week 6 compared to baseline and week 3 (P ≤ .03). Serum triglyceride, insulin, soluble E-Selectin and intracellular adhesion molecule-1 decreased (P < .01) from baseline at week 3, and this effect was maintained at week 6. In conclusion, these findings demonstrate that individuals undergoing statin therapy experience additional improvements in metabolic and vascular health from a 6 weeks CRD as evidenced by increased insulin sensitivity and resistance vessel endothelial function, and decreased blood pressure, triglycerides, and adhesion molecules.

Role of forearm vasoconstriction in the development of primary raynaud's disease

Raynaud's Disease has been characterized as arteriolar constriction with a subsequent reduction of blood flow to the fingers. Few studies have investigated the regulation of blood flow into the hand in individuals with the disease. Therefore, the purpose of this study was to determine the relationship between Raynaud's disease and the forearm blood flow (FBF) response. Ten females (20.2±1.0 years), five control (CON) and five with the disease (RAY), completed two trials: a control visit and a cold‐induced visit. During the cold‐induced trial the left hand was placed in a cold bath (12°C) to induce Raynaud's symptoms. FBF was measured using venous occlusion plethysmography (Hokanson EC6). Reactive hyperemia was then determined by occluding the forearm for five minutes at 250 mmHg followed by peak FBF measurements. FBF and mean arterial pressure (MAP) were recorded pre, during the occlusion, and post trial. RAY exhibited the typical triphasic coloration changes indicating severe ischemia. Peak FBF after the occlusion in the cold trial was greater in RAY than CON indicating greater hyperemia (28.3 ± 4.8 vs. 26.2 ± 2.2 ml/100ml/min). MAP for CON was not different from RAY (87.37 ± 1.4 vs. 87.11 ± 2.37 mmHg). RAY demonstrated the typical ischemic response in the hand in response to a cold challenge in spite of a greater reactive hyperemia in the forearm suggesting a greater vasoconstriction response between the hand and forearm.

Influence of hand dominance on peak forearm blood flow and cardiovascular responses to isometric handgrip exercise in recreationally active racquet players

The purpose of this study was to determine if recreationally active racquet players (6.3 ± 2.4 years played) exhibit different responses to isometric handgrip exercise (IHG) between the dominant (D) and non‐dominant (ND) forearms than age‐, sex‐ and upper body aerobic fitness‐matched controls (n=8 per group). Two separate protocols were performed with each forearm: A) 5‐min of arterial occlusion (AO) combined with 1 min of IHG (15% max force), and B) 2‐min of IHG (40% max force) followed by 2‐min of AO. Forearm blood flow (FBF, plethysmography), heart rate (HR) and mean arterial pressure (MAP, Portapres®) data were recorded. Peak FBF was higher in both forearms (p&lt;0.01) of the racquet players than controls (D; 21.2 ± 4.9 vs. 14.9 ± 4.5, ND; 20.2 ± 5.7 vs. 13.3 ± 2.8 ml/100ml/min). During protocol B, HR (D; 23.6 ± 11.7 vs. 15.1 ± 9.0, ND; 22.4 ± 11.9 vs. 12.6 ± 8.0 beats/min) and MAP (D; 128 ± 16 vs. 105 ± 17, ND; 123 ± 23 vs. 96 ± 21 mmHg) increased more during IHG in both limbs of the racquet players (all, p &lt;0.05). MAP was also greater (p &lt;0.05) during post‐exercise AO in both limbs of the racquet players (D; 112 ± 16 vs. 99 ± 13, ND; 111 ± 19 vs. 91 ± 13 mmHg). Compared to similar results from elite racquet sport players, differences in peak FBF, HR and MAP responses to IHG between groups were not isolated to the dominant forearm. These data suggest an absence of a localized training effect to the dominant forearm in recreationally active racquet players.

Roles of nitric oxide and prostaglandins in the hyperemic response to a maximal metabolic stimulus: redundancy prevails

Vasodilatory mechanisms controlling post-exercise or post-ischemic hyperemia are thought to be under redundant control and remain incompletely understood. A maximal metabolic stimulus evoked by ischemic exercise (IE) might limit redundancy by full activation of multiple pathways. We tested whether nitric oxide (NO) and/or prostaglandins contribute to the hyperemic response to IE. 17 subjects were randomized into two groups and performed three trials of IE during control (saline), N (G)-monomethyl-L-arginine (L-NMMA; NOS inhibition) (protocol 1) or ketorolac (cyclooxygenase inhibition) infusion (protocol 2), and combined L-NMMA/ketorolac infusion via a brachial arterial catheter. Forearm blood flow (FBF) was measured with venous occlusion plethysmography following IE trials consisting of 5 min of ischemia and simultaneous rhythmic handgrip exercise (final 2 min). Peak and total (area under the curve) FBF and blood pressure (MAP) were measured for 3 min after each trial. Forearm vascular conductance (FVC) was calculated as FBF/MAP. Change (Δ) in peak FBF and FVC from baseline differed only between peak FBF for the saline and L-NMMA + ketorolac trials in protocol 1. Peak ΔFBF was 26.8 ± 2.5, 30.0 ± 2.8, and 33.9 ± 3.6 ml 100 ml(-1) min(-1) for saline, L-NMMA, and L-NMMA + ketorolac trials (P = 0.04). For protocol 1 (n = 8), total ΔFVC was 59.6 ± 4.3, 57.8 ± 6.0, and 59.9 ± 5.6 ml 100 ml(-1) 100 mmHg(-1) for saline, L-NMMA, and L-NMMA + ketorolac trials, (P = 0.82). For protocol 2 (n = 9), total ΔFVC was 54.2 ± 5.0, 56.9 ± 4.5, and 56.5 ± 5.3 ml 100 ml(-1) 100 mmHg(-1) for saline, ketorolac, and ketorolac + L-NMMA trials, (P = 0.69). These results suggest that NO and PGs are not obligatory for the hyperemic response to IE, and other vasodilator mechanisms predominate.

In elderly women moderate hypercholesterolemia is associated to endothelial and microcirculatory impairments

How cholesterol influences the microcirculation on aging subjects is not well known. This study evaluated moderate hypercholesterolemia effects in, treated or not, lean elderly women on brachial artery reactivity and microcirculatory function using venous occlusion plethysmography (VOP) and nailfold videocapillaroscopy (NVC). Patients (mean age 73years) were divided into healthy elderly (HE, n=15), treated dyslipidemia with statins during at least 6months (TDL, n=9) and dyslipidemia (DL, n=9, cholesterol, 257±11 and LDL-cholesterol, 157±24mg/dl). Young, mean age 23years, women (YC, n=24), served as controls. Laboratory and anthropometrical analysis, VOP peak forearm blood flow (FBF) during the reactive hyperemia response/baseline FBF (%HYPER) and peak FBF after 0.4mg sublingual nitroglycerin/baseline FBF (%NITRO) were assessed. NVC capillary density and diameters, maximum red blood cell velocity (RBCVmax) during reactive hyperemia/baseline RBCV and time to reach RBCVmax were evaluated. Correlations between %HYPER, %NITRO and plasma cholesterol fractions were performed.Total and LDL-cholesterol were increased only in DL group. Capillary diameters were larger in elderly groups than YC. RBCVmax/baseline RBCV was reduced in the DL group compared to HE, TDL and YC. %HYPER was lower in DL and normalized in TDL group. YC %HYPER was double of HE. %NITRO decreased from (HE=YC) to TDL and DL groups. There was a significant inverse correlation between LDL-cholesterol, non-HDL-cholesterol and %HYPER/% Nitro. In conclusion, moderate hypercholesterolemia reversibly impaired the vasodilatatory response in the microcirculation but the endothelial-independent vasodilator response to nitroglycerine remained irreversibly lower in healthy aged women.

Endothelium‐dependent dilation is inversely related to hematocrit among healthy young and older adults

Hemoglobin (Hb) is a catalytic sink for endothelial‐released nitric oxide (NO) into the artery lumen. Because elevated hematocrit (Hct) within the “normal range” is related to cardiovascular (CV) events, we hypothesized that a higher normal Hct would be associated with lower endothelium‐dependent dilation (EDD) in both young and older adults. Forearm blood flow (FBF) responses to incremental brachial artery infusions of acetylcholine (EDD) and sodium nitroprusside (endothelium‐independent dilation, EID) were assessed in young (n=22; mean ± SE; age 24 ± 1 yrs) and older (n=58; 62 ± 1 yrs) healthy adults with normal Hct. EDD (peak FBF) was lower in young and older adults (Young: 15.1 ± 2.6 vs. 25.1 ± 3.7 ml/ml FAV/min; Older: 12.1 ± 1.4 vs.16.8 ± 1.8, both P&lt;0.05) with Hct above vs. below sex‐adjusted median values, but EID was not different. EDD was inversely related to Hct (n=80, r=−0.43, P&lt;0.01), and this remained significant after adjustment for age, sex and other clinical characteristics. In a subset (n=18), inhibition of NO (Ng‐monomethyl‐L‐arginine) reduced EDD more in adults with higher (−63%) vs. lower (−39%) Hct, abolishing group differences (P&gt;0.05). High‐normal Hb is associated with lower EDD in both young and older healthy adults as a consequence of reduced NO bioavailability. Impaired endothelial function may contribute to the increased CV risks of high normal Hct. NIH AG013038, AG000279, UL1 RR025780

Vascular Dysfunction and Physical Activity in Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory disorder of the brain and spinal cord. Disability status and progression are associated with reduced physical activity (PA) and cardiovascular function. Lack of adequate PA combined with inflammation may create high susceptibility to subclinical atherosclerosis and vascular dysfunction. The purpose of this study was to compare subclinical atherosclerosis and arterial function between individuals with and without MS matched for age, sex, and body mass index. Thirty-three individuals diagnosed with MS and 33 controls underwent strain gauge plethysmography for resting forearm blood flow (FBF) and peak reactive hyperemia for the microvascular function. Intima-media thickness and arterial compliance (AC) were measured using carotid ultrasound for vascular function. C-reactive protein and PA (7-d accelerometer data) were also measured. There was a significant difference (P < 0.05) in resting FBF, peak reactive hyperemia, central pulse wave velocity, and AC between the MS and control groups. PA was associated with peak FBF and central pulse wave velocity but not FBF and carotid AC. Individuals with MS exhibit reduced arterial function but similar intima-media thickness compared with controls. Persons with MS had significantly reduced PA levels compared with controls, and PA accounted for differences in arterial function between groups. These results indicate that subclinical markers of atherosclerosis are higher in individuals with MS, suggesting a higher risk of cardiovascular disease in this population. However, the higher levels of subclinical atherosclerosis were accounted for by the low PA in persons with MS, suggesting that increasing PA may reduce the increase in cardiovascular disease risk in patients with MS.

Eicosapentaenoic Acid Supplementation Changes Fatty Acid Composition and Corrects Endothelial Dysfunction in Hyperlipidemic Patients

We investigated the effects of purified eicosapentaenoic acid (EPA) on vascular endothelial function and free fatty acid composition in Japanese hyperlipidemic subjects. In subjects with hyperlipidemia (total cholesterol ≥220 mg/dL and/or triglycerides ≥150 mg/dL), lipid profile and forearm blood flow (FBF) during reactive hyperemia were determined before and 3 months after supplementation with 1800 mg/day EPA. Peak FBF during reactive hyperemia was lower in the hyperlipidemic group than the normolipidemic group. EPA supplementation did not change serum levels of total, HDL, or LDL cholesterol, apolipoproteins, remnant-like particle (RLP) cholesterol, RLP triglycerides, or malondialdehyde-modified LDL cholesterol. EPA supplementation did not change total free fatty acid levels in serum, but changed the fatty acid composition, with increased EPA and decreased linoleic acid, γ-linolenic acid, and dihomo-γ-linolenic acid. EPA supplementation recovered peak FBF after 3 months. Peak FBF recovery was correlated positively with EPA and EPA/arachidonic acid levels and correlated inversely with dihomo-γ-linolenic acid. EPA supplementation restores endothelium-dependent vasodilatation in hyperlipidemic patients despite having no effect on serum cholesterol and triglyceride patterns. These results suggest that EPA supplementation may improve vascular function at least partly via changes in fatty acid composition.

Effects of resistance exercise training on resting and post-exercise forearm blood flow and wave reflection in overweight and obese women

The vascular responses to acute resistance exercise and resistance exercise training (RET) in overweight women are unclear. Therefore, the purpose of this study was to examine the vasodilatory and wave reflection responses to acute resistance exercise before and after RET. In all, 24 overweight/obese (28.5±0.6 kg m(-2)) women (44±1 years of age) volunteered for this study. Forearm blood flow (FBF), vasodilatory capacity in response to reactive hyperemia (peak FBF) and wave reflection (radial tonometry) were measured, before and 15 min after five sets of leg press at 10-repetition maximum (RM). Measures of pulse wave reflection included the augmentation index (AIx) and the time of the reflected wave (Tr). Measurements were collected at baseline, after a 4-week control period (before RET) and after 12 weeks of whole-body RET using three sets of five exercises at 50-60% of 1-RM. There were no differences in vascular measurements at baseline or before RET for any variable. Resting FBF (66.7%) and peak FBF (51.6%) increased significantly (P<0.05) after RET compared with before RET. Post-exercise FBF (48.9%) and peak FBF (41.1%) also increased significantly (P<0.05) after RET compared with before RET. Post-exercise AIx decreased significantly (P<0.05), whereas Tr increased significantly (P<0.05) compared with rest at all time points. However, AIx and Tr were unaltered by RET. The 12-week whole-body RET increased the resting and post-exercise FBF as well as vasodilatory capacity without changing wave reflection in premenopausal overweight women. RET may be an important non-pharmacological therapy for reducing cardiovascular risk in overweight and obese premenopausal women.

Abnormal Peripheral Vasodilatory Reserve Without Endothelial Dysfunction in Patients With Aortic Dissection.

Structural changes in the aortic wall have been reported to be present in aortic dissection (AD), while there have been no investigations concerning peripheral vasomotion characteristics. Peripheral arterial stiffness is an important factor in the regulation of the central aortic pressure because it produces excessive wave reflection. The present study investigated in AD patients endothelium-dependent peripheral vasodilation and the reactive hyperemic response which is considered to be altered by the structural abnormality of the peripheral resistance artery. Forearm blood flow (FBF) changes induced by intra-arterial infusion of acetylcholine (ACh), sodium nitroprusside (SNP), and by occlusion-induced reactive hyperemia (RH) were measured plethysmographically in 10 AD patients, 7 healthy volunteers, and 7 patients with uncomplicated hypertension (UHT). There were no significant differences in the peak FBF response to ACh and SNP infusion for the three groups (ACh, 14.2 +/- 1.8 vs 17.2 +/- 4.5 vs 15.7 +/- 2.3 ml/min/dl tissue, NS; SNP 9.5 +/- 1.3 vs 10.6 +/- 1.7 vs 11.9 +/- 0.8 vs ml/min/dl tissue, NS). In the case of RH, however, peak FBF and maximum conductance were significantly lower in AD patients than in healthy volunteers and UHT patients (21.1 +/- 2.6 vs 36.1 +/- 4.7 and 32.4 +/- 2.6 ml/min/dl tissue volume, p < 0.01, and 0.25 +/- 0.03 vs 0.46 +/- 0.06 and 0.37 +/- 0.03 ml/min/dl per mmHg, p < 0.05, respectively). Peripheral vasodilatory function depending on the endothelium and smooth muscle in AD patients was not significantly different from that in healthy volunteers and UHT patients. However, reactive hyperemic vasodilatory reserve, which is a well-established, noninvasive measure of arterial structure, was significantly impaired in AD. These findings indicate that arterial structural abnormalities rather than systemic atherosclerotic changes represented by endothelial dysfunction may be present. We speculated that this aspect of peripheral resistance artery might possibly have an unfavorable effect on the postonset aortic conditions in AD patients.

Roles of Nitric Oxide and Prostaglandins in the Hyperemic Response to a Maximal Metabolic Stimulus: Redundancy Prevails

We tested whether NO and prostaglandins (PG) contribute to the post hyperemic response to ischemic exercise (IE). Forearm blood flow (FBF) was measured with venous occlusion plethysmography following IE trials consisting of 5 min of ischemia and rhythmic handgrip exercise (final 2 minutes of ischemia). 17 subjects were randomized into 2 groups and performed 3 trials of IE during control (saline), NG-monomethyl-L-arginine (L-NMMA; NOS inhibition) or ketorolac (cyclooxygenase inhibition) alone, and combined L-NMMA/ketorolac infusion via a brachial arterial catheter. Peak and total (area under the curve; AUC) FBF and blood pressure (MAP) were measured for 3 min after each trial. Forearm vascular conductance (FVC) was calculated as FBF/MAP. No significant difference was detected between trials, regardless of drug order. For those receiving L-NMMA first (n=8), total ΔFVC was 59.6±4.3, 57.8±6.0, and 59.9±5.6 ml·100ml−1·100mmHg−1 (p =0.82) for saline, L-NMMA alone, and L-NMMA+ketorolac infusions, respectively. For those receiving ketorolac first (n=9), total ΔFVC was 54.2±5.0, 56.9±4.5, and 56.5±5.3 ml·100ml−1·100mmHg−1 (p=0.69) for saline, ketorolac alone, and ketorlac+L-NMMA infusions, respectively. These results suggest that NO and PGs are not obligatory for the post hyperemic response to ischemic exercise and that redundant vasodilator mechanisms predominate.

Renal dysfunction impairs circadian variation of endothelial function in patients with essential hypertension

Some cardiovascular disorders disturb circadian variation of endothelial function. We investigated whether deterioration of renal function alters circadian variation of endothelial function in patients with hypertension. Endothelial function was assessed by the peak forearm blood flow (FBF) response to reactive hyperemia, and 24-hour ambulatory blood pressure monitoring was performed in 25 patients with essential hypertension (61 ± 17 years). Relationships among renal function, 24-hour blood pressure, and endothelial function were analyzed. The ratio of nighttime to daytime mean arterial pressure was inversely correlated with estimated glomerular filtration rate (eGFR) ( r = −0.43, P = .03). The FBF response to reactive hyperemia examined at 21:00, but not at 6:30 or 11:30, was significantly correlated with eGFR ( r = 0.44, P = .03). Furthermore, the ratio of FBF response measured at 21:00 to that measured at 6:30 was independently correlated with eGFR (β = 0.47, P = .02). Renal dysfunction is associated with the derangement of circadian variation of both endothelial function and blood pressure. Nocturnal blood pressure is elevated, and evening endothelial function deteriorates in parallel with a decline in renal function in hypertensive patients.

Impact of chronic intermittent external compressions on forearm blood flow capacity in humans

During dynamic exercise, the vasculature embedded within skeletal muscle intermittently collapses due to increased intramuscular pressure (IMP). The aim of this study was to ascertain whether oscillations in IMP during muscle contractions independently contribute to exercise training-induced increases in blood flow capacity (BFC). Based on IMP measurements during handgrip exercise, we attempted to mimic the action of repeated vascular compressions by using external inflatable cuffs. Thus, 24 healthy young male subjects underwent a 4-week program (5 days/week, 1 h/day) of application of external compressions of the non-dominant forearm, while the dominant limb served as an internal control. To evaluate the impact of compression pressures of different magnitudes, subjects were randomly assigned to one of three groups: 50, 100 and 150 mmHg of external compression. Prior to the intervention and after 2 and 4 weeks of treatment, we measured peak forearm blood flow (PBF) (Doppler ultrasound) and calculated peak vascular conductance (PVC) following 10 min of forearm ischemia. In the 50 and 100 mmHg groups, application of intermittent compressions did not alter PBF in either control or intervention forearms. In the 150 mmHg group, there was a trend (P = 0.04) for greater increases in PBF from baseline after 4 weeks in the intervention forearm compared to the control forearm (delta PBF: 4.2 ± 2.5 vs. -2.1 ± 2.0 (ml(100 ml)(-1) min(-1)), in the intervention and control forearms, respectively), but the changes in PVC were not significant (P = 0.1). These findings suggest that repeated oscillations in IMP contribute minimally to exercise-induced increase in forearm BFC in healthy young humans.

Acute effect of a single bout of aerobic exercise on vascular and baroreflex function of young males with a family history of hypertension

The effect of one single bout of aerobic exercise on the vascular and baroreceptor function of individuals with a family history of hypertension was investigated. Forty young males, mean age 21 years, comprising offspring with (FH(+); n=20) and without (FH(-); n=20) a family history of hypertension participated in this study. Acute exercise was performed on a stationary bike for 20 min at 60% of maximal oxygen uptake. Peak forearm blood flow (FBF) was assessed using plethysmography and was determined as the highest blood flow after 5 min of reactive hyperaemia. Cardiopulmonary baroreceptor (CPBR) sensitivity was measured using lower-body negative pressure (LBNP) for 5 min at -20 mm Hg. CPBR was determined by calculating change of stroke volume and forearm vascular resistance (FVR) at baseline and during LBNP. Carotid baroreceptor (CBR) sensitivity was assessed using neck suction at -20, -40, -60 and -80 mm Hg pressures and was determined from RR interval divided by systolic blood pressure. Augmentation index (AIx), a measure of wave reflection, was assessed using applanation tonometry, and was calculated as the ratio of augmented pressure and pulse pressure. The peak FBF at pre-exercise was lower in FH(+) than in FH(-) subjects. Twenty minutes of acute cycle exercise resulted in significantly increased peak FBF by 22% in FH(+) and by 11% in FH(-) subjects, whereas peak FVR of both groups decreased by 17% and 11%, respectively. No change occurred in CPBR, CBR or AIx. It is concluded that 20 min of acute cycle exercise normalised baseline FBF and forearm vasodilation during hyperaemia in FH(+) subjects.

Influence of age, sex, and aerobic capacity on forearm and skin blood flow and vascular conductance

This study investigated the influence of age, sex, and aerobic capacity on resting and peak forearm and cutaneous blood flow (FBF, CBF). We recruited 93 female and 129 male subjects (age range 16-76 years). FBF and CBF were assessed by plethysmography and laser-Doppler flowmetry, respectively. Peak FBF was obtained following 5 min forearm vascular occlusion and peak CBF in response to local skin heating of 42 degrees C. Blood pressure was measured manually and by Finapres. Maximal oxygen uptake (VO2max) was obtained from a treadmill exercise stress test. Age was associated with declines in resting FBF (y = -1.176 ln(x) + 6.6899, r(2) = 0.45) and peak FBF (y = -17.21 ln(x) + 93.843, r(2) = 0.53) (both p < 0.05). Peak CBF decreased with increasing age (y = -223.6 ln(x) + 1,102.9, r(2) = 0.34) (p < 0.05), but resting CBF was unchanged (p > 0.05). Males had higher resting and peak FBF than females (p < 0.05) and these variables were related to ageing better in males (y = -1.245 ln(x) + 7.188, r(2) = 0.71 and y = -18.53 ln(x) + 102.82, r(2) = 0.69) than in females (y = -1.149 ln(x) + 6.4307, r(2) = 0.38 and y = -16.59 ln(x) + 88.872, r(2) = 0.55). There were no sex differences in resting CBF (p > 0.05). Peak CBF was much better related to ageing in males than females (y = -276.1 ln(x) + 1,365.4, r(2) = 0.53 vs. y = -183.1 ln(x) + 907.86, r(2) = 0.28). VO2max decreased with advancing age and this decline was associated with the decline in peak FBF (y = -0.5933x + 10.91, r(2) = 0.36, p < 0.05) but not with peak CBF (p > 0.05). These results suggest that healthy ageing is associated with a curvilinear decline in resting and peak forearm and peak cutaneous vasodilator capacity, with males more severely affected than females. The data indicate that peak FBF is influenced by VO2max but peak CBF is not.