Blood Pressure Distribution Research Articles

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network. Part II: Flow variations induced by global or localized modifications of arteriolar diameters

In a companion paper (Lorthois et al., Neuroimage, in press), we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical vascular network (~10000 segments), using a 1D non-linear model taking into account the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, volumes of functional vascular territories, regional flow at voxel and network scales, etc. Using the same approach, we study flow reorganizations induced by global arteriolar vasodilations (an isometabolic global increase in cerebral blood flow). For small to moderate global vasodilations, the relationship between changes in volume and changes in flow is in close agreement with Grubb's law, providing a quantitative tool for studying the variations of its exponent with underlying vascular architecture. A significant correlation between blood flow and vascular structure at the voxel scale, practically unchanged with respect to baseline, is demonstrated. Furthermore, the effects of localized arteriolar vasodilations, representative of a local increase in metabolic demand, are analyzed. In particular, localized vasodilations induce flow changes, including vascular steal, in the neighboring arteriolar trunks at small distances (<300μm), while their influence in the neighboring veins is much larger (about 1mm), which provides an estimate of the vascular point spread function. More generally, for the first time, the hemodynamic component of various functional neuroimaging techniques has been isolated from metabolic and neuronal components, and a direct relationship with several known characteristics of the BOLD signal has been demonstrated.

Treating high blood pressure: Is reaching the target more important than the means? Yes, the target is more important

The effectiveness of hypertension treatments is attributed either to the change in blood pressure, independent of the means used, or to an important contribution of appropriate drug selection: this debate probably stems from an inappropriate comparison. Treating essential hypertension in relatively healthy patients without advanced vascular disease and co-morbidities affords cardio-vascular protection by the lowering of the mechanical shear stress determined by blood pressure per se: thus, lowering blood pressure is the critical step, while the methods used can only differ through side effects. This treatment is, in fact, a lifetime prophylaxis, as hypertension, rather than a disease, is a symptom affecting one tail of the Gaussian distribution of blood pressure across the normal population. Treating hypertension in the context of diseases, like diabetes mellitus, congestive heart failure, left ventricular hypertrophy, and advanced atherosclerosis, would be improper if focused on just one symptom, while the appropriate treatment must include options which exhibit a more extended profile to include effectiveness on cardiac hypertrophy, insulin resistance, cardiac output, and systemic hemodynamics: thus, drugs may be different in their effectiveness and in the cardio-vascular protection afforded, even though the trials quoted in favour of this thesis were designed to compare drugs in their ability to lower blood pressure rather than in improving the overall complex clinical derangements. In conclusion, while the answer to the question is a sharp YES when dealing with primary prevention, it might be a NO, still clouded by contradictory and inconclusive evidence when dealing with secondary prevention and/or treatment of complex disease conditions and co-morbidities.

Estimation of the burden of cardiovascular disease attributable to modifiable risk factors and cost-effectiveness analysis of preventative interventions to reduce this burden in Argentina

BackgroundCardiovascular disease (CVD) is the primary cause of mortality and morbidity in Argentina representing 34.2% of deaths and 12.6% of potential years of life lost (PYLL). The aim of the study was to estimate the burden of acute coronary heart disease (CHD) and stroke and the cost-effectiveness of preventative population-based and clinical interventions.MethodsAn epidemiological model was built incorporating prevalence and distribution of high blood pressure, high cholesterol, hyperglycemia, overweight and obesity, smoking, and physical inactivity, obtained from the Argentine Survey of Risk Factors dataset. Population Attributable Fraction (PAF) of each risk factor was estimated using relative risks from international sources. Total fatal and non-fatal events, PYLL and Disability Adjusted Life Years (DALY) were estimated. Costs of event were calculated from local utilization databases and expressed in international dollars (I$). Incremental cost-effectiveness ratios (ICER) were estimated for six interventions: reducing salt in bread, mass media campaign to promote tobacco cessation, pharmacological therapy of high blood pressure, pharmacological therapy of high cholesterol, tobacco cessation therapy with bupropion, and a multidrug strategy for people with an estimated absolute risk > 20% in 10 years.ResultsAn estimated total of 611,635 DALY was lost due to acute CHD and stroke for 2005. Modifiable risk factors explained 71.1% of DALY and more than 80% of events. Two interventions were cost-saving: lowering salt intake in the population through reducing salt in bread and multidrug therapy targeted to persons with an absolute risk above 20% in 10 years; three interventions had very acceptable ICERs: drug therapy for high blood pressure in hypertensive patients not yet undergoing treatment (I$ 2,908 per DALY saved), mass media campaign to promote tobacco cessation amongst smokers (I$ 3,186 per DALY saved), and lowering cholesterol with statin drug therapy (I$ 14,432 per DALY saved); and one intervention was not found to be cost-effective: tobacco cessation with bupropion (I$ 59,433 per DALY saved)ConclusionsMost of the interventions selected were cost-saving or very cost-effective. This study aims to inform policy makers on resource-allocation decisions to reduce the burden of CVD in Argentina.

Distribution of Skinfold Thickness and Blood Pressure among Children and Adolescents in Shandong, China

This article reported the distribution of skinfold thickness (SFT) and blood pressure (BP) among children and adolescents in Shandong, China. A total of 8568 students (4333 boys and 4235 girls) aged 7-18 years participated in this study. Triceps and subscapular SFT and BP of all subjects were measured, the sum of Triceps and subscapular SFT (SSFT) was used as an indicator of the overall SFT. The overall prevalence of relative high BP was 24.07% for boys and 22.36% for girls. The prevalence of relative high BP was increasing with SSFT percentiles, this trend was obvious especially in upper percentiles of SSFT. The prevalence of relative high BP increased from 13.27% (boys) and 13.33% (girls) in <5th SSFT percentile group to 55.50% (boys) and 48.17% (girls) in ≥95th SSFT percentile group, which increased by 3.2 and 2.6 times. There is a higher level of SSFT and higher prevalence of relative high BP among children and adolescents in Shandong, China.

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network: Part I: Methodology and baseline flow

Hemodynamically based functional neuroimaging techniques, such as BOLD fMRI and PET, provide indirect measures of neuronal activity. The quantitative relationship between neuronal activity and the measured signals is not yet precisely known, with uncertainties remaining about the relative contribution by their metabolic and hemodynamic components. Empirical observations have demonstrated the importance of the latter component and suggested that micro-vascular anatomy has a potential influence. The recent development of a 3D computer-assisted method for micro-vascular cerebral network analysis has produced a large quantitative library on the microcirculation of the human cerebral cortex (Cassot et al., 2006), which can be used to investigate the hemodynamic component of brain activation through fluid dynamic modeling. For this purpose, we perform the first simulations of blood flow in an anatomically accurate large human intra-cortical vascular network (~10000 segments), using a 1D non-linear model taking account of the complex rheological properties of blood flow in microcirculation. This model predicts blood pressure, blood flow and hematocrit distributions, as well as volumes of functional vascular territories, and regional flow at voxel and network scales. First, the influence of the prescribed boundary conditions (BCs) on the baseline flow structure is investigated, highlighting relevant lower- and upper-bound BCs. Independent of these BCs, large heterogeneities of baseline flow from vessel to vessel and from voxel to voxel, are demonstrated. These heterogeneities are controlled by the architecture of the intra-cortical vascular network. In particular, a correlation between the blood flow and the proportion of vascular volume occupied by arterioles or venules, at voxel scale, is highlighted. Then, the extent of venous contamination downstream to the sites of neuronal activation is investigated, demonstrating a linear relationship between the catchment surface of the activated area and the diameter of the intra-cortical draining vein.

Blood pressure distribution according to age in a study population of 35,869 participants aging 18 to 99 years

Objective: Only few studies examined in detail the distribution of blood pressure in populations according to age, sex and cardiovascular risk factors. Here we analyzed blood pressure data from a nation-wide cross-sectional study in Germany with 35,869 participants aging 18–99 years. Methods: Percentiles (pctl, 5th, 25th, 50th, 75th, 95th) for systolic blood pressure (SBP),and prevalence of hypertension according to JNC-7 were computed stratified by 5 year age-groups, sex and CVD risk factors (abnormal waist, high triglycerides, low HDL, diabetes, history of CVD, antihypertensive treatment). Results: According to the guidelines of JNC-7 half of all men and half of all women above 30 years of age had to be classified at least as pre-hypertensive. With the exception of the 5th pctl in all pctl-categories a constant age-related shift of 20mmHg was observed in men (5th pct: increase of 10mmHg). We found a similar pattern in women with the exception of the 95th pctl where a shift of &gt;35mmHg was noticed, reaching an SBP &gt;170mmHg at the age of 55+. In subjects without CVD, intake of antihypertensives and/or CVD risk factors this SBP shift was still present, i.e. men in the 5th pctl showed a maximum increase of 20mmHg reaching 120mmHg by the age of 85. However, in this group without CVD risk factor and intake of antihypertensives from the age of &gt;70 years still 50% of men had to be classified as hypertensive according to JNC-7 guidelines. Conclusion: In our sample we observed a constant SBP shift by age even in subjects without CVD risk factors. If this observation is an effect of age or a birth cohort effect will be studied further using longitudinal data from a population-based prospective cohort study.

Cerebral Blood Flow Modeling in Primate Cortex

We report new results on blood flow modeling over large volumes of cortical gray matter of primate brain. We propose a network method for computing the blood flow, which handles realistic boundary conditions, complex vessel shapes, and complex nonlinear blood rheology. From a detailed comparison of the available models for the blood flow rheology and the phase separation effect, we are able to derive important new results on the impact of network structure on blood pressure, hematocrit, and flow distributions. Our findings show that the network geometry (vessel shapes and diameters), the boundary conditions associated with the arterial inputs and venous outputs, and the effective viscosity of the blood are essential components in the flow distribution. In contrast, we show that the phase separation effect has a minor function in the global microvascular hemodynamic behavior. The behavior of the pressure, hematocrit, and blood flow distributions within the network are described through the depth of the primate cerebral cortex and are discussed.

HYPERTENSION IN DIABETIC NEPHROPATHY PATIENTS IN SAUDI ARABIA: ANTIHYPERTENSIVE MEDICATION AND OUTCOME: PP.30.191

Background: Despite the increasing burden of hypertension End-Stage Renal Disease and Cardiovascular disease, data is limited regarding prevalence and control of hypertension. Aim: To examine distribution, treatment and outcome of blood pressure in Saudi DN patients. Method: Retrospective study conducted between January 1989 and January 2004 on 503 DN patients with proteinuria in a tertiary, hospital in Riyadh, SA. Definitions of hypertension and its appropriate or inappropriate treatment were according to the seventh report of the Joint National Committee of the prevention, detection, evaluation and treatment of high blood pressure (JNC 7). Patients demographic, renal function, treatment, medication, and blood pressure were kept in record. Results: 503 patients 269 (53.5%) males. age 64.5¡ 3/4 12.3 yrs. prevalence of hypertension was 409(81.3%) during first year and 447(88.9%) during last visit. isolated systolic hypertension was present in 97 (35.5%)patients. The patient had initial systolic blood pressure 136¡ 3/4 20 mmHg (100–200), diastolic blood pressure was 79.9¡ 3/4 10.6 (60–130). 136 patients were controlled, 372(74%) patients took medication during 1st year while 443(88.1%) patients during last year of follow up. ACE inhibitors were used by 254 (50.4%) of patients. Calcium Channel Blockers by 189(37.5%), ARB 72(14.3%), diuretics 44(8.7%), beta blocker by 3(0.6%) patients. Multiple drug therapy was given to 158(31.3%). Hypertension was controlled in 267 (53.1%) patients at last year of follow up. Comparing the outcome end points, patients with uncontrolled hypertension were having significantly higher incidence of of stroke p < 0.05. Higher incidence of myocardial infarction, retinopathy, proteinuria, hospitalization frequency and stay days in CCU were obtained in patients with uncontrolled hypertension. Patients as show in the table below.Conclusion: Hypertension is common in Saudi DN patients. Isolated systolic hypertension was frequent. Higher incidences of complications were found in patients with uncontrolled blood pressure. Aggressive approach is warranted to minimize the complications and to achieve target blood pressure levels according to recommended guidelines of JNC7.

Issues in multiple imputation of missing data for large general practice clinical databases

Missing data are a substantial problem in clinical databases. This paper aims to examine patterns of missing data in a primary care database, compare this to nationally representative datasets and explore the use of multiple imputation (MI) for these data. The patterns and extent of missing health indicators in a UK primary care database (THIN) were quantified using 488 384 patients aged 16 or over in their first year after registration with a GP from 354 General Practices. MI models were developed and the resulting data compared to that from nationally representative datasets (14 142 participants aged 16 or over from the Health Survey for England 2006 (HSE) and 4 252 men from the British Regional Heart Study (BRHS)). Between 22% (smoking) and 38% (height) of health indicator data were missing in newly registered patients, 2004-2006. Distributions of height, weight and blood pressure were comparable to HSE and BRHS, but alcohol and smoking were not. After MI the percentage of smokers and non-drinkers was higher in THIN than the comparison datasets, while the percentage of ex-smokers and heavy drinkers was lower. Height, weight and blood pressure remained similar to the comparison datasets. Given available data, the results are consistent with smoking and alcohol data missing not at random whereas height, weight and blood pressure missing at random. Further research is required on suitable imputation methods for smoking and alcohol in such databases.

Histological Assessment of Selected Blood Vessels of the Phocid Seals (Northern Elephant and Harbour Seals)

Phocid seals exhibit vascular adaptations that allow them to undertake prolonged deep dives. These vascular adaptations are either unique to phocids, or are modified vascular equivalents to those present in terrestrial mammals. One such adaptation, the aortic bulb, is a spherical enlargement of the ascending aorta specific to phocid seals. Its histological make-up consists of a reinforced tunica media with circular and longitudinal layers of elastic fibres. This reinforcement enables multi-axial deformation of the aortic bulb, thus complementing its function as a prominent elastic reservoir or 'windkessel'. A second adaptation, the hepatic sinus, is an asymmetrical dilation of the abdominal portion of the caudal vena cava and accompanying hepatic veins. The hepatic sinus is comprised of a relatively thin tunica media, with a scant smooth muscle component. The bulk of the sinus wall is comprised of tunica adventitia. A third vascular adaptation distinctive to the phocids is the pericardial venous plexus, composed of convoluted veins circumnavigating the perimeter of the heart. Microscopically, these veins have a thick tunica media and also contain valves. Smaller arteries, venules and distinct capillary beds are observed interspersed in-between these veins. It can be hypothesized, that in seals, certain vascular embryonic development may be arrested at an earlier embryonic stage, resulting in these unusual vascular formations. These modifications play a vital role in blood pressure regulation and distribution of oxygenated blood during prolonged deep diving. The purpose of this work was to elucidate the histological aspects of these unique vascular modifications and relate them to specific function.

Analysis on vascular risk factors accompanied with high-normal blood pressure among Uygur, Kazak, Mongolian and Han populations in Boertala region of Xinjiang, China.

To study the prevalence and distribution of high-normal blood pressure (BP) and the prevalence rates of risk factors related to cardiovascular diseases (CVD) among Uygur, Kazak, Mongolian and Han populations in Boertala Mongol Autonomous Prefecture of Xinjiang. 4325 Subjects, with numbers of Uygur, Kazak, Mongolian, Han ethnicities as 1247, 1047, 817, 1214 cases, respectively and aged 20 - 79 years, were selected from the cross-sectional study on hypertension in Boertala Mongol Autonomous Prefecture of Xinjiang. The prevalence rates of related risk factors on CVD were analyzed among multiethnic populations with high-normal BP. (1) The prevalence rates of high-normal BP were 39.2%, 34.5%, 36.0%, 36.5% respectively in Uygur, Kazak, Mongolian, Han populations. The prevalence rate of aged < 40 years in Uygur, Kazak, Mongolian was higher than that of aged 40 - 60 (P = 0.000, 0.006, 0.016 respectively in Uygur, Kazak, Mongolian) and > 60 years (all the P = 0.000 in the three ethnic populations) in the same ethnic population. (2) In the high-normal BP groups, subjects with both SBP (120 - 139 mm Hg) and DBP (80 - 89 mm Hg) at high-normal BP level accounted for the majority (> 45%) while subjects with only DBP (80 - 89 mm Hg) at high-normal BP level had the lowest prevalence rate (> 13%). (3) The prevalence rates of overweight-obesity (body mass index >/= 24.0 kg/m(2)), visceral obesity (waist circumference >/= male 85 cm/female 80 cm), dyslipidemia and >/= 1 risk factors of CVD in multiethnic populations respectively were >/= 57%, 62%, 43% and 82%. (4) Analyzed by multiple regression, aging, over-weight and or obesity, being male etc. were risk factors for high-normal BP. High-normal blood pressure was common among aged 20 - 79 years Uygur, Kazak, Mongolian, Han populations, especially among people < 40 years, in Xinjiang Boertala region, which was often accompanied by others risk factors of cardiovascular disease. Prevention and control programs on risk factors for population with high-normal blood pressure need to be strongly advocated.

Body mass index trend and its association with blood pressure distribution in children

The aim of the study was to examine the association of a trend in body mass index (BMI) status with current blood pressure in a cohort of school children from South India. A population of 25,228 children was selected using stratified random sampling method. Height and weight were measured in 2003-2004. Height, weight and blood pressure were measured in 2005-2006. A total of 12,129 children aged 5-16 years having paired data were analysed. Blood pressure and BMI values were converted to Z scores using International paediatric reference values. An increase in Z BMI meant that the child is moving to a higher BMI level with respect to his or her age and sex. In the cohort, 62.4% children had a higher Z BMI at follow-up than at baseline. Children with higher Z BMI at follow-up were labelled as positive BMI status group (PBSG) and the remaining as negative BMI status group (NBSG). The positive trend in BMI was more in rural areas, government schools and girls. In all subgroups, PBSG showed significantly higher systolic blood pressures (SBPs) than NBSG. PBSG showed significantly higher diastolic blood pressures (DBPs) in urban area, government schools and girls when compared with NBSG. Prevalence of first instance systolic hypertension was more in PBSG in all the subgroups except in rural children. Prevalence of diastolic hypertension was significantly higher in PBSG in urban subgroup only. BMI status trends are associated with blood pressure distribution in children.

Different diagnostic criteria significantly affect the rates of hypertension in 18-year-old high school students

IntroductionChildhood hypertension is defined based on the normative distribution of blood pressure (BP), but from the age of 18 years high BP is diagnosed using adult criteria. We compared the rates of diagnosis of hypertension in a group of 18-year-old subjects using BP percentiles and the adult criteria.Material and methodsBlood pressure was measured by registered nurses in 1472 18-year-old high-school students (780 men and 692 women). Also weight, height and waist circumference were recorded.ResultsThe prevalence of hypertension was 9% (16.2% in men and 0.9% in women, p < 0.001) using adult cut-off values and 14.7% (21.9% in men and 6.6% in women, p < 0.001) using percentile charts. Obesity was diagnosed in 2.4% and overweight in 13% of subjects, respectively. The relative risk ratio of diagnosing hypertension according to the adult criteria in overweight or obese subjects was 2.94 (95% CI 2.25-3.86) in men and 6.44 (95% CI 3.51-11.82) in women.ConclusionsOur study indicates high prevalence of hypertension in 18-year-old students – especially in men – and the importance of obesity as a risk factor of hypertension. The use of percentile charts instead of adult cut-off values increases the prevalence of hypertension in men by 35% from 16.2% to 21.9% and in women more than 7 times, i.e. from 0.9% to 6.6%. It seems reasonable to use higher (i.e. 98th) percentile values for definition of high blood pressure.

CARDIAC CONTRACTILITY MEASURES OF LEFT VENTRICULAR SYSTOLIC FUNCTIONAL ASSESSMENT OF NORMAL AND DISEASED HEARTS

Left ventricular (LV) contraction is the basis of LV systolic function, impairment of which underlies heart failure pathophysiology. Its accurate quantification in the form of LV contractility indices is imperative for diagnostic and follow-up assessment of LV systolic function in heart failure. Herein, we analyze LV contractile performance by focusing on LV contractility indices at different physiological organizational levels: from sarcomere dynamics to LV myocardial properties (such as elastic modulus and elastance), and from LV wall contractile stress development to the generation of intra-LV blood flow velocities and pressure distributions. Further, we present the development analyses of these indices and their medical applications. Using improved development of invasive and noninvasive techniques for measuring ventricular pressure, geometry, and volume, we show how these indices have become more amenable for clinical usage to obtain better patient assessment. The purpose of this paper is to present a comprehensive coverage of LV contraction physiology, indices to qualify LV contraction, formulation, and medical applications of some major intrinsic LV contractility indices, so as to provide the basis of functional assessment of normal versus diseased hearts.

A mathematical model for the distribution of hemodynamic parameters in the human retinal microvascular network

To quantitatively assess the arteriovenous distribution of hemodynamic parameters throughout the microvascular network of the human retina, we constructed a retinal microcirculatory model consisting of a dichotomous symmetric branching system. This system is characterized by a diameter exponent of 2.85, instead of 3 as dictated by Murray’s law, except for the capillary networks. The value of 2.85 was the sum of a fractal dimension (1.70) and a branch exponent (1.15) of the retinal vasculature. Following the feeding artery (central retinal artery), each bifurcation was recursively developed at a distance of an individual branch length [L(r) = 7.4r 1.15] by a centrifugal scheme. The venular tree was formed in the same way. Using this model, we evaluated hemodynamic parameters, including blood pressure, blood flow, blood velocity, shear rate, and shear stress, within the retinal microcirculatory network as a function of vessel diameter. The arteriovenous distributions of blood pressure and velocity in the simulation were consistent with in vivo measurements in the human retina and other vascular beds of small animals. We therefore conclude that the current theoretical model was useful for quantifying hemodynamics as a function of vessel diameter within the retinal microvascular network.

Long-Term Stability of Cardiovascular and Catecholamine Responses to Stress Tests

Cardiovascular (CV) hyperreactivity to stress must be reasonably stable if it is considered to be important in the development of hypertension and CV disease. The aim of the present study was to assess long-term stability of blood pressure, heart rate, epinephrine, and norepinephrine responses to a cold pressor test and a mental arithmetic stress test. Eighty-one subjects selected from the first (n=30), 50th (n=30), and 95th to 99th (n=39) percentiles of the mean blood pressure distribution at a military draft procedure were tested on 2 occasions 18 years apart. Stress responses were measured during a cold pressor test (hand immersed in ice water for 1 minute) and during a mental stress test (subtraction for 5 minutes). Intra-arterial blood pressure measurements and arterial catecholamine samples were taken at the initial examination. At follow-up, noninvasive Finapres beat-to-beat blood pressure measurements and venous plasma catecholamine samples were used. The 18-year correlations of the CV and epinephrine absolute responses during mental stress ranged from 0.6 to 0.8. The entry/follow-up correlation of systolic blood pressure during the mental stress test (95% CI: 0.69 to 0.86) was significantly higher than during the cold pressor test (95% CI: 0.30 to 0.65), and responses to mental stress overall appeared to be more stable than responses to the cold pressor test. Our study suggests that CV and sympathoadrenal reactivity, specifically to mental stress, are relatively stable individual characteristics. These results support one of the necessary preconditions to consider hyperreactivity involved in the development of hypertension and CV disease.

Migration and Hypertension: A Cross-Sectional Study Among Neo-Migrants and Settled-Migrants in Delhi, India

Understanding the blood pressure (BP) distribution within populations is fundamental to an understanding of the etiology of cardiovascular diseases and to develop effective preventive strategies. This study focuses on whether the BP levels and hypertension prevalence differ between neo-migrants and settled-migrants in the city of Delhi. Data on BP, anthropometry, social variables, and demographic variables were collected from a cross-sectional sample of 226 settled-migrants and 227 neo-migrants. Men possessed significantly higher BP levels than women. Settled-migrants possessed higher BP levels, except diastolic BP in males. The prevalence of hypertension ranges from 15% (neo-migrant women) to 25% (settled-migrant men), with no significant gender differences. Group differences were significant for men. Hypertension was more prevalent in older settled-migrants and younger neo-migrants. Recent migration was found to be a significant contributor to hypertension prevalence. Age contributed significantly to BP variation in both groups except in neo-migrant men. Pulse rate also contributed to systolic BP among neo-migrant women and settled-migrant men. Thus, urban residence and migration to urban areas can be a leading cause of increased prevalence of hypertension. Neo-migrants were subjected to more lifestyle insults and the stress generated during the adjustment process may be contributing to rise of BP even at younger ages.

Blood pressure distribution in Indian children

To determine blood pressure distribution in schoolchildren and to derive population specific reference values appropriate for age, gender and height status. Cross sectional observational study. Schools in Ernakulam district, Kerala, India, during 2005-06. Stratified random cluster sampling method was used to select the children. Blood pressure and anthropometric data were collected from 20,263 students of 5-16 years age. Three readings of blood pressures of each child were taken by mercury sphygmomanometer and mean was taken for analysis. Blood pressure percentiles in relation to gender, age and height were estimated from a non-overweight population of 18,931 children using polynomial regression models. Children from study population have higher diastolic pressures for both sexes than international standard across all age groups. For systolic blood pressure, girls showed higher values than the international standard while for boys, the difference appears to be minimal. Blood pressure distribution in children from our study population demonstrates a different pattern in comparison to existing international reference. Higher blood pressure values in the study population are of considerable public health significance.

Le réseau micro-vasculaire structure la distribution de la pression sanguine

Cerebral micro-vascular networks control the blood pressure distribution when considering in vitro blood rheology models. Blood rheology is complex and non-linear. In small vessels, the effective viscosity variations are important due to red blood cells packing in capillaries, the so-called Fahraeus-Lindquist effect, whilst concomitantly phase segregation appears in bifurcations. Direct numerical simulations of different non-linear rheological models of the blood are performed on realistic three-dimensional micro-vascular networks. These simulations exhibit two significant results. First, various rheological models lead to very similar pressure distribution over the whole range of physiologically relevant hematocrits. Secondly, different models for phase segregation lead to very distinct hematocrit distributions in the micro-vacular network. Nevertheless, the hematocrit distribution very weakly affects the pressure distribution. Hence, our results suggest that the micro-vacular network structure mainly controls the pressure distribution in micro-circulation, whilst the effect of hematocrit distribution is weak.

Overweight and Obesity in Children Starting School in Augsburg – Prevalence and Influencing Factors: Percentiles May Be Confusing

The authors have studied pediatric overweight—one of the most important current topics in health prevention—and have shown the factors that influence this development very convincingly. The influences of mother tongue, exercise, dietary behavior, and media consumption that were analyzed in the study were particularly interesting. To investigate these influential factors in a cross sectional comparison, the chosen definition of overweight and obesity based on the percentile method is acceptable (above the 90th and 97th age and sex specific percentiles), and differences by national origin become obvious. In a longitudinal study, however, the percentile method may cause confusion. Even if each new starter at school in the study period 2005/6 (theoretically) weighs 10 kg more than their peers in 2003/4, the prevalence of overweight according to the percentile method will not change substantially—in spite of the children’s massive weight gain. The percentile method is problematic for health related risk factors—for example, cardiovascular risk factors. In Germany in persons older than 60 years, the prevalence of hypertension is currently about 60%. On the basis of the threshold value of 140/90 mm Hg, which takes into account cardiovascular risk, arterial hypertension can be assumed above the 40th percentile of blood pressure distribution. For overweight in children, threshold values should be defined as for blood pressure, which takes into account health risk and not statistical distribution. It is possible that for this risk factor, the risk may be present for notably lower percentiles. In any case, the absolute values for body weight or body mass index should be calculated above which the health risk increases.