The technique of detecting systolic and diastolic pressure from the transducer output of a PC-based blood pressure monitoring system

A pressure to voltage transducer is used along with a cuff, in a PC-based blood pressure and pulse rate monitoring system for human body. During the blood pressure measurement cycle, the output voltage of the pressure to voltage transducer is recorded digitally using a data acquisition system. The recorded data are then analyzed using software routines to determine the blood pressure and pulse rate of the person under test. However, it is difficult to identify the points of systole and diastole correctly from the recorded data. This paper presents the technique that may be used to determine the systolic and diastolic pressure from the collected data.     

The technique of detecting systolic and diastolic pressure from the transducer output of a PC-based blood pressure monitoring system

A pressure to voltage transducer is used along with a cuff, in a PC-based blood pressure and pulse rate monitoring system for human body. During the blood pressure measurement cycle, the output voltage of the pressure to voltage transducer is recorded digitally using a data acquisition system. The recorded data are then analyzed using software routines to determine the blood pressure and pulse rate of the person under test. However, it is difficult to identify the points of systole and diastole correctly from the recorded data. This paper presents the technique that may be used to determine the systolic and diastolic pressure from the collected data.     

Afterload and blood pressure amplitude in dilated cardiomyopathy]

The beat-to-beat variability of the diastolic blood pressure induces small variations in the afterload of the left ventricle. These variations influence myocardial contractility, and thus blood pressure amplitude. We assessed the interdependence of blood pressure and changes in the afterload. We continuously recorded blood pressure (duration 200 s, at rest) in 20 patients with dilated cardiomyopathy (ejection fraction 32 +/- 13%, left ventricular diameter 67 +/- 8 mm) and in 20 healthy volunteers. Interbeat intervals, diastolic pressures, systolic pressure amplitudes and mean slopes of systolic pressure amplitudes were measured. Correlation coefficients (r) were calculated to assess the interdependence of blood pressure amplitudes/mean systolic slopes and the preceding diastolic pressures/interbeat intervals, respectively. In healthy volunteers we found a strong interdependence between blood pressure amplitude and the preceding diastolic pressures (r = 0.62 +/- 0.21 and 0.47 +/- 0.22). Higher diastolic pressures were followed by higher blood pressure amplitudes, and by steeper slopes of the systolic peaks. In patients with dilated cardiomyopathy, such interdependence was significantly lower (r = 0.33 +/- 22 and r = 0.28 +/- 0.35), and in patients with severely reduced left ventricular function (ejection fraction < 32%) was only marginal (r = 0.23 +/- 0.27 and 0.21 +/- 0.44, respectively). The forces of the isovolumetric contraction necessary to initiate the ejection phase of the left ventricle depend on the afterload, i.e. on the diastolic pressure. The responses of amplitude and slope of the systolic blood pressure to small changes in the afterload make it possible to assess left ventricular contractility. The latter is impaired in dilated cardiomyopathy.     

Relationship between African admixture and blood pressure variation in the Caribbean

The genetic contribution to blood pressure variance is examined by studying a selected group of genes. Of 368 individuals, 48.1% received one-half or more of their genes from an African ancestor and of this group 18.1 and 17.0% exhibit systolic and diastolic hypertension, respectively. A chi-square test was used to examine the dependence of blood pressure on percentage African ancestry. The chi-square values were not significant for systolic or diastolic pressures. It is likely that other factors are strongly related to African admixture and these factors are the true modifiers of blood pressure.     

Pressor reactions to psychological stress and prediction of future blood pressure: data from the Whitehall II Study.

OBJECTIVE--To examine whether reactions of blood pressure to psychological stress predict future blood pressure. DESIGN--Blood pressure was recorded at a medical screening examination after which pressor reactions to a psychological stress task were determined. Follow up measurement of blood pressure was undertaken, on average, 4.9 years later. SETTING--20 civil service departments in London. SUBJECTS--1003 male civil servants aged between 35 and 55 years at entry to the study. MAIN OUTCOME MEASURE--Blood pressure at follow up screening. RESULTS--Reactions of systolic blood pressure to stress correlated positively with systolic blood pressure at follow up screening (r = 0.22, P < 0.01). The dominant correlate of follow up blood pressure was blood pressure at initial screening (r = 0.60; P < 0.01 between initial and follow up systolic blood pressure; r = 0.59, P < 0.01 between initial and follow up diastolic blood pressure). Stepwise multiple regression analysis indicated that reactions to the stressor provided minimal prediction of follow up blood pressure over and above that afforded by blood pressure at initial screening. In the case of follow up systolic blood pressure, systolic reactions to stress accounted for only 1% of follow up variance; systolic blood pressure at initial screening accounted for 34%. With regard to diastolic blood pressure at follow up, the independent contribution from diastolic reactions to stress was less than 1%. CONCLUSION--Pressor reactions to psychological stress provide minimal independent prediction of blood pressure at follow up. Measurement of reactivity is not a useful clinical index of the course of future blood pressure.     

The influence of wine Zweigeltrebe and Breslava Chateau Karvaj on blood pressure in healthy volunteers

Efficacy of varies wine sorts on blood pressure in 21 healthy individuals was prospectively studied. White wine Breslava most significantly decreased systolic blood pressure in comparison to wines from supermarket Veltlin or Frankovka (Blaufr?nkisch, Caberner Franc) (Raca). Decrease in diastolic blood pressure is similar in both white wines Breslava respectively Veltlin. In the second experiment during 8 hours blood pressure measurement, white wine Breslava from Nove Zamky region more significantly decreased systolic blood pressure in comparison to Low Carpathian wines (region Raca). Both white wines significantly decreased diastolic blood pressure. Red wines from both regions did not have significant influence on systolic or diastolic blood pressure in doses of 1, 2 or 3 dcl.     

Criteria for set point estimation in the volume clamp method of blood pressure measurement.

When blood pressure is measured in the finger using the volume clamp method the value at which the vascular volume is clamped is of crucial importance. Since the discovery of the method, several criteria of finding a correct set point have been elaborated: 1. The volume oscillations reach their maximum amplitude at cuff pressure equalling mean blood pressure. 2. The form of the diastolic portion of volume pulsations changes if the cuff pressure moves around the mean blood pressure. 3. The set point can be positioned at one third of the arterial volume. 4. The dynamic vascular compliance (DVC) may be continuously measured as the instantaneous amplitude of vascular volume oscillations is elicited by a relatively small and rapid vibration of the cuff pressure. The shape of the DVC pulse characteristically depends on the transmural pressure (TP): at negative TP (cuff pressure exceeding the blood pressure) it shows a distinct positive systolic peak, at positive TP the polarity of the DVC pulse is reversed. In contrast to the first three ways to find the set point, the last one may operate even in closed-loop performance, i.e. during the blood pressure measurement.     

New methodology for measuring blood pressure in awake baboons with use of behavioral training techniques

Adult male baboons were behaviorally conditioned to extend an arm outside of the living cage and to accept repeated cuff inflations for manual auscultatory blood pressure measurements. Frequency distributions of systolic and diastolic blood pressure for both normotensive and renovascular hypertensive baboons generally were normally distributed. The procedure accurately tracked rapid changes in blood pressure after oral administration of antihypertensive drugs. Advantages over direct arterial cannulation for blood pressure measurement during extended, chronic experiments are discussed.     

Accuracy of mean arterial pressure and blood pressure measurements in predicting pre-eclampsia: systematic review and meta-analysis

Objective To determine the accuracy of using systolic and diastolic blood pressure, mean arterial pressure, and increase of blood pressure to predict pre-eclampsia.Design Systematic review with meta-analysis of data on test accuracy.Data sources Medline, Embase, Cochrane Library, Medion, checking reference lists of included articles and reviews, contact with authors.Review methods Without language restrictions, two reviewers independently selected the articles in which the accuracy of blood pressure measurement during pregnancy was evaluated to predict pre-eclampsia. Data were extracted on study characteristics, quality, and results to construct 2×2 tables. Summary receiver operating characteristic curves and likelihood ratios were generated for the various levels and their thresholds.Results 34 studies, testing 60 599 women (3341 cases of pre-eclampsia), were included. In women at low risk for pre-eclampsia, the areas under the summary receiver operating characteristic curves for blood pressure measurement in the second trimester were 0.68 (95% confidence interval 0.64 to 0.72) for systolic blood pressure, 0.66 (0.59 to 0.72) for diastolic blood pressure, and 0.76 (0.70 to 0.82) for mean arterial pressure. Findings for the first trimester showed a similar pattern. Second trimester mean arterial pressure of 90 mm Hg or more showed a positive likelihood ratio of 3.5 (95% confidence interval 2.0 to 5.0) and a negative likelihood ratio of 0.46 (0.16 to 0.75). In women deemed to be at high risk, a diastolic blood pressure of 75 mm Hg or more at 13 to 20 weeks’ gestation best predicted pre-eclampsia: positive likelihood ratio 2.8 (1.8 to 3.6), negative likelihood ratio 0.39 (0.18 to 0.71). Additional subgroup analyses did not show improved predictive accuracy.Conclusion When blood pressure is measured in the first or second trimester of pregnancy, the mean arterial pressure is a better predictor for pre-eclampsia than systolic blood pressure, diastolic blood pressure, or an increase of blood pressure.     

Biofeedback of R-wave-to-pulse interval normalizes blood pressure

We investigated whether biofeedback of the R-wave-to-pulse interval, a measure related to the pulse wave velocity, enables participants with either high or low arterial blood pressure to modify their blood pressure. Twelve participants with high blood pressure (mean systolic blood pressure = 142.6 ± 13.5 mmHg; mean diastolic blood pressure = 99.9 ± 12.3 mmHg) and 10 participants with low blood pressure (mean systolic blood pressure = 104.8 ± 6.6 mmHg; mean diastolic blood pressure = 73.2 ± 4.2 mmHg) received 3 individual sessions of RPI biofeedback within a 2-week period. Participants with high blood pressure were rewarded for decreasing and participants with low blood pressure for increasing their blood pressure. Standard arm-cuff blood pressure measurements across the sessions served as dependent variables. Participants with high blood pressure achieved significant reductions of systolic (15.3 mmHg) and diastolic (17.8 mmHg) blood pressure levels from the beginning of the first to the end of the last training session. In contrast, participants with low blood pressure achieved significant increases in systolic (12.3 mmHg) and diastolic (8.4 mmHg) blood pressure levels. The degree of blood pressure changes in this study might be of clinical relevance. With prolonged and refined training regimens, even larger effects seem to be likely.     

Modelling adolescent blood pressure patterns and their prediction of adult pressures.

Tracking of blood pressure in adolescent boys is investigated using a mathematical model that corresponds to progression along a constant percentile. A more general analysis, based on the method of principal components, is also proposed that determines various alternative tracks or patterns that are most prevalent in the longitudinal blood pressure data. The degree of tracking along a constant percentile curve for systolic pressure was moderately high, as evidenced by a tracking index of .78 explaining 81% of the variance, but less strong for diastolic (tracking index of .60) where tracking along a percentile explained 66% of the variance. The value of the more general analysis of blood pressure patterns may lie in the assessment of adolescent risk factors for elevated adult blood pressure. Using adolescent patterns determined by either statistical model, adult systolic at age 38 was predicted (R2 = .22) by the concept of a systolic fixed percentile curve in adolescence, and similarly for diastolic (R2 = .21). However, the more general analysis based on longitudinal principal components further suggests that boys who have a larger than usual systolic peak at age 14 years, which is near the time of the adolescent physical growth spurt in these boys, may be more likely to have higher systolic pressures at age 38. Because the adult data were incomplete and highly unbalanced, these findings were obtained using random-effects models for longitudinal data.     

Relation between mortality and treated blood pressure in elderly patients with hypertension: report of the European Working Party on High Blood Pressure in the Elderly.

OBJECTIVE--To investigate the relation between mortality and treated systolic and diastolic blood pressures. DESIGN--Randomised double blind placebo controlled trial. Mortality in the two treatment groups was examined in thirds of treated systolic and diastolic blood pressures. PATIENTS--339 And 352 patients allocated to placebo and active treatment, respectively. The groups were similar at randomisation in sex ratio (70% women), mean age (71.5 years), blood pressure (182/101 mm Hg), and proportion of patients with cardiovascular complications (35%). MEASUREMENTS AND MAIN RESULTS--In the placebo group total mortality rose with increasing systolic pressure whereas it had a U shaped relation with diastolic pressure, the total lowest mortality being in patients in the middle third of the distribution of diastolic pressure. In the group given active treatment total mortality showed a U shaped relation with systolic pressure and an inverse association with treated diastolic pressure. In both groups cardiovascular and non-cardiovascular mortality followed the same trends as total mortality. The increased mortality in the lowest thirds of pressure was not associated with an increased proportion of patients with cardiovascular complications at randomisation or with a fall in diastolic pressure exceeding the median fall in pressure in each group. In contrast, patients in the lowest thirds of pressure showed greater decreases in body weight and haemoglobin concentration than those in the middle and upper thirds of pressure. CONCLUSIONS--In patients taking active treatment total mortality was increased in the lowest thirds of treated systolic and diastolic blood pressures. This increased mortality is not necessarily explained by an exaggerated reduction in pressure induced by drugs as for diastolic pressure a U shaped relation also existed during treatment with placebo. In addition, patients in the lowest thirds of systolic and diastolic pressures were characterised by decreases in body weight and haemoglobin concentration, and the patients in the lowest thirds of diastolic pressure taking active treatment also by an increased non-cardiovascular mortality, suggesting some deterioration of general health.     

Blood pressure responsiveness to sympathetic agonists in anaesthetised diabetic rats

Chronic diabetes alters sympathetic modulation of the cardiovascular system. In the present work, we examined if the cardiovascular system also demonstrates an impaired responsiveness to sympathetic control. The effects of streptozotocin-induced diabetes on pressure responses to noradrenaline or isoproterenol infusion of diabetic rats in vivo are studied. Systolic and diastolic pressures were recorded through a cannula implanted in the right carotid artery. Increasing doses of noradrenaline or isoproterenol were infused through a catheter implanted in the left jugular vein. The dose-response curves for the effects of noradrenaline on blood pressure were altered in streptozotozin-induced diabetic rats. Noradrenaline induced a statistically significant higher increase of both systolic and diastolic pressure in control than in diabetic rats. The maximum depressor response of systolic pressure to isoproterenol was lower in diabetic than in control animals. Diabetes fully abolishes the effect of beta-adrenoceptor stimulation on diastolic blood pressure. The present results demonstrate that streptozotocin-induced diabetes reduces systolic and diastolic arterial pressure, and diminishes the arterial pressure reactivity to sympathetic stimulation.     

Relation of low diastolic blood pressure to coronary heart disease death in presence of myocardial infarction: the Framingham Study.

OBJECTIVE--To examine the hypothesis that a J curve relation between blood pressure and death from coronary heart disease is confined to high risk subjects with myocardial infarction. DESIGN--Cohort longitudinal epidemiological study with biennial examinations since 1950. SETTING--Framingham, Massachusetts, USA. SUBJECTS--5209 subjects in the Framingham study cohort followed up by a person examination approach. MAIN OUTCOME MEASURES--Coronary heart disease deaths and non-cardiovascular disease deaths in men and women with or without myocardial infarction relative to blood pressure. RESULTS--Among subjects without myocardial infarction non-cardiovascular disease deaths were twice to three times as common as coronary heart disease deaths. Furthermore, there was no significant relation between non-cardiovascular disease death and diastolic or systolic blood pressure. Also coronary heart disease deaths were linearly related to diastolic and systolic blood pressures. Among high risk patients (that is, people with myocardial infarction but free of congestive heart failure) death from coronary heart disease was more common than non-cardiovascular disease death. There was a significant U shaped relation between coronary heart disease death and diastolic blood pressure. Although there was an apparent U shaped relation between coronary heart disease death and systolic blood pressure, it did not attain statistical significance when controlling for age and change in systolic blood pressure from the pre-myocardial infarction level. None of the above conclusions changed when adjustments were made for risk factors such as serum cholesterol concentration, antihypertensive treatment, and left ventricular function. The U shaped relation between diastolic blood pressure and high risk subjects existed for both those given antihypertensive treatment and those not. CONCLUSIONS--These data suggest that an age and sex independent U curve relation exists for diastolic blood pressure and coronary heart disease deaths in patients with myocardial infarction but not for low risk subjects without myocardial infarction. The relation seems to be independent of left ventricular function and antihypertensive treatment.     

Path analysis of familial resemblance in blood pressure in Middle Dalmatia,Croatia

The familial resemblance in blood pressure in Middle Dalmatia, Croatia, has been analyzed using the Path-analytic approach. The sample consisted of 1,126 examinees (526 males and 600 females, aged 17 to 87), inhabitants of the Middle Dalmatia's islands of Brac, Hvar, Korcula and the Peljesac peninsula. The Path analysis was performed with the assumption that each family member (father, mother, offspring 1 and 2) has a latent variable (C) that influences both the blood pressure values (P) and the morphological dimensions significantly correlated with blood pressure (Q). According to the estimates revealed from the most parsimonious models, the diastolic blood pressure has a more pronounced genetic component (h2 = 30-32%) than the systolic blood pressure (h2 = 15%). In contrast to the low intergenerational influences, the members of the same generation showed pronounced effects of shared environment. Common (non-transmitted) offsprings' environment (B) explains 44% of variance of the individual offspring's environment (C) in systolic and 33-35% in diastolic blood pressure. The correlation of father's and mother's environment (u2) was high in the case of diastolic blood pressure (33-44%) but for the systolic blood pressure it was not significantly different from zero. According to the presented results in insular/peninsular population of Middle Dalmatia, family resemblance of systolic and diastolic blood pressure differs. The resemblance is higher in diastolic blood pressure with stronger additive genetic component and stronger environmental and/or genetic component related with morphology. The sources of high heritability of diastolic blood pressure in Middle Dalmatia as well as the sources of high prevalence of hypertension in the same population are the phenomena that might be connected and thus deserve to be further explored in incoming analyses.     

Maintenance of relaxation-induced blood pressure reductions: the importance of continued relaxation practice

This study examined the long-term importance of continued relaxation practice in the maintenance of relaxation-induced blood pressure reductions. An ABAB withdrawal-reinstatement design was employed with two hypertensive subjects. An objective, unobtrusive measure of home relaxation practice was used to monitor compliance. Subject 1 showed substantial reductions in systolic and diastolic blood pressure during 3 months of relaxation practice, followed by a 60% return to baseline during withdrawal, and a subsequent decrease with reinstatement of relaxation. Subject 2 showed a pattern similar to that of Subject 1 for systolic blood pressure, though the trend for diastolic pressure was unclear owing to a marginal treatment response. These preliminary data suggest that continued relaxation practice may be an important factor in the maintenance of relaxation-induced blood pressure reductions.     

Regional vascular influences on tail-cuff measurements of drug-induced changes in systolic pressure.

When drug effects are quantified using the tail-cuff method, changes in systemic arterial pressure are extrapolated from those occurring in the caudal artery. The validity of this extrapolation was tested in anesthetized rats by recording drug-induced changes in phasic arterial pressure simultaneously from catheters inserted into the lower abdominal aorta, carotid, and caudal arteries. Pressor responses to norepinephrine or angiotensin were of equal magnitude at all three sites, but phentolamine reduced systolic pressure in the aorta or caudal artery more than that in the carotid artery. Unlike previous discrepancies between carotid and tail-cuff systolic pressures, aortic hypotension caused by injections of phentolamine or pentolinium in awake normotensive or spontaneously hypertensive rats was accurately predicted by the tail-cuff method. Because drug-induced changes in diastolic pressure always varied much less than those in systolic pressure, should indirect measurement of diastolic pressure become technically feasible, it might be preferable for assessing drug effects on blood pressure.     

Blood pressure and five year survival in the very old

During 1977-8 we measured blood pressure in 561 old people (83% of those aged 85 or more living in Tampere) and analysed their five year survival according to their blood pressure group. The subjects were divided into six groups on the basis of their blood pressures (from <120 to >200 mm Hg systolic, from <70 to >110 diastolic). The greatest mortality was observed in those in the lowest systolic and lowest diastolic groups. Mortality was least in subjects with systolic pressures of 160 mm Hg or more and diastolic pressures of 90 mm Hg or more.The most essential finding in this series of the very old was an increased mortality in the lowest blood pressure groups.     

Segregation analysis of systolic and diastolic blood pressure in Middle Dalmatia Island population

A complex segregation analysis of systolic and diastolic blood pressure has been performed on pedigree data from rural populations inhabiting Middle Dalmatian islands of Brac, Hvar and Korcula and the Peljesac peninsula. The purpose of the performed analysis was to possibly elucidate a signal of a large-effect gene responsible for high prevalence of hypertension present in this population (the age-adjusted prevalence of developed hypertension being 31.82% in males and 28.23% in females). The analysis was performed on a sample of 389 two- and three-generation families consisting of 2 to 19 observed individuals (1126 examinees in total, 526 males and 600 females, aged 17 to 83). Since the examinees were randomly selected from census data encompassing 22.6% of the total population--the family relations having been established afterwards--the selected sample can be considered representative for the examined populations. By applying the usual transmission probability tests, the major gene model has been accepted for systolic as well as for diastolic blood pressure. The most parsimonious models showed that: (a) inheritance of blood pressure in the Middle Dalmatia population can be attributed to the effect of a major gene responsible for 34% (systolic) and 36% (diastolic) blood pressure variation; (b) alleles of that major gene act in co-dominant fashion; (c) allele frequency for high blood pressure (A2) is 18% (systolic) and 15% (diastolic blood pressure); and (d) the residual (non-major gene) familial correlation is negligible and can be constrained to zero. Since the results are also indicating heterogeneity within the sample in the genetic determination of the systolic blood pressure, the obtained results thus justify further search for the most promising subpopulation for incoming genetic epidemiological investigations of hypertension.     

Non-invasive model-based estimation of aortic pulse pressure using suprasystolic brachial pressure waveforms

Elevated central arterial (aortic) blood pressure is related to increased risk of cardiovascular disease. Methods of non-invasively estimating this pressure would therefore be helpful in clinical practice. To achieve this goal, a physics-based model is derived to correlate the arterial pressure under a suprasystolic upper-arm cuff to the aortic pressure. The model assumptions are particularly applicable to the measurement method and result in a time–domain relation with two parameters, namely, the wave propagation transit time and the reflection coefficient at the cuff. Central pressures estimated by the model were derived from completely automatic, non-invasive measurement of brachial blood pressure and suprasystolic waveform and were compared to simultaneous invasive catheter measurements in 16 subjects. Systolic blood pressure agreement, mean (standard deviation) of difference was ?1 (7) mm Hg. Diastolic blood pressure agreement was 4 (4) mm Hg. Correlation between estimated and actual central waveforms was greater than 90%. Individualization of model parameters did not significantly improve systolic and diastolic pressure agreement, but increased waveform correlation. Further research is necessary to confirm that more accurate brachial pressure measurement improves central pressure estimation.