Reference Blood Pressure Research Articles

Non-invasive monitoring of central blood pressure by electrical impedance tomography: first experimental evidence

There is a strong clinical demand for devices allowing continuous non-invasive monitoring of central blood pressure (BP). In the state of the art a new family of techniques providing BP surrogates based on the measurement of the so-called pulse wave velocity (PWV) has been proposed, eliminating the need for inflation cuffs. PWV is defined as the velocity at which pressure pulses propagate along the arterial wall. However, no technique to assess PWV within central arteries in a fully unsupervised manner has been proposed so far. In this pilot study, we provide first experimental evidence that electrical impedance tomography (EIT) is capable of measuring pressure pulses directly within the descending aorta. To obtain a wide range of BP values, we administrated noradrenalin and nitroglycerine to an anesthetized pig under mechanical ventilation. An arterial line was inserted into the ascending aorta for measuring reference BP. EIT images were generated from 32 impedance electrodes placed around the chest at the level of the axilla. Regions of Interest (ROI) such as the descending aorta and the lungs were automatically identified by a novel time-based processing algorithm as the respective EIT pixels representing these structures. The correct positions of these ROIs were confirmed by bolus injections of highly conductive concentrated saline into the right heart and into the ascending aorta. Aortic pulse transit time (PTT) values were determined as the delay between the opening of the aortic valve (obtained from arterial line) and the arrival of pressure pulses at the aortic ROI within the EIT plane. For 11 experimental conditions, with mean BP ranging from 73 to 141 mmHg, strongly significant correlation (r = -0.97, P < 0.00001) between central BP and aortic PTT was observed, suggesting that EIT-derived aortic PTT is a potential non-invasive surrogate of central BP.

Ultrafiltration intensification for achievement of dry weight and hypertension control is not always the therapeutic gold standard

Extracellular volume excess is an important factor in the pathogenesis of arterial hypertension, and control of volume status by ultrafiltration and achievement of dry weight is considered as an essential therapeutical approach. In the present issue of the Journal of Nephrology, Curatola and coworkers present challenging data indicating that ultrafiltration intensification improves hypertension control but increases the risks for cardiovascular events, with peripheral arteriopathy as the principal complication. This is another challenge for determination of dry weight on the basis of blood pressure (BP) measurement. The reference BP is brachial blood pressure. Brachial blood pressure is lower than limb BP. In normal conditions, lower-limb BP (ankle blood pressure) is higher than brachial BP, and the so-called ankle-brachial systolic pressure index is between 0.9 and 1.3. An ankle-brachial index <0.90 indicates the presence of lower-limb arteriopathy, and it should be measured systematically in end-stage renal disease (ESRD) patients because a large proportion of these patients present asymptomatic peripheral arteriopathies. In these conditions, taking into account brachial BP to determine dry weight and BP control can lead to a decline in the perfusion pressure of the lower limbs, with dramatic clinical consequences. The study by Curatola et al (J Nephrol, 2011, present issue) illustrates that the therapeutic approach to cardiovascular risk and hypertension in ESRD patients is still challenging. It underlines the necessity of considering the pathophysiology and mechanisms associated with cardiovascular risk, instead of systematically applying a generally accepted "gold standard" approach.

Effects of Casein Hydrolysate on the Systolic Blood Pressure and Serum Lipid Profiles in Spontaneously Hypertensive Rats

The effects of casein hydrolysate on blood pressure (BP) and serum lipid profiles were investigated in spontaneouslyhypertensive rats (SHR). Twenty-four 6-wk old male SHRs were assigned to 3 groups in a completely randomized design.Experimental groups were as follow: control, market milk group (MLG) and casein hydrolysate group (CHG). Referenceblood pressure (RBP) showed average 198.94±1.46 mmHg. Blood pressure (BP) of CHG reduced 24 mmHg after 2 wk oftreatment, but these increased after 3 wk. BP of CHG was significantly lower than BP of Control in experimental time(p<0.05). Serum lipid profiles were not differ significantly among groups ( p<0.05). These data suggest that casein hydroly-sate may beneficially improvement of blood pressure level in SHR.Key words: casein hydrolysate, blood pressure, serum lipid, spontaneously hypertensive rat

Cuff width alters the amplitude envelope of wrist cuff pressure pulse waveforms

The accuracy of noninvasive blood pressure (BP) measurement with any method is affected by cuff width. Measurement with a too narrow cuff overestimates BP and measurement with a too wide cuff underestimates BP. Automatic wrist cuff BP monitors use permanently attached narrow cuffs with bladders about 6 cm wide. Such narrow cuffs should result in under-cuffing for wrist circumferences larger than 15 cm. The objective of this qualitative study was to show that a narrow wrist cuff results in increased BP values when a cuff pulse amplitude ratio algorithm is used. According to the algorithm used in this study, systolic pressure (SBP) corresponds to the point of 50% of maximal amplitude; for diastolic pressure (DBP) the ratio is 70%. Data were acquired from 12 volunteers in the sitting position. The mean wrist circumference was 18 cm. The acquired cuff pulse data were used to compute SBP, mean pressure (MAP) and DBP. The mean values for a 6 cm cuff were SBP = 144 mmHg, MAP = 104 mmHg and DBP = 88 mmHg. The values for a 10 cm cuff were SBP = 128 mmHg, MAP = 93 mmHg and DBP = 78 mmHg. The reference BP values were SBP = 132 mmHg, MAP = 96 mmHg and DBP = 80 mmHg. All narrow (6 cm) cuff BP values were higher than wide (10 cm) cuff or reference BP values. The results indicate that wider wrist cuffs may be desirable for more accurate and reliable BP measurement with wrist monitors.

Non-constrained monitoring of systolic blood pressure on a weighing scale

In this study, we developed a novel technique for estimating non-constrained and cuffless blood pressure (BP) that was based on electrocardiogram (ECG) and ballistocardiogram (BCG). The BCG was non-invasively measured using a common electronic weighing scale when a subject was standing on it. The ECG was measured using three different methods: on the chest using Ag/AgCl electrodes, on the hands using dry electrodes and on the feet also using dry electrodes. For a BP correlated parameter, a time interval parameter, which was defined as the time difference between the ECG R-peak and BCG J-peak, was employed for evaluating and estimating beat-to-beat BP. Under a BP varying experiment with a Valsalva manoeuvre, the R–J intervals were extracted at every beat cycle and a systolic blood pressure (SBP) estimation equation was established using linear regression analysis for each subject. In the case of feet delivered ECG (F-ECG), an ensemble average technique synchronized at the BCG J-peak point was applied to extract the ECG signal from the feet. The performance of the proposed method was evaluated using Finapres, a non-invasive blood pressure measurement system, as a reference BP signal, and a scatter plot was used to find the regression line between the reference values and estimated BPs. A moving-window averaging technique was applied to remove the high-frequency noise in the R–J intervals and was applied to enhance the accuracy of the SBP estimation. For all individuals, the estimated SBP was similar to the measured SBP with a reliable correlation, which makes the proposed method suitable for use in a home healthcare system to monitor blood pressure on a weighing scale at the same time as measuring weight.

Out-of-office blood pressure measurement in children and adolescents

Out-of-office blood pressure measurement in children and adolescents

Discrepancies in office and ambulatory blood pressure in adolescents: help or hindrance?

The goal of this commentary is to review the most relevant topics concerning the clinical utility of ambulatory blood pressure (BP) monitoring, such as the state of the art "reference BP values", the importance of the discrepant situations between office and ambulatory BP (white-coat and masked hypertension) and those of the recommended clinical indications to now. From a small number of studies, operational thresholds to define hypertension have been established. They are useful tools even though more studies are necessary to create strong reference values. Ambulatory BP measurement is increasingly recognized as being indispensable to the diagnosis and management of hypertension, and it has contributed significantly to our understanding of hypertension by revealing or "unmasking" BP phenomena that were not readily apparent using traditional techniques of measurement in clinical practice. Ambulatory BP monitoring should be performed in adolescents with either office mild essential hypertension before starting antihypertensive drug treatment or a strong family history of hypertension or an early cardiovascular event. Obese children with normal office BP values will also benefit from ambulatory BP monitoring. Other indications are the assessment of refractory hypertension or drug-induced hypotension. Finally, additional BP information in chronic renal failure, diabetes, and autonomic neuropathy can be obtained by using ambulatory BP monitoring.

Development of hypertension over 6 years in a birth cohort of young middle-aged men: the Cardiovascular Risk Factor Study in southern Sweden (CRISS).

To explore the development of hypertension (HT) in a cohort of young middle-aged men. Prospective birth-cohort study of men surveyed over 6 years. Helsingborg County Hospital, Sweden, 1990-97. A total of 628 men born in 1953-54, all surveyed at 37, 40 and 43 years of age. Systolic blood pressure (SBP), diastolic blood pressure (DBP), S-cholesterol, body mass index (BMI), alcohol consumption, ethnicity. HT was defined as SBP > or = 140 mmHg and/or DBP > or = 90 mmHg, or ongoing treatment. Using SBP < 130 mmHg and DBP < 85 mmHg as reference, the odds of conversion to HT in men with high normal blood pressure (BP) (SBP 130-139 mmHg and DBP 85-89 mmHg) was investigated. At age 37, 243 men (39%) had reference BP, 167 (26%) had high normal BP and 218 (35%) were hypertensive. Corresponding numbers at age 40 were 265 (42%), 166 (27%) and 197 (31%); and at age 43, 180 (29%), 142 (22%) and 306 (49%), respectively. High normal BP at baseline was associated with the development of HT both at age 40 (odds ratio (OR)=2.45 confidence interval (CI): 1.42-4.22) and at age 43 (OR=2.46, CI: 1.59-3.80), independent of other cardiovascular disease risk factors and ethnicity. The progression to HT was predicted also by S-cholesterol, alcohol consumption, BMI and weight gain. Over a short-term period, a substantial proportion of young middle-aged men with high normal BP develop HT with overweight and alcohol consumption as important determinants. These findings have implications for the prevention, screening and medical care of HT in this target population.