Search results for "Blood"

Role of causality in the evaluation of coherence and transfer function between heart period and systolic pressure in humans

2004

To elicit the effects of considering causality in the study of the interactions between RR interval and systolic pressure (SP) variability, the traditional noncausal cross-spectral analysis was compared with a causal method able to separate the two arms of the RR-SP regulatory loop. Estimates of coherence (K) and causal coherences from SP to RR (Ksr) and from RR to SP (Krs), and of noncausal (G) and causal (Gsr) baroreflex gain were evaluated at 0.1 Hz in 10 healthy young subjects in the supine position and after head-up tilt. While K was high in both conditions, at rest Ksr was significantly lower than Krs. After tilt, Ksr increased and Krs decreased significantly. With respect to G, Gsr w…

Information domain approach to the investigation of cardio-vascular, cardio-pulmonary, and vasculo-pulmonary causal couplings

2011

The physiological mechanisms related to cardio-vascular (CV), cardio-pulmonary (CP), and vasculo-pulmonary (VP) regulation may be probed through multivariate time series analysis tools. This study applied an information domain approach for the evaluation of non-linear causality to the beat-to-beat variability series of heart period (t), systolic arterial pressure (s), and respiration (r) measured during tilt testing and paced breathing (PB) protocols. The approach quantifies the causal coupling from the series i to the series j (C(ij)) as the amount of information flowing from i to j. A measure of directionality is also obtained as the difference between two reciprocal causal couplings (D(i…

Transmission of arterial oxygen partial pressure oscillations to the cerebral microcirculation in a porcine model of acute lung injury caused by cycl…

2013

Cyclic recruitment and derecruitment (R/D) play a key role in the pathomechanism of acute lung injury (ALI) leading to respiration-dependent oscillations of arterial partial pressure of oxygen (Pa(O(2))). These Pa(O(2)) oscillations could also be forwarded to the cerebral microcirculation.In 12 pigs, partial pressure of oxygen was measured in the thoracic aorta (Pa(O(2))) and subcortical cerebral tissue (Pbr(O(2))). Cerebral cortical haemoglobin oxygen saturation (Sbr(O(2))), cerebral blood flow (CBF), and peripheral haemoglobin saturation (Sp(O(2))) were assessed by spectroscopy and laser Doppler flowmetry. Measurements at different fractions of inspired oxygen (F(I(O(2)))) were performed …

European Society of Hypertension Working Group on Obesity: background, aims and perspectives.

2007

Clinica Medica, University ofMilano-Bicocca, Ospedale San Gerardo, Monza, Milan, ItalyCorrespondence and requests for reprints to Professor Jens Jordan, ChairmanWorking Group on Obesity, Franz Volhard Clinical Research Center, HELIOSKlinikum Berlin and Medical Faculty of the Charite´, Wiltbergstrase 50, 13125Berlin, GermanyTel: +49 30 9417 2220; fax: +49 30 9417 2265; e-mail: jens.jordan@charite.de

Renal artery denervation for treating resistant hypertension: Definition of the disease, patient selection and description of the procedure

2012

Arterial hypertension is responsible for a significant burden of cardiovascular morbidity and mortality, worldwide. Although several rational and integrated pharmacological strategies are available, the control of high blood pressure still remains largely unsatisfactory. Failure to achieve effective blood pressure control in treated hypertensive patients may have a substantial impact on individual global cardiovascular risk, since it significantly increases the risk of developing hypertension-related macrovascular and microvascular complications. Arterial hypertension is arbitrarily defined as 'resistant' or 'refractory' when the recommended blood pressure goals (clinic blood pressure below…

Sympathetic Overactivity and 24-Hour Blood Pressure Pattern in Hypertensives with Chronic Renal Failure

1995

In order to assess the activity of the sympathetic system and to evaluate the 24-h blood pressure pattern in hypertensives with chronic renal failure (CRF), 12 CRF patients and 16 essential hypertensives (EHs) were studied. In all subjects, plasma samples for catecholamines and renin activity were obtained both in the basal condition and after standing, and 24-h blood pressure monitoring (ABPM) was performed. The 24-h mean blood pressure results were quite similar between CRFs and EHs. In 50% of the CRFs, ABPM showed a nighttime decrease in diastolic BP (DBP) greater than 10%, while in the remaining 50% the ABPM indicated a nondipper blood pressure pattern. Of the 16 EHs, 4 had a nighttime …

ESH position paper: renal denervation - an interventional therapy of resistant hypertension

2012

Experts from the European Society of Hypertension prepared this position paper in order to summarize current evidence, unmet needs and practical recommendations on the application of percutaneous transluminal ablation of renal nerves [renal denervation (RDN)] as a novel therapeutic strategy for the treatment of resistant hypertension. The sympathetic nervous activation to the kidney and the sensory afferent signals to the central nervous system represent the targets of RND. Clinical studies have documented that catheter-based RDN decreases both efferent sympathetic and afferent sensory nerve traffic leading to clinically meaningful systolic and diastolic blood pressure (BP) reductions in pa…

Patterns of sympathetic responses induced by different stress tasks.

2008

Stress tasks are used to induce sympathetic nervous system (SNS) arousal. However, the efficacy and the patterns of SNS activation have not been systematically compared between different tasks. Therefore, we analyzed SNS activation during the following stress tasks: Presentation of negative, positive, and – as a control – neutral affective pictures, Color-Word interference test (CWT), mental arithmetic under time limit, singing a song aloud, and giving a spontaneous talk. We examined 11 healthy subjects and recorded the following SNS parameters: Activation of emotional sweating by quantitative sudometry, skin vasoconstriction by laser-Doppler flowmetry, heart rate by ECG, blood pressure by …

The challenge of the volume status assessment in heart failure.

2009

Umbilical artery blood flow velocity waveforms during variable decelerations of the fetal heart rate

1991

Blood flow velocities of the umbilical arteries were measured by Doppler ultrasonography during variable decelerations of the fetal heart rate. The flow velocity waveforms, being normal between uterine contractions, showed either an unchanged flow velocity waveform with an exclusive fetal heart rate effect on end-diastolic velocities or a rapid change to absent and reverse diastolic flow during the decelerations, indicating an abrupt increase in placental resistance with a halt in placental perfusion. Computer-aided reconstruction of the fetal heart rate curve revealed the exact temporal relationship between the reduction of umbilical artery perfusion and deceleration of fetal heart rate. W…