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Invasive Measurements (invasive + measurement)

Distribution by Scientific Domains

Medical Sciences	66%
Life Sciences	33%

Selected Abstracts

Systematic review: endoscopic and imaging-based techniques in the assessment of portal haemodynamics and the risk of variceal bleeding

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 10 2009
S. N. SGOUROS
Summary Background, Invasive measurement of the hepatic venous pressure gradient (HVPG) is regarded as the gold standard for risk stratification and the evaluation of pharmaceutical agents in patients with portal hypertension. Aim, To review the techniques for endoscopic and imaging-based assessment of portal haemodynamics, with particular emphasis on trials where the results were compared with HVPG or direct portal pressure measurement. Methods, Systematic search of the MEDLINE electronic database with keywords: portal hypertension, variceal bleeding, variceal pressure, endoscopic ultrasound, Doppler ultrasonography, magnetic resonance angiography, CT angiography, hepatic venous pressure gradient. Results, Computed tomography angiography and endoscopic ultrasound (EUS) have been both employed for the diagnosis of complications of portal hypertension and for the evaluation of the efficacy of endoscopic therapy. Colour Doppler ultrasonography and magnetic resonance angiography has given discrepant results. Endoscopic variceal pressure measurements either alone or combined with simultaneous EUS, correlate well with HVPG and risk of variceal bleeding and have a low interobserver variability. Conclusions, Endoscopic and imaging-based measurements of portal haemodynamics provide an alternate means for the assessment of complications of portal hypertension. Further studies are required to validate their use in risk stratification and the evaluation of drug therapies in patients with portal hypertension. [source]

In situ effective diffusion coefficient profiles in live biofilms using pulsed-field gradient nuclear magnetic resonance

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2010
Ryan S. Renslow
Abstract Diffusive mass transfer in biofilms is characterized by the effective diffusion coefficient. It is well documented that the effective diffusion coefficient can vary by location in a biofilm. The current literature is dominated by effective diffusion coefficient measurements for distinct cell clusters and stratified biofilms showing this spatial variation. Regardless of whether distinct cell clusters or surface-averaging methods are used, position-dependent measurements of the effective diffusion coefficient are currently: (1) invasive to the biofilm, (2) performed under unnatural conditions, (3) lethal to cells, and/or (4) spatially restricted to only certain regions of the biofilm. Invasive measurements can lead to inaccurate results and prohibit further (time-dependent) measurements which are important for the mathematical modeling of biofilms. In this study our goals were to: (1) measure the effective diffusion coefficient for water in live biofilms, (2) monitor how the effective diffusion coefficient changes over time under growth conditions, and (3) correlate the effective diffusion coefficient with depth in the biofilm. We measured in situ two-dimensional effective diffusion coefficient maps within Shewanella oneidensis MR-1 biofilms using pulsed-field gradient nuclear magnetic resonance methods, and used them to calculate surface-averaged relative effective diffusion coefficient (Drs) profiles. We found that (1) Drs decreased from the top of the biofilm to the bottom, (2) Drs profiles differed for biofilms of different ages, (3) Drs profiles changed over time and generally decreased with time, (4) all the biofilms showed very similar Drs profiles near the top of the biofilm, and (5) the Drs profile near the bottom of the biofilm was different for each biofilm. Practically, our results demonstrate that advanced biofilm models should use a variable effective diffusivity which changes with time and location in the biofilm. Biotechnol. Bioeng. 2010;106: 928,937. © 2010 Wiley Periodicals, Inc. [source]

Non-invasive measurement of cardiac output by Finometer in patients with cirrhosis

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2010
N. Kaltoft
Summary The Finometer measures haemodynamic parameters including cardiac output (CO) using non-invasive volume-clamp techniques. The aim of this study was to determine the accuracy of the Finometer in hyperdynamic cirrhotic patients using an invasive indicator dilution technique as control. CO was measured in twenty-three patients referred for invasive measurements of the hepatic venous pressure gradient on suspicion of cirrhosis. Invasive measurements of CO were performed using indicator dilution technique (COI) and simultaneous measurements of CO were recorded with the Finometer (COF). In six patients, measurements of CO were performed with invasive technique and the Finometer both before and after ,-blockade using 80 mg of propranolol and the changes in CO (,COI and ,COF respectively) were calculated to evaluate the Finometers ability to detect relative changes in CO. Mean COI was 6·1 ± 1·6 [3·9;9·7] l min,1 (mean ± SD [range]) compared to mean COF of 7·2 ± 2·3 [3·1;11·9] l min,1. There was a mean difference between COF and COI of 1·0 ± 1·8 [,2·1;4·0] l min,1 and 95% confidence interval of [0·2;1·8], P<0·001. In patients with measurements before and after ,-blockade, mean ,COI was 1·6 ± 1·4 [,0·1;3·3] l min,1 compared to mean ,COF of 1·9 ± 1·3 [0·4;3·8] l min,1. Mean difference between ,COF and ,COI was 0·3 ± 0·3 [,0·2;0·7] l min,1 with a 95% confidence interval of [,0·1;0·6], P = 0·11. Compared with invasive measurements, the Finometer can be used to measure changes in CO, whereas absolute measurements are associated with higher variation in patients with cirrhosis. The Finometer seems useful for repeated determinations such as in studies of effect of pharmacotherapy. [source]

The Use of B-Type Natriuretic Peptides in the Intensive Care Unit

CONGESTIVE HEART FAILURE, Issue 2008
Christian Mueller MD
B-type natriuretic peptide levels are quantitative markers of cardiac stress and heart failure that summarize the extent of systolic and diastolic left ventricular dysfunction, valvular dysfunction, and right ventricular dysfunction. Initial observational pilot studies have addressed 7 potential indications in the intensive care unit: identification of cardiac dysfunction, diagnosis of hypoxic respiratory failure, risk stratification in severe sepsis and septic shock, evaluation of patients with shock, estimation of invasive measurements, weaning from mechanical ventilation, as well as perioperative and postoperative risk prediction. Although additional studies are required to better define the clinical utility of B-type natriuretic peptide values in the intensive care unit, current data suggest that the diagnosis of hypoxic respiratory failure and timing of extubation seem to be the most promising indications. Congest Heart Fail. 2008;14(4 suppl 1):43,45. ©2008 Le Jacq [source]

Aging in inbred strains of mice: study design and interim report on median lifespans and circulating IGF1 levels

AGING CELL, Issue 3 2009
Rong Yuan
Summary To better characterize aging in mice, the Jackson Aging Center carried out a lifespan study of 31 genetically-diverse inbred mouse strains housed in a specific pathogen-free facility. Clinical assessments were carried out every 6 months, measuring multiple age-related phenotypes including neuromuscular, kidney and heart function, body composition, bone density, hematology, hormonal levels, and immune system parameters. In a concurrent cross-sectional study of the same 31 strains at 6, 12, and 20 months, more invasive measurements were carried out followed by necropsy to assess apoptosis, DNA repair, chromosome fragility, and histopathology. In this report, which is the initial paper of a series, the study design, median lifespans, and circulating insulin-like growth factor 1 (IGF1) levels at 6, 12, and 18 months are described for the first cohort of 32 females and 32 males of each strain. Survival curves varied dramatically among strains with the median lifespans ranging from 251 to 964 days. Plasma IGF1 levels, which also varied considerably at each time point, showed an inverse correlation with a median lifespan at 6 months (R = ,0.33, P = 0.01). This correlation became stronger if the short-lived strains with a median lifespan < 600 days were removed from the analysis (R = ,0.53, P < 0.01). These results support the hypothesis that the IGF1 pathway plays a key role in regulating longevity in mice and indicates that common genetic mechanisms may exist for regulating IGF1 levels and lifespan. [source]