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Fick principle

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https://www.readbyqxmd.com/read/28587512/accuracy-of-predicted-haemoglobin-concentration-on-cardiopulmonary-bypass-in-paediatric-cardiac-surgery-effect-of-different-formulae-for-estimating-patient-blood-volume
#1
Matthias Redlin, Wolfgang Boettcher, Frank Dehmel, Mi-Young Cho, Marian Kukucka, Helmut Habazettl
INTRODUCTION: When applying a blood-conserving approach in paediatric cardiac surgery with the aim of reducing the transfusion of homologous blood products, the decision to use blood or blood-free priming of the cardiopulmonary bypass (CPB) circuit is often based on the predicted haemoglobin concentration (Hb) as derived from the pre-CPB Hb, the prime volume and the estimated blood volume. We assessed the accuracy of this approach and whether it may be improved by using more sophisticated methods of estimating the blood volume...
June 1, 2017: Perfusion
https://www.readbyqxmd.com/read/28570147/estimating-arterial-partial-pressure-of-carbon-dioxide-in-ventilated-patients-how-valid-are-surrogate-measures
#2
Boulos S Nassar, Gregory A Schmidt
The arterial partial pressure of carbon dioxide (PaCO2) is an important parameter in critically ill, mechanically ventilated patients. To limit invasive procedures or for more continuous monitoring of PaCO2, clinicians often rely on venous blood gases, capnography, or transcutaneous monitoring. Each of these has advantages and limitations. Central venous Pco2 allows accurate estimation of PaCO2, differing from it by an amount described by the Fick principle. As long as cardiac output is relatively normal, central venous Pco2 exceeds the arterial value by approximately 4 mm Hg...
June 2017: Annals of the American Thoracic Society
https://www.readbyqxmd.com/read/28497497/simultaneous-measurement-of-macro-and-microvascular-blood-flow-and-oxygen-saturation-for-quantification-of-muscle-oxygen-consumption
#3
Erin K Englund, Zachary B Rodgers, Michael C Langham, Emile R Mohler, Thomas F Floyd, Felix W Wehrli
PURPOSE: To investigate the relationship between blood flow and oxygen consumption in skeletal muscle, a technique called "Velocity and Perfusion, Intravascular Venous Oxygen saturation and T2*" (vPIVOT) is presented. vPIVOT allows the quantification of feeding artery blood flow velocity, perfusion, draining vein oxygen saturation, and muscle T2*, all at 4-s temporal resolution. Together, the measurement of blood flow and oxygen extraction can yield muscle oxygen consumption ( V˙O2) via the Fick principle...
May 11, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28444930/does-postexercise-modelled-capillary-blood-flow-accurately-reflect-cardiovascular-effects-by-different-exercise-intensities
#4
F Stöcker, C Von Oldershausen, F K Paternoster, T Schulz, R Oberhoffer
Blood flow (BF) in exercising muscles is an important factor for exercise capacity. Recently, a non-invasive method to estimate capillary BF (Qcap ) was introduced. Using this method, the Fick principle is re-arranged by using relative differences in deoxygenated haemoglobin (ΔHHb) as a surrogate for arteriovenous O2 difference and pulmonary oxygen uptake (VO2 ) instead of muscular oxygen uptake. The aim of this study was to examine (I) the relationship between Qcap and exercise intensity during and following exercise, and (II) to critically reflect the Qcap approach...
April 26, 2017: Clinical Physiology and Functional Imaging
https://www.readbyqxmd.com/read/28174344/glucagon-like-peptide-1-elicits-vasodilation-in-adipose-tissue-and-skeletal-muscle-in-healthy-men
#5
Ali Asmar, Meena Asmar, Lene Simonsen, Sten Madsbad, Jens J Holst, Bolette Hartmann, Charlotte M Sorensen, Jens Bülow
In healthy subjects, we recently demonstrated that during acute administration of GLP-1, cardiac output increased significantly, whereas renal blood flow remained constant. We therefore hypothesize that GLP-1 induces vasodilation in other organs, for example, adipose tissue, skeletal muscle, and/or splanchnic tissues. Nine healthy men were examined twice in random order during a 2-hour infusion of either GLP-1 (1.5 pmol kg(-1) min(-1)) or saline. Cardiac output was continuously estimated noninvasively concomitantly with measurement of intra-arterial blood pressure...
February 2017: Physiological Reports
https://www.readbyqxmd.com/read/28163837/simultaneous-ramp-right-heart-catheterization-and-echocardiography-in-a-reliantheart-left-ventricular-assist-device
#6
Dipanjan Banerjee, Debleena Dutt, Sebastien Duclos, Karim Sallam, Matthew Wheeler, Richard Ha
Many clinicians caring for patients with continuous flow left ventricular assist devices (CF-LVAD) use ramp right heart catheterization (RHC) studies to optimize pump speed and also to troubleshoot CF-LVAD malfunction. An investigational device, the ReliantHeart Heart Assist 5 (Houston, TX), provides the added benefit of an ultrasonic flow probe on the outflow graft that directly measures flow through the CF-LVAD. We performed a simultaneous ramp RHC and echocardiogram on a patient who received the above CF-LVAD to optimize pump parameters and investigate elevated flow through the CF-LVAD as measured by the flow probe...
January 26, 2017: World Journal of Cardiology
https://www.readbyqxmd.com/read/28153941/decreases-in-maximal-oxygen-uptake-following-long-duration-spaceflight-role-of-convective-and-diffusive-o2-transport-mechanisms
#7
Carl J Ade, Ryan M Broxterman, Alan Moore, Thomas J Barstow
We have previously predicted that the decrease in maximal oxygen uptake (VO2max) that accompanies time in microgravity reflects decrements in both convective and diffusive O2 transport to the mitochondria of the contracting myocytes. The aim of this investigation was therefore to quantify the relative changes in convective O2 transport (QO2) and O2 diffusing capacity (DO2) following long duration spaceflight. In 9 astronauts, resting hemoglobin concentration ([Hb]), VO2max, maximal cardiac output (QTmax), and differences in arterial and venous O2 contents (CaO2-CvO2) were obtained retrospectively for International Space Station Increments 19 through 33 (April 2009-November 2012)...
February 2, 2017: Journal of Applied Physiology
https://www.readbyqxmd.com/read/27911393/a-detailed-protocol-for-perspiration-monitoring-using-a-novel-small-wireless-device
#8
Kazuhiro Ogai, Masakazu Fukuoka, Kei-Ichiro Kitamura, Kiyoshi Uchide, Tetsu Nemoto
Perspiration monitoring can be utilized for the detection of certain diseases, such as thermoregulation and mental disorders, particularly when the patients are unaware of such disorders or are having difficulty expressing their symptoms. Until now, several devices for perspiration monitoring have been developed; however, such devices tend to have a relatively large exterior, considerable power consumption, and/or less sensitivity. Recently, we developed a small, wireless device for perspiration monitoring...
November 24, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27881556/nitrite-and-s-nitrosohemoglobin-exchange-across-the-human-cerebral-and-femoral-circulation-relationship-to-basal-and-exercise-blood-flow-responses-to-hypoxia
#9
RANDOMIZED CONTROLLED TRIAL
Damian M Bailey, Peter Rasmussen, Morten Overgaard, Kevin A Evans, Aske M Bohm, Thomas Seifert, Patrice Brassard, Morten Zaar, Henning B Nielsen, Peter B Raven, Niels H Secher
BACKGROUND: The mechanisms underlying red blood cell (RBC)-mediated hypoxic vasodilation remain controversial, with separate roles for nitrite () and S-nitrosohemoglobin (SNO-Hb) widely contested given their ability to transduce nitric oxide bioactivity within the microcirculation. To establish their relative contribution in vivo, we quantified arterial-venous concentration gradients across the human cerebral and femoral circulation at rest and during exercise, an ideal model system characterized by physiological extremes of O2 tension and blood flow...
January 10, 2017: Circulation
https://www.readbyqxmd.com/read/27866929/long-term-outcomes-of-pulmonary-arterial-hypertension-under-specific-drug-therapy-in-eisenmenger-syndrome
#10
Sébastien Hascoët, Alban-Elouen Baruteau, Marc Humbert, Gérald Simonneau, Xavier Jais, Jérôme Petit, Daniela Laux, Olivier Sitbon, Virginie Lambert, André Capderou
BACKGROUND: The long-term effectiveness of pulmonary arterial hypertension-specific drug therapy (PAH-SDT) in Eisenmenger syndrome is controversial. We investigated short-term and long-term hemodynamic changes under PAH-SDT and their associations with outcomes in a bicentric cohort. METHODS: Over 20 years, we included 69 patients with congenital heart disease, an indexed pulmonary vascular resistance (PVRi) >8 WU·m(2), and 292 standardized catheterizations at baseline and after PAH-SDT initiation or intensification...
October 15, 2016: Journal of Heart and Lung Transplantation
https://www.readbyqxmd.com/read/27456179/comparison-of-pulsioflex%C3%A2-uncalibrated-pulse-contour-method-and-a-modified-fick-principle-with-transpulmonary-thermodilution-measurements-in-critically-ill-patients
#11
COMPARATIVE STUDY
J Grensemann, J M Defosse, C Wieland, U W Wild, F Wappler, S G Sakka
Monitoring of cardiac index (CI) by uncalibrated pulse contour (PC) methods has been shown to be inaccurate in critically ill patients. We tested accuracy and trending of a new pulse contour method and a modified Fick method using central venous oxygen saturation. We studied 21 critically ill and mechanically ventilated patients (age 20-86 years) monitored by PC (PulsioFlex®) and transpulmonary thermodilution (TPTD, PiCCO2®) as reference. At baseline, reference and PC-derived CI (CIPC) were recorded and CI obtained by Fick's method (FM, CIFICK)...
July 2016: Anaesthesia and Intensive Care
https://www.readbyqxmd.com/read/27292274/a-physiological-increase-in-maternal-cortisol-alters-uteroplacental-metabolism-in-the-pregnant-ewe
#12
O R Vaughan, K L Davies, J W Ward, M J de Blasio, A L Fowden
Fetal nutrition is determined by maternal availability, placental transport and uteroplacental metabolism of carbohydrates. Cortisol affects maternal and fetal metabolism but whether maternal cortisol concentrations within the physiological range regulate uteroplacental carbohydrate metabolism remains unknown. This study determined the effect of maternal cortisol infusion (1.2 mg kg(-1)  day(-1) iv. for 5 days, n = 20) on fetal glucose, lactate and oxygen supplies in pregnant ewes on day ∼130 of pregnancy (term = 145 days)...
June 13, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27258938/insulin-plays-a-permissive-role-for-the-vasoactive-effect-of-gip-regulating-adipose-tissue-metabolism-in-humans
#13
RANDOMIZED CONTROLLED TRIAL
Meena Asmar, Lene Simonsen, Ali Asmar, Jens Juul Holst, Flemming Dela, Jens Bülow
CONTEXT AND OBJECTIVE: Glucose-dependent insulinotropic polypeptide (GIP) in combination with hyperinsulinemia increases blood flow and triglyceride (TAG) clearance in subcutaneous (sc) abdominal adipose tissue in lean humans. The present experiments were performed to further investigate the role of insulin for the vasoactive effect of GIP in adipose tissue metabolism and whether the vasodilatory effect of GIP is dependent on C-peptide. METHODS: Six lean healthy subjects were studied...
August 2016: Journal of Clinical Endocrinology and Metabolism
https://www.readbyqxmd.com/read/27074812/right-heart-catheterisation-may-be-cautiously-performed-through-a-mechanical-valve-prosthesis-in-the-tricuspid-position
#14
Stephen Pettit, Steven Tsui, Jayan Parameshwar
Right heart catheterisation (RHC) may be performed through a mechanical valve prosthesis in the tricuspid position using a partially inflated pulmonary artery flotation catheter. Preprocedural preparation should include an ex vivo trial with an identical valve prosthesis and the type of catheter to be used for the procedure. The operator should expect immediate unloading of the right ventricle due to catheter-associated tricuspid regurgitation, but it is possible to estimate pulmonary vascular resistance using the Fick principle...
2016: BMJ Case Reports
https://www.readbyqxmd.com/read/26997923/conceptual-foundations-of-diffusion-in-magnetic-resonance
#15
Cheng Guan Koay, Evren Özarslan
A thorough review of the q-space technique is presented starting from a discussion of Fick's laws. The work presented here is primarily conceptual, theoretical and hopefully pedagogical. We offered the notion of molecular concentration to unify Fick's laws and diffusion MRI within a coherent conceptual framework. The fundamental relationship between diffusion MRI and the Fick's laws are carefully established. The conceptual and theoretical basis of the q-space technique is investigated from first principles...
July 2013: Concepts in Magnetic Resonance. Part A, Bridging Education and Research
https://www.readbyqxmd.com/read/26956188/glucagon-like-peptide-1-does-not-have-acute-effects-on-central-or-renal-hemodynamics-in-patients-with-type-2-diabetes-without-nephropathy
#16
Ali Asmar, Lene Simonsen, Meena Asmar, Sten Madsbad, Jens J Holst, Erik Frandsen, Cedric Moro, Charlotte M Sorensen, Thomas Jonassen, Jens Bülow
During acute administration of native glucagon-like peptide-1 (GLP-1), we previously demonstrated central hemodynamic effects in healthy males, whereas renal hemodynamics, despite renal uptake of GLP-1 in excess of glomerular filtration, was unaffected. In the present study, we studied hemodynamic effects of GLP-1 in patients with type 2 diabetes under fixed sodium intake. During a 3-h infusion of GLP-1 (1.5 pmol·kg(-1)·min(-1)) or saline, intra-arterial blood pressure and heart rate were measured continuously, concomitantly with cardiac output estimated by pulse contour analysis...
May 1, 2016: American Journal of Physiology. Endocrinology and Metabolism
https://www.readbyqxmd.com/read/26918133/pharmacokinetic-pharmacodynamic-relationship-of-anesthetic-drugs-from-modeling-to-clinical-use
#17
REVIEW
Valerie Billard
Anesthesia is a combination of unconsciousness, amnesia, and analgesia, expressed in sleeping patients by limited reaction to noxious stimulations. It is achieved by several classes of drugs, acting mainly on central nervous system. Compared to other therapeutic families, the anesthetic drugs, administered by intravenous or pulmonary route, are quickly distributed in the blood and induce in a few minutes effects that are fully reversible within minutes or hours. These effects change in parallel with the concentration of the drug, and the concentration time course of the drug follows with a reasonable precision mathematical models based on the Fick principle...
2015: F1000Research
https://www.readbyqxmd.com/read/26598322/cardiac-output-and-vasodilation-in-the-vasovagal-response-an-analysis-of-the-classic-papers
#18
REVIEW
Wouter Wieling, David L Jardine, Frederik J de Lange, Michele Brignole, Henning B Nielsen, Julian Stewart, Richard Sutton
The simple faint is secondary to hypotension and bradycardia resulting in transient loss of consciousness. According to Ohm's law applied to the circulation, BP = SVR × CO, hypotension can result from a decrease in systemic vascular resistance (SVR), cardiac output (CO), or both. It is important to understand that when blood pressure (BP) is falling, SVR and CO do not change reciprocally as they do in the steady state. In 1932, Lewis, assuming that decreased SVR alone accounted for hypotension, defined "the vasovagal response" along pathophysiologic lines to denote the association of vasodilation with vagal-induced bradycardia in simple faint...
March 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/26355542/modeling-of-the-bacillus-subtilis-bacterial-biofilm-growing-on-an-agar-substrate
#19
Xiaoling Wang, Guoqing Wang, Mudong Hao
Bacterial biofilms are organized communities composed of millions of microorganisms that accumulate on almost any kinds of surfaces. In this paper, a biofilm growth model on an agar substrate is developed based on mass conservation principles, Fick's first law, and Monod's kinetic reaction, by considering nutrient diffusion between biofilm and agar substrate. Our results show biofilm growth evolution characteristics such as biofilm thickness, active biomass, and nutrient concentration in the agar substrate...
2015: Computational and Mathematical Methods in Medicine
https://www.readbyqxmd.com/read/26334507/elevated-global-cerebral-blood-flow-oxygen-extraction-fraction-and-unchanged-metabolic-rate-of-oxygen-in-young-adults-with-end-stage-renal-disease-an-mri-study
#20
Gang Zheng, Jiqiu Wen, Hanzhang Lu, Yaxian Lou, Zhiying Pan, Wei Liu, Hui Liu, Xue Li, Zhe Zhang, Huijuan Chen, Xiang Kong, Song Luo, Xiaolu Jiang, Ya Liu, Zongjun Zhang, Long Jiang Zhang, Guang Ming Lu
OBJECTIVES: To noninvasively assess global cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2) in young adults with end-stage renal disease (ESRD). METHODS: Thirty-six patients and 38 healthy volunteers were included and took part in MR examinations, blood and neuropsychological tests. CBF and OEF were measured by phase-contrast and T2-relaxation-under-spin-tagging MRI techniques, respectively. CMRO2 was computed from CBF, OEF and hematocrit according to Fick's principle...
June 2016: European Radiology
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