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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 15 (1979), S. 73-81 
    ISSN: 1432-1041
    Keywords: simulation model ; diazoxide hypotension ; haemodynamics ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The acute haemodynamic effects of injected diazoxide (Hyperstat® Schering) have been studied in 8 hypertensive subjects. Aortic blood pressure was measured and cardiac output and peripheral conductance were assessed continuously using a simulation model. In six of the patients pulmonary artery end-diastolic pressure was also measured. Blood pressure fell in all subjects 5–10 min after injection of the drug cardiac output increased in all patients studied. However, the initial change in cardiac output differed, as it decreased in two subjects and did not change in one. The largest initial increases in cardiac output were seen in the subjects with the highest pulmonary artery end-diastolic pressure. Patients with an initial decrease in cardiac output were those with the least compliant (stiffest) aortas. We consider that the responsiveness of the baroreceptors determines the size of the increase in cardiac output immediately after reduction of blood pressure by diazoxide. Thus in a patient with a stiff aorta, particularly at low cardiac filling pressure, diazoxide might cause a fall in blood pressure to an unacceptable level.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 29 (1991), S. 104-108 
    ISSN: 1741-0444
    Keywords: Air embolism ; Bubble production ; Decompression sickness ; Foam ; Instrumentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 16 (1978), S. 697-706 
    ISSN: 1741-0444
    Keywords: Aortic-pressure curves ; Aortic compliance ; Cardiac output ; Intensive care ; Pulse transmission time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire L'article présente une méthode permettant de calculer le débit cardiaques à partir des courbes de pression aortique. Cette méthode est basée sur un modèle de simulation du système cardiovasculaire humain. La conformité aortique est calculée à partir du temps de transmission de la pulsation dans l'aorte. Cette méthode a été testée par rapport à des mesures de débit cardiaque standard dans 61 cas et sur 39 personnes. Quarante mesures ont été effectuées au repos et 21 durant divers changements de l'état cardiovasculaire. La différence moyenne entre la méthode par impulsions et la détermination standard du débit cardiaque était de 9% avec une erreur standard sur la difference de 7%. Le coefficient de corrélation était égal à 0·96. La plus forte différence a été enregistrée chez les sujets atteints de fibrillation auriculaire, auquel cas les changements de pression dans l'aorte rendent difficiles des estimations de conformité basées sur le temps de transmission de l'impulsion. En utilisant un servosystème, ce modèle est capable de suivre des changements de l'état cardiovasculaire en l'espace de quelques battements. Cette méthode debrait donc être utile pour calculer le débit cardiaque durant les soins intensifs.
    Abstract: Zusammenfassung Es wird ein Verfahren zur Berechnung der Herzleistung aus aortischen Druckkurven dargestellt. Das Verfahren basiert auf einem Simulationsmodell des menschlichen Herzgefäßsystems. Die Herzkomplianz wird aud der Pulsübertragungszeit in der Aorta kalkuliert. Dieses Verfahren wurde im Test mit den Standardmessungen der Herzleistung in 61 Fällen bei 39 Personen verglichen. 40 Messungen wurden während der Ruhestellung ausgeführt, während 21 während verschiedener Veränderungen des Herzgefäßzustands durchgeführt wurden. Der durchschnittliche Unterschied zwischen der Pulsmethode und der Standardbestimmung der Herzleistung wurde mit 9% und einem Standardfehler der Differenz von 7% festgestellt. Der Korrelationskoeffizient warr=0·96. Die größten Differenzen wurden bei Patienten festgestellt, die unter Atrialfibrillation litten, bei denen Druckveränderungen in der Aorta die auf der Pulstransmissionszeit basierenden Komplianzwerte schwer bestimmbar machten. Mit einem Servosystem kann das Modell Veräanderungen im Herzgefäßzustand innerhalb weniger Schläge verfolgen. Deshalb dürfte sich diese Methode bei der Bewertung der Herzleistung bei Wachstationsfällen als nützlich erweisen.
    Notes: Abstract A method for calculating cardiac output from aortic pressure curves is presented. The method is based on a simulation model of the human cardiovascular system. The aortic compliance is calculated from the pulse transmission time in the aorta. The method has been tested against standard cardiac output measurements in 61 instances in 39 persons. 40 measurements have been performed at rest, while 21 have been performed during various changes in the cardiovascular state. The mean difference between the pulse method and the standard cardiac output determination was found to be 9% with a standard error of the difference of 7%. The correlation coefficient was r=0·96. The largest differences were found in patients suffering from atrial fibrillation, where changes in pressure in the aorta made compliance estimates based on pulse transmission time difficult. Using a servosystem, the model is capable of following changes in the cardiovascular state within a few beats. This method should therefore be useful for calculating cardiac output in the intensive-care situation.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 31 (1993), S. 627-633 
    ISSN: 1741-0444
    Keywords: Bubble detection ; Bubble size ; Decompression ; Diving ; Gas content ; Ultrasonic imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Medical & biological engineering & computing 16 (1978), S. 231-242 
    ISSN: 1741-0444
    Keywords: Analogue computer model ; Aortic Compliance ; Aortic volume elasticity ; Haemodynamics ; Pulse transmission time ; Stroke volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Sommaire Un modèle de simulation est proposé pour l'analyse de la dynamique aortique chez l'homme. Le modèle aortique comprend six segments et fait partie d'un plus grand modèle de la circulation humaine à anse fermée. Le modèle est simulé sur un ordinateur analogue, à des fins spéciales Trois paramètres sont utilisés pour caractériser le système artériel: résistance périphérique, conformité aortique et amortissement aortique. Avec une mèthode d'adaptation du modèle au patient individuel, des mesures de pression aortique, sortie cardiaque et durée de transmission du pouls furent pratiquées sur 29 patients, afin de contrôler la validité de cette approche. Le modèle est capable de simuler, de façon satisfaisante, la marche de pression le long de l'aorte. La conformité calculée à partir des propriétés ce transmission de l'aorte fut comparée à celle calculée à partir du volume de battement et de la pression du pouls. Une relation adéquate (r=0.98) fut découverte entre ces deux méthodes indépendantes. La conformité moyenne de l'aorte totale était de 0.6 ml/mm Hg, à une pression moyenne de 104 mm Hg. La conformité montra de grandes variations individueles et des valeurs décroissantes, en proportion de l'âge avancé du patient. On en conclut que le modèle permet la simulation de l'aorte individuelle.
    Abstract: Zusammenfassung Es wird ein Simulationsmodell zur Analyse der aortabezüglichen Dynamik im Menschen vorgeschlagen. Das aortabezügliche Modell besteht aus sechs Segmenten und ist Teil eines großeren Modells des geschlossenen menschlichen Kreislaufs. Das Modell ist nach einem Spezial-Analogrechner simuliert. Es werden drei Parameter zur Darstellung des arteriellen Systems verwendet; Umfangswiderstand, aortabezügliche Compliance und Umfangsdämpfung. Unter Verwendung einer Methode zur Adaption des Modells an den individuellen Patienten, wurden Messungen der Übertragungszeit des Aortadrucks, Herztons und Puls von 29 Patienten verwendet, um die Gültigkeit dieses Versuchs zu testen. Das Modell ist fähig, den Druckverlauf entlang der Aorta zufriedenstellend zu simulieren. Die aus den Übertragungsfaktoren der Aorta kalkulierte Compliance wurde mit der Compliance des Schlagvolumens und des Druckimpluses verglichen. Es wurde eine ädequate Korrelation compliance der gesamten Aorta betrug 0.6 ml/mm Hg bei einem Durchschnittsdruck von 104 mm Hg. Die Compliance zeigte große, individuelle Variationen und abnehmende Werte mit zunehmendem Alter des Patienten. Zusammenfassend wird gesagt, daß das Modell die Simulation der individuellen Aorta ermöglicht.
    Notes: Abstract A simulation model is suggested for the analysis of aortic dynamics in man. The aortic model consists of six segments and is part of a larger model of the closed-loop human circulation. The model is simulated on a special-purpose analogue computer. Three parameters are employed to characterise the arterial system; peripheral resistance, aortic compliance and peripheral damping. Using a method for adapting the model to the individual patient, measurements of aortic pressure, cardiac output and pulse transmission time from 29 patients were used to test the validity of this approach. The model is able to simulate the pressure course along the aorta satisfactorily. The compliance calculated from the transmission properties of the aorta was compared with the complicance calculated from the stroke volume and pressure pulse. An adequate correlation (r=0.98) was found between these two independent methods. The mean compliance of the total aorta was 0.6 ml/mm Hg at a mean pressure of 104 mm Hg. The compliance showed large individual variations and decreasing values with increasing age of the patient. It is concluded that the model enables simulation of the individual aorta.
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  • 6
    Publication Date: 1979-01-01
    Print ISSN: 0031-6970
    Electronic ISSN: 1432-1041
    Topics: Chemistry and Pharmacology , Medicine
    Published by Springer
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  • 7
    Publication Date: 2022-05-25
    Description: © The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proceedings of the Royal Society B Biological Sciences 279 (2012): 1041-1050, doi:10.1098/rspb.2011.2088.
    Description: Decompression sickness (DCS; ‘the bends’) is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N2) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N2 tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N2 loading to management of the N2 load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.
    Description: This paper and the workshop it stemmed from were funded by the Woods Hole Oceanographic Institution Marine Mammal Centre.
    Keywords: Diving physiology ; Marine mammals ; Gas bubbles ; Embolism ; Decompression sickness
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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