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Starling resistor

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https://www.readbyqxmd.com/read/27598891/starling-resistors-autoregulation-of-cerebral-perfusion-and-the-pathogenesis-of-idiopathic-intracranial-hypertension
#1
Roberto De Simone, Angelo Ranieri, Vincenzo Bonavita
Two critical functions for the control of intracranial fluids dynamics are carried on the venous side of the perfusion circuit: the first is the avoidance of cortical veins collapse during the physiological increases of cerebrospinal fluid (CSF) pressure in which they are immersed. The second, is the generation of an abrupt venous pressure drop at the confluence of the cortical veins with the dural sinuses that is required to allow a CSF outflow rate balanced with its production. There is evidence that both of these effects are ensured by a Starling resistor mechanism (a fluid dynamic construct that governs the flow in collapsible tubes exposed to variable external pressure) acting at the confluence of cortical veins in the dural sinus...
September 6, 2016: Panminerva Medica
https://www.readbyqxmd.com/read/27581321/cerebral-venous-overdrainage-an-under-recognized-complication-of-cerebrospinal-fluid-diversion
#2
Kaveh Barami
Understanding the altered physiology following cerebrospinal fluid (CSF) diversion in the setting of adult hydrocephalus is important for optimizing patient care and avoiding complications. There is mounting evidence that the cerebral venous system plays a major role in intracranial pressure (ICP) dynamics especially when one takes into account the effects of postural changes, atmospheric pressure, and gravity on the craniospinal axis as a whole. An evolved mechanism acting at the cortical bridging veins, known as the "Starling resistor," prevents overdrainage of cranial venous blood with upright positioning...
September 2016: Neurosurgical Focus
https://www.readbyqxmd.com/read/27417037/retinal-venous-pulsation-expanding-our-understanding-and-use-of-this-enigmatic-phenomenon
#3
REVIEW
William H Morgan, Martin L Hazelton, Dao-Yi Yu
Retinal vein pulsation was first noted soon after the invention of the ophthalmoscope 170 years ago and was seen to change with cerebrospinal fluid pressure (CSFP) variation in the 1920s. The classical explanation for vein pulsation was that the cardiac cycle induced systolic peak in intraocular pressure (IOP) tended to intermittently collapse the retinal vein close to its exit in the central optic disk, causing pulsation to be counter-phase to IOP. Recently, improved ophthalmodynamometry and video recording techniques have allowed us to explore the fundamentals of retinal vein pulsation...
November 2016: Progress in Retinal and Eye Research
https://www.readbyqxmd.com/read/26992969/hemodynamics-of-critical-venous-stenosis-and-stent-treatment
#4
Seshadri Raju, Orla Kirk, Micah Davis, Jake Olivier
BACKGROUND: The concept of "critical" stenosis at which there is a sharp reduction in forward flow is derived from arterial disease. The critical element in venous stenoses is upstream pressure, not downstream flow. Many venous symptoms and microvascular injury are related to venous hypertension. We studied the effect of venous stenosis on upstream pressure using a mechanical model and with clinical measurements after stenting of iliac vein segments (common and external). METHODS: The experimental model consisted of a Starling Resistor - Penrose tubing enclosed in a pressurized plastic chamber to simulate abdominal venous flow...
January 2014: Journal of Vascular Surgery. Venous and Lymphatic Disorders
https://www.readbyqxmd.com/read/26767844/the-cerebral-venous-system-and-the-postural-regulation-of-intracranial-pressure-implications-in-the-management-of-patients-with-cerebrospinal-fluid-diversion
#5
REVIEW
Kaveh Barami, Sandeep Sood
Loss of cerebrospinal fluid (CSF) occurs commonly in daily neurosurgical practice. Understanding the altered physiology following CSF loss is important for optimization of patient care and avoidance of complications. There is overwhelming evidence now that the cerebral venous system plays a major role in intracranial pressure (ICP) dynamics especially when one takes into account the effects of postural changes, atmospheric pressure, and gravity on the craniospinal axis as a whole. The CSF and cerebral venous compartments are tightly coupled in two important ways...
April 2016: Child's Nervous System: ChNS: Official Journal of the International Society for Pediatric Neurosurgery
https://www.readbyqxmd.com/read/26036249/impact-of-ccsvi-on-cerebral-haemodynamics-a-mathematical-study-using-mri-angiographic-and-flow-data
#6
L O Müller, E F Toro, E M Haacke, D Utriainen
BACKGROUND: The presence of abnormal anatomy and flow in neck veins has been recently linked to neurological diseases. The precise impact of extra-cranial abnormalities such as stenoses remains unexplored. METHODS: Pressure and velocity fields in the full cardiovascular system are computed by means of a global mathematical model that accounts for the relationship between pulsating cerebral blood flow and intracranial pressure. RESULTS: Our model predicts that extra-cranial strictures cause increased pressure in the cerebral venous system...
June 2016: Phlebology
https://www.readbyqxmd.com/read/25766708/all-apaps-are-not-equivalent-for-the-treatment-of-sleep-disordered-breathing-a-bench-evaluation-of-eleven-commercially-available-devices
#7
COMPARATIVE STUDY
Kaixian Zhu, Gabriel Roisman, Sami Aouf, Pierre Escourrou
STUDY OBJECTIVES: This study challenged on a bench-test the efficacy of auto-titrating positive airway pressure (APAP) devices for obstructive sleep disordered breathing treatment and evaluated the accuracy of the device reports. METHODS: Our bench consisted of an active lung simulator and a Starling resistor. Eleven commercially available APAP devices were evaluated on their reactions to single-type SDB sequences (obstructive apnea and hypopnea, central apnea, and snoring), and to a long general breathing scenario (5...
July 2015: Journal of Clinical Sleep Medicine: JCSM: Official Publication of the American Academy of Sleep Medicine
https://www.readbyqxmd.com/read/25581045/-central-retinal-vein-its-pulsation-and-pressure-in-glaucoma
#8
REVIEW
R Stodtmeister
BACKGROUND: The ocular perfusion pressure (PP) is presently calculated by subtracting the intraocular pressure (IOP) from the mean ophthalmic artery pressure. In recent years papers have been published in which it has been shown that the pressure in the central retinal vein (CRV) may be higher than the IOP in half the glaucoma patients resulting in a lower perfusion pressure in the retina and in the prelaminar layer of the optic nerve head. OBJECTIVES: A review of these papers is given in which the pulsation of the CRV was assessed or in which the pressure in the CRV has been measured on comparing glaucoma patients and control subjects...
February 2015: Klinische Monatsblätter Für Augenheilkunde
https://www.readbyqxmd.com/read/25548569/nasal-involvement-in-obstructive-sleep-apnea-syndrome
#9
REVIEW
Daniel de Sousa Michels, Amanda da Mota Silveira Rodrigues, Márcio Nakanishi, André Luiz Lopes Sampaio, Alessandra Ramos Venosa
Numerous studies have reported an association between nasal obstruction and obstructive sleep apnea syndrome (OSAS), but the precise nature of this relationship remains to be clarified. This paper aimed to summarize data and theories on the role of the nose in the pathophysiology of sleep apnea as well as to discuss the benefits of surgical and medical nasal treatments. A number of pathophysiological mechanisms can potentially explain the role of nasal pathology in OSAS. These include the Starling resistor model, the unstable oral airway, the nasal ventilatory reflex, and the role of nitric oxide (NO)...
2014: International Journal of Otolaryngology
https://www.readbyqxmd.com/read/25528245/simulation-using-novel-equipment-designed-to-explain-spirometric-abnormalities-in-respiratory-disease-enhances-learning-in-higher-cognitive-domains
#10
J P Jamison, M T Stewart
Simulation of disorders of respiratory mechanics shown by spirometry provides insight into the pathophysiology of disease but some clinically important disorders have not been simulated and none have been formally evaluated for education. We have designed simple mechanical devices which, along with existing simulators, enable all the main dysfunctions which have diagnostic value in spirometry to be simulated and clearly explained with visual and haptic feedback. We modelled the airways as Starling resistors by a clearly visible mechanical action to simulate intra- and extra-thoracic obstruction...
October 2015: Advances in Health Sciences Education: Theory and Practice
https://www.readbyqxmd.com/read/25324514/test-of-the-starling-resistor-model-in-the-human-upper-airway-during-sleep
#11
Andrew Wellman, Pedro R Genta, Robert L Owens, Bradley A Edwards, Scott A Sands, Stephen H Loring, David P White, Andrew C Jackson, Ole F Pedersen, James P Butler
The human pharyngeal airway during sleep is conventionally modeled as a Starling resistor. However, inspiratory flow often decreases with increasing effort (negative effort dependence, NED) rather than remaining fixed as predicted by the Starling resistor model. In this study, we tested a major prediction of the Starling resistor model--that the resistance of the airway upstream from the site of collapse remains fixed during flow limitation. During flow limitation in 24 patients with sleep apnea, resistance at several points along the pharyngeal airway was measured using a pressure catheter with multiple sensors...
December 15, 2014: Journal of Applied Physiology
https://www.readbyqxmd.com/read/25190664/a-theoretical-model-to-allow-prediction-of-the-csf-pressure-from-observations-of-the-retinal-venous-pulse
#12
Peter S Stewart, Oliver E Jensen, Alexander J E Foss
PURPOSE: There is no easy way to estimate the intracranial pressure (ICP) noninvasively. The retinal vein can exhibit large amplitude oscillations at the level of the lamina cribrosa under certain circumstances. The aims of this study were to develop a theoretical understanding of the conditions required to establish this vigorous oscillatory behavior and to determine whether observations of it could lead to a noninvasive estimate of the ICP. METHODS: A mathematical model was constructed in which the central retinal vein was modeled as 2 Starling resistors in series, 1 located in the eye and the other in the cerebrospinal fluid (CSF) space, separated by a region where it was not collapsible, corresponding to its course within the optic nerve itself...
October 2014: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/25169660/enhanced-global-mathematical-model-for-studying-cerebral-venous-blood-flow
#13
Lucas O Müller, Eleuterio F Toro
Here we extend the global, closed-loop, mathematical model for the cardiovascular system in Müller and Toro (2014) to account for fundamental mechanisms affecting cerebral venous haemodynamics: the interaction between intracranial pressure and cerebral vasculature and the Starling-resistor like behaviour of intracranial veins. Computational results are compared with flow measurements obtained from Magnetic Resonance Imaging (MRI), showing overall satisfactory agreement. The role played by each model component in shaping cerebral venous flow waveforms is investigated...
October 17, 2014: Journal of Biomechanics
https://www.readbyqxmd.com/read/25020212/influence-of-pharyngeal-muscle-activity-on-inspiratory-negative-effort-dependence-in-the-human-upper-airway
#14
Pedro R Genta, Robert L Owens, Bradley A Edwards, Scott A Sands, Danny J Eckert, James P Butler, Stephen H Loring, Atul Malhotra, Andrew C Jackson, David P White, Andrew Wellman
The upper airway is often modeled as a Starling resistor, which predicts that flow is independent of inspiratory effort during flow limitation. However, while some obstructive sleep apnea (OSA) patients exhibit flat, Starling resistor-like flow limitation, others demonstrate considerable negative effort dependence (NED), defined as the percent reduction in flow from peak to mid-inspiration. We hypothesized that the variability in NED could be due to differences in phasic pharyngeal muscle activation between individuals...
September 15, 2014: Respiratory Physiology & Neurobiology
https://www.readbyqxmd.com/read/24458746/the-classical-starling-resistor-model-often-does-not-predict-inspiratory-airflow-patterns-in-the-human-upper-airway
#15
Robert L Owens, Bradley A Edwards, Scott A Sands, James P Butler, Danny J Eckert, David P White, Atul Malhotra, Andrew Wellman
The upper airway is often modeled as a classical Starling resistor, featuring a constant inspiratory airflow, or plateau, over a range of downstream pressures. However, airflow tracings from clinical sleep studies often show an initial peak before the plateau. To conform to the Starling model, the initial peak must be of small magnitude or dismissed as a transient. We developed a method to simulate fast or slow inspirations through the human upper airway, to test the hypothesis that this initial peak is a transient...
April 15, 2014: Journal of Applied Physiology
https://www.readbyqxmd.com/read/24313607/acute-subdural-hematoma-from-bridging-vein-rupture-a-potential-mechanism-for-growth
#16
REVIEW
Jimmy D Miller, Remi Nader
Most acute subdural hematomas (ASDHs) develop after rupture of a bridging vein or veins. The anatomy of the bridging vein predisposes to its tearing within the border cell layer of the dura mater. Thus, the subdural hematoma actually forms within the dura. The hematoma grows by continued bleeding into the border cell layer. However, the venous pressure would not be expected to cause a large hematoma. Therefore, some type of mechanism must account for the hematoma's expansion. Cerebral venous pressure (CVP) has been demonstrated in animal models to be slightly higher than intracranial pressure (ICP), and CVP tracks the ICP as pressure variations occur...
June 2014: Journal of Neurosurgery
https://www.readbyqxmd.com/read/24283578/intracranial-pressure-is-a-fraction-of-arterial-blood-pressure
#17
O Gustafsson, S Rossitti
The relation between cerebrospinal fluid pressure (pcsf ) and arterial blood pressure (pa ) was studied in pigs and in rabbits before and after an ischemia-induced impairment of the cerebral autoregulation, in order to predict the effect of changes of pa on the pcsf . Before the ischemic brain episode no clear correlation between pa and pcsf was found. A close dependence emerged after the ischemic episode, and after each change in pa the pcsf assumed immediately a new stationary level. The results suggest that intracranial pressure is at any moment a fraction of arterial blood pressure quantitatively determined by the coordinated action of cerebrovascular resistance, i...
March 1995: European Journal of Neurology: the Official Journal of the European Federation of Neurological Societies
https://www.readbyqxmd.com/read/24199949/the-meniere-attack-an-ischemia-reperfusion-disorder-of-inner-ear-sensory-tissues
#18
C A Foster, R E Breeze
We believe Meniere attacks arise as a chance association of endolymphatic hydrops and vascular risk factors for intracerebral ischemia. Hydrops acts as a variable Starling resistor upon the inner ear vasculature that is capable of inducing ischemic attacks only in people with reduced perfusion pressure in the ear. The unique characteristics of the attacks (loss of vestibular response and hearing acutely followed by a return to apparent normalcy over hours) are explained by the differential sensitivity of the inner ear tissues to transient ischemia, with the sensory tissues (dendrites, hair cells) vulnerable to hours-long ischemia/reperfusion injury, and the stria vulnerable to ischemia due to its high metabolic rate...
December 2013: Medical Hypotheses
https://www.readbyqxmd.com/read/23997698/bench-test-evaluation-of-adaptive-servoventilation-devices-for-sleep-apnea-treatment
#19
Kaixian Zhu, Haissam Kharboutly, Jianting Ma, Mourad Bouzit, Pierre Escourrou
RATIONALE: Adaptive servoventilation devices are marketed to overcome sleep disordered breathing with apneas and hypopneas of both central and obstructive mechanisms often experienced by patients with chronic heart failure. The clinical efficacy of these devices is still questioned. STUDY OBJECTIVES: This study challenged the detection and treatment capabilities of the three commercially available adaptive servoventilation devices in response to sleep disordered breathing events reproduced on an innovative bench test...
September 15, 2013: Journal of Clinical Sleep Medicine: JCSM: Official Publication of the American Academy of Sleep Medicine
https://www.readbyqxmd.com/read/23740880/crosstalk-opposing-view-the-human-upper-airway-during-sleep-does-not-behave-like-a-starling-resistor
#20
James P Butler, Robert L Owens, Atul Malhotra, Andrew Wellman
No abstract text is available yet for this article.
May 1, 2013: Journal of Physiology
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