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Mastropasqua R, Brescia L, Di Antonio L, Guarini D, Giattini D, Zuppardi E, Agnifili L. Angiographic biomarkers of filtering bleb function after XEN gel implantation for glaucoma: an optical coherence tomography-angiography study. Acta Ophthalmol 2020; 98:e761-e767. [PMID: 32020755 DOI: 10.1111/aos.14371] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 01/14/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE To evaluate, using optical coherence tomography-angiography (OCT-A), the vascular features of good bleb function after XEN gel implantation (XGI) for uncontrolled glaucoma. METHODS Forty-three patients (43 eyes), who underwent XGI, were enrolled. According to the intraocular pressure (IOP) reduction, patients were classified into Group 1 (21 eyes; success) and Group 2 (22 eyes; failure). Optical coherence tomography-angiography (OCT-A) was performed to image the vascularization of the conjunctival bleb-wall. The main outcomes were as follows: vessel displacement areas (VDAs), major vessel displacement area (MVDA; mm2 ), non-flow whole area (NFWA; mm2 ) and bleb-wall vessel density (BVD; %). Co-registered B-scans were also considered to evaluate the bleb-wall cyst-like structure density and area (BCSD, cysts/mm2 ; BCSA, mm2 ), and the bleb-wall thickness (BT, µm). RESULTS Mean postoperative follow-up was 7.5 ± 0.14 months; Group 1 and 2 IOP were 14.0 ± 2.5 and 25.3 ± 2.1 mmHg, respectively (p < 0.001). Greater VDA (p < 0.001), MVDA (p = 0.046) and NFWA (p = 0.001) values, and lower BVD (p < 0.001) was found in Group 1 compared to Group 2. Group 1 showed higher BSCD, BSCA and BT values compared to Group 2 (p < 0.001). Postoperative IOP positively correlated with BVD (r = 0.567; p = 0.003), but negatively with VDAs, MVDA (r = -0.581, p = 0.002; r = -0.619, p = 0.001, respectively), BCSD, BCSA (r = -0.580; p = 0.002; r = -0.664; p < 0.001) and BT (r = -0.627, p = 0.001). CONCLUSION Successful filtration blebs after XGI present numerous and large areas of vessel displacement within the bleb-wall, along with a rarefied vascular network. These OCT-A features can be considered angiographic biomarkers of a good aqueous humour percolation through the bleb-wall layers.
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Affiliation(s)
- Rodolfo Mastropasqua
- Institute of Ophthalmology, University of Modena and Reggio Emilia, Modena, Italy
| | - Lorenza Brescia
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Luca Di Antonio
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Daniele Guarini
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Dario Giattini
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Eduardo Zuppardi
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Luca Agnifili
- Department of Medicine and Aging Sciences, Ophthalmology Clinic, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
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Zakaria ELR, Rippe B. Peritoneal Fluid and Tracer Albumin Kinetics in the Rat. Effects of Increases in Intraperitoneal Hydrostatic Pressure. Perit Dial Int 2020. [DOI: 10.1177/089686089501500206] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Objectives To study the peritoneal fluid loss rate, the clearance (CI) of radioactive tracer albumin (RISA) eliminated from the peritoneal cavity (PC), as well as the peritoneal-to-plasma RISA clearance (CI -+ P) during acute peritoneal dialysis (PD) at large elevations in intraperitoneal hydrostatic pressure (IPP). Design Experimental study in anesthetized Wistar rats. Methods The intraperitoneal volume (IPV) was assessed using RISA dilution, correcting for the RISA CI from the PC. Volume recovery at termination of the dwells was obtained using graduated cylinders and preweighed gauze tissues. Measurements of CI and CI -+ P were obtained by repeated micro-sampling of dialysate and plasma, respectively. The IPP was continuously measured, and could be varied by external concentric abdominal compression using an inflatable cuff. On termination of the experiments, samples from tissues lining the PC were analyzed with respect to their content of RISA and edema, the latter being assessed from wet/dry weight ratios. Results At 2 mm Hg of IPP (control) the RISA CI was 27.1:1:2.0(:1:SE)μL.min-l, whereas CI→ Pwasonly 8.07:1:0.67 μL.min-l, at a total fluid loss rate of 10.1:1:5.4μL.min-1 for 1.36% Dianeal. At an IPP of 14 mm Hg, the CI increased to 55.3±4.1 μL.min -1 and the peritoneal fluid absorption rate was 34.4±5.6 μL.min -l, whereas CI -+ P was just moderately increased as compared to control (11.2:1:1.4 μL. min -I). Furthermore, a pleural effusion of 1.16:1:0.08 mL was detectable at elevated IPPs. The degree of edema formation in the anterior abdominal muscles (AAM) and the diaphragm (DIA) was largely insignificant during 150 min at 2 mm Hg of IPP, but increased markedly at 14 mm Hg, as did the RISA uptake to the AAM and DIA. The discrepancy between CI and CI -+ P was largely accounted for by tracer entrance into tissues lining the peritoneal cavity, mainly the AAM. Conclusions At a nearly unchanging capillary Starling equilibrium, the losses of fluid and of RISA from the PC were markedly elevated at increased IPPs. However, the RISA clearance to the plasma appeared to be only moderately altered at elevated IPP and represented only a minor fraction of the RISA clearance out of the PC. Tissues lining the PC apparently act as a variable ‘sink’ for intraperitoneal proteins and fluid during peritoneal dialysis (PD).
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Affiliation(s)
- EL Rasheid Zakaria
- Departments of Nephrology and Physiology, University Hospital of Lund, S-221 85 Lund, Sweden
| | - Bengt Rippe
- Departments of Nephrology and Physiology, University Hospital of Lund, S-221 85 Lund, Sweden
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Retinal venous pulsation: Expanding our understanding and use of this enigmatic phenomenon. Prog Retin Eye Res 2016; 55:82-107. [DOI: 10.1016/j.preteyeres.2016.06.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Revised: 06/22/2016] [Accepted: 06/30/2016] [Indexed: 11/24/2022]
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Abstract
The vascular myogenic response is an inherent property of VSM in the walls of small arteries and arterioles, allowing these principal resistance segments of the microcirculation to respond to changes in transmural pressure. Elevated intraluminal pressure leads to myogenic constriction, whereas reduced pressure leads to myogenic dilation. This review focuses on the physiological significance of the myogenic response in microvascular networks. First, historical concepts related to the detection of stretch by the vessel wall are reviewed, including the wall tension hypothesis, and the implications of the proposal that the arteriolar network responds to Pp changes as a system of series-coupled myogenic effectors. Next, the role of the myogenic response in the local regulation of blood flow and/or Pc is examined. Finally, the interaction of myogenic constriction and dilation with other local control mechanisms, including metabolic, neural and shear-dependent mechanisms, is discussed. Throughout the review, an attempt is made to integrate historical and current literature with an emphasis on the physiological role, rather than the underlying signaling mechanisms, of this important component of vascular control.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology & Physiology, University of Missouri School of Medicine, Columbia, MO 65212, USA.
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Niederer P, Fankhauser F, Kwasniewska S. [Hydrodynamics of aqueous humor in chronic simple glaucoma : Mechanisms of pressure normalization by an artificial outflow system]. Ophthalmologe 2012; 109:30-6. [PMID: 22274295 DOI: 10.1007/s00347-011-2478-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To help elucidate the interplay of physical forces, in particular pressure and flow, controlling the distribution and absorption of aqueous humor in subconjunctival tissue, a recently published computational model was considered where the fluid production in the eye, its removal via the trabecular/uveoscleral pathways and a surgical pathway are taken into account. The target quantity is the intraocular pressure. The surgical outflow pathway is linked to a fluid bleb that is positioned below the subconjunctival tissue and is modeled as a porous medium. The computational study was conducted on the basis of the geometry and relevant parameters characterizing fluid production, the surgically formed fluid pathway as well as absorption by the subconjunctival vessels, the hydraulic and geometrical characteristics of the bleb and the outflow facility. Clinical observations can be physically interpreted on the basis of parametric studies.
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Affiliation(s)
- P Niederer
- Institut für Biomedizinische Technik, Universität und ETH Zürich, Gloriastr. 35, 8092, Zürich, Schweiz.
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Gardiner BS, Smith DW, Coote M, Crowston JG. Computational modeling of fluid flow and intra-ocular pressure following glaucoma surgery. PLoS One 2010; 5. [PMID: 20957178 PMCID: PMC2949396 DOI: 10.1371/journal.pone.0013178] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 08/12/2010] [Indexed: 01/23/2023] Open
Abstract
Background Glaucoma surgery is the most effective means for lowering intraocular pressure by providing a new route for fluid to exit the eye. This new pathway is through the sclera of the eye into sub-conjunctival tissue, where a fluid filled bleb typically forms under the conjunctiva. The long-term success of the procedure relies on the capacity of the sub-conjunctival tissue to absorb the excess fluid presented to it, without generating excessive scar tissue during tissue remodeling that will shut-down fluid flow. The role of inflammatory factors that promote scarring are well researched yet little is known regarding the impact of physical forces on the healing response. Methodology To help elucidate the interplay of physical factors controlling the distribution and absorption of aqueous humor in sub-conjunctival tissue, and tissue remodeling, we have developed a computational model of fluid production in the eye and removal via the trabecular/uveoscleral pathways and the surgical pathway. This surgical pathway is then linked to a porous media computational model of a fluid bleb positioned within the sub-conjunctival tissue. The computational analysis is centered on typical functioning bleb geometry found in a human eye following glaucoma surgery. A parametric study is conducted of changes in fluid absorption by the sub-conjunctival blood vessels, changes in hydraulic conductivity due to scarring, and changes in bleb size and shape, and eye outflow facility. Conclusions This study is motivated by the fact that some blebs are known to have ‘successful’ characteristics that are generally described by clinicians as being low, diffuse and large without the formation of a distinct sub-conjunctival encapsulation. The model predictions are shown to accord with clinical observations in a number of key ways, specifically the variation of intra-ocular pressure with bleb size and shape and the correspondence between sites of predicted maximum interstitial fluid pressure and key features observed in blebs, which gives validity to the model described here. This model should contribute to a more complete explanation of the physical processes behind successful bleb characteristics and provide a new basis for clinically grading blebs.
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Affiliation(s)
- Bruce S Gardiner
- School of Computer Science and Software Engineering, The University of Western Australia, Crawley, Western Australia, Australia.
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Gehlert S, Theis C, Weber S, Schiffer T, Hellmich M, Platen P, Bloch W. Exercise-Induced Decline in the Density of LYVE-1-Positive Lymphatic Vessels in Human Skeletal Muscle. Lymphat Res Biol 2010; 8:165-73. [DOI: 10.1089/lrb.2009.0035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Sebastian Gehlert
- Department for Molecular and Cellular Sports Medicine, Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Christian Theis
- Department for Molecular and Cellular Sports Medicine, Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Sebastian Weber
- Department for Molecular and Cellular Sports Medicine, Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany
| | - Thorsten Schiffer
- Outpatient Clinic for Sports Traumatology and Public Health Consultation, German Sport University Cologne, Cologne, Germany
| | - Martin Hellmich
- Institute of Medical Statistics, Informatics and Epidemiology, University Hospital of Cologne, Cologne, Germany
| | - Petra Platen
- Institute of Sports Medicine and Sports Nutrition, Ruhr University Bochum, Bochum, Germany
| | - Wilhelm Bloch
- Department for Molecular and Cellular Sports Medicine, Institute of Cardiology and Sports Medicine, German Sport University Cologne, Cologne, Germany
- The German Research Center of Elite Sport, German Sport University Cologne, Cologne, Germany
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Krix M, Weber MA, Kauczor HU, Delorme S, Krakowski-Roosen H. Changes in the micro-circulation of skeletal muscle due to varied isometric exercise assessed by contrast-enhanced ultrasound. Eur J Radiol 2009; 76:110-6. [PMID: 19541442 DOI: 10.1016/j.ejrad.2009.05.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 04/17/2009] [Accepted: 05/06/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE To quantitatively assess local muscle micro-circulation with real-time contrast-enhanced ultrasound (CEUS) during different exercises and compare the results with performed muscle work and global blood flow. MATERIALS AND METHODS Sixteen low mechanical index CEUS examinations of the right lower leg flexors of healthy volunteers were performed using a continuous infusion of SonoVue(®) (4.8 mL/300 s). Several muscle perfusion parameters were extracted from derived CEUS signal intensity time curves during different isometric exercises (10-50% of maximum individual strength for 20-30s) and then correlated with the performed muscle work or force, and the whole lower leg blood flow which we measured simultaneously by venous occlusion plethysmography (VOP). RESULTS The shapes of the CEUS curve during and after exercise differed individually depending on the performed muscle work. The maximum blood volume MAX was observed only after exercise cessation and was significantly correlated with the performed muscle force (r=0.77, p<0.0001). The blood volume over exercise time was inversely correlated with the spent muscle work (r=-0.60, p=0.006). CEUS and VOP measurements correlated only at rest and after the exercise. During exercise, mean CEUS local blood volume decreased (from 3.48 to 2.19 (∼mL)), while mean VOP global blood flow increased (mean, from 3.96 to 7.71 mL/100 mg/min). CONCLUSION Real-time low-MI CEUS provides complementary information about the local muscle micro-circulation compared to established blood flow measures. CEUS may be used for a better understanding of muscle perfusion physiology and in the diagnosis of micro-circulation alterations such as in peripheral arterial occlusive disease or diabetic angiopathy.
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Affiliation(s)
- Martin Krix
- German Cancer Research Center, Research Program Imaging and Radiooncology, Department of Radiology, Heidelberg, Germany.
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Truslow JG, Price GM, Tien J. Computational design of drainage systems for vascularized scaffolds. Biomaterials 2009; 30:4435-43. [PMID: 19481796 DOI: 10.1016/j.biomaterials.2009.04.053] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 04/28/2009] [Indexed: 01/09/2023]
Abstract
This computational study analyzes how to design a drainage system for porous scaffolds so that the scaffolds can be vascularized and perfused without collapse of the vessel lumens. We postulate that vascular transmural pressure--the difference between lumenal and interstitial pressures--must exceed a threshold value to avoid collapse. Model geometries consisted of hexagonal arrays of open channels in an isotropic scaffold, in which a small subset of channels was selected for drainage. Fluid flow through the vessels and drainage channel, across the vascular wall, and through the scaffold were governed by Navier-Stokes equations, Starling's Law of Filtration, and Darcy's Law, respectively. We found that each drainage channel could maintain a threshold transmural pressure only in nearby vessels, with a radius-of-action dependent on vascular geometry and the hydraulic properties of the vascular wall and scaffold. We illustrate how these results can be applied to microvascular tissue engineering, and suggest that scaffolds be designed with both perfusion and drainage in mind.
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Affiliation(s)
- James G Truslow
- Department of Biomedical Engineering, Boston University, 44 Cummington Street, Boston, MA 02215, USA
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Jäger C, Echtermeyer V. Kompartmentsyndrom des Unterschenkels und des Fußes. Unfallchirurg 2008; 111:768-70, 772-5. [DOI: 10.1007/s00113-008-1491-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ceelen KK, Oomens CWJ, Baaijens FPT. Microstructural analysis of deformation-induced hypoxic damage in skeletal muscle. Biomech Model Mechanobiol 2007; 7:277-84. [PMID: 17710456 PMCID: PMC2798056 DOI: 10.1007/s10237-007-0097-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Accepted: 04/29/2007] [Indexed: 12/01/2022]
Abstract
Deep pressure ulcers are caused by sustained mechanical loading and involve skeletal muscle tissue injury. The exact underlying mechanisms are unclear, and the prevalence is high. Our hypothesis is that the aetiology is dominated by cellular deformation (Bouten et al. in Ann Biomed Eng 29:153–63, 2001; Breuls et al. in Ann Biomed Eng 31:1357–364, 2003; Stekelenburg et al. in J App Physiol 100(6):1946–954, 2006) and deformation-induced ischaemia. The experimental observation that mechanical compression induced a pattern of interspersed healthy and dead cells in skeletal muscle (Stekelenburg et al. in J App Physiol 100(6):1946–954, 2006) strongly suggests to take into account the muscle microstructure in studying damage development. The present paper describes a computational model for deformation-induced hypoxic damage in skeletal muscle tissue. Dead cells stop consuming oxygen and are assumed to decrease in stiffness due to loss of structure. The questions addressed are if these two consequences of cell death influence the development of cell injury in the remaining cells. The results show that weakening of dead cells indeed affects the damage accumulation in other cells. Further, the fact that cells stop consuming oxygen after they have died, delays cell death of other cells.
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Affiliation(s)
- K K Ceelen
- Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands.
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Goswami J, Lynn R, Street G, Harlander M. Walking in a vacuum-assisted socket shifts the stump fluid balance. Prosthet Orthot Int 2003; 27:107-13. [PMID: 14571940 DOI: 10.1080/03093640308726666] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Gains in stump volume have been documented in trans-tibial amputees while walking in custom made under-sized, total surface-bearing, vacuum-assisted sockets (Board et al., 2001). These gains raised doubts as to whether the sockets were truly under-sized and concerns that using an over-sized socket with vacuum-assist could lead to swelling, resulting, in discomfort or pain. The purposes of the present study were to determine if: (a) walking in a vacuum-assisted socket causes the stump to retain or gain volume in excess of the available socket volume and (b) the resulting increase in stump volume with an over-sized socket causes discomfort, pain, and/or the skin to redden. The results of this study showed the stump retained or gained volume in excess of the available socket volume while walking in vacuum-assisted sockets of various sizes. The stump lost less volume than predicted, or gained volume, in under-sized sockets. It also gained more volume than predicted in over-sized sockets. No discomfort, pain, or skin reddening, resulting from the volume gain was reported by any of the subjects after walking in an over-sized socket. This change in fluid balance towards a net gain supports the findings by Board et al. (2001) that vacuum-assist ensures a good fit during the day in ambulatory trans-tibial traumatic amputees with mature stumps.
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Affiliation(s)
- J Goswami
- Health, Physical Education, Recreation and Sport Science, St. Cloud University, Minnesota 56301-4498, USA
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Morgan WH, Yu DY, Cooper RL, Alder VA, Cringle SJ, Constable IJ. Retinal artery and vein pressures in the dog and their relationship to aortic, intraocular, and cerebrospinal fluid pressures. Microvasc Res 1997; 53:211-21. [PMID: 9211399 DOI: 10.1006/mvre.1997.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The relationship between retinal arterial (Pra) and aortic (Pa) pressures is unknown, and the relationship between retinal vein (Prv) pressure and intraocular pressure (IOP) is not clear. Also unclear is the effect of cerebrospinal fluid pressure (CSFp) upon retinal venous pressure. We aimed to measure the relationships among Pra, Prv, Pa, IOP, and CSFp. Dogs were anesthetized while IOP, CSFp, and Pa were monitored. Pipettes with 2.5-micron diameter tips, connected to a servonulling pressure transducer, were used to record pressures from the retinal arteries and veins. Across a range of IOP (16-22 mmHg), CSFp (0-21 mmHg), and Pa (23-195 mmHg) the Pra = 0.72 Pa + 4.3 (r = 0.99, n = 61, P < 0.01), which suggests that the relationship between Pra and Pa is linear over a broad range of systemic blood pressures. The correlation coefficient between Prv and IOP was greater than 0.96 (P < 0.01) at all venous sites and whether IOP was greater than or less than CSFp. The transmural pressure varied along the retinal vein from 1.3 +/- 0.3 mmHg (+/-95% CI, n = 30) at 1 disk diameter from the optic disk rim to 0.3 +/- 0.2 mmHg (n = 66) at the optic disk, with a 0.9-mmHg/mm pressure gradient. These are the first measurements demonstrating a retinal vein transmural pressure close to zero.
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Affiliation(s)
- W H Morgan
- McCusker Glaucoma Centre, Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands
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Sejersted OM, Hargens AR. Intramuscular pressures for monitoring different tasks and muscle conditions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 384:339-50. [PMID: 8585463 DOI: 10.1007/978-1-4899-1016-5_27] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Intramuscular fluid pressure (IMP) can easily be measured in man and animals. It follows the law of Laplace which means that it is determined by the tension of the muscle fibers, the recording depth and by fiber geometry (fiber curvature or pennation angle). Thick, bulging muscles create high IMPs (up to 1000 mmHg) and force transmission to tendons becomes inefficient. High resting or postexercise IMPs are indicative of a compartment syndrome due to muscle swelling within a low-compliance osseofascial boundary. IMP increases linearly with force (torque) independent of the mode or speed of contraction (isometric, eccentric, concentric). IMP is also a much better predictor of muscle force than the EMG signal. During prolonged low-force isometric contractions, cyclic variations in IMP are seen. Since IMP influences muscle blood flow through the muscle pump, autoregulating vascular elements, and compression of the intramuscular vasculature, alterations in IMP have important implications for muscle function.
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Affiliation(s)
- O M Sejersted
- Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, Norway
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