Pressure Gradients Affecting the Labyrinth during Hypobaric Pressure

1997 ◽  
Vol 106 (6) ◽  
pp. 495-502 ◽  
Author(s):  
Konrád S. Konrádsson ◽  
Björn I. R. Carlborg ◽  
Joseph C. Farmer
Keyword(s):  
Cerebrospinal Fluid ◽  
Eustachian Tube ◽  
Ambient Pressure ◽  
Pressure Gradients ◽  
Cochlear Aqueduct ◽  
Fluid Compartment ◽  
Large Pressure ◽  
Fluid Compartments ◽  
Pressure Changes ◽  
Considerable Pressure

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

Functional Patency of the Cochlear Aqueduct

1982 ◽  
Vol 91 (2) ◽  
pp. 209-215 ◽  
Author(s):  
Björn Carlborg ◽  
Barbara Densert ◽  
Ove Densert
Keyword(s):  
Cerebrospinal Fluid ◽  
Inner Ear ◽  
Middle Ear ◽  
Ambient Pressure ◽  
Ear Canal ◽  
Cochlear Aqueduct ◽  
Pressure Release ◽  
Release Capacity ◽  
Before And After ◽  
Pressure Changes

The perilymphatic (P P) and cerebrospinal fluid (P CSF) pressures were investigated in relation to pressure variations in the ear canal, middle ear and intracranial compartment before and after occlusion of the cochlear aqueduct (CA). Experiments using intracranial infusion showed that the CA was responsible for a perfect hydrodynamic balance between the CSF and the perilymph. There are indications of additional pressure release factors but their capacities were not sufficient to prevent the appearance of a longstanding and substantial pressure gradient following occlusion of the CA. A gradual P P build-up, from zero to its original level after the CA was opened and occluded, indicated perilymph production within the labyrinth. Investigation of pressure transfer from the ear canal and middle ear to the perilymph showed that the CA was the major pressure release route from the cochlea. Occlusion of the CA reduced the compliance of the inner ear and severely reduced the pressure release capacity. In such a situation the inner ear is almost incapable of equilibrating ambient pressure changes.

Barotrauma Vis-a-Vis the “Chronic Otitis Media Syndrome”: Two Conditions with Middle Ear Gas Deficiency

2003 ◽  
Vol 112 (3) ◽  
pp. 230-235 ◽  
Author(s):  
Jacob Sadé ◽  
Amos Ar ◽  
Camil Fuchs
Keyword(s):  
Otitis Media ◽  
Middle Ear ◽  
Ambient Pressure ◽  
Chronic Otitis Media ◽  
Mastoid Pneumatization ◽  
Large Pressure ◽  
Pass Through ◽  
Pressure Changes ◽  
Gas Volume ◽  
Normal Controls

We compared 17 patients (29 ears) with barotrauma with 171 patients suffering from “chronic ears” (secretory otitis media, atelectasis, or previously operated cholesteatoma). The patients with “chronic ears” were followed up prospectively, and none were found to suffer from barotrauma after flying on a commercial airplane. The mastoid pneumatization (seen on lateral mastoid radiographs) was significantly larger in ears with barotrauma, averaging 16.85 cm2, versus 12.9 cm2 in normal controls, whereas in “chronic ears” it was only 3.6 cm2. During flight on a commercial airplane, the middle ear has to equalize about 20% of its gas volume with the ambient pressure. This equalization must happen within 15 to 20 minutes of ascent and descent in order to avoid barotrauma. This 20% is a fivefold greater task for ears with a large mastoid pneumatization than for ears with an undeveloped pneumatization; “chronic ears” usually have an undeveloped mastoid pneumatization. The smaller the middle ear (mastoid) volume, the smaller the volume of gas needed to pass through the eustachian tube in order to equalize pressure changes during flying. This factor may explain why “chronic ears” rarely suffer from barotrauma. It also implies that eustachian tubes of secretory otitis, atelectatic, and cholesteatomatous ears have little problem in equalizing large pressure differences (over 2,000 mm H2O) within 15 to 20 minutes of landing, in contrast to what has been traditionally believed. Individuals with “chronic ears” can be advised that they can fly safely.

The Influence of Coughing on Cerebrospinal Fluid Pressure in an In Vitro Syringomyelia Model With Spinal Canal Stenosis

2009 ◽  
Author(s):  
Bryn A. Martin ◽  
Francis Loth
Keyword(s):  
Cerebrospinal Fluid ◽  
Spinal Canal ◽  
Fluid Pressure ◽  
In Vitro Models ◽  
Spinal Canal Stenosis ◽  
Pressure Gradients ◽  
Canal Stenosis ◽  
Large Pressure ◽  
Type Flow

Five in vitro models were constructed which were representative of various pathologies of the spinal canal (SC) associated with syringomyelia (SM). The models were subjected to a cough type flow impulse while monitoring the pressure environment in the syrinx and subarachnoid space (SAS) regions of the model. The results indicated that conditions can arise during a cough which would provide pressure forces to encourage cerebrospinal fluid (CSF) movement into the syrinx cavity. The flow obstruction (stenosis) acted as an inflection point for transmural pressure (TP) in which the far region of the syrinx was expanded and the near region was compressed. In the case when a stenosis was present, but no syrinx had formed, the longitudinal pressure gradient and pulse pressures were highest on the SC. However, when a syrinx was present, the pressures were reduced, but still pathological. The primary point of pressure gradients in all of the experiments was the stenosis which caused large pressure dissociation in the system which could aid in SC ripping or tearing of the tissue. The presence of a syrinx appeared to decrease some of these forces, but without removal of the flow obstruction, a pathological biomechanical environment persists.

scholarly journals Extracellular fluid, cerebrospinal fluid and plasma biomarkers of axonal and neuronal injury following intracerebral hemorrhage

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lovisa Tobieson ◽  
Henrik Zetterberg ◽  
Kaj Blennow ◽  
Niklas Marklund
Keyword(s):  
Cerebrospinal Fluid ◽  
Intracerebral Hemorrhage ◽  
Brain Tissue ◽  
Single Molecule ◽  
Tissue Injury ◽  
Extracellular Fluid ◽  
Neurofilament Light ◽  
Aβ Peptides ◽  
Post Surgery ◽  
Fluid Compartments

AbstractSpontaneous intracerebral hemorrhage (ICH) is the most devastating form of stroke. To refine treatments, improved understanding of the secondary injury processes is needed. We compared energy metabolic, amyloid and neuroaxonal injury biomarkers in extracellular fluid (ECF) from the perihemorrhagic zone (PHZ) and non-injured (NCX) brain tissue, cerebrospinal fluid (CSF) and plasma. Patients (n = 11; age 61 ± 10 years) undergoing ICH surgery received two microdialysis (MD) catheters, one in PHZ, and one in NCX. ECF was analysed at three time intervals within the first 60 h post- surgery, as were CSF and plasma samples. Amyloid-beta (Aβ) 40 and 42, microtubule associated protein tau (tau), and neurofilament-light (NF-L) were analysed using Single molecule array (Simoa) technology. Median biomarker concentrations were lowest in plasma, higher in ECF and highest in CSF. Biomarker levels varied over time, with different dynamics in the three fluid compartments. In the PHZ, ECF levels of Aβ40 were lower, and tau higher when compared to the NCX. Altered levels of Aβ peptides, NF-L and tau may reflect brain tissue injury following ICH surgery. However, the dynamics of biomarker levels in the different fluid compartments should be considered in the study of pathophysiology or biomarkers in ICH patients.

Congenital Cerebrospinal Otorrhea

1979 ◽  
Vol 88 (3) ◽  
pp. 358-365 ◽  
Author(s):  
Richard R. Gacek ◽  
Bruce Leipzig
Keyword(s):  
Cerebrospinal Fluid ◽  
Initial Segment ◽  
Congenital Defects ◽  
Facial Canal ◽  
Cerebrospinal Fluid Fistula ◽  
Fallopian Canal ◽  
Cochlear Aqueduct ◽  
Cerebrospinal Fluid Leaks ◽  
Fluid Fistula ◽  
Petromastoid Canal

Four locations for congenital cerebrospinal fluid fistula in the region of a normal labyrinth are reviewed. A congenital leak may occur through the petromastoid canal, a wide cochlear aqueduct, Hyrtl's fissure, or the facial canal. A fistula through the initial segment of the fallopian canal was successfully repaired in a two-year-old boy who had three episodes of meningitis following otitis media. Knowledge of these four sites of congenital defects provides a guideline for the surgeon in the identification and repair of cerebrospinal fluid leaks in the region of the labyrinth.

Epidural versus subdural spinal cord cooling: cerebrospinal fluid temperature and pressure changes

2000 ◽  
Vol 70 (1) ◽  
pp. 222-227 ◽  
Author(s):  
Sven A Meylaerts ◽  
Cor J Kalkman ◽  
Peter de Haan ◽  
Marjolein Porsius ◽  
Michael J.H.M Jacobs
Keyword(s):  
Spinal Cord ◽  
Cerebrospinal Fluid ◽  
Fluid Temperature ◽  
Temperature And Pressure ◽  
Pressure Changes

Activated Shale Creep and Potential Micro-Annulus Investigated in the Field

2021 ◽  
Author(s):  
Andreas Bauer ◽  
Matteo Loizzo ◽  
Laurent Delabroy ◽  
Tron Golder Kristiansen ◽  
Kristian Klepaker
Keyword(s):  
Core Sample ◽  
Inversion Algorithm ◽  
Log Data ◽  
Sealing Capacity ◽  
Large Pressure ◽  
Elastic Rebound ◽  
Zonal Isolation ◽  
Pressure Changes ◽  
Drilling Muds ◽  
The Impact

Abstract It has been demonstrated that creeping shales can form effective hydraulic well barriers. Shale barriers have been used for many years in P&A of wells in Norway. More recently, shale barriers for zonal isolation have also been used in new wells where shale creep was found to occur within days. In some cases, shale creep is activated by a reduction in annulus pressure, in other cases shale creep sets in without any active activation, possibly by time-dependent formation-pressure changes. However, the presence of thixotropic fluids (drilling muds) in the annulus may prevent full closure of the annulus as it requires large pressure differentials to squeeze the fluid out of a microannulus. Furthermore, elastic rebound of an actively activated shale barrier could result in a microannulus and hence a possible leakage pathway. Improved logging technology is needed for identifying shale barriers and the presence of micro-annuli in shale-barrier zones. We use cement bond log data and standard bond logging criteria to evaluate the quality of the shale well barriers (Williams et al., 2009). In addition, in order to detect microannuli on the outside of the casing, a new inversion algorithm for the bond logging data was developed and tested on field data. Later, we had the chance to apply the inversion algorithm to bond-log data obtained in the laboratory with a miniature bond-logging tool inside a cased hollow-cylinder shale-core sample place. It turned out that both the micro-annulus widths and shale velocities determined by the inversion technique were too high. By constraining the shale velocities to more realistic values, the updated microannulus widths were smaller and more consistent with the experimental results. Small microannuli may not cause any measurable leakage along the well, especially if filled with a thixotropic fluid. However, more studies are needed to quantify the impact of microannuli on the sealing capacity of shale barriers.

Studies on the "labile-bound" glucose compartment in erythrocytes: studies on Psammomys obesus (sand rat) and preliminary studies on human erythrocytes.

1985 ◽  
Vol 31 (7) ◽  
pp. 1219-1221 ◽  
Author(s):  
M Halperin ◽  
J H Adler
Keyword(s):  
Glucose Oxidase ◽  
Glucose Concentration ◽  
Human Erythrocytes ◽  
Psammomys Obesus ◽  
Sand Rat ◽  
Fluid Compartment ◽  
Fast Kinetic ◽  
Fluid Compartments

Abstract Enzymatic (glucose oxidase) measurement of glucose concentration in the fluid compartment of Psammomys erythrocytes (Gfe) and of its concentration in the fluid compartment of blood plasma (Gfp) gives the ratio (mean +/- SD): Gfe/Gfp = 1.50 +/- 0.43 (n = 12, 23 degrees C). However, when we added 3H-labeled glucose (G*) in vitro to the whole blood, the ratio after 2 min was G*fe/G*fp = 0.90 (SD 0.11) and after 5 min G*fe/G*fp = 0.97 (SD 0.12). These calculations were based on previous determination of the fractional volumes of the fluid and non-fluid compartments in Psammomys blood. The results suggest that there is more than one compartment of measurable glucose in Psammomys erythrocytes. Glucose undergoes a fast free transfer between the plasma and the erythrocyte fluids, and a much slower transmission to another measurable compartment in the erythrocyte, where it is loosely bound to other molecules. This loosely bound glucose does not participate in the fast kinetic transmission across the erythrocyte membrane, but it is measurable by the glucose-oxidase-based method. Preliminary studies on human erythrocytes lead to similar conclusions.

Measurement of alveolar gas volume by ambient pressure changes in isolated lungs

1988 ◽  
Vol 65 (3) ◽  
pp. 1281-1285
Author(s):  
R. R. Martin ◽  
R. Peslin ◽  
C. Duvivier ◽  
C. Gallina
Keyword(s):  
Water Vapor ◽  
Ambient Pressure ◽  
Water Vapor Pressure ◽  
Volumetric Method ◽  
The Body ◽  
Highly Correlated ◽  
Isolated Lungs ◽  
Pressure Changes ◽  
Gas Volume ◽  
The Relationship

Alveolar gas volume (AGV) may be measured in humans (Peslin et al., J. Appl. Physiol. 62: 359-363, 1987) by applying very slow sinusoidal variations of ambient pressure (delta Pam) around the body and studying the relationship between delta Pam and the resulting gas displacement at the mouth (delta Vaw): AGVapc = (PB.delta Vaw)/(delta Pam.cos phi), where AGVapc is AGV measured by ambient pressure changes, PB is barometric minus alveolar water vapor pressure, and phi is the phase angle between Pam and Vaw. The applicability of this method to excised lungs at various transpulmonary pressures was assessed in six rabbit lungs and three dog lobes by reference to AGV measurements by He dilution (AGVdil) and by a volumetric method (AGVvol). Except in one instance, AGVapc did not change significantly when the frequency of delta Pam was varied from 0.02 to 0.2 Hz. AGVapc was highly correlated (P less than 0.001) to both AGVdil and AGVvol. It did not differ significantly from AGVdil (81.4 +/- 50.6 vs. 80.2 +/- 44.2 ml) and was only marginally higher than AGVvol (64.6 +/- 26.9 vs. 62.4 +/- 24.4 ml, P less than 0.05). We conclude that the method usually provides accurate results in excised lung preparations. Its main advantages are that it does not require manipulating the lung or changing its volume and that the measurement takes less than 1 min.

Sign in / Sign up

Export Citation Format

Share Document