Brain elasticity changes with ventriculomegaly

1980 ◽  
Vol 53 (2) ◽  
pp. 173-179 ◽  
Author(s):  
Frederick H. Sklar ◽  
Jan T. Diehl ◽  
Chester W. Beyer ◽  
W. Kemp Clark
Keyword(s):  
Absorptive Capacity ◽  
Pulse Amplitude ◽  
Variable Rate ◽  
Ventricular Size ◽  
Content Type ◽  
Natural Logarithm ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Relationship Of ◽  
Fine Print

✓ The pressure-volume relationship of brain elasticity was determined in 32 patients during servo-controlled variable-rate lumbar infusions to measure net cerebrospinal fluid (CSF) absorptive capacity. Several indices were used to estimate ventricular size from computerized tomography scans. The results show a linear relationship between ventricular size and the elasticity slope which relates the natural logarithm of pressure to volume. It follows that a hydrocephalic patient should show a greater intracranial pulse amplitude at a given pressure than does a patient with normal-sized ventricles. Although these elasticity changes may simply be the result of the ventriculomegaly, it seems possible that the pressure-volume elasticity relationship may be of etiological importance in disorders of the CSF system.

Physiological features of the pressure-volume function of brain elasticity in man

1980 ◽  
Vol 53 (2) ◽  
pp. 166-172 ◽  
Author(s):  
Frederick H. Sklar ◽  
Chester W. Beyer ◽  
W. Kemp Clark
Keyword(s):  
Intracranial Pressure ◽  
Clinical Value ◽  
Content Type ◽  
Absorptive Capacities ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Relationship Of ◽  
The Relationship ◽  
Infusion Technique ◽  
Elasticity Measurements

✓ The intracranial pressure-volume relationship of brain elasticity was examined in 20 patients with suspected disorders of the cerebrospinal fluid (CSF) system. Elasticity measurements were made as the patients were studied with a servo-controlled lumbar infusion technique to measure CSF absorptive capacity. The data were evaluated to determine the relationship between intracranial pressure (ICP) and volume, and between ICP variability and the level of ICP. The results confirm the exponential nature of the pressure-volume elasticity function in patients who are not critically ill. Eight of the 20 patients were shown to have normal CSF absorptive capacities, and there was no difference between their elasticity measurements and those of patients with absorptive defects. In addition, ICP variability was shown to be linearly related to the actual level of ICP. The physiological features of the pressure-volume elasticity function are reviewed. Based on these considerations, the clinical value and significance of elasticity measurements is questioned.

Imaging correlates of successful endoscopic third ventriculostomy

2000 ◽  
Vol 92 (6) ◽  
pp. 915-919 ◽  
Author(s):  
Abhaya V. Kulkarni ◽  
James M. Drake ◽  
Derek C. Armstrong ◽  
Peter B. Dirks
Keyword(s):  
Clinical Success ◽  
Subjective Assessment ◽  
Third Ventriculostomy ◽  
Ventricular Size ◽  
Content Type ◽  
Exact Test ◽  
Subjective Assessments ◽  
Flow Void ◽  
Fine Print

Object. The goal of this study was to determine and compare imaging correlates in pediatric patients who underwent successful or failed endoscopic third ventriculostomies (ETVs). To this end, the authors measured ventricular size changes and the presence of cerebrospinal fluid (CSF) flow void in both groups of children following ETV.Methods. Images obtained in children with hydrocephalus immediately before and at least 30 days after having undergone ETV were reviewed by four independent observers (two blinded and two nonblinded). Each observer independently measured the frontal and occipital horn ratio ([FOR], a reliable and valid measure of ventricular size) and provided a subjective assessment of the presence of a flow void at the ETV site, the degree of periventricular edema, and the amount of CSF over the cerebral hemispheres.There were 29 children whose mean age was 6.6 years at the time of ETV and who had a mean postoperative follow-up period lasting 1.6 years. Postoperatively, the mean reduction in ventricular size (as measured using the FOR) was 7% (95% confidence interval [CI] 3–11%) in cases that were deemed failures (eight patients) and 16% (95% CI 12–20%) in clinically successful cases (21 patients). This reduction was significantly greater in cases of clinical success compared with those that were deemed failures (p = 0.03, t-test). There were no substantial differences between blinded and nonblinded assessments. Flow void was present in 94% of successes and absent in 75% of failures (p = 0.01, Fisher's exact test). The other subjective assessments were not significantly different between the groups of successes and failures.Conclusions. Ventricular size appears to be somewhat reduced in both groups of patients who underwent clinically successful and failed ETV; however, the reduction is significantly greater among clinically successful cases. The presence of a flow void also appears to correlate with clinical success and its absence with clinical failure.

Subtle deterioration in shunted childhood hydrocephalus

1986 ◽  
Vol 65 (2) ◽  
pp. 211-216 ◽  
Author(s):  
Arno Fried ◽  
Kenneth Shapiro
Keyword(s):  
Buffering Capacity ◽  
Volume Index ◽  
Shunt Revision ◽  
Pressure Waves ◽  
Ventricular Size ◽  
Csf Shunts ◽  
Content Type ◽  
The Mean ◽  
Childhood Hydrocephalus ◽  
Fine Print

✓ Eighteen hydrocephalic children who presented with subtle deterioration when their shunts malfunctioned were studied during shunt revision by means of the pressure-volume index (PVI) technique. Bolus manipulation of cerebrospinal fluid (CSF) was used to determine the PVI and the resistance to the absorption of CSF (Ro). Ventricular size was moderately to severely enlarged in all the children. Steady-state intracranial pressure (ICP) at the time of shunt revision was 17.5 ± 7.3 mm Hg (range 8 to 35 mm Hg). Pressure waves could not be induced by bolus injections in the 8- to 35-mm Hg range of ICP tested. The mean ± standard deviation (SD) of the predicted normal PVI for this group was 18.5 ± 2.7 ml. The mean ± standard error of the mean of the measured PVI was 35.5 ± 2.1 ml, which represented a 187% ± 33% (± SD) increase in volume-buffering capacity (p < 0.001). The ICP did not fall after bolus injections in three children, so that the Ro could not be measured. In the remaining 15 patients, Ro increased linearly as a function of ICP (r = 0.74, p < 0.001). At ICP's below 20 mm Hg, Ro ranged from 2.0 to 5.0 mm Hg/ml/min, but increased to as high as 21 mm Hg/ml/min when ICP was above 20 mm Hg. This study documents that subtle deterioration in shunted hydrocephalic children is accompanied by abnormally compliant pressure-volume curves. These children develop ventricular enlargement and neurological deterioration without acute episodic pressure waves. The biomechanical profile of this group differs from other children with CSF shunts.

scholarly journals Under Pressure: Intraluminal Filling Pressures of Postpartum Hemorrhage Tamponade Balloons

2017 ◽  
Vol 07 (02) ◽  
pp. e86-e92 ◽  
Author(s):  
Kathleen Antony ◽  
Diana Racusin ◽  
Michael Belfort ◽  
Gary Dildy
Keyword(s):  
Postpartum Hemorrhage ◽  
Ex Vivo ◽  
Volume Ratio ◽  
Intraluminal Pressure ◽  
Acute Hemorrhage ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Relationship Of ◽  
Condom Catheter ◽  
Filling Capacity

Objective Uterine tamponade by fluid-filled balloons is now an accepted method of controlling postpartum hemorrhage. Available tamponade balloons vary in design and material, which affects the filling attributes and volume at which they rupture. We aimed to characterize the filling capacity and pressure-volume relationship of various tamponade balloons. Study Design Balloons were filled with water ex vivo. Intraluminal pressure was measured incrementally (every 10 mL for the Foley balloons and every 50 mL for all other balloons). Balloons were filled until they ruptured or until 5,000 mL was reached. Results The Foley balloons had higher intraluminal pressures than the larger-volume balloons. The intraluminal pressure of the Sengstaken-Blakemore tube (gastric balloon) was initially high, but it decreased until shortly before rupture occurred. The Bakri intraluminal pressure steadily increased until rupture occurred at 2,850 mL. The condom catheter, BT-Cath, and ebb all had low intraluminal pressures. Both the BT-Cath and the ebb remained unruptured at 5,000 mL. Conclusion In the setting of acute hemorrhage, expeditious management is critical. Balloons that have a low intraluminal pressure-volume ratio may fill more rapidly, more easily, and to greater volumes. We found that the BT-Cath, the ebb, and the condom catheter all had low intraluminal pressures throughout filling.

Pulmonary interstitial compliance and microvascular filtration coefficient

1980 ◽  
Vol 239 (2) ◽  
pp. H189-H198 ◽  
Author(s):  
H. S. Goldberg
Keyword(s):  
Dynamic Properties ◽  
Transpulmonary Pressure ◽  
Filtration Coefficient ◽  
Alveolar Pressure ◽  
Fluid Movement ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Relationship Of ◽  
The Relationship

Static and dynamic properties governing the fluid movement into the pulmonary interstitium were examined in isolated canine lobes. The system was driven by altering intravascular presure (Piv) when the lobe was isogravimetric (change in weight (W) = 0) and allowing the lobe to become isogravimetric again. By making use of an analogy to charging a capacitor across a resistor, calculation of the filtration coefficient for transvascular fluid movement (KF) and determination of the pressure-volume relationship of the pulmonary interstitial space (Pis-Vis), with a minimum of untested assumptions, was possible. KF was found to be the same for fluid moving out of or into the intravascular space, and when the relationship between Piv and alveolar pressure (PAlv) was constant, KF was independent of transpulmonary pressure (PL). When PAlv exceeded Piv, changes in Piv did not influence KF, suggesting no significant change in either surface area available for fluid transudation or vascular permeability. The Pis-Vis curve for increasing values of Vis and Pis is best described by an exponential relationhip and is independent of PL. However, the Pis-Vis curve with decreasing values of Vis and Pis is dependent on PL.

scholarly journals PRESSURE-VOLUME RELATIONSHIP OF THE FUNDULUS EGG IN SEA WATER AND IN SUCROSE

1956 ◽  
Vol 40 (1) ◽  
pp. 91-105 ◽  
Author(s):  
C. Y. Kao
Keyword(s):  
Plasma Membrane ◽  
Hydrostatic Pressure ◽  
Sea Water ◽  
Sucrose Solution ◽  
Limiting Factor ◽  
Egg Volume ◽  
Rectangular Hyperbola ◽  
Volume Relationship ◽  
Pressure Volume Relationship ◽  
Relationship Of

Upon activation, an internal hydrostatic pressure develops within the Fundulus egg, and compresses the egg proper to a reduced volume. When the perivitelline pressure is abolished by a highly hypertonic sucrose solution, the egg volume increases. As sucrose penetrates the chorion, the volume again decreases. The relation between P and V in these conditions is inverse, and approximates a rectangular hyperbola. The limiting factor causing most of the deviation is shown to be the incompressible fraction. It is concluded that the volume of the egg proper is controlled by the perivitelline pressure, and that the effect of hypertonic sucrose solution is exerted by lowering the pressure and thereby increasing membrane permeability non-specifically. It is also shown that some permanent alterations occur within the plasma membrane during activation that reduce the permeance, and thereby, increase the incompressible fraction.

A simple, inexpensive technique for accurate mass localization by computerized tomography

1980 ◽  
Vol 52 (5) ◽  
pp. 733-735 ◽  
Author(s):  
John I. Moseley ◽  
Steven L. Giannotta ◽  
Justin W. Renaudin
Keyword(s):  
Computerized Tomography ◽  
Accurate Mass ◽  
Content Type ◽  
Accurate Localization ◽  
Relationship Of ◽  
The Relationship ◽  
Inexpensive Technique ◽  
Tomography Scanning ◽  
Fine Print

✓ A simple wire template is placed on the patient's head during computerized tomography scanning, and the results of the scan are later reproduced on the scalp prior to surgery. Measurements of the distance between the wires and the relationship of the mass provide the key to accurate localization of the mass on the scalp surface.

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