Showing papers on "Pressure measurement published in 1998"

An experimental study of combustion dynamics of a premixed swirl injector

Abstract: A comprehensive experimental study has been conducted on combustion instabilities in a premixed swirler injector system at various equivalence ratios, chamber pressures, and inlet air temperatures. A stability map has been determined to indicate the range of operating conditions conductive to the occurrence of instabilities. The amplitude of instabilities was found to be a strong function of the equivalence ratio, with pressure oscillations as high as 20% of the mean chamber pressure and unsteady velocities comparable to the mean flow values observed for equivalence ratios around 0.6. On the other hand, beyond an initial threshold value of inlet air temperature at which instability suddenly initiated, variations in inlet air temperature had minimal effect on the strength of instabilities. Measurements of steady and unsteady flame structures carried out using CH chemiluminescence and photographic imaging techniques indicate that the onset of instabilities can potentially cause significant alterations in flame structure, sometimes even causing near extinction of the flame during certain periods of the oscillation cycle. Coupled longitudinal oscillations were observed in the combustion chamber and upstream duct. Instability characteristics such as frequency, mode shape, and phase obtained through pressure measurements were found to be in excellent agreement with predictions from a linear acoustic analysis. A strong correlation was found between the heat release and pressure fluctuations near the dump plane, indicating a possible mechanism for creating and sustaining instabilities.

Equation of state and radial distribution functions of FCC particles in a CFB

Abstract: Kinetic theory of granular flow was verified experimentally for flow of fluid catalytic cracking particles in a vertical pipe. Measurements of particle pressure using a differential transducer and granular temperature with a digital camera as a function of bulk density, determined using an X-ray densitometer, showed that a relation exists among pressure, temperature, and density, analogous to the ideal gas law. In the limit of zero solids volume fraction: (Solid Pressure)/[(Granular Temperature) × (Bulk Density)] = 1.0. Measurements of radial distribution functions using the digital camera showed that their peak values occur at particle contact and lie between the predictions from the Bagnold equation and Carnahan–Starling equation. The hard sphere model was corrected for a cohesive pressure using the minimum in the measured radial distribution function. The new model agrees with the pressure measurements in the dense regime.

A comparison of indirect blood pressure monitoring techniques in the anesthetized cat.

Abstract: OBJECTIVE: To determine the accuracy of three indirect blood pressure monitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measurement in cats. STUDY DESIGN: Prospective study. ANIMAL POPULATION: Eight healthy (five female, three male), domestic short-hair cats weighing 3.5 +/- 0.8 kg METHODS: Cats were anesthetized with isoflurane. The inspired concentration of isoflurane was adjusted to produce mild hypotension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (< 60 mm Hg direct systolic). Indirect pressure measurements were obtained from the thoracic limb and compared with concurrent direct measurement using regression analysis and a modification of Bland and Altman's technique. RESULTS: All three techniques underestimated systolic pressure. OS produced the best prediction of systolic pressure with a bias +/- precision of -15.9 +/- 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias +/- precision of -25 +/- 7.4 mm Hg and -25 +/- 7.5 mm Hg. All three techniques correlated well with direct pressure with r values of 0.81, 0.88, and 0.88 for OS, DOP, and OP. DOP and OP provided an accurate prediction of direct mean arterial pressure with a bias +/- precision of -0.8 +/- 6 mm Hg and 0.6 +/- 5.5 mm Hg. Correlation was good between DOP and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90. CONCLUSIONS: OS provided the most accurate prediction of direct systolic pressure. DOP and OP provided a good prediction of mean arterial pressure in the cat. CLINICAL RELEVANCE: All three of these techniques are useful for detecting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required.

Apparatus and method for detection of a leak in a membrane of a fluid flow control system

Abstract: An apparatus, method, and computer program product for detection of fluid leakage through a membrane in a fluid flow control system. The fluid flow control system has a first chamber and a second chamber. A membrane is disposed between the first chamber and the second chamber. The second chamber has a connection to a pressure tank, the pressure tank has a fluid with a pressure, and the connection defines a fluid path. The method indudes in a first step, blocking the fluid path. The pressure of the fluid in the pressure tank is then adjusted. The pressure is measured in the pressure tank which creates a pressure measurement at each of a first set of multiple timed intervals while the fluid path is blocked and after the pressure is adjusted. A blocked pressure rate is calculated based on the pressure measurements in the pressure tank at the first set of multiple timed intervals. Next, the fluid path is unblocked. The pressure is measured within the pressure tank creating a pressure measurement at each of a second set of multiple timed intervals after the fluid path is unblocked. Then, an unblocked pressure rate is calculated based on the pressure measurements in the pressure tank at the second set of multiple timed intervals. Finally a leakage rate is calculated based on the blocked pressure rate and the unblocked pressure rate. An alarm is caused when the leakage rate becomes greater than a predetermined threshold value.

On laser induced single bubble near a solid boundary: Contribution to the understanding of erosion phenomena

Abstract: Cavitation erosion is an especially destructive and complex phenomenon. In order to understand its basic mechanism, the dynamics of laser-induced vapor bubbles have been investigated. Special experimental devices have been used to record ultrafast visualizations and pressure measurements. From these measurements, the different sources of stresses, induced on the solid wall by the presence of the bubble (shock wave, microjet), have been characterized. The “water hammer” pressure associated with the microjet velocity varies up to 210 MPa. When the bubble collapses near a solid wall, the pressure emitted is less than in an infinite medium. Pressure values up to 2.5 MPa have been found. These values have been associated with the duration of the pressure applied to the solid wall, which is about 30 ns for the microjet and more than 300 ns for the shock wave. These results have been correlated with the analysis of damage created on the surface sample.

Passive remote sensing for temperature and pressure using SAW resonator devices

Abstract: Wireless sensing using passive sensors based on surface acoustic wave (SAW) technology is necessary for many applications. In this paper a new sensor design that uses the differential frequency output from two SAW resonators (SAWR) for temperature and pressure measurement is presented. The sensor, which consists of two SAWRs on the same substrate with different SAW propagation directions, relies on the variations of the SAW propagation velocity to measure environmental quantities such as pressure or temperature. The aim of this approach is to suppress the disturbing influences of the RF link (radio channel) between the interrogation unit and the passive sensor device. In this case, the output signal is a frequency difference and does not depend on changes in the radio channel during the transmission of the sensor signal.

Vacuum-sealed silicon micromachined pressure sensors

Abstract: Considerable progress in silicon pressure sensors has been made in recent years. This paper discusses three types of vacuum-sealed silicon micromachined pressure sensors that represent the present state of the art in this important area. The devices are a capacitive vacuum sensor, a surface-micromachined microdiaphragm pressure sensor, and a resonant pressure sensor. Vacuum sealing for these devices is accomplished using anodic bonding, films deposited using low-pressure chemical vapor deposition, and thermal out-diffusion of hydrogen, respectively. These sensors emphasize high sensitivity, small size, and excellent stability, respectively. The silicon-diaphragm vacuum sensor uses electrostatic force balancing to achieve a wide pressure measurement range.

Automated, ambulatory, or conventional blood pressure measurement in pregnancy: Which is the better predictor of severe hypertension? ☆ ☆☆ ★ ★★

Abstract: OBJECTIVES: Our purpose was to investigate the benefit, if any, of automated blood pressure monitoring over obstetric day unit conventional blood pressure measurement in the assessment of hypertensive pregnancies. STUDY DESIGN: A prospective, observational study was carried out in two large teaching hospitals. Three hundred and forty-eight women with a confirmed clinic blood pressure of at least 140/90 mm Hg were recruited. Conventional blood pressure measurements (≤5) were obtained on the day unit and simultaneously an ambulatory blood pressure monitor was applied for 24 hours. The predictive ability of day unit assessment (blood pressure >140/90 mm Hg) and automated blood pressure monitoring (blood pressure >130/85 mm Hg) was compared. Principal outcome measures included the occurrence of severe hypertension (>160/110 mm Hg) and proteinuria (>500 mg or 2+) within (a) 2 weeks and (b) the remainder of the pregnancy. Thompson's method was used to compare sensitivity and specificity of the day unit blood pressure and automated blood pressure monitoring. RESULTS: Three hundred and forty-eight women were recruited to the study. The comparison between automated blood pressure monitoring and conventional blood pressure measurement for both sensitivity and specificity for systolic and diastolic blood pressure revealed increased sensitivity and decreased specificity with automated blood pressure monitoring for all principal outcomes except development of proteinuria for systolic blood pressure. Sensitivity for the outcomes was increased with automated blood pressure monitoring by between 14% and 27% for systolic blood pressure and between 7% and 39% for diastolic blood pressure, with the greatest improvement seen for the development of severe hypertension within 2 weeks of assessment. CONCLUSIONS: In the assessment of hypertensive pregnancies, automated blood pressure measurement was a significantly better predictor (compared with conventional day unit assessment) for the development of severe hypertension within 2 weeks of assessment for both systolic and diastolic blood pressure. (Am J Obstet Gynecol 1998;178:521-6.)

Accuracy limits for planar measurements of flow field velocity, temperature and pressure using Filtered Rayleigh Scattering

Abstract: We present experimental results using Filtered Rayleigh Scattering to make planar measurements of velocity, temperature and pressure in ambient air and in a Mach 2 free jet. The ambient air measurements are used to identify and calibrate experimental uncertainties. The Mach 2 measurements demonstrate the usefulness of the technique for making accurate planar measurements in a high speed flow. The measured values for velocity, temperature and pressure in the Mach 2 jet ranged, through a shock system, from 205 to 235 m/s, 150 to 170 K and 700 to 1000 torr, with estimated uncertainties of ±5.4 m/s, ±3.2 K and ±38 torr (±2 to 3%, ±2% and ±4–5%, respectively).

A fiber-optic pressure microsensor for biomedical applications

Abstract: A fiber-optic pressure microsensor with a sensing element only 270 μm × 270 μm × 150 μm in size has been developed and applied to actual balloon catheters. The sensing principle is based on the detection of optical reflection intensity changes from a diaphragm located in front of an optical fiber. The sensors have been fabricated using silicon micromachining, such as anisotropic etching and direct wafer bonding. For the transmitting source and signal light, a multimode optical fiber 125 μm in diameter is used. This paper describes the miniaturization of the sensing element through an improved design and the use of thinner silicon wafers, and application of the pressure microsensor to actual balloon catheters 1.5 mm in outer diameter. We have found that there is a large pressure difference between the injector and the balloon, which is due to the transmission loss that occurs in the tube from the injector to the balloon.

In vivo zeroing of catheter pressure sensor

Abstract: A catheter-based physiological pressure sensing device, which can be calibrated in vivo, is disposed in the distal end of a catheter, and is preferably in the form of a bulb-like device. The pressure sensing device includes a pressure sensor tip and pressure sensor element disposed in the pressure sensor tip. The pressure sensor element has first and second opposing surfaces which form separate and isolatable first and second chambers. An aperture is formed in an external wall of the pressure sensor tip to provide a passageway into the first chamber and expose the first surface of the pressure sensor element to a physiological pressure. A blocking element, such as a balloon, is disposed in the first chamber and is adapted for selectively blocking the aperture. To measure a physiological pressure, the aperture is unblocked to allow an outside pressure into the first chamber and a reference pressure is presented to the second chamber so that the surfaces of the pressure sensing element can measure the differential pressure. To calibrate or zero the device, the blocking element blocks the aperture to seal the first chamber with respect to external pressure and a fluid at a known pressure is introduced to the first and second chambers. The pressure sensor element provides an output signal indicative of a zero offset pressure to a pressure monitoring circuit to calibrate, or zero, the sensor and enhance the accuracy of subsequent pressure measurements.

Pressure sensitivity of side-hole optical fiber sensors

Abstract: The dependency of the pressure-induced birefringence of a side-hole fiber on its geometry has been numerically investigated using the finite element method. We demonstrate that the pressure sensitivity of such a fiber shows a linear dependence on /spl phi//sup 2/, where /spl phi/ is the angle between the side hole center and core center axis and the core center to side-hole tangent. Experimental data obtained with two different side-hole fiber sensors are shown to agree extremely well (to within 10%) with theoretical predictions.

Ventilator suitable for miniaturization

Abstract: A ventilator includes a gas flow generator for generating a gas with an adjustable pressure and/or flow rate, an inspiratory line with a proximal end, connected to the gas flow generator and a distal end, devised for connection to a patient, an expiratory valve connected to the inspiratory line at a specific distance from the distal end of the inspiratory line to evacuate gas exhaled by the patient, a pressure gauge and/or a flow meter arranged to measure pressure and/or the rate of gas flow in the inspiratory line and a control unit for controlling at least the maintenance of a positive end-expiratory pressure (PEEP). For PEEP to be maintained in a simple and reliable manner, the ventilator is devised with the pressure gauge and/or the flow meter connected to the inspiratory line between the expiratory valve and the distal end of the inspiratory line, and the control unit is devised to open the expiratory valve and regulate, on the basis of the pressure and/or flow measured, a flow of gas through the inspiratory line during expiration so that the desired positive end-expiratory pressure is maintained.

Pressure effects on soft tissues monitored by changes in tissue optical properties

Abstract: For pulsed laser tissue welding, an appropriate pressure needs to be applied to the tissues to achieve successful welds. In this study, we investigated the influences of pressure on in vitro optical properties of elastin biomaterial. The optical properties were measured as a function of pressure with a double integrating-sphere system. A He-Ne laser (633 nm) was used for all measurements. Each sample was sandwiched between microscope slides and then compressed with a spring-loaded apparatus. Transmittance and diffuse reflectance of each sample were measured under a pressure (0 - 1.5 kg/cm2 and then released to 0). Absorption and reduced scattering coefficients were calculated using the inverse doubling method from the measured transmittance and reflectance values. Results from this study demonstrated: (1) The overall transmittance increased while the reflectance decreased as the tissue thicknesses were reduced up to 72% and the tissue weights were decreased about 40%, (2) The absorption and scattering coefficients increased with increasing the pressure, and (3) The pressure effects on the tissue optical properties were irreversible. Possible mechanisms responsible for the changes in the tissue optical properties were also investigated by changing tissue thicknesses or weights (through dehydration). This study implies that changes in tissue thickness and water content are important factors that affect tissue optical properties in different ways.

Analysis of radiometric, lifetime and fluorescent lifetime imaging for pressure sensitive paint

Abstract: Optical pressure measurement using fluorescent techniques is being widely researched for use in windtunnels. The technique offers global coverage of model surface pressures. A paint, the fluorescence of which is dependent on air pressure, is applied to the surface of a windtunnel model and the pressure distribution is obtained from the intensities measured. There are three principle techniques used to produce the surface pressure distributions: radiometric imaging, lifetime measurement and fluorescent lifetime imaging. Radiometric imaging produces global images. A constant illumination is used to excite the paint. The fluorescent intensity distribution is dependent on the surface pressure. Error analysis reveals that the technique has the highest precision at low absolute pressures. However, wind-off reference images are required to compensate for illumination and paint non-uniformity. Experimental investigation found that although this is able to compensate for rigid structures, model movement introduces registration and geometric errors. These errors can be corrected by processing at the expense of accuracy. Lifetime measurement is a technique that uses pulsed illumination. The fluorescent lifetime is dependent on the pressure. A wind-off reference image is not required and error analysis predicts that the technique holds an advantage at high absolute pressures. Fluorescent lifetime imaging produces global images using a modulated light source to excite the paint. The phase and modulation depth of the fluorescent signal are proportional to the pressure. A wind-off reference image is not required and error analysis predicts that the technique has the same advantages as lifetime imaging. Preliminary results from fluorescent lifetime imaging indicate that this technique can be implemented using robust, solid-state technology.

Measurement of continuous pressure and shear distributions using coating and imaging techniques

Abstract: The pressure-sensitive paint (PSP) method and the shear-sensitive liquid crystal coating (SSLCC) method were sequentially applied to measure the areal pressure and shear stress vector distributions on a planar test surface beneath an inclined, axisymmetric, turbulent impinging jet. The combined results provide the first-ever consolidated measurements of the continuous normal and tangential force distributions beneath a fundamental flowfield. Results indicate that the PSP method can be extended to the measurement of small pressure differences (< ∼0.1 psig) encountered in low-speed atmospheric flows. Further, these results provide the first demonstration of the capability of the SSLCC method to measure continuous shear stress vector distributions on planar surfaces beneath flowfields where shear vectors of all possible orientations are present

Non-contaminating pressure transducer module

Abstract: A non-contaminating pressure transducer module having an isolation member is disclosed. The isolation member isolates a pressure sensor (88) within the transducer module from exposure to ultra high purity fluids flowing through a conduit in the module without significantly affecting the accuracy of the pressure measurement. The transducer module may be positioned with a fluid flow circuit carrying corrosive materials, wherein the pressure transducer module produces a control signal proportional to either a gauge pressure or an absolute pressure of the fluid flow circuit. The pressure transducer module of the present invention also avoids the introduction of particulate, unwanted ions, or vapors into the flow circuit.

Treating temperature-sensitivity effects of pressure-sensitive paint measurements

Abstract: While pressure-sensitive paint (PSP) is evolving into a viable alternative to conventional pressure taps for surface pressure measurements, the inherent temperature-sensitivity of the coating’s fluorescence intensity is a prominent drawback. Unless the PSP is applied to a temporally and spatially isothermal surface, this inherent temperature-sensitivity effect severely limits the accuracy of the two-dimensional pressure distribution obtained from the coating. In this study, the pressure- and temperature-sensitivity effects of three commonly used PSPs and two temperature-sensitive paints (TSPs) are evaluated over pressure and temperature ranges found in many compressible flow experiments. In addition, four PSP data reduction methods are compared by applying PSP to a transverse jet-in-crossflow experiment. Each data reduction method encompasses a different degree of temperature correction. Conventional pressure tap measurements are used to evaluate the accuracy of each method.

Bourdon tube pressure gauge with integral optical strain sensors for measuring tension or compressive strain

Abstract: A Bourdon tube pressure gauge is mounted for sensing the pressure of a system. The Bourdon tube is connected to at least one optical strain sensor mounted to be strained by movement of the Bourdon tube such that when the Bourdon tube is exposed to the pressure of the system, movement of the tube in response to system pressure causes a strain in the optical sensor. The optical sensor is responsive to the strain and to an input optical signal for providing a strain optical signal which is directly proportional to the pressure. A reference or temperature compensation optical sensor is isolated from the strain associated with the pressure of the system and is responsive to temperature of the system for causing a temperature-induced strain. The reference optical sensor is responsive to the temperature induced strain and the input optical signal for providing a temperature optical signal which is directly proportional to the temperature of the system. The temperature optical signal is provided for temperature compensation of the strain optical signal. The optical sensors include an optical fiber having intrinsic Bragg grating sensors formed in the optical fiber. The optical fiber is attached to a reference point and to the Bourdon tube such that changes in the position of the tube changes the strain on the optical fiber resulting in a wavelength shift of light reflected by the Bragg grating. The magnitude of the wavelength shift is directly proportional to a change in pressure.

Solenoid pressure transducer

Abstract: A solenoid pressure transducer for measuring and controlling pressure within a system includes pressure sensing technology incorporated into a solenoid valve such that a common pressure chamber is used to sense pressure of a fluid and to control the flow of the same fluid. A solenoid sleeve forms the pressure chamber and a sensing element attached to the sleeve is used to measure pressure within the sleeve. The pressure measurement is then used by the solenoid sleeve to control the position of the solenoid valve.

Estimating Wave Heights from Pressure Measured in Sand Bed

Abstract: Comparison of predicted with observed attenuation of pressure fluctuations shows that wave heights can be estimated with observations from a pressure sensor that is buried a known depth in fine sand. The attenuation of pressure fluctuations within the sand bed under unbroken shoaling waves, bores in the surf zone, and swash near the shoreline was measured with vertical stacks of buried pressure sensors. The attenuation increased with increasing frequency and depth below the bed surface, consistent with previous observations under nonbreaking waves in deeper water and with model predictions based on poro-elastic theory. In the limit of an infinitely deep soil skeleton that is much more compressible than the pore fluid, the predicted pressure fluctuations decrease exponentially with increasing burial depth, and the attenuation is independent of the sediment properties. For the fine-grained sand beds considered here, this exponential limit accurately predicts the observed attenuation.

Measurement of air-gun bubble oscillations

Abstract: In this paper, I provide a theoretical basis for a practical approach to measuring the pressure field of an air gun array and present an algorithm for computing its wavefield from pressure measurements made at known positions in the vicinity of the gun ports. The theory for the oscillations of a single bubble is essentially a straight‐forward extension of Lamb’s original paper and provides a continuous, smooth transition from the oscillating wall of the bubble to the far‐field, preserving both the fluid flow and the acoustic radiation, all to the same accuracy and valid for bubbles with initial pressures up to about 200 atm (3000 psi or 20 MPa). The simplifying assumption, based on an argument of Lamb, is that the particle velocity potential obeys the linear acoustic wave equation. This is used then in the basic dynamic and kinematic equations to lead, without further approximations, to the nonlinear equation of motion of the bubble wall and the wavefield in the water. Given the initial bubble radius, the...

Quartz thickness-shear mode pressure sensor design for enhanced sensitivity

Abstract: Companies in the oil and gas industry rely upon acquisition of accurate downhole pressure data for management of reservoir resources. Pressure data must be acquired in extreme environments present in wells, including high pressures, high temperatures, and high levels of shock and vibration. A primary concern of oil and gas companies is that pressure transducers provide reliable data throughout the duration of well-testing jobs. Important performance parameters for well-test pressure gauges include inaccuracy arising from nonlinearity, hysteresis, nonrepeatability, and temperature. Accurate pressure measurements are required for determination of reservoir resources. Sensor output per unit pressure (sensitivity) and the corresponding minimum resolvable pressure (resolution) are important performance considerations. Pressure resolution is the key parameter for dynamic well-test analyses used to determine reservoir properties. Design limits, including maximum allowable pressure over the operating temperature range, also must be known. Pressure transducers must retain acceptable performance characteristics including accuracy, sensitivity, and resolution for long periods of operation to provide reliable data and reduce the frequency and cost of recalibration. This paper describes a unique quartz thickness-shear mode sensor that was developed for downhole pressure measurements. Pressure transducers that use this sensor meet the demanding requirements of downhole testing.

High-sensitivity silicon capacitive sensors for measuring medium-vacuum gas pressures

Abstract: The design, construction, and preliminary testing of an experimental capacitive silicon pressure sensor are described. The prototype sensor is designed as a robust, precision barometer suitable for measurements on the planet Mars where the mean atmospheric pressure is ~ 6 mbar (600 Pa). Most commercially available silicon pressure sensors tend to operate over pressure ranges ≥ 1 bar, or measure gauge pressure, but this sensor is specifically constructed to measure absolute pressure of 0–10 mbar with a very high sensitivity ~ 1 pF mbar −1 . The transductional mechanism is the deflection of a silicon diaphragm under applied pressure across a sealed vacuum cavity. Under storage conditions of 1 bar, the diaphragm displacement is mechanically constrained by an underlying stopping surface. Finite-element analysis shows that typical structures are extremely resistant to overpressure: fracture occurs at many tens of bar. The device is fabricated using a silicon fusion-bonded vacuum cavity which provides for relative insensitivity to temperature changes.

Stable algorithm for estimating airdata from flush surface pressure measurements

Abstract: An airdata estimation and evaluation system and method, including a stable algorithm for estimating airdata from nonintrusive surface pressure measurements. The airdata estimation and evaluation system is preferably implemented in a flush airdata sensing (FADS) system. The system and method of the present invention take a flow model equation and transform it into a triples formulation equation. The triples formulation equation eliminates the pressure related states from the flow model equation by strategically taking the differences of three surface pressures, known as triples. This triples formulation equation is then used to accurately estimate and compute vital airdata from nonintrusive surface pressure measurements.

Continuous long-term measurements of the middle ear pressure in subjects without a history of ear disease

Abstract: A new method was used for continuous measurement of the middle ear (ME) pressure during a 24-h period. In 10 subjects without a history of ear disease a small perforation was made through the tympanic membrane. A tight rubber stopper containing a small polyethylene tube was fitted into the external ear canal. Conventional tubal function tests were performed. The equipment was then carried by the subjects for 24 h of normal activity to monitor any slow or rapid dynamic pressure change in the ME. Body position was found to be the most important factor affecting ME pressure variation, during the 24-h continuous pressure measurements. A significant pressure rise occurred in the recumbent position in all but one subject. Few rapid pressure equilibrations were seen during the recordings, indicating few tubal openings. This implies that the pressure changes in the ME seen in this study were mainly the result of gas exchange over the mucosa. The investigation might be a base for reference when investigating different kinds of pathologic conditions in the ear.

Non-invasive method of measuring cerebral spinal fluid pressure

Abstract: The invention provides a method of non-invasively determining intracranial pressure from measurements of an eye. A parameter of an optic nerve of the eye is determined, along with an intraocular pressure of the eye. The intracranial pressure may be determined from the intraocular pressure and the parameter.