Journal articles: 'Pressure'

1

Dinamarco, Nelson, Grazia Maria Guerra, Frida Liane Plavnik, Luis Cuadrado Martin, and Luiz Aparecido Bortolotto. "MELHORANDO O CONTROLE DA PRESSÃO ARTERIAL COM A ADOÇÃO DA AUTOMEDIÇÃO DA PRESSÃO ARTERIAL– AMPA." Revista Brasileira de Hipertensão 29, no. 2 (June 1, 2022): 34–36. http://dx.doi.org/10.47870/1519-7522/2022290234-6.

Full text

Abstract:

Blood Pressure Self-Measurement (BPSM) has gained interest lately and its practice can contribute to the diagnosis and follow-up of arterial hypertension. In Brazil, due to difficulties in carrying out Home Blood Pressure Monitoring (HBPM) and the unavailability of Ambulatory Blood Pressure Monitoring (ABPM) in most facilities, AMPA, which differs from the aforementioned methods, has widespread use in our country. Therefore, it seems important to discuss this method, which is largely used and poorly studied. In this paper, we will describe the methods for measuring blood pressure, auscultatory and oscillometric, in addition to listing the advantages and disadvantages of measuring blood pressure in the office, comparing them with AMPA. We will also make an alert about the need for the patient to receive guidance on blood pressure measurement and, finally, we will cite the Brazilian and European Guidelines regarding the mention they make about this method.

APA, Harvard, Vancouver, ISO, and other styles

2

DS, Dr Rajeev. "Peripheral Venous Pressure: An Alternative to Central Venous Pressure?" Journal of Medical Science And clinical Research 05, no. 04 (April 27, 2017): 20685–91. http://dx.doi.org/10.18535/jmscr/v5i4.154.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Ruth, P. J. van, R. R. Hillis, and R. E. Swarbrick. "DETECTING OVERPRESSURE USING POROSITY-BASED TECHNIQUES IN THE CARNARVON BASIN, AUSTRALIA." APPEA Journal 42, no. 1 (2002): 559. http://dx.doi.org/10.1071/aj01032.

Full text

Abstract:

Overpressure has been encountered in many wells drilled in the Carnarvon Basin. Sonic logs are used to estimate pore pressure in shales in the Carnarvon Basin using the Eaton and equivalent depth methods of estimating pore pressure from velocity data with reference to a normal compaction trend. The crux of pore pressure estimation from the sonic log lies in the determination of the normal compaction trend, i.e. the acoustic travel time (Δt)/depth (z) trend for normally pressured sediments. The normal compaction trend for shales in the Carnarvon Basin was established by fitting an Athy-type exponential relationship to edited sonic log data, and is: Δt = 225 + 391exp(-0.00103z) Vertical stress estimates are also needed for the Eaton and equivalent depth methods used herein. A vertical stress (σv) relationship was obtained by fitting a regression line to vertical stress estimates from the density log, and is: σv = 0.0131 z1.0642 The Eaton and equivalent depth methods yield similar pressure estimates. However, the equivalent depth method can only be applied over a limited range of acoustic travel times, a limitation that does not apply to the Eaton method. The pressure estimates from the Eaton method were compared to pressures measured by direct pressure tests in adjacent permeable units. There is a good correlation between Eaton and test pressures in normally pressured intervals in three wells and overpressured intervals in two wells. Eaton pressure estimates underestimate overpressured direct pressure measurements in four wells by up to 13 MPa. This is consistent with overpressure being generated (at least in part) by a fluid expansion mechanism or lateral transfer of overpressure. The Eaton pressures in one well are, on average, 11 MPa lower than hydrostatic pore pressure recorded in direct pressure measurements below the Muderong Shale. The sediments in this well appear to be overcompacted due to exhumation. Mud weights can be used as a proxy for pore pressure in shales where direct pressure measurements are not available in the adjacent sandstones. The Eaton pressure estimates are consistent with mud weight in the Gearle Siltstone and Muderong Shale in 4 of the 8 wells studied. The Eaton pressures are on average 10 Mpa in excess of mud weight in the Muderong Shale and Gearle Siltstone in three wells. It is unclear whether the predicted Eaton pressures in these three wells accurately reflect pore pressure (i.e. the mud weights do not accurately reflect pore pressure), or whether they are influenced by changes in shale mineralogy (because the gamma ray filter does not differentiate between shale mineralogy).

APA, Harvard, Vancouver, ISO, and other styles

4

M.B, Pushpa, and Varsha Vijay AKhade A.V. "Study of Intraocular Pressure (IOP) Changes in Relation Blood Pressure." International Physiology 5, no. 2 (2017): 107–9. http://dx.doi.org/10.21088/ip.2347.1506.5217.12.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

John, Ajesh, Ashutosh Kumar, Karthikeyan G., and Pankaj Gupta. "An integrated pore-pressure model and its application to hydrocarbon exploration: A case study from the Mahanadi Basin, east coast of India." Interpretation 2, no. 1 (February 1, 2014): SB17—SB26. http://dx.doi.org/10.1190/int-2013-0078.1.

Full text

Abstract:

An integrated pore-pressure modeling approach was adopted to understand the basin architecture from a pressure perspective and its inference toward possible hydrocarbon occurrence. Kriging-based 3D pore-pressure modeling was used with offset well data and seismic velocities to establish the pressure stratigraphy of the northeast coast (NEC) field (southern part) in the Mahanadi Basin. Late Pliocene sediment is moderately pressured ([Formula: see text]), whereas early Pliocene sediment is normally pressured ([Formula: see text]) and compacted, representing a regional seal for this part of the basin. Miocene represents the onset window for major undercompaction and associated high pressures ([Formula: see text]) in conformance with the regional pressure trend. Overpressure distribution and its mechanisms in the late Miocene level across the NEC field shows distinct patterns with highly elevated pressures ([Formula: see text]) in the northern part resulting from a hybrid unloading mechanism, whereas moderate to high pressure ([Formula: see text]) toward the southern part is associated with undercompaction. Regional pressure correlation across the study area suggests a pressure dependent habitat of hydrocarbons in the Miocene and late Pliocene levels. Pressure distribution and an excess pressure pattern within the Miocene stratigraphy shows a regression trend from north to south, possibly indicating a preferred subsurface fluid flow direction, which is supported by high-quality gas reservoirs discovered in the southern part of the study area. A similar but reverse pressure regression trend is observed within the late Pliocene stratigraphy, which is also validated by the presence of gas reservoirs in the northern part of the study area. Major hydrocarbon reservoirs in the Miocene and Pliocene stratigraphy from the southern part of study area exhibit a strong correlation with effective stress distribution. High-quality gas reservoirs are mostly associated with high effective stress ([Formula: see text]), whereas a high probability for reservoirs to be water wet are observed below this threshold value.

APA, Harvard, Vancouver, ISO, and other styles

6

Varan, Nilufer Yildiz. "Wireless pressure sensors for pressure garments treated with chitosan." International Journal of Clothing Science and Technology 29, no. 5 (September 4, 2017): 732–42. http://dx.doi.org/10.1108/ijcst-12-2016-0136.

Full text

Abstract:

Purpose The purpose of this paper is to analyze the effects of chitosan treatments on exerted pressures of nylon 6.6/elastane pressure garments in three different knit structures using wireless pressure sensors for an accurate and a precise scar management for future designs. Design/methodology/approach Pressure garments designed in different structures consist of 70/30 and 75/25 nylon 6.6/elastane were treated with chitosan and the exerted pressures were analyzed using wireless pressure sensors including ultra-thin and flexible printed circuit sensors in comparison with untreated control samples. Antimicrobial activities and washing tests were also evaluated. Findings It is found that chitosan treatments have a significant effect on final pressures. Exerted pressures increased significantly for all samples after chitosan treatments. Higher pressures were measured for weft knit structured designs while lower pressures were recorded for powernet structured garments. It is found that the elasticity showed a small significant decrease and it has attributed due to a small significant shrinkage during processes. The mean scores of pressures were found in the acceptable medical range which will continue to help hypertrophic scar management for future designs. The exerted pressures of the fabrics remained constant after five washes and showed a small significant decrease after 10 and 50 washes which will provide a long period of compression. Permanent antimicrobial effectiveness has gained at around 90 percent after five washes and 50 percent after 50 washes. A small significant increase was observed for stiffness (CD, MD) after ten washes. Originality/value Chitosan treatments impact exerted pressures of pressure garments significantly. It is a reference to evaluate pressure functions of pressure garments using wireless pressure sensors while imparting antimicrobial activity.

APA, Harvard, Vancouver, ISO, and other styles

7

Rajkumar, R. Vinodh. "DIASTOLIC BLOOD PRESSURE OR ACTUALLY IT IS BASELINE SYSTOLIC BLOOD PRESSURE?" International Journal of Physiotherapy and Research 3, no. 4 (August 11, 2015): 1126–32. http://dx.doi.org/10.16965/ijpr.2015.155.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Sreenidi, Rangadhamaiah. "Comparison of Conventional Central Venous Pressure with Peripheral Venous Pressure and External Jugular Venous Pressure in Patients with Sepsis." Indian Journal of Anesthesia and Analgesia 7, no. 4 (July 1, 2020): 979–85. http://dx.doi.org/10.21088/ijaa.2349.8471.7420.19.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Pickering, L. A., and G. J. lndelicato. "Abnormal Formation Pressure: A Review." Mountain Geologist 22, no. 2 (April 1, 1985): 78–89. http://dx.doi.org/10.31582/rmag.mg.22.2.78.

Full text

Abstract:

Abnormal formation pressure is defined as any pressure that deviates from the normal hydrostatic gradient. In order for these pressures to form and be preserved, a near-seal is required. The seal is not necessarily impermeable but may be a low permeability formation, such as shale, or a fault-related barrier. The possible causes of abnormal formation pressure are: 1) compaction of sediments, 2) tectonic activities, 3) temperature changes, 4) osmosis, 5) diagenesis, 6) methane generation, and 7) buoyancy. Temperature changes due to decay, diagenesis, and changes in burial depth of the formation are one of the two most important causes of abnormal formation pressure. The other important cause is compaction pressure related to the weight of overburden with increased depth of burial. If the pore fluids cannot escape, they will support a greater proportion of the total overburden stress and become abnormally highly pressured. Tectonic activities such as faulting as well as removal of overburden by erosion also play an important role in either raising or lowering pore fluid pressure. Osmosis, diagenesis, methane generation, and buoyancy are all additive to the overall effects of pressure and temperature.

APA, Harvard, Vancouver, ISO, and other styles

10

Popivanov, Georgi, Ivan Inkov, Georgi Kovachev, Kirien Kjossev, Anthony Philipov, Mihail Tabakov, Hristo Petrov, et al. "NEGATIVE PRESSURE WOUND THERAPY IN WARTIME WOUNDS - CASE SERIES AND REVIEW OF THE LITERATURE." International Journal of Surgery and Medicine 4, no. 3 (2018): 138. http://dx.doi.org/10.5455/ijsm.negative-pressure-wound-therapy.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Mahler, C., P. Kloosterziel, J. Eshuis, G. Weverling, W. Bemelman, and M. Boermeester. "CORRELATION BETWEEN BLADDER PRESSURE AND INTRA-ABDOMINAL PRESSURE IN RELATION TO RESPIRATORY PRESSURES." Shock 21, Supplement (March 2004): 110. http://dx.doi.org/10.1097/00024382-200403001-00437.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Sanders, J. S., and D. W. Ferguson. "Diastolic pressure determines autonomic responses to pressure perturbation in humans." Journal of Applied Physiology 66, no. 2 (February 1, 1989): 800–807. http://dx.doi.org/10.1152/jappl.1989.66.2.800.

Full text

Abstract:

Arterial baroreceptors reflexly regulate sympathetic and heart rate responses to alteration of blood pressure. The primary mechanical determinant of arterial baroreceptor activity in humans remains unclear. We examined the influence of systolic, diastolic, pulse, and mean arterial pressures on efferent muscle sympathetic nerve activity (MSNA, microneurography) and heart rate responses during perturbation of arterial pressure in 10 normal human subjects [age 25 +/- 2 (SE) yr]. We directly measured arterial pressure, heart rate, and MSNA during intravenous vasodilator infusion (nitroprusside, 6 +/- 1 micrograms.kg-1.min-1, n = 6; or hydralazine, 16 +/- 2 mg, n = 4) while central venous pressure was held constant by simultaneous volume expansion. Changes in arterial pressures were compared with changes in heart rate and MSNA over 3-min periods of vasodilator infusion during which we observed increases in systolic and pulse pressures with simultaneous decreases in mean and diastolic pressures. During vasodilator infusion, there were increases in systolic (124.2 +/- 2.1 to 131.7 +/- 2.9 Torr, P less than 0.001) and pulse pressures (57.0 +/- 2.2 to 72.7 +/- 2.7 Torr, P less than 0.001) although mean arterial pressure fell (88.0 +/- 2.6 to 80.4 +/- 2.7 Torr, P less than 0.001) because of decreases in diastolic pressure (67.2 +/- 3.0 to 59.0 +/- 2.7 Torr, P less than 0.001). The changes in arterial pressures were accompanied by simultaneous increases in heart rate (66.4 +/- 3.0 to 92.6 +/- 4.8 beats/min, P less than 0.001) and MSNA (327 +/- 59 to 936 +/- 171 U, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

APA, Harvard, Vancouver, ISO, and other styles

13

Fike, C. D., and S. J. Lai-Fook. "Effect of airway and left atrial pressures on microcirculation of newborn lungs." Journal of Applied Physiology 69, no. 3 (September 1, 1990): 1063–72. http://dx.doi.org/10.1152/jappl.1990.69.3.1063.

Full text

Abstract:

To determine the effect of lung inflation and left atrial pressure on the hydrostatic pressure gradient for fluid flux across 20- to 60-microns-diam venules, we isolated and perfused the lungs from newborn rabbits, 7-14 days old. We used the micropuncture technique to measure venular pressures in some lungs and perivenular interstitial pressures in other lungs. For all lungs, we first measured venular or interstitial pressures at a constant airway pressure of 5 or 15 cmH2O with left atrial pressure greater than airway pressure (zone 3). For most lungs, we continued to measure venular or interstitial pressures as we lowered left atrial pressure below airway pressure (zone 2). Next, we inflated some lungs to whichever airway pressure had not been previously used, either 5 or 15 cmH2O, and repeated venular or interstitial pressures under one or both zonal conditions. We found that at constant blood flow a reduction of left atrial pressure below airway pressure always resulted in a reduction in venular pressure at both 5 and 15 cmH2O airway pressures. This suggests that the site of flow limitation in zone 2 was located upstream of venules. When left atrial pressure was constant relative to airway pressure, the transvascular gradient (venular-interstitial pressures) was greater at 15 cmH2O airway pressure than at 5 cmH2O airway pressure. These findings suggest that in newborn lungs edema formation would increase at high airway pressures only if left atrial pressure is elevated above airway pressure to maintain zone 3 conditions.

APA, Harvard, Vancouver, ISO, and other styles

14

VERSI, E., LINDA CARDOZO, and D. J. COOPER. "Urethral Pressures: Analysis of Transmission Pressure Ratios." British Journal of Urology 68, no. 3 (September 1991): 266–70. http://dx.doi.org/10.1111/j.1464-410x.1991.tb15320.x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Dunstan, D. J., N. W. A. Van Uden, and G. J. Ackland. "High Pressure Instrumentation: Low and Negative Pressures." High Pressure Research 22, no. 3-4 (January 2002): 773–78. http://dx.doi.org/10.1080/08957950212441.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

KOCA, Uğur. "Airway Pressure Release Ventilation." Turkiye Klinikleri Journal of Anesthesiology Reanimation 16, no. 1 (2018): 14–17. http://dx.doi.org/10.5336/anesthe.2017-57257.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Shavkat o‘g‘li, Fayzullayev Jahongir. "BLOOD PRESSURE MEDICINAL PLANTS." International Journal of Medical Science and Public Health Research 03, no. 04 (April 1, 2022): 5–8. http://dx.doi.org/10.37547/ijmsphr/volume03issue04-02.

Full text

Abstract:

In this article all about medicinal herbs are widely used in folk medicine due to their blood pressure effectiveness. It is also widely used in the pharmaceutical industry to obtain extracts from them.

APA, Harvard, Vancouver, ISO, and other styles

18

Vlachopoulos, Charalambos, and Michael O’Rourke. "Diastolic pressure, systolic pressure, or pulse pressure?" Current Hypertension Reports 2, no. 3 (May 2000): 271–79. http://dx.doi.org/10.1007/s11906-000-0010-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

John, Ajesh. "Pore-pressure prediction challenges in chemical compaction regimes: An alternative VP/VS-based approach." Interpretation 4, no. 4 (November 1, 2016): T443—T454. http://dx.doi.org/10.1190/int-2015-0106.1.

Full text

Abstract:

Understanding pressure mechanisms and their role in porosity-effective stress relationship is crucial in pore-pressure prediction estimation, particularly in complex geologic and high-temperature regimes. Overpressures are commonly associated with undercompaction and/or unloading mechanisms; those associated with undercompaction generally possess a direct relationship between effective stress and porosity, whereas those associated with unloading do not provide such direct indications from porosity trends. The type of associated unloading mechanism can be correlated when the effective stress and velocity become distorted with the onset of unloading. In the Ravva field, the pore-pressure distribution and overpressure mechanism in the Miocene and below it is a classic example of the unloading mechanism related to chemical compaction, thereby making it difficult to resolve the magnitude and trend of pore pressures. Here, the ratio of P- and S-wave velocities ([Formula: see text]) is analyzed from the drilled locations to understand the effects of lithology, pressure, and fluids on formation velocities and indicates a distinct decreasing trend across the overpressure formations, which I have corresponded to excess pressure resulting from chemical compaction. Across the high-pressured zones, [Formula: see text] ratios show low values compared with normally pressured zones possibly due to the presence of hydrocarbon and/or overpressures. A velocity correction coefficient ranging 0.83–0.71 is resolved for overpressure zones by normalizing the [Formula: see text] values across the normally pressured formations, and thereby assuring that a pore-pressure estimation using corrected velocity from [Formula: see text] analysis shows a high degree of accuracy on prediction trends. Pore-pressure predictions based on [Formula: see text] are a more effective and valid approach in high-temperature settings, in which numerous factors can contribute to pressure generation and a direct effective stress-porosity relationship deviates from the trend.

APA, Harvard, Vancouver, ISO, and other styles

20

Ihsan Ali, Safia, David Patton, Kimberley A. Myers, and Julio Garcia. "Repaired Tetralogy of Fallot Pressure Assessment: Insights from 4D-Flow Pressure Mapping." Fluids 8, no. 7 (June 29, 2023): 196. http://dx.doi.org/10.3390/fluids8070196.

Full text

Abstract:

Tetralogy of Fallot (TOF) is the most prevalent cyanotic congenital heart defect (CHD) that alters normal blood flow through the heart and accounts for 10% of all CHD. Pulmonary stenosis and regurgitation are common in adults who have undergone TOF repair (rTOF) and can impact the load on the right ventricle, blood flow pressure, and pulmonary hemodynamics. Pressure mapping, obtained through 4D-flow magnetic resonance imaging (4D-flow MRI), has been applied to identify abnormal heart hemodynamics in CHD. Hence, the aim of this research was to compare pressure drop and relative pressures between patients with repaired TOF (rTOF) and healthy volunteers. An in vitro validation was performed, followed by an in vivo validation. We hypothesized that pressure drop is a more stable pressure mapping method than relative pressures to detect altered hemodynamics. A total of 36 subjects, 18 rTOF patients and 18 controls underwent cardiac MRI scans and 4D-flow MRI. Pressure drops and relative pressures in the MPA were higher in rTOF patients compared to the controls (p < 0.05). Following the in vitro validation, pressure drops proved to be a more stable pressure mapping method than relative pressures, as the flow loses its laminarity and becomes more turbulent. In conclusion, this study demonstrated that flow hemodynamics in rTOF can exhibit altered pressure maps. Pressure mapping can help provide further insight into rTOF patients’ hemodynamics to improve patient care and clinical decisions.

APA, Harvard, Vancouver, ISO, and other styles

21

Godbey, P. S., J. A. Graham, R. G. Presson, W. W. Wagner, and T. C. Lloyd. "Effect of capillary pressure and lung distension on capillary recruitment." Journal of Applied Physiology 79, no. 4 (October 1, 1995): 1142–47. http://dx.doi.org/10.1152/jappl.1995.79.4.1142.

Full text

Abstract:

To investigate the effect of capillary pressure and alveolar distension on capillary recruitment, we used video-microscopy to quantify capillary recruitment in individual subpleural alveolar walls. Canine lobes were perfused with autologous blood either while inflated by positive airway pressure or while inflated by negative intrapleural pressure in the intact thorax with airway pressure remaining atmospheric. Low flow rates minimized the arteriovenous pressure gradient (< 5 mmHg), permitting capillary pressure estimation by averaging these pressures. Capillary pressure was varied stepwise from airway pressure to 30 mmHg above airway pressure. Capillary recruitment always began as capillary pressure exceeded airway pressure. At low positive airway pressures, the capillaries of the excised lobes opened suddenly over a narrow pressure range. AT higher airway pressures and in the intact thorax, recruitment occurred over a wide range of capillary pressures. We conclude that capillary perfusion begins when intracapillary pressure just exceeds alveolar pressure but that further increases in capillary pressure recruit capillaries depending on tension in the alveolar wall, whether imposed by positive airway pressure or by gravity when the lung is suspended in an intact thorax.

APA, Harvard, Vancouver, ISO, and other styles

22

VAN ROEKEL, H. E., and A. J. THURSTON. "Tourniquet Pressure: The Effect of Limb Circumference and Systolic Blood Pressure." Journal of Hand Surgery 10, no. 2 (April 1985): 142–44. http://dx.doi.org/10.1016/0266-7681_85_90002-6.

Full text

Abstract:

Complications attributable to direct pressure may result from the use of pneumatic tourniquets during surgical procedures. Traditional estimates have determined the pressures employed rather than the minimal pressure necessary to produce a bloodless field. To determine this pressure, pre-operative and post-operative systolic blood pressures and the tourniquet pressure at which capillary bleeding occurred were measured in a group of patients undergoing elective surgery of the upper and lower limbs. From these results two equations were derived, one for each of the upper and lower limbs, which give the minimum tourniquet pressures to produce bloodless fields. In an average sized, normotensive patient, 200mm Hg was found to be adequate for the upper limb and 250mm Hg for the lower limb.

APA, Harvard, Vancouver, ISO, and other styles

23

Mendelowitz, D., and A. M. Scher. "Pulsatile pressure can prevent rapid baroreflex resetting." American Journal of Physiology-Heart and Circulatory Physiology 258, no. 1 (January 1, 1990): H92—H100. http://dx.doi.org/10.1152/ajpheart.1990.258.1.h92.

Full text

Abstract:

In a previous study [Am. J. Physiol. 255 (Heart Circ. Physiol. 24): H673-H678, 1988] we demonstrated that baroreflex responses decay (reset) to increased static sinus pressures, but with increased pulsatile pressure, responses are maintained. To determine more conclusively whether pulsatile pressure prevents rapid baroreflex resetting in this study we examined resetting as shifts of the baroreflex (sinus pressure-arterial pressure) curve. In seven anesthesized rabbits the left sinus was vascularly isolated and conditioned for 5 min to static or pulsatile pressures of 60, 100, or 140 mmHg mean pressure, 0 or 35–40 mmHg pulse pressure. The baroreflex curve was then determined by stepwise changing sinus pressure from 40 to 160 mmHg in 20-mmHg increments. Threshold, midpoint, and saturation sinus pressures shifted 25-39% with static conditioning pressures but did not shift significantly with pulsatile pressures. Also, the baroreflex responses to step increases in static sinus pressure decayed, as resetting occurred, but did not decay with pulsatile sinus pressure increases. Thus the baroreflex rapidly resets with static pressures, but there is minimal, if any, resetting with pulsatile pressures.

APA, Harvard, Vancouver, ISO, and other styles

24

Fike, C. D., S. J. Lai-Fook, and R. D. Bland. "Alveolar liquid pressures in newborn and adult rabbit lungs." Journal of Applied Physiology 64, no. 4 (April 1, 1988): 1629–35. http://dx.doi.org/10.1152/jappl.1988.64.4.1629.

Full text

Abstract:

To study the effects of lung maturation and inflation on alveolar liquid pressures, we isolated lungs from adult and newborn rabbit pups (1-11 days old). We used the micropuncture technique to measure alveolar liquid pressure at several transpulmonary pressures on lung deflation. Alveolar liquid pressure was greater than pleural pressure but less than airway pressure at all transpulmonary pressures. Alveolar liquid pressure decreased further below airway pressure with lung inflation. At high transpulmonary pressure, alveolar liquid pressure was less in newborn than in adult lungs. To study the effects of edema, we measured alveolar liquid pressures in newborn lungs with different wet-to-dry weight ratios. Alveolar liquid pressure increased with progressive edema. In addition, we compared alveolar liquid and perivenular interstitial pressures in perfused newborn lungs and found that they were similar. Thus alveolar liquid pressure can be used to estimate perivenular interstitial pressure. We conclude that the transvascular pressure gradient for fluid flux into the interstitium might increase with lung inflation and decrease with progressive edema. Furthermore, this gradient might be greater in newborn than adult lungs at high inflation pressures.

APA, Harvard, Vancouver, ISO, and other styles

25

Attard, J., S. V. S. Rithalia, and J. Kulkarni. "Pressure relief characteristics in alternating pressure air cushions." Prosthetics and Orthotics International 21, no. 3 (December 1997): 229–33. http://dx.doi.org/10.3109/03093649709164561.

Full text

Abstract:

In this study a computerised system was used which continuously measured air pressure, interface pressure and pressure-time cycle characteristics of an alternating pressure air cushion (APAC), and calculated the time the interface pressure remained below three chosen thresholds of 20,40 and 60mm Hg. Ten healthy volunteers were used to evaluate the pressure relieving characteristics of four APACs. Results indicated significant differences between products when the threshold periods were analysed, showing some devices were not capable of relieving interface pressures below 20mm Hg. Though deflation pressure decreased to nearer zero, interface pressure did not follow suit.

APA, Harvard, Vancouver, ISO, and other styles

26

Bazhin, N. M., and V. N. Parmon. "Hydroosmotic pressure." Доклады Академии наук 484, no. 1 (May 1, 2019): 52–55. http://dx.doi.org/10.31857/s0869-5652484152-55.

Full text

Abstract:

This work proposes the term “hydroosmotic pressure” to define hydrostatic pressure emerging from an osmotic process during solvent diffusion through membranes. The usage of this term potentially clears the ambiguity of the term “osmotic pressure,” referring to the concentration of dissolved solids in a solution regardless of the existence of hydrostatic pressure. Hydroosmotic pressure is the difference between hydrostatic pressures on either side of the membrane; thus, the term “hydroosmotic pressure” allows for the most correct definition of many processes associated with osmotic phenomena.

APA, Harvard, Vancouver, ISO, and other styles

27

Salem, M. Ramez, Keith W. Bruninga, Jyothi Dodlapatii, and Ninos J. Joseph. "Metoclopramide Does Not Attenuate Cricoid Pressure–induced Relaxation of the Lower Esophageal Sphincter in Awake Volunteers." Anesthesiology 109, no. 5 (November 1, 2008): 806–10. http://dx.doi.org/10.1097/aln.0b013e31818a37dc.

Full text

Abstract:

Background The authors examined the influence of metoclopramide on cricoid pressure-induced relaxation of the lower esophageal sphincter (LES) in awake human volunteers. Methods With local institutional review board approval, measurements of LES and intragastric pressures were made in 10 consenting volunteers before cricoid pressure application, during 15 s of cricoid pressure application, and after release of cricoid pressure. The measurements were repeated after 0.15 mg/kg intravenous metoclopramide. Cricoid pressure was applied by one investigator trained to consistently apply a force of 44 N. Results Cricoid pressure resulted in immediate decrease in LES and barrier pressures from 14.1 +/- 2.9 mmHg to 3.2 +/- 3.7 mmHg and from 9.6 +/- 3.4 mmHg to -1.8 +/- 2.9 mmHg, respectively. These pressures promptly returned to baseline values after release of cricoid pressure. LES and barrier pressures increased after metoclopramide from 14.5 +/- 3.1 to 19.6 +/- 4.7 mmHg and from 10.2 +/- 3.6 to 14.1 +/- 5.5 mmHg, respectively. Cricoid pressure applied after metoclopramide resulted in immediate decreases in LES and barrier pressures to levels comparable to cricoid pressure before metoclopramide, but immediately returned to precricoid values after release of pressure. Conclusions The current investigation demonstrates that cricoid pressure reflexly decreases LES tone and barrier pressure in awake subjects. Although metoclopramide increased LES and barrier pressures, it did not attenuate cricoid pressure-induced relaxation of the LES and barrier pressures and thus seems to have no value in preventing gastroesophageal reflux during cricoid pressure. Metoclopramide may be useful in preventing reflux when there is need to release or discontinue cricoid pressure.

APA, Harvard, Vancouver, ISO, and other styles

28

Mistik, Selcuk, Kevser Goktas, Demet Unalan, Abdurrahman Oguzhan, and Bulent Tokgöz. "Normal Variations in Blood Pressure in Ambulatory Blood Pressure Measurements." Eurasian Journal of Family Medicine 10, no. 1 (March 30, 2021): 1–6. http://dx.doi.org/10.33880/ejfm.2021100101.

Full text

Abstract:

Aim: Hypertension is very common in primary care patients. The diagnosis of hypertension is made by office measurements and home blood pressure measurements. The aim of this study was to define the normal variation levels of blood pressure in individuals in primary care by using ambulatory blood pressure measurement. Methods: This study was performed in primary care. Individuals who had no hypertension history were included in the study. Subjects were evaluated by using three office measurements, seven days home blood pressure measurements and 24 hours ambulatory blood pressure measurement. The ambulatory blood pressure gave us the variations in blood pressure values. Results: The study started in January 2018 and ended in May 2018. Of the 47 subjects, 70.2% were women and 29.8% were men. The mean age was 41.63±12.00. The most common educational level was elementary school graduates. The most common occupation was housewives. Of the participants, 84.2% were married. At ambulatory blood pressure measurements, 34.0% of the subjects had mean systolic blood pressures 24 hours between 120-129 mmHg. Of the diastolic blood pressure 24 hours mean values, 15.3% had values between 80-89, where 51.0% were between the 71-79 mmHg groups. The mean value of 24 hours variation in systolic blood pressure was 15.75±18.59 (median=11.40, min=8.80, max=106.00). The 24 hours variation in the mean values of diastolic blood pressures was 12.12±10.90 (median=9.70, min=6.80, max=64.00). Conclusion: The results of this study demonstrated that there were high levels of variations in normal blood pressures, which could show candidates for hypertension. Keywords: ambulatory monitoring, blood pressure, variability, primary care

APA, Harvard, Vancouver, ISO, and other styles

29

Davis, M. J. "Microvascular control of capillary pressure during increases in local arterial and venous pressure." American Journal of Physiology-Heart and Circulatory Physiology 254, no. 4 (April 1, 1988): H772—H784. http://dx.doi.org/10.1152/ajpheart.1988.254.4.h772.

Full text

Abstract:

The extent to which capillary hydrostatic pressure might be protected from increases in local arterial and venous pressure was examined in the wing microcirculation of unanesthetized pallid bats (Antrozous pallidus). Arterial inflow and venous outflow pressures to the wing were elevated using a box technique to increase pressure around the body of the animal in steps of 12 mmHg between 0 and +60 mmHg for 3-min periods. During this time, hydrostatic pressure, diameter, and red cell velocity in single microvessels were continuously recorded. All branching orders of arterioles constricted significantly during increases in box pressure (Pb), while capillaries and venules dilated. First-order arteriole and venule pressures increased 1:1 with Pb. Capillary pressures increased by only a fraction of Pb up to +36 mmHg, but at higher Pb, the change in capillary pressure was equivalent to the change in Pb. Calculations of vascular resistance indicate that changes in both pre- and postcapillary resistance in this tissue act to prevent increases in capillary pressure during moderate, but not during large, increases in arterial and venous pressure.

APA, Harvard, Vancouver, ISO, and other styles

30

Lowrie, Allen, and Susan Moffett. "Pressure Compartments, Existent and Suggested, along the Louisiana Continental Margin." Energy Exploration & Exploitation 16, no. 4 (August 1998): 345–54. http://dx.doi.org/10.1177/014459879801600404.

Full text

Abstract:

Pressure compartments are the result of lithology, the ability to contain/expell fluids, and stresses from the dynamics of whatever tectonics operate in the area. In the northern Gulf of Mexico, a normal pressured unit overlies a geopressured or over-pressured compartment that both rest above the salt. Directly northward of the Sigsbee Escarpment, there is a relatively thin, low-velocity zone known locally as a “gumbo zone”. Here two other pressure compartments are proposed. The origin of them is two-fold. First, initial sedimentation consists of pelagic clay draped over oceanic and transitional crust. Later, as the continental margin progrades nearer sedimentation becomes hemipelagic and coarser as gravity-driven sediments predominate. Secondly, as the salt wedge overrides a given spot of the basement, it is possible to develop a shear couple between the migrating salt and the stationary basement. The resultant shear (the site of the next strike-slip fault) may change pressures beneath the salt such that the shear may create two pressure compartments. The differences between the two compartments may be accentuated by lithologic changes caused by depositional mechanisms.

APA, Harvard, Vancouver, ISO, and other styles

31

Barbenel, J. C. "Pressure management." Prosthetics and Orthotics International 15, no. 3 (December 1991): 225–31. http://dx.doi.org/10.3109/03093649109164292.

Full text

Abstract:

The prevention or minimisation of the occurrence of pressure sores is an important consideration in the rehabilitation of physically disabled people, especially for the wheelchair user with a spinal cord injury. Although there is little definitive information on the cause of pressure sores, several intrinsic and extrinsic factors have been highlighted. Probably the most significant causative factor is the application of force to the skin surface. The relationship between the magnitude of pressure and its duration; the temperature and humidity at the interface; and the physiological effects that this has on the microcirculation and lymphatic drainage are discussed in this article. It is suggested that a rationale for the prevention of pressure sores includes the limitation of the duration of pressures applied to the skin surface and the reduction of the peak pressures particularly at vulnerable sites. In this context the design criteria for a clinical interface pressure measurement system, and the uses and limitations of the commercially available options, are considered. The development of a structured programme of wheelchair and support surface provision, assessment and follow-up is required.

APA, Harvard, Vancouver, ISO, and other styles

32

Harley, James, David Mott, John Celona, Bruno Degazio, and James Tenney. "Sound Pressure: Pressure Points." Computer Music Journal 19, no. 1 (1995): 112. http://dx.doi.org/10.2307/3681310.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Kiberstis, P. A. "GENETICS: Pressure Under Pressure." Science 310, no. 5755 (December 16, 2005): 1745a. http://dx.doi.org/10.1126/science.310.5755.1745a.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Plummer, Caryn E. "Pressure! So Much Pressure!" Advances in Small Animal Medicine and Surgery 28, no. 1 (January 2015): 1–3. http://dx.doi.org/10.1016/j.asams.2015.01.001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

House, S. D., and P. C. Johnson. "Microvascular pressure in venules of skeletal muscle during arterial pressure reduction." American Journal of Physiology-Heart and Circulatory Physiology 250, no. 5 (May 1, 1986): H838—H845. http://dx.doi.org/10.1152/ajpheart.1986.250.5.h838.

Full text

Abstract:

It has been suggested from whole organ studies that the viscosity of blood in skeletal muscle venules varies inversely with flow over physiological flow ranges. If this is the case, the hydrostatic pressure gradient in venules should change less than flow as flow is altered. To test this hypothesis, pressure in venules of cat sartorius muscle was measured during stepwise arterial pressure reduction to 20 mmHg. Large vein pressure remained constant at about 5 mmHg. Average pressures in the large venules (40–185 microns) ranged from 13.6 to 10.0 mmHg. The difference between pressure in these venules and large vein pressure fell in proportion to the reduction in blood pressure and blood flow. Pressures in the smallest venules studied (25 microns) averaged 19.7 +/- 6.2 (SD) mmHg. The pressure difference between the smallest venules and the large vein fell less than the arteriovenous pressure difference or blood flow when arterial pressure was reduced. During reactive hyperemia the pressure gradient between the smallest venules and the large vein rose proportionately less than blood flow. The stability of pressure in the smallest venules is consistent with the hypothesis that blood viscosity varies inversely with flow rate.

APA, Harvard, Vancouver, ISO, and other styles

36

Maric, Filip, Margherita Poto, and Giuliana Panieri. "Under pressure." Septentrio Educational, no. 1 (April 28, 2023): 78–80. http://dx.doi.org/10.7557/8.7056.

Full text

Abstract:

Focus: To understand and feel how water pressure changes with depth. Learning objectives: In this activity, pupils will recognize the relationship between water depth and pressure. Pupils will be able to reflect on how lifeforms in the deep sea might be affected by the high water pressures in their ecosystems. Key words: Depth, weight, pressure.

APA, Harvard, Vancouver, ISO, and other styles

37

Gnida, Anna, and Dagmara Witecy. "PRELIMINARY STUDIES ON THE INFLUENCE OF NEGATIVE PRESSURE ON ACTIVATED SLUDGE FLOCS." Zeszyty Naukowe Uniwersytetu Zielonogórskiego / Inżynieria Środowiska 170, no. 50 (July 2, 2018): 51–60. http://dx.doi.org/10.5604/01.3001.0012.7462.

Full text

Abstract:

A sludge from municipal wastewater plant operated for biological contaminant removal was exposed to three different negative pressures (-200, -500 and -800 hPa) for three different duration times (30 second, 1 and 2 minutes). Sludge volume index, shear sensitivity of the sludge and activated sludge floc characteristic was the object of the study before and after negative pressure treatment. After the treatment the sludge settled better independently on the pressure value and duration time. The shear sensitivity changed the most when the pressure exposure of -800 hPa was 1 minute and longer. The flocs structure was more open after negative pressur and larger part of activated sludge was comprised by large flocs.

APA, Harvard, Vancouver, ISO, and other styles

38

Tilmont, Antoine, Benjamin Coiffard, Takeshi Yoshida, Florence Daviet, Karine Baumstarck, Geoffrey Brioude, Sami Hraiech, et al. "Oesophageal pressure as a surrogate of pleural pressure in mechanically ventilated patients." ERJ Open Research 7, no. 1 (January 2021): 00646–2020. http://dx.doi.org/10.1183/23120541.00646-2020.

Full text

Abstract:

BackgroundOesophageal pressure (Poes) is used to approximate pleural pressure (Ppl) and therefore to estimate transpulmonary pressure (PL). We aimed to compare oesophageal and regional pleural pressures and to calculate transpulmonary pressures in a prospective physiological study on lung transplant recipients during their stay in the intensive care unit of a tertiary university hospital.MethodsLung transplant recipients receiving invasive mechanical ventilation and monitored by oesophageal manometry and dependent and nondependent pleural catheters were investigated during the post-operative period. We performed simultaneous short-time measurements and recordings of oesophageal manometry and pleural pressures. Expiratory and inspiratory PL were computed by subtracting regional Ppl or Poes from airway pressure; inspiratory PL was also calculated with the elastance ratio method.Results16 patients were included. Among them, 14 were analysed. Oesophageal pressures correlated with dependent and nondependent pleural pressures during expiration (R2=0.71, p=0.005 and R2=0.77, p=0.001, respectively) and during inspiration (R2=0.66 for both, p=0.01 and p=0.014, respectively). PL values calculated using Poes were close to those obtained from the dependent pleural catheter but higher than those obtained from the nondependent pleural catheter both during expiration and inspiration.ConclusionsIn ventilated lung transplant recipients, oesophageal manometry is well correlated with pleural pressure. The absolute value of Poes is higher than Ppl of nondependent lung regions and could therefore underestimate the highest level of lung stress in those at high risk of overinflation.

APA, Harvard, Vancouver, ISO, and other styles

39

Mathew, Oommen P. "Effects of transient intrathoracic pressure changes (hiccups) on systemic arterial pressure." Journal of Applied Physiology 83, no. 2 (August 1, 1997): 371–75. http://dx.doi.org/10.1152/jappl.1997.83.2.371.

Full text

Abstract:

Mathew, Oommen P. Effects of transient intrathoracic pressure changes (hiccups) on systemic arterial pressure. J. Appl. Physiol. 83(2): 371–375, 1997.—The purpose of the study was to determine the effect of transient changes in intrathoracic pressure on systemic arterial pressure by utilizing hiccups as a tool. Values of systolic and diastolic pressures before, during, and after hiccups were determined in 10 intubated preterm infants. Early-systolic hiccups decreased systolic blood pressure significantly ( P < 0.05) compared with control (39.38 ± 2.72 vs. 46.46 ± 3.41 mmHg) and posthiccups values, whereas no significant change in systolic blood pressure occurred during late-systolic hiccups. Diastolic pressure immediately after the hiccups remained unchanged during both early- and late-systolic hiccups. In contrast, diastolic pressure decreased significantly ( P < 0.05) when hiccups occurred during diastole (both early and late). Systolic pressures of the succeeding cardiac cycle remained unchanged after early-diastolic hiccups, whereas they decreased after late-diastolic hiccups. These results indicate that transient decreases in intrathoracic pressure reduce systemic arterial pressure primarily through an increase in the volume of the thoracic aorta. A reduction in stroke volume appears to contribute to the reduction in systolic pressure.

APA, Harvard, Vancouver, ISO, and other styles

40

Aldea, G. S., H. Mori, W. K. Husseini, R. E. Austin, and J. I. E. Hoffman. "Effects of increased pressure inside or outside ventricles on total and regional myocardial blood flow." American Journal of Physiology-Heart and Circulatory Physiology 279, no. 6 (December 1, 2000): H2927—H2938. http://dx.doi.org/10.1152/ajpheart.2000.279.6.h2927.

Full text

Abstract:

Increasing pressures to 30 mmHg in right (RV) and left (LV) ventricles and surrounding heart (SH) in isolated, arrested, maximally vasodilated, blood-perfused dog hearts shifted pressure-flow (PF) curves rightward and increased zero flow pressure (Pzf) by an amount equal to the RV applied pressure, SH applied pressure, or two-thirds of the LV applied pressure. There were comparable increases in coronary venous pressures. Increasing LV or SH pressures decreased coronary blood flows, especially in the subendocardium. Decreases in driving pressure decreased flows in all layers, but even with driving pressure of 5 mmHg, a few subepicardial pieces had flow. We conclude with the following: 1) raising pressures inside or outside the heart shifts PF curves and raises Pzfby increasing coronary venous pressure; 2) the effects are most prominent in the subendocardial muscle layer; and 3) as driving pressures are decreased, there is a range of Pzfin the heart with the final Pzfrecorded due to the last little piece of muscle to be perfused.

APA, Harvard, Vancouver, ISO, and other styles

41

Yuting Li, Yuting Li, Wentao Zhang Wentao Zhang, Zhaogang Wang Zhaogang Wang, Hongbin Xu Hongbin Xu, Jing Han Jing Han, and Fang Li Fang Li. "Low-cost and miniature all-silica Fabry–Perot pressure sensor for intracranial pressure measurement." Chinese Optics Letters 12, no. 11 (2014): 111401–4. http://dx.doi.org/10.3788/col201412.111401.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Biellmann, Claudine, Francois Guyot, Philippe Gillet, and Bruno Reynard. "High-pressure stability of carbonates: quenching of calcite-II, high-pressure polymorph of CaCO3." European Journal of Mineralogy 5, no. 3 (June 14, 1993): 503–10. http://dx.doi.org/10.1127/ejm/5/3/0503.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Wain, Alice, David Waters, Andrew Jephcoat, and Helmut Olijynk. "The high-pressure to ultrahigh-pressure eclogite transition in the Western Gneiss Region, Norway." European Journal of Mineralogy 12, no. 3 (May 31, 2000): 667–87. http://dx.doi.org/10.1127/0935-1221/2000/0012-0667.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Yano, Tetsuya, Kiyotaka Osanai, and Seiichi Sudo. "OS8-2-7 Analysis of flow fields in pressure hole for semiconductor pressure sensor." Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics 2007.6 (2007): _OS8–2–7–1—_OS8–2–7–5. http://dx.doi.org/10.1299/jsmeatem.2007.6._os8-2-7-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Armstrong, David G., Kristin Kunze, Billy R. Martin, Heather R. Kimbriel, Brent P. Nixon, and Andrew J. M. Boulton. "Plantar Pressure Changes Using a Novel Negative Pressure Wound Therapy Technique." Journal of the American Podiatric Medical Association 94, no. 5 (September 1, 2004): 456–60. http://dx.doi.org/10.7547/0940456.

Full text

Abstract:

This study evaluated changes in pressure imparted to diabetic foot wounds using a novel negative pressure bridging technique coupled with a robust removable cast walker. Ten patients had plantar pressures assessed with and without a bridged negative pressure dressing on the foot. Off-loading was accomplished with a pressure-relief walker. Plantar pressures were recorded using two pressure-measurement systems. The location and value of peak focal pressure (taken from six midgait steps) were recorded at the site of ulceration. Paired analysis revealed a large difference (mean ± SD, 74.6% ± 6.0%) between baseline barefoot pressure and pressure within the pressure-relief walker (mean ± SD, 939.1 ± 195.1 versus 235.7 ± 66.1 kPa). There was a mean ± SD 9.9% ± 5.6% higher pressure in the combination device compared with the pressure-relief walker alone (mean ± SD, 258.0 ± 69.7 versus 235.7 ± 66.1 kPa). This difference was only 2% of the initial barefoot pressure imparted to the wound. A modified negative pressure dressing coupled with a robust removable cast walker may not impart undue additional stress to the plantar aspect of the foot and may allow patients to retain some degree of freedom (and a potentially reduced length of hospital stay) while still allowing for the beneficial effects of negative pressure wound therapy and sufficient off-loading. (J Am Podiatr Med Assoc 94(5): 456–460, 2004)

APA, Harvard, Vancouver, ISO, and other styles

46

Bono, F., D. Salvino, T. Tallarico, D. Cristiano, F. Condino, F. Fera, PL Lanza, A. Lavano, and A. Quattrone. "Abnormal pressure waves in headache sufferers with bilateral transverse sinus stenosis." Cephalalgia 30, no. 12 (May 12, 2010): 1419–25. http://dx.doi.org/10.1177/0333102410370877.

Full text

Abstract:

Introduction: Bilateral transverse sinus stenosis (BTSS) has been reported to be associated with idiopathic intracranial hypertension without papilloedema in headache sufferers. Subjects and methods: To test the accuracy of short-term cerebrospinal fluid (CSF) pressure monitoring through a lumbar needle for detection of elevated intracranial pressure in headache sufferers with BTSS, we prospectively performed lumbar puncture in order to measure lumbar CSF opening pressures and to monitor, for 1 h, the CSF pressure in 48 consecutive headache sufferers with BTSS and in 50 consecutive headache sufferers with normal appearance of transverse sinuses or stenosis of one transverse sinus. Results: Of the 48 headache sufferers with BTSS, 18 (37.5%) had elevated CSF opening pressure and abnormal pressure waveforms, but short-term CSF pressure monitoring revealed abnormal pressure waves associated with elevated mean CSF pressure also in 26 (86.6%) out of 30 patients who had normal opening pressures. None of the 50 headache sufferers with normal appearance of transverse sinuses or stenosis of one transverse sinus had abnormal pressure waves and elevated CSF pressures. Conclusions: In this study, short-term CSF pressure monitoring through a lumbar needle revealed abnormal pressure waves and elevated mean CSF pressures in the majority of headache sufferers with BTSS who had normal CSF opening pressures. These findings demonstrate the accuracy of short-term CSF pressure monitoring through a lumbar needle in estimating CSF pressure; they also highlight that a single-spot opening pressure measurement has a low accuracy for recognition of increased intracranial pressure in headache sufferers with BTSS.

APA, Harvard, Vancouver, ISO, and other styles

47

Stasney, C. Richard, Mary Es Beaver, and Margarita Rodriguez. "Hypopharyngeal Pressure in Brass Musicians." Medical Problems of Performing Artists 18, no. 4 (December 1, 2003): 153–55. http://dx.doi.org/10.21091/mppa.2003.4027.

Full text

Abstract:

Brass instrument players are exposed to unique health risks due to increased pharyngeal pressures necessary for performance. One such risk is development of laryngoceles, or “blowout” of the larynx. This cross-sectional observational study was performed to determine the pressure required to play different frequencies in a variety of brass instruments. The hypothesis tested was that enharmonic frequencies require the same pharyngeal pressure regardless of the instrument. The brass instruments tested were high-pressure, low-flow instruments (trumpet or French horn) or low-pressure, high-flow instruments (tuba or trombone). We were not able to substantiate Jacobs’ theory that enharmonic frequencies resulted in equal pressures regardless of instrument, but we did elicit some high pressures in the hypopharynx when playing the trumpet or horn at higher frequencies.

APA, Harvard, Vancouver, ISO, and other styles

48

Buchler, B., S. Magder, H. Katsardis, Y. Jammes, and C. Roussos. "Effects of pleural pressure and abdominal pressure on diaphragmatic blood flow." Journal of Applied Physiology 58, no. 3 (March 1, 1985): 691–97. http://dx.doi.org/10.1152/jappl.1985.58.3.691.

Full text

Abstract:

The aim of this experiment was to determine if blood flow to the diaphragm is affected by generating the transdiaphragmatic pressure mainly with positive abdominal pressure or mainly with negative pleural pressure, during both sustained and intermittent diaphragmatic contractions. Diaphragmatic blood flow was measured in anesthetized mongrel dogs by the radionuclide-labeled microsphere method. Sustained and intermittent tetanic diaphragmatic contractions were produced with 1) free abdomen and closed chest (high negative pleural pressure) and 2) bound abdomen and open chest (high positive abdominal pressure). During sustained contractions, diaphragmatic blood flow at maximum levels of activation was significantly higher with negative pleural pressure (P less than 0.05). In contrast with this, intermittent diaphragmatic contractions did not yield a significant difference between diaphragmatic blood flow with negative pleural pressure and with positive abdominal pressure at maximal levels of transdiaphragmatic pressure. During both sustained and intermittent contractions, blood pressure, as measured from the carotid artery, did not vary significantly between negative pleural pressure and positive abdominal pressure. We conclude that during sustained tetanic diaphragmatic contractions, diaphragmatic blood flow is obstructed by high positive abdominal pressures, but during intermittent diaphragmatic contractions, high positive abdominal pressures do not affect total blood flow, since any inhibition of blood flow during the contractile period can be compensated for during the relaxation period between contractions.

APA, Harvard, Vancouver, ISO, and other styles

49

Verweij, J. M., H. J. Simmelink, J. Underschultz, and N. Witmans. "Pressure and fluid dynamic characterisation of the Dutch subsurface." Netherlands Journal of Geosciences - Geologie en Mijnbouw 91, no. 4 (December 2012): 465–90. http://dx.doi.org/10.1017/s0016774600000342.

Full text

Abstract:

AbstractThis paper presents and discusses the distribution of fluid and leak-off pressure data from the subsurface of onshore and offshore Netherlands in relation to causes of formation fluid overpressure and the permeability framework. The observed fluid pressure conditions demonstrate a clear regional difference between the southern and the north and north-eastern part of the study area. In the southern area, formation fluid pressures are close to normal and well below measured leak-off pressures. In the north, formation fluids are overpressured and may locally even approach the measured leak-off pressures. The regional differences in fluid overpressure can, in large part, be explained by differences in geologic framework and burial history. In the south, relatively low rates of sedimentary loading and the presence of relatively permeable sedimentary units have led to the currently observed normally pressured conditions. In the northern area, relatively rapid Neogene sediment loading plays an important role in explaining the observed overpressure distributions in Cenozoic mudstones, Cretaceous Chalk and Rijnland groups, and probably also in Jurassic units. The permeability framework of the northern and north-eastern area is significantly affected by Zechstein and Triassic salt deposits and structures. These units are characterised by very low permeability and severely restrict fluid flow and pressure dissipation. This has created hydraulically restricted compartments with high overpressures (for example overpressures exceeding 30 MPa in the Lower Germanic Trias Group in the Terschelling Basin and Dutch Central Graben).

APA, Harvard, Vancouver, ISO, and other styles

50

Rediniotis, Othon K. "A Computer-Controlled Pressure Standard." Journal of Fluids Engineering 121, no. 1 (March 1, 1999): 210–12. http://dx.doi.org/10.1115/1.2822006.

Full text

Abstract:

The operating principles, as well as the technical aspects of the implementation of a new computer-controlled pressure standard are presented. The instrument can have dual use: either as a pressure source or as a pressure sensor. The device is intended mostly for use in problems where small differential pressures are of interest, i. e., 0–2.5 KPa and high accuracy is desired. Such a pressure range encompasses, for example, most of the pressure measurement applications in subsonic wind-tunnel testing. The device interfaces to a PC and is ideal for fully-automated pressure transducer calibration applications. The accuracy of the pressures produced or measured by the device is 0.08 percent F. S. (Full Scale).

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Pressure'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles