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 (P) [presh´ur]
force per unit area.
arterial pressure (arterial blood pressure) blood pressure (def. 2).
atmospheric pressure the pressure exerted by the atmosphere, usually considered as the downward pressure of air onto a unit of area of the earth's surface; the unit of pressure at sea level is one atmosphere. Pressure decreases with increasing altitude.
barometric pressure atmospheric p.
blood pressure
2. pressure of blood on walls of any blood vessel.
capillary pressure the blood pressure in the capillaries.
central venous pressure see central venous pressure.
cerebral perfusion pressure the mean arterial pressure minus the intracranial pressure; a measure of the adequacy of cerebral blood flow.
cerebrospinal pressure the pressure of the cerebrospinal fluid, normally 100 to 150 mm Hg.
continuous positive airway pressure see continuous positive airway pressure.
filling pressure see mean circulatory filling pressure.
high blood pressure hypertension.
intracranial pressure see intracranial pressure.
intraocular pressure the pressure exerted against the outer coats by the contents of the eyeball.
intrapleural pressure (intrathoracic pressure) pleural pressure.
intrinsic positive end-expiratory pressure elevated positive end-expiratory pressure and dynamic pulmonary hyperinflation caused by insufficient expiratory time or a limitation on expiratory flow. It cannot be routinely measured by a ventilator's pressure monitoring system but is measurable only using an expiratory hold maneuver done by the clinician. Its presence increases the work needed to trigger the ventilator, causes errors in the calculation of pulmonary compliance, may cause hemodynamic compromise, and complicates interpretation of hemodynamic measurements. Called also auto-PEEP and intrinsic PEEP.
maximal expiratory pressure maximum expiratory pressure.
maximal inspiratory pressure the pressure during inhalation against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.
maximum expiratory pressure (MEP) a measure of the strength of respiratory muscles, obtained by having the patient exhale as strongly as possible against a mouthpiece; the maximum value is near total lung capacity.
maximum inspiratory pressure (MIP) the inspiratory pressure generated against a completely occluded airway; used to evaluate inspiratory respiratory muscle strength and readiness for weaning from mechanical ventilation. A maximum inspiratory pressure above −25 cm H2O is associated with successful weaning.
mean airway pressure the average pressure generated during the respiratory cycle.
mean circulatory filling pressure a measure of the average (arterial and venous) pressure necessary to cause filling of the circulation with blood; it varies with blood volume and is directly proportional to the rate of venous return and thus to cardiac output.
negative pressure pressure less than that of the atmosphere.
oncotic pressure the osmotic pressure of a colloid in solution.
osmotic pressure the pressure required to stop osmosis through a semipermeable membrane between a solution and pure solvent; it is proportional to the osmolality of the solution. Symbol π.
partial pressure the pressure exerted by each of the constituents of a mixture of gases.
peak pressure in mechanical ventilation, the highest pressure that occurs during inhalation.
plateau pressure in mechanical ventilation, the pressure measured at the proximal airway during an end-inspiratory pause; a reflection of alveolar pressure.
pleural pressure the pressure between the visceral pleura and the thoracic pleura in the pleural cavity. Called also intrapleural or intrathoracic pressure.
positive pressure pressure greater than that of the atmosphere.
positive end-expiratory pressure (PEEP) a method of control mode ventilation in which positive pressure is maintained during expiration to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. A PEEP higher than the critical closing pressure prevents alveolar collapse and can markedly improve the arterial Po2 in patients with a lowered functional residual capacity, as in acute respiratory failure.
Effects of the application of positive end-expiratory pressure (PEEP) on the alveoli. A, Atelectatic alveoli before PEEP application. B, Optimal PEEP application has reinflated alveoli to normal volume. C, Excessive PEEP application overdistends the alveoli and compresses adjacent pulmonary capillaries, creating dead space with its attendant hypercapnia. From Pierce, 1995.
pulmonary artery wedge pressure (PAWP) (pulmonary capillary wedge pressure (PCWP)) intravascular pressure, reflecting the left ventricular end diastolic pressure, measured by a swan-ganz catheter wedged into a small pulmonary artery to block the flow from behind.
pulse pressure the difference between the systolic and diastolic pressures. If the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg, the pulse pressure is 40 mm Hg; the normal pulse pressure is between 30 and 40 mm Hg.
urethral pressure the pressure inwards exerted by the walls of the urethra, which must be counteracted in order for urine to flow through; see also urethral pressure profile.
venous pressure the blood pressure in the veins; see also central venous pressure.
water vapor pressure the tension exerted by water vapor molecules, 47 mm Hg at normal body temperature.
wedge pressure blood pressure measured by a small catheter wedged into a vessel, occluding it; see also pulmonary capillary wedge pressure and wedged hepatic vein pressure.
wedged hepatic vein pressure the venous pressure measured with a catheter wedged into the hepatic vein. The difference between wedged and free hepatic vein pressures is used to locate the site of obstruction in portal hypertension; it is elevated in that due to cirrhosis, but low in cardiac ascites or portal vein thrombosis.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pres·sure (P, P),

1. A stress or force acting in any direction against resistance.
2. physics, physiology the force per unit area exerted by a gas or liquid against the walls of its container or that would be exerted on a wall immersed at that spot in the middle of a body of fluid:The pressure can be considered either relative to some reference pressure, such as that of the ambient atmosphere (imagined as on the other side of the wall) or in absolute terms (relative to a perfect vacuum).
[L. pressura, fr. premo, pp. pressus, to press]
Farlex Partner Medical Dictionary © Farlex 2012


Vox populi A force or stress applied to a suface by a fluid or object, and measured in units of mass per unit area. See Blood pressure, Continuous positive airway pressure, Coronary perfusion pressure, End-diastolic pressure, End-systolic pressure, Intracranial pressure, Intraocular pressure, Intrauterine pressure, Negative pressure, Negative end-expiratory pressure, Oncotic pressure, Osmotic pressure, PEEP, Pulmonary-capillary pressure, Transpulmonary pressure, Wedge pressure.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


1. A stress or force acting in any direction against resistance.
2. physics, physiology The force per unit area exerted by a gas or liquid against the walls of its container or that would be exerted on a wall immersed at that spot in the middle of a body of fluid. The pressure can be considered either relative to some reference pressure, such as that of the ambient atmosphere (gauge pressure), or relative to a perfect vacuum (absolute pressure).
[L. pressura, fr. premo, pp. pressus, to press]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


The force per unit area exerted by a gas or liquid over a surface in a direction perpendicular to that surface. The SI unit of pressure is the pascal (Pa), although blood pressure and intraocular pressure remain specified in the non-SI unit millimetres of mercury (mmHg). See oxygen permeability.
blood pressure See sphygmomanometer.
equivalent oxygen pressure See equivalent oxygen pressure.
intraocular pressure (IOP) The pressure within the eyeball occurring as a result of the constant formation and drainage of the aqueous humour. This is measured by means of a manometer. What is actually measured in the human eye is the ocular tension by means of a tonometer. This is an indirect measure of the IOP as it depends on the thickness and rigidity of the tunics of the eye besides the IOP. Both terms, intraocular pressure and ocular pressure, are usually regarded as synonymous. Normal IOP is usually considered to be between 11 mmHg and 21 mmHg. However, there may be cases of glaucoma with lower IOP than 21 mmHg and there are also many normal cases with IOP greater than 21 mmHg. There is a slight increase in IOP with age (about 2 mmHg), in the morning as compared to the evening (about 3-4 mmHg), in the supine position as compared to the sitting position (about 3-4 mmHg), and a decrease during accommodation (about 4 mmHg). See in intraocular pressure diurnal variations; glaucoma; aqueous humour; ocular hypertension; ocular hypotony; scleral indentation; Imbert-Fick law; ocular rigidity; differential intraocular pressure test; provocative test; tonometer.
osmotic pressure The pressure required to stop the movement of water through a semipermeable membrane (e.g. corneal endothelium) from one solution of a given concentration to another of a different concentration. When the concentration of the solution on both sides of the membrane is equal, i.e. at equilibrium, the pressure of water on both sides of the membrane will be equal to the osmotic pressure and the movement of water will stop. The more concentrated the solution, the greater the osmotic pressure. See osmosis; hypertonic solution; hypotonic solution; isotonic solution.
pulse pressure See sphygmomanometer.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann


(P) (presh'ŭr)
Stress or force acting in any direction against resistance.
[L. pressura, fr. premo, pp. pressus, to press]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about pressure

Q. how can i reduce my blood pressure?

A. The main steps in lowering high blood pressure is to take some very important changes in lifestyle- consuming much less salt in food, losing weight and exercising regulary. If this doesn't help (and usually it doesn't help mainly when people don't try hard enought and make an effort), medications can be added to control the blood pressure.

Q. what do i need to do to bring down my blood pressure? what cause a high blood pressure? what are the risks? of high blood pressure ? how can i deal with it effectively ?

A. here are two really good sites that show you specifics: Hope this helps.

Q. What Are the Complications of High Blood Pressure? My wife suffers from high blood pressure. What are the possible complications that are so dangerous? Why is it important to keep high blood pressure under balance?

A. While elevated blood pressure alone is not an illness, it often requires treatment due to its short and long-term effects on many organs. The risk is increased for: Cerebrovascular accident (CVAs or strokes), myocardial infarction (heart attack), hypertensive cardiomyopathy (heart failure due to chronically high blood pressure),hypertensive retinopathy - damage to the retina, hypertensive nephropathy- chronic renal failure due to chronically high blood pressure and hypertensive encephalopathy- confusion, headache and convulsions due to edema in brain that can lead to death. Therefore, it is considered very important to reduce blood pressure to normal levels with strict medical supervision.

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References in periodicals archive ?
Compared with the type curve based on gradient threshold model (type ii), the type curves based on variable-permeability model (type iii) result in gentle upturn in the later section, and its calculation method is more stable than that based on moving boundary model with threshold pressure gradient.
The general non-Darcy flow well-testing model based on variable-permeability effect and its calculation method are more stable and more practical than those based on threshold pressure gradient.
The threshold pressure gradient greatly affects the pressure distribution in tight sandstone oil reservoirs.
The percolation curves are rescaled with the threshold pressure and plotted in Figure 9b and the figure shows that the [phi] vs.
Experimentations of flow behavior and formation properties in tight gas reservoir bearing water [25-27] have shown that water influences stress sensitivity of tight reservoirs and increases threshold pressure gradient.
For packing pressures higher than the threshold pressure, the plaque is fully constrained throughout the completion of the glass transition (till the entire material becomes a glassy polymer) and is not affected by the type of in-plane boundary condition.
Current progress is in the direction of measuring an oral phonation threshold pressure (OPTP) that involves no tissue invasion of any kind.
This would then trigger a rise in phonation threshold pressure, which would make phonation more effortful.
When engineering towards the most efficient system of breath control for singing, the phonation threshold pressure (i.e., the minimum amount of air pressure needed to power the voice) is critical.
Supraglottal inertance is known to support vocal fold oscillation by lowering the phonation threshold pressure. The frequency range of about 1500 Hz to 3000 Hz lies in an inertance region (the upskirt of the third formant) in females.
This produces hoarseness, breathiness, increased phonation threshold pressures, decreased vocal efficiency and, commonly, voice fatigue.
The problem with diagnosing hypertension in kids is that there are too many threshold pressures for most physicians to keep straight, Charlene K.