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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.
1. see 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.
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.
the blood pressure in the veins. It is elevated in congestive heart failure, acute or chronic constrictive pericarditis, and venous obstruction caused by a clot or external pressure against a vein. Indications of increased venous pressure are continued distension of veins on the back of the hand when it is raised above the sternal notch and distension of the neck veins when the individual is sitting with the head elevated 30 to 45 degrees.
The pressure of the blood within the veins. It is highest near the periphery, diminishing progressively from capillaries to the heart. Near the heart the venous pressure may be below zero (negative pressure) owing to negative intrathoracic pressure.
See also: pressure
stress or strain, by compression, expansion, pull, thrust or shear.
the blood pressure in the arteries.
the pressure exerted by the atmosphere, about 15 lb per square inch (2.17 kPa) at sea level.
the blood pressure in the capillaries.
central venous pressure (CVP)
see central venous pressure.
the pressure of the cerebrospinal fluid, normally 100 to 150 mmHg.
the lowest pressure recorded in the arterial blood pressure cycle. Represents the minimal pressure in the left ventricle which can maintain its ejection phase. See also blood pressure.
a device attached to the outlet of gas tanks to measure internal pressure which indicates the quantity of gas remaining.
the rate of increase (or decrease) in the magnitude of the pressure being measured.
intracranial pressure (ICP)
see intracranial pressure.
intraocular pressure (IOP)
the pressure exerted against the outer coats by the contents of the eyeball.
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.
thought to participate in regulating the volume of extracellular fluid levels when the normal neurohumoral mediators are impaired; the increase in water and sodium ion excretions which occur when blood pressure is elevated because of an increase in the circulating blood volume.
necrosis of tissue caused by exclusion of circulation by external compression, e.g. in prolonged recumbency, or due to too-tight bandage, collar, harness.
pressure less than that of the atmosphere.
the osmotic pressure of a colloid in solution.
the potential pressure of a solution directly related to its solute osmolar concentration; it is the maximum pressure developed by osmosis in a solution separated from another by a semipermeable membrane, i.e. the pressure that will just prevent osmosis between two such solutions.
pressure point granuloma
see pressure points (below).
pressure point pyoderma
see pressure points (below).
parts of the body subject to pressure when the animal is recumbent, wearing harness or saddlery, or during restraint. Usually bony prominences such as the point of the hock, hip, shoulder, elbow and lateral aspects of limbs. These are predisposed to callus formation, infection pyoderma and granulomas.
pressure greater than that of the atmosphere.
difference between systolic and diastolic pressures in arteries.
e.g. the blood pressure receptors in the aortic arch and the carotid sinus.
the highest reading in the arterial blood pressure cycle. A reflection of the ejection pressure of left ventricular systole, and the elasticity of the arterial system.
the blood pressure in the veins. See also central venous pressure.
intravascular pressure as measured by a swan-ganz catheter introduced into the pulmonary artery; it permits indirect measurement of the mean left atrial pressure.
bandages which apply pressure to underlying tissues; used after trauma to limit the development of edema, and in the management of lymphedema.