partial pressure

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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.

par·tial pres·sure (P),

the pressure exerted by a single component of a mixture of gases, commonly expressed in mm Hg or torr; for a gas dissolved in a liquid, the partial pressure is that of a gas that would be in equilibrium with the dissolved gas. Formerly, symbolized by p, followed by the chemical symbol in capital letters (for example, pCO2, pO2); now, in respiratory physiology, P, followed by subscripts denoting location and/or chemical species (for example, Pco2, Po2, Paco2.
Farlex Partner Medical Dictionary © Farlex 2012

par·tial pres·sure

(pahr'shăl presh'ŭr)
The pressure exerted by a single component of a mixture of gases, commonly expressed in mm/Hg or torr; for a gas dissolved in a liquid, the partial pressure is that of a gas that would be in equilibrium with the dissolved gas. In respiratory physiology, symbolized by P, followed by subscripts denoting location and/or chemical species (e.g., PCO2, PO2, PaCO2).
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

partial pressure

the total pressure of the mixture of gases within which a gas occurs, multiplied by the percentage of the total volume the gas occupies. Thus if the normal total pressure of the atmospheric gases is 760 mm Hg and there is 21% oxygen in this mixture, the partial pressure of O2 is: 760×0.21 = 160 mm Hg.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Partial pressure

The pressure exerted by one of the gases in a mixture of gases. The partial pressure of the gas is proportional to its concentration in the mixture. The total pressure of the gas mixture is the sum of the partial pressures of the gases in it (Dalton's Law) and as the total pressure increases, each partial pressure increases proportionally.
Mentioned in: Nitrogen Narcosis
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

par·tial pres·sure

(pahr'shăl presh'ŭr)
The pressure exerted by a single component of a mixture of gases, commonly expressed in mm/Hg or torr.
Medical Dictionary for the Dental Professions © Farlex 2012
References in periodicals archive ?
However, it reveals that the method is not sensitive to moderate deviations from spatially uniform partial pressures of additives [Funk and others 1970], as long as the main contribution to the Bartels functions arise by the integrals from regions around the discharge axis [Franke and Schneidenbach 2007].
Cr is the noblest among the above four elements; the formation of [Cr.sub.2] [O.sub.3] needs high oxygen partial pressure. It is reported in the literature that Cr in steel can also cause a wetting problem, but there is no direct evidence for the bad wetting behavior of [Cr.sub.2] [O.sub.3].
The variation in the concentrations of oxy-, deoxy-, and carbamino-haemoglobin are the result of the changes in the partial pressures of oxygen and carbon dioxide throughout the evolution of the process.
In addition, as a result of carried out investigations it was discovered for the first time that values of equilibrium concentrations of nitrogen within investigated range of its partial pressures in different melting methods are close to each other.
The determination of the effective diffusion coefficient is performed by means of curve fitting, i.e., the change during time of partial pressure of the cell gases is determined and then it is matched on the solution of Fick's law.
The partial pressure of oxygen in brain tissue is an important new way of evaluating cerebral perfusion and oxygenation in the TBI patient.
The major operating parameters like reactor temperature, pressure, permeate side hydrogen partial pressure and steam feed rate, and design parameters like membrane area are investigated for both the reactors and compared with each other.
In the second case, knowledge of the precursor partial pressure as well as knowledge of the carrier gas flow rate and the total pressure at the optical cell (e.g., obtained from an MFC and a pressure transducer reading, respectively) permits the determination of the precursor flow rate using the "bubbler equation" [12, 16, 21, 22, 24, 26, 27]:
The average partial pressure of the reaction gases ([H.sub.2] and [O.sub.2]) in the PEMFC system can be calculated according to the relations [13]:
The children with severe pneumonia were divided into a mild hypoxia group, a moderate hypoxia group and a severe hypoxia group according to arterial partial pressure of oxygen; the myocardial enzymes, hepatic and renal function and cTnT of the children in the three groups were compared.
After the rise to high elevation, the low partial pressure of oxygen (PaO2) takes to an increase in minute ventilation, known as hypoxic ventilatory response (HVR).
The full menu includes pH, partial pressure of oxygen, partial pressure of carbon dioxide, sodium, potassium, ionized calcium, hematocrit, glucose, lactate, creatinine, chloride, BUN, and TC02.

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