pressure /pres·sure/ (P ) (presh´er) force per unit area.
pulmonary artery wedge pressure.
pressure (P) [presh´ur]
arterial pressure blood p. (2).
blood pressure
1. the pressure of blood against the walls of any blood vessel.
2. the pressure of blood on the walls of the arteries, dependent on the energy of the heart action, elasticity of the arterial walls, and volume and viscosity of the blood; the maximum or systolic pressure occurs near the end of the stroke output of the left ventricle, and the minimum or diastolic late in ventricular diastole.
central venous pressure (CVP) the venous pressure as measured at the right atrium, done by means of a catheter introduced through the median cubital vein to the superior vena cava.
cerebrospinal pressure the pressure or tension of the cerebrospinal fluid, normally 100–150 mm. as measured by the manometer.
detrusor pressure the pressure exerted inwards by the detrusor urinae muscles of the bladder wall.
diastolic pressure , diastolic blood pressure see blood p.
end-diastolic pressure the pressure in the ventricles at the end of diastole, usually measured in the left ventricle as an approximation of the end-diastolic volume, or preload.
intracranial pressure (ICP) pressure of the subarachnoidal fluid.
intraocular pressure the pressure exerted against the outer coats by the contents of the eyeball.
intravesical pressure the pressure exerted on the contents of the urinary bladder; the sum of the intra-abdominal pressure from outside the bladder and the detrusor pressure.
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) a measure of the strength of respiratory muscles, obtained by having the patient inhale as strongly as possible with the mouth against a mouthpiece; the maximum value is near the residual volume.
mean arterial pressure (MAP) the average pressure within an artery over a complete cycle of one heartbeat.
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 due to the presence of colloids in solution.
osmotic pressure the pressure required to prevent 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.
positive pressure pressure greater than that of the atmosphere.
positive end-expiratory pressure (PEEP) a method of mechanical ventilation in which pressure is maintained to increase the volume of gas left in the lungs at the end of exhalation, reducing shunting of blood through the lungs and improving gas exchange.
pulmonary artery wedge pressure (PAWP), pulmonary capillary wedge pressure (PCWP) intravascular pressure as measured by a catheter wedged into the distal pulmonary artery ; used to measure indirectly the mean left atrial pressure.
pulse pressure the difference between systolic and diastolic pressures.
systolic pressure , systolic blood pressure see blood p.
Valsalva leak point pressure the amount of pressure on the bladder by a Valsalva maneuver at which leakage of urine occurs; a measure of strength of the urethral sphincters.
venous pressure the pressure of blood in the veins.
wedge pressure blood pressure measured by a small catheter wedged into a vessel, occluding it, e.g., pulmonary capillary wedge p.
wedged hepatic vein pressure the venous pressure measured with a catheter wedged into the hepatic vein; used to locate the site of obstruction in portal hypertension.
pulmonary artery wedge pressure.
pressure (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
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.
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.
pulmonary
pertaining to the lungs, or to the pulmonary artery. See also lung.
pulmonary abscess
causes a syndrome of chronic toxemia, cough, loss of body weight. Careful auscultation may elicit squeaky rales around the lesions. See also caudal vena caval thrombosis, aspiration pneumonia.
pulmonary acinus
basic structural unit of the lung parenchyma; the gas exchange unit, supplied by a single terminal bronchiole and includes branches of the terminal bronchiole, alveolar ducts, alveolar sacs, alveoli and associated blood vessels. A pulmonary lobule consists of many acini.
pulmonary agenesis
incompatible with life; found only in fetal or neonatal necropsy specimens.
pulmonary alveolar microlithiasis
see microlithiasis alveolaris pulmonum.
pulmonary alveolar parenchyma
include epithelial cells (pneumonocytes or pneumocytes), alveolar capillary endothelial cells, and interstitial cells (fibroblasts) and alveolar macrophages.
pulmonary alveolar proteinosis
a disease of unknown etiology marked by chronic filling of the alveoli with a proteinaceous, lipid-rich, granular material consisting of surfactant and the debris of necrotic cells.
pulmonary arteriopathy
see aelurostrongylus.
pulmonary artery wedge pressure
see wedge pressure.
pulmonary atelectasis
see atelectasis.
pulmonary bed
the network of capillaries in lung tissue.
pulmonary calcinosis
see microlithiasis alveolaris pulmonum.
pulmonary calculus
see bronchial calculus.
pulmonary carcinomatosis
see ovine pulmonary adenomatosis (below).
pulmonary circulation
the circulation of blood to and from the lungs. Deoxygenated blood from the right ventricle flows through the right and left pulmonary arteries to the right and left lung. After entering the lungs, the branches subdivide, finally emerging as capillaries which surround the alveoli and release the carbon dioxide in exchange for oxygen. The capillaries unite gradually and assume the characteristics of veins. These veins join to form the pulmonary veins, which return the oxygenated blood to the left atrium. See also circulatory system.
pulmonary compliance
a measure of the ability of the lung to distend in response to pressure without disruption. Expressed as the unit volume of change in the lung per unit of pressure. Compliance or distensibility of the lung is increased in conditions such as emphysema in which the lung distends more readily, and is decreased in fibrotic conditions in which the lung distends with difficulty. See also compliance.
pulmonary congestion
caused by engorgement of the pulmonary vascular bed and it may precede pulmonary edema when the intravascular fluid escapes into the parenchyma and the alveoli. There is a loss of air space and the development of respiratory embarrassment.
pulmonary cysts
may be congenital or acquired, caused by trauma, parasites (Paragonimus spp.), or associated with bronchiectasis. Rarely, metastatic tumors cavitate forming cysts.
pulmonary defense mechanisms
include aerodynamic filtration in nasal cavities, sneezing, local nasal antibody, laryngeal and cough reflexes, mucociliary transport mechanisms, alveolar macrophages, systemic and local antibody systems.
pulmonary edema
an effusion of serous fluid into the pulmonary interstitial tissues and alveoli. Preceded by pulmonary congestion (see above). If the extravascular exudation is sufficiently severe a critical level of hypoxia may be reached. The breathing will then be labored, the normal breath sounds on auscultation may be absent, and a frothy nasal discharge, often blood-tinged, may appear. At this stage the animal's life is about to terminate.
pulmonary embolus
obstruction of the pulmonary artery or one of its branches by an embolus. The embolus usually is a blood clot swept into circulation from a large peripheral vein.
Signs vary greatly, depending on the extent to which the lung is involved. Simple, uncomplicated embolism produces such cardiopulmonary signs as dyspnea, tachypnea, persistent cough, pleuritic pain and hemoptysis. On rare occasions the cardiopulmonary signs may be acute, occurring suddenly and quickly producing cyanosis and shock. A septic embolus can lead to local pulmonary abscess or an extension to pneumonia as in caudal vena caval syndrome. See also caudal vena caval thrombosis, pulmonary abscess (above).
pulmonary eosinophilic granulomatosis
a lesion common in heartworm disease; eosinophiles and neutrophils surround trapped microfilariae causing nodules as large as 3 inches diameter. May be preceded by lesions of allergic pneumonitis.
exercise-induced pulmonary hemorrhage
traces of blood can be found in about 60% of horses after racing. Less than 1% of these bleed from the nostrils. See also epistaxis.
pulmonary function tests
tests used to evaluate lung mechanics, gas exchange, pulmonary blood flow and blood acid-base balance. Pulmonary function testing is used to detect emphysema and chronic obstructive bronchitis at an early stage.
pulmonary hemorrhage
as distinct from hemothorax, is recognized because of a syndrome of dyspnea, increased lung density radiographically, and hemorrhagic anemia. If a large vessel ruptures into an abscess cavity there is usually a massive hemoptysis and instant death. Frothy blood-stained nasal discharge is an indication of pulmonary edema rather than of pulmonary hemorrhage. See also exercise-induced pulmonary hemorrhage (above).
pulmonary horse sickness
the predominantly pulmonary form of african horse sickness.
pulmonary hypertrophic osteoarthropathy
see hypertrophic osteopathy.
pulmonary hypoplasia
a congenital defect resulting in decreased lung development.
pulmonary infarction
see pulmonary infarction, pulmonary embolus (above).
pulmonary infiltration with eosinophilia (PIE)
see pie syndrome.
pulmonary malformation
includes accessory lungs, pulmonary hypoplasia, pulmonary agenesis, congenital pulmonary cysts, endodermal heteroplasia, respiratory distress syndrome, neonatal maladjustment syndrome, immotile cilia syndrome.
pulmonary mycoses
includes aspergillosis, mortierellosis, blastomycosis, cryptococcosis, coccidioidomycosis.
pulmonary neoplasm
many types are recorded in all species but the prevalence is very low in food animals. A common site for metastases in companion animals. Characterized clinically by decreased exercise tolerance, progressive dyspnea, chronic cough and emaciation. Most diagnoses result from radiographic examination of the thorax for secondary growths.
neurogenic pulmonary edema
results from head trauma, central nervous system lesions and toxins, which may cause increased pulmonary blood pressure and alteration to sympathetic innervation leading to fluid leakage from vessels.
overriding pulmonary artery
ovine pulmonary adenomatosis
a very chronic progressive pneumonia of sheep and goats caused by a retrovirus. Dyspnea, emaciation and a profuse nasal discharge are the cardinal signs, but coughing is not evident. The disease is always fatal. It is of great importance if it occurs in flocks that are housed for long periods. Characteristically the extensive lung involvement includes large areas of neoplastic tissue. Called also jaagsiekte, pulmonary carcinomatosis.
pulmonary patterns
re-expansion pulmonary edema
edema, emphysematous bullae and serosanguinous fluid in the airways with generalized pulmonary capillary endothelial damage; associated with chronic pulmonary collapse and removal of pleural effusions or pneumothorax with rapid re-expansion.
pulmonary rupture
traumatic, especially when there is rib fracture, or spontaneous due to coughing and a weak parenchyma. The most common cause of pneumothorax.
pulmonary thromboembolic disease
thromboembolism causing blockage of large sections of the pulmonary vascular bed will result in at least temporary severe dyspnea. It may also lead to right heart congestive failure, i.e. cor pulmonale.
pulmonary thrombosis
see thromboembolism.
pulmonary valve
the pocket-like structure that guards the orifice between the right ventricle and the pulmonary artery.
pulmonary valve stenosis
causes right ventricular hypertrophy and a poststenotic dilatation of the pulmonary artery. There is a systolic murmur and thrill on the left side of the chest. A common congenital defect in dogs.
pulmonary vein
the large vein (right and left branches) that carries oxygenated blood from the lungs to the left atrium of the heart.
pulmonary wedge pressure
see wedge pressure.
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