pulmonary artery wedge pressure


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Related to pulmonary artery wedge pressure: Pulmonary artery catheter, central venous pressure, PAOP

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
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 artery wedge pressure

Abbreviation: PAWP
Pressure measured in the pulmonary artery after catheterization. The catheter is positioned in the pulmonary artery, and the distal portion of the catheter is isolated from pressure behind it in the artery by inflating a balloon with air. This allows the catheter to float into a wedged position and permits sensing of transmission of pressures ahead of the catheter (in the pulmonary capillary bed) by the transducer. Because no valve is present between this location and the left atrium, the measurement reflects left atrial pressure, and, in the presence of a competent mitral valve, the measurement provides an indication of left ventricular end-diastolic pressure. The balloon is then passively deflated after measurements of wedge pressure are completed. Elevated wedge pressures are found characteristically in patients with congestive heart failure or fluid overload. Synonym: pulmonary artery occlusive pressure; wedge pressure See: Swan-Ganz catheter

Patient care

The nurse prepares and sets up the transducer equipment to monitor pulmonary artery pressure and PAWP according to institutional protocol and the manufacturer's instructions. The transducer is balanced and calibrated as required (every 4 to 8 hr). Hemodynamic status is monitored, and findings are documented, including pulmonary artery pressure (normally 20 to 30 mm Hg systolic and 8 to 12 mm Hg diastolic) every hour as directed. To measure PAWP every 1 to 4 hr as directed, the nurse inflates the balloon with 0.75 to 1.5 cc of air depending on balloon size (the balloon is never inflated with fluid) while watching for change in waveform (indicating wedging) and assessing for balloon rupture (lack of resistance on inflation, with absence of wedging). If this occurs, the wedging procedure is discontinued (because of concern for air embolism), and therapy is managed based on pulmonary artery diastolic pressures. Pulmonary artery wedge pressure is read, documented (normally 4 to 12 mm Hg), and correlated to clinical findings and other hemodynamic values, and any abnormal findings are reported. The nurse then removes the syringe and permits passive deflation of the balloon while observing for reappearance of pulmonary artery pressure waveform. If the balloon remains inflated, the patient is at risk for pulmonary artery necrosis. The patient should be positioned on the right side and encouraged to take deep breaths and to cough as the nurse mobilizes the right arm. If the balloon remains wedged, the physician should be notified. Fluid and diuretic therapy are adjusted based on PAWP and other values as prescribed. Impedance cardiography may be employed as an alternative to invasive monitoring with a pulmonary artery catheter.

See also: pressure
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