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NU 624

Exam 3 - Pressure/Surface Tension/Pascale/LaPlace/Fluids

How is pressure measured under the Systeme Internationale? Newton/meter sq., or Pascale
How is the Pascale usually referred to as? kPa
What does Pascale's principle state? Pressure applied to a completely enclosed fluid is transmitted undiminished to all parts of the fluid and its enclosing walls
What do we now know about pressure in a fluid that is enclosed in a container? There are differences in wall tension in different parts of the fluid
What is an aneurysm? Localized enlargement of an artery caused by weakening of the artery wall
The pressures exerted on the walls of an aneurysm are (lesser/greater) than the pressures exerted on the surrounding arterial walls. greater
Why are the dilated walls of a vessel more prone to rupturing or dissection? The forces exerted at the weak point are greater than elsewhere in the vessel that do not have a weak point
What does LaPlace’s Law state? Wall tension increases with vessel radius
What are four physiologic scenarios where LaPlace's Law is seen? COPD, difficulty of a baby's first breath, alveolar role in exhalation, aneurysms
LaPlace's Law explains the relationship between what three factors? Pressure, surface tension, radius
What is the LaPlace equation? P=2T/R
Pressure and surface tension are expressed as _________. dynes/cm sq
The Law of LaPlace describes the magnitude of (inward/outward) pressure. Inward
What is the implication of LaPlace’s Law in regards to alveoli? Larger surface tension involves a larger force pushing inward into the alveoli and with 2 alveoli connected in the airway, it is implied that the smaller alveoli would collapse and push its gases into larger alveoli (smaller radius=more pressure)
What prevents the collapse of contents of smaller alveoli into larger alveoli? surfactant
What does pulmonary surfactant decrease and where does it have a greater effect? decreases surface tension; greater effect in smaller alveoli
Increased wall tension is described by ________ Law, but offset by the effects of ________. LaPlace's; surfactant
What is the function of the aortic cross clamp in open heart surgery? Divert blood to the cardio-bypass machine
What determines LV response to the aortic cross clamp? Length-tension-velocity relation of the myocardium
Tension is obtained by multiplying what two factors? pressure & radius
What are the principle determinants of afterload? ventricular dimensions (radius) and systolic intraventricular pressure
What are two other surgical scenarios that utilize cross-clamping? Abdominal aneurysmectomy and infrarenal aortic cross-clamping
Tubes are pathways in which the ________ is greater than the _______. Length; diameter
An orifice is a pathway whose ______ is greater than its ______. Diameter; length
What are the 5 factors that determine the rate of flow through a tube? 1)Cross section (radius) 2)proximal to distal pressure gradient (P1-P2) 3)tube length 4)fluid viscosity 5)solution density
What is the definition of the “flow” of fluid? Quantity of fluid (gas or liquid) passing through in a unit of time
What is the equation for flow? F=Q/T
What must be present in order for flow to occur through a tube? Proximal to distal pressure gradient
Flow rate is (directly/indirectly) proportional to pressure. directly
How much is flow reduced if the diameter of a tube is reduced to ½ the original size? Reduced to 1/16th the original value
How does flow change if a tube is cut in half? Flow is doubled
What has more influence on flow through a tube: altering the diameter or the length? Diameter
What is the definition of the meniscus? A curve in the surface tension of a liquid caused by the contact of liquid against the sides of a container
What are two possible shapes of a meniscus? Concave or convex
When does a convex meniscus occur? When the molecules of the liquid repel the molecules of the container or object
Where can a convex meniscus be seen? mercury barometers
When does a concave meniscus occur? When the molecules of a liquid attract those of the container
When can an example of a concave meniscus be seen? water in a glass
What property creates the concave meniscus of water up the sides of a glass and downward in the center? surface tension
The force exerted by atoms and molecules is defined as __________. Pressure
How is pressure generated? kinetic energy
Kinetic energy is produced by atoms and molecules that are in __________. motion
What is the equation for pressure? force/area
The English unit of pressure, the pound, is a unit of (mass/force). force
What are two ways that the English unit of pressure is measured? lbs/ft sq; lbs/sq in
What is the international unit of pressure? newton/meter sq or "Pascal"
1 atmosphere of pressure is equivalent to _______ kPa or _______ lbs/sq in. 101.3 kPa; 14.69 lbs/sq in
When is pressure exerted at the molecular level? When molecules of gases collide
What is cylinder pressure? The sum of molecular forces in a closed container
How is cylinder pressure measured? lbs per square in. gauge (PSIG)
What two values are equal when a gas cylinder is empty? cylinder and atmospheric pressures
A full E cylinder of oxygen measures _________ PSIG. 1900-2200
A full tank of N2O measures __________ PSIG. 745
What does the Bourdon Gauge measure? Pipeline or cylinder pressures
What type of measurement is the Bourdon Gauge based on? Aneroid
An aneroid gauge operates (with/without fluid). without
What governing body sets standards for the readings on Bourdon-type gauges? ASTM
What do the terms mmHg and cmH20 measure? Pressure of a gas other than compressed gas
mmHg is also referred to as ______. torr
The tourniquet applied during knee surgery utilizes _______ as a form of measurement since it is not a compressed gas. mmHg or torr
High pressure and continuing pressure in an anesthesia machine is measured in units of _______. cmH20
What are the three physics principles that apply to pressure in a liquid source? 1)pressure in a liquid at a certain level is proportional to the height of the liquid 2)pressure in a liquid increases with the depth below the surface 3)pressure in a liquid is the same in all directions at the same depth
Patients undergoing TURP are at risk of developing ____________. Dilutional hyponatremia
Why are TURP patients at risk of developing dilutional hyponatremia? High-hanging bags of irrigation lead to absorption of irrigating solution by open venous channels
What is the function of the pressure relief valve near the CGO? Prevents transmission of high-pressures in the anesthesia machine to the patient
What safety feature on the anesthesia machine may limit the ability to provide adequate jet ventilation? Pressure relief valve
What are the features in the anesthesia machine that ensure unidirectional flow of gases toward the patient from machine and away from the patient on exhalation? Inspiratory and expiratory valves
How is incompetence of unidirectional valves prevented? Opening, cleaning, and if necessary, replacing discs
What is the function of the pressure regulator (pressure reducing valve)? Reduce pressure and control gas supply from the pipeline or cylinder
How do pressure regulators function? Balances force of a spring against the force of the compressed gas
What is surface tension? Attractive forces that occur between molecules at the surface of a liquid
Where does surface tension occur? At the air-liquid interface
Surface tension creates a strong barrier between ______ and _____ molecules. Air; liquid
What property prevents fast evaporation of water as well as certain insects to walk on water? Surface tension
The dyne is a unit of (force/mass). Force
How is surface tension measured and at what temperature is it measured at? Dynes/cm at 20 degrees celsius
What lines the walls of alveoli in the lungs? Thin film of liquid
How does the surface tension of fluid in the lungs influence the alveoli? The surface tension of the liquid influences the alveoli to want to collapse
What endogenous chemical prevents the collapse of alveoli? Surfactant
Lung surfactant is secreted by _____________. Type 2 alveolar epithelial cells
What does the lung surfactant decrease? Cohesive force of the liquid film, or surface tension
What are the three physiological benefits of lung surfactant? 1)increases lung compliance 2)reduces the tendency of small alveoli to empty into larger ones (collapse) 3)reduce fluid leak from pulmonary capillaries into alveoli
Created by: philip.truong
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