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Stack #681116

Respiratory A & P Chapter 2 flashcards

what is ventilation the process that moves gases between the external environment and the aveoli. mechanism by which oxygen is carried from the atmosphere to the aveloi and by which carbon dioxide is carried from the aveoli
Pressure difference across the lungs relative to the atmospheric pressure and is an essential buling block in the study of ventilation and pulmonary mechanics
Pressure gradient Difference between 2 pressures
What is pressure gradient responsible for moving air in and out of the lung
gas always flows from high to low pressures
No gas flows between 2 equal points
Driving pressure pressure difference between 2 points in a tube or vessel. It is the force moving gas or fluid through the tube or vessel
Transairway pressure or transrespiratory pressure the barometric pressure difference between the mouth pressure Pm and the alveolar pressure (Palv)
Transairway pressure is written Pta = Pm - Palv (mmHg)
Transmural pressure the pressure differences that occur across the airway wall (Ptm)
How is the transmural pressure calculated by subtracting the intra-airway pressure (Piaw) from the Pressure on the outside of the airway (Poaw)
Transmural pressure is written Ptm = Piaw - Poaw
Define Positive transmural pressure Said to exist when pressure is greater within the airway than the pressure outside the airway
Define Negative transmural pressure Said to exist when pressure is greater outside the airway than the pressure inside the airway
Transpulmonary pressure difference between the alveolar pressure (Palv) and the pleural pressure (Ppl)
Transpulmonary pressure is writeen Ptp = Palv - Ppl
Transthoracic pressure (Ptt)the difference between the alveolar pressure (Palv) and the body surface pressure (Pbs)
Transthoracic pressure is written Ptt = Palv - Pbs
the flow of gas in and out of the lungs is caused by the transpulmonary and transairway pressure changes that occur in response to the action of the diaphragm
When the diaphragm moves down thoracic volume increases and intrapleural and intra-alveolar pressure decreases
When the diaphragm moves up Thoracic volume decreases and intraplueral and intra-alveolar pressure increase
Define end-inspiration During inspiration gas from the atmosphere moves down the trachea-bronchial tree until the intra-alveolar pressure ant he barometric pressure are in equalibrium (pre-expiration)
Define end-expiration gas flows out of the lungs until the intra-alveolar pressure and the barometric pressure are once again in equilibrium (pre-inspiration)
at rest normal excursion (movement) of the diaphragm is about 1.5 cm
normal intra pleural change is about 3 to 6 cm H20 pressure (2 to 4 mmHg)
during deep inspiration the diaphragm may move 6 to 10 cm
during food expiration the intrapleural pressure may climbe between 70 and 100 cmH2O above atmospheric pressure
when the patient receives a positive pressure breath from a mechanical ventilator... the intra-alveolar pressure progressively rises above atmospheric pressure
during exhalation... the intra-alveolar pressure decreases toward atmospheric pressure
at end-expiration the intra-alveolar pressure is in equilibrium with atmospheric pressure
botht he lungs and the chest wall each have their own elastic properties
the chest wall has a natural tendancy properties of the lung tissue to move outward or expand as a result of the bones of the thorax and surrounding muscles
The lungs have a natural tendancy to move inward or collapse, because of the natural elastic
What is lung compliance how readily the elastic force of the lungs accepts a volume of inspired air, defined as the change in lung volume per unit pressure change (CL)
mathematically lung compliance is expressed in liters per centimeter of water pressure (L/cm H2O)
at rest the average CL for each breath is about 0.1 L/cm H2O (Approximately 100mL of air is delivered into the lungs per 1 cm H2O pressure change)
when lung compliance is increased the lungs accept a greater volume of gas per unit of pressure change
Both in the normal and abnormal lung CL progressively decreases as the alveoli approach their total filling capacity
What is FRC Functional residual capacity
Hooke's law provides another way to explain compliance by describing the physical properties of an elastic substance
What is Elastance The natural ability of matter to respond directly to force and to return to its original resting position or shape after external force no longer exists (change in pressure per change in volume)
Elastance is the reciprocal of compliance
Hookes law states when a truely elastic body like a spring is acted on by 1 unit of force, the elastic body will stretch 1 unit of length, and when acted on by 2 units of force it will stretch 2 units of length and so forth
When Hookes law is applied to the elastic properties of the lungs, volume is substituted for _________ and pressure is substituted for _________ length, force
tension pneumothorax is a condition if the presssure during mechanical ventilation (positive pressure breath) causes the lung unit to expand beyond its elastic capability the lung unit could rupture allowing alveolar gas to move into intrapleural space and thus causing the lungs to collapse
Define surface tension When a liquid-gas interface exists the liquid molecues at the liquid-gas interface are strongly attracted to the liquid molecues within the liquid mass This molecular cohesive force at the liquid-gas interface is called surface tension
surface tension is measured in dynes per centimeter
one dyne/cm is the force necessary to cause a tear 1 cm long in the surface layer of a liquid.
1 cm H2O pressure equals 980 dynes/cm
laplace's law describes how the distending pressure of a liquid bubble(not an alveolus) is influenced by (1) the surface tension of the bubble and (2) the size of the bubble itself.
WHen laplaces law is applied to a sphere with one liquid-gas interface the equasion is written as 2 ST P = ---- r where P is the pressure difference (dynes/cm2), ST is surface tension (dynes/cm) and r is the radius of the liquid sphere (cm) The factor 2 is required when the law is applied to a liquid sphere with one liquid-gas interface
when laplace's law is applied to a bubble with two liquid-gas interfaces the numerator contains the factor 4 rather than 2
Laplace's law shows that the distending pressure of a liquid sphere is directly proportional to the surface tension of the liquid, inversely proportional to the radius of the sphere
the numerator of laplaces law shows as the surface tension of a liquid bubble increases the distending pressure necessary to hold the bubble open increases, or the opposite-- when the surface tension of a liquid bubble decreases, the distending pressure of the bubble decreases
the denominator of laplace's law shows tht when the size of a liquid bubble inccreases the distending pressure necessary to hold the bubble open decreases, or when the size of the bubble decreases the distending pressure of the bubble increases
Define critical opoening pressure the high pressure (With little volume change) that is initially required to overcome the liquid molecular force during the formation of a new bubble
Before the bubble is formed the distending pressure is directly proportional to the radius of the bubble (opposite of what laplace's law states)
define critical closing pressure when the size of the bubble decreases beyond this point, the liquid molecular force of the bubble becomes greater than the distending pressure and the bubble collapses
Laplace's law can be restated as k P = --- r K = constand (surface tension) P = pressure and is inversely proportional to R (radius) Can be stated as Pr = k
The liquid film that lines the alveolus resembles a bubble or sphere
when the alveolar fluid is permitted to behave according to its natural tendency, a high transpulmonary pressure must be generated to keep the small alveoli open
Pulmonary surfactand is an important and complex substance that is produced and stored in the alveolar type II cells
Pulmonary surfactant is composed of phospholipids (about 90 percent) and protein (about 10 percent)
the primary surface tension-lowering chemical in pulmonary surfactant is the phospholipid dipalmitoyl phosphatidylcholine (DPPC)
The DPPC molecule at the alveolar gas-liquid interface causes surface tension to decrease in proportion to its ratio to alveolar surface area
it is estimated that surface tension of the average alveolus varies from 5 to 15 dynes/cm when the alveolus is small to about 50 dynes/cm when the alveolus is full distended
what are the 2 major elastic forces in the lungs that cause an inflated lung to recoil inward the elastic properties of the lungs, the surface tension of the liquid film that lines the alveoli
define atelectasis complete alveolar collapse
define dynamic refers to the study of forces in action
in the lungs dynamic refers to the movement of gas in and out of the lungs and the pressure changes required to move the gas.
general causes of pulmonary surfactant deficiency acidosis, hypoxia, hyperoxia, atelectasis, pulmonary vascular congestion
specific causes of pulmonary surfactant deficiency acute respiratory distress syndrome (ARDS), infant resporatory distress syndrome (IRDS), pulmonary edema, pulmonary embolism, pneumonia, excessive pulmonary lavage or hydration, drowning, extracorporeal oxygenation
What structures pierce the diaphragm vena cava, esophagus, aorta
What are the 4 critical life functions in order of importance Ventilation, Oxygenation, Circulation, perfusion
Ventilation includes the movement of air down to and including the terminal bronchioles
the best ways to assess ventilation Measure PaCO2
Normal PaCO2 is 35-45 mmHg
Any PaCO2 reading below 35 is hypocapnea
hypocapnea is caused by hyperventilation
any PaCO2 reading above 45 is hypercapnea
hypercapnea is caused by hypoventilation (Failure to ventilate well)
How is PaCO2 measured ABG
Oxygenation is oxygen moving into the blood and transported to the body tissue
define external respiration oxygen getting to the bloodstream
define internal respiration oxygen getting from the blood stream to the body tissues
what are 3 ways to measure oxygenation SpO2, SaO2, PaO2
What are the normals for SpO2, SaO2, and PaO2 SpO2 and SaO2 norms are 95 to 98% and PaO2 is 80 to 100%
What is a critical factor of oxygenation hemoglobin
What are two ways to check circulation pulse, blood pressure
define circulation movement of blood throughout the body
define perfusion pushing or forcing of oxygenated blood into the tissues
shock is a drop in blood pressure
what monitors CO2 levels Medulla
What does FRC stand for Functional Residual Capacity
Define FRC amount of air left in your lungs following a normal exhalation
what creates transairway pressure diaphragm moving downward
diaphragms natural tendency is to relax and move upward
movement of intrathoracic airways tend to what when you breath dialate when ou breath in and constrict womewhat when you exhale
intrapleural pressure is always sub atmospheric (Negative)
compliance is the ease at which lungs accept air
measurement of normal compliance 100 ml per cm of water
during a normal inspiration, intrapleural pressure decreases from its normal resting level which causes the bronchial airways to lengthen and to increase in diameter (passive dialation)
during expiration intrapleural pressure increases which causes the bronchial airways to decrease in length and in diameter
poiseuille's law arranged for flow states flow is directly proportional to P and r4 and inversely proportional to l and n (Flow will decrease in response to decreased P andn tube radius
flow is profoundly affected by the radius of the tube
poiseuille's law arranged for pressure states pressure is directly proportional to v, l, and n (presssure will increase in response to a decreased tube radius and decreased in response to a decreased flow rate, tube length, or viscosity)
pressure is a function of the radius to the forth power and therefore is profoundly affected by the radius of a tube
based on the proportionality for flow, it can be stated that because gas flow varies directly with r4 of teh bronchial airway, flow must diminish during exhalation because radius of the bronchial airways decreases
airway resistance (Raw) teh pressure difference between the mouth and the alveoli divided by flow rate.
normal Raw in the tracheobronchial tree is about .5 to 1.5 cm H2O/L/sec
the movement of gas through a tube or bronchial airway can be classified as laminar flow, turbulent flow, or a combination of laminar flow and turbulent flow (tracheobronchial flow)
define laminar gas flow gas flow that is streamlined
define turbulent flow gas molecules that move through a tue in random manner
tracheobronchial or transitional flow occurs in the areas where the airways branch. one or the other may be dominant
dynamic compliance clinically how readily a lung region fills with gas during a specific timie period
frequency dependent the alveoli distal to the obstruction do not have enough time to fill to their potiential filling capacity as the breathing frequency increases. The compliance of such alveoli is said to be frequency dependent
positive end-expiratory pressure (PEEP) the pressure in the alveoli distal to the airways with Raw may still be positive when the next inspiration begins
Created by: murphyismyname
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