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Phys2 Airflow-Airway

2 main forces opposing air movement 1.Compliance (ease of inflation). 2.Frictional Resistance (tissue and airway resistnace).
What is the predominant resistance to air flow? AIRWAY resistance: 80% of total frictional resistance. Tissue resistance is only 20%
What creates Tissue resistance to air flow? The friction b/w the two pleural layers sliding over eachother AND the b/w the diaphragm and abdomen.
How can air resistance be measured? by measuring the flow rate of air at the mouth when the pressure difference between the alveoli and mouth is known. R(airway)=Chang in Pressue (mouth & alveoli)/Volume.
What are the 3 types of Air flow through the airways? 1.Laminar (terminal bronchioles). 2.Turbulent (Trachea). 3.Transitional (Most of lung)
Laminar airflow Straight parallel lines. **seen in terminal bronchioles.
Turbulent airflow Random flow. Occurs in large diameter airways where there is fast flow. **Seen in trachea.
Transitional airflow Mostly straight but a few Eddie Distlers at junctions. **Everewhere in the lung b/w the trachea and terminal bronchioles.
What determines airway resistance in LAMINAR Flow? 1.Radius (inversely proptional). 2.Length (proportional) **Poiseuille's law
airway resistance in LAMINAR flow: radius doubles? resistance DECREASES 16 fold.
airway resistance in LAMINAR flow: radius decreases? resistance INCREASES by a fact of r^4
airway resistance in LAMINAR flow: length increases? resistance INCREASES
airway resistance in LAMINAR flow: length decreases? resistance DECREASES
What happens when there is not a linear increase in laminar flow rate with an increase in pressure? the flow has become TURBULENT! there is much more frictional resistance now
What is used to predict if turbulence will occur? How is it used? Reynolds number. When it is >2000, there is a high chance of turbulence.
What increases Reynolds number? 1.Inc velocity of gas. 2.Inc airway diameter (opposite of laminar flow). 3.Inc in gas density **is inversely proportional to viscosity
Where is the main site of airway resistance? Medium bronchi b/w trachea and bronchioles (small cross area, high gas vel). **based on Poiseuille's law, the smallest airways would have highest but since they have high cross-sectional area & paralleled resistances, they do not
What is the connective tissue in the lung? Parenchyma
radial traction The pulling open of the airways by the parenchyma as the lung expands. **Airway diameter INCREASES and lung inflates
How will Increased radial traction affect the airway resistance? DECREASES it. as lung volume increases, the radial traction increases and resistance decreases. **Diameter is INC.
Why would people with COPD ventilate at higher lung volumes? B/c they are creating radial traction to counter the increased airway resistance they suffer from.
Factors that affect Bronchiale smooth muscle tone 1.Irritants (smoking). 2.Parasymp tone (M receptors). 3.B2 receptors stimulation (EPI). **1&2 will decrease radius, thus INCREASE resistnace. **3 will Inc radius, DECREASING the resistance.
What happens with an obstructive lung disease? what are the 3 main types? 1.Chronic Bronchitis (dec radius by Inc mucus production in airway). 2.Asthma (Inflammatory Inc smooth muscle tone). 3.Emphysema (dec radius by dec radial traction from loss of elastic tissue).
What happens to the airways during FORCED expiration? Peripheral airways are compressed which limits flow. **medium bronchi are no longer the main resistance.
What does a flow-volume curve show? Flow limitation occurs in forced expiration. **Shows that flow DECLINES down to RV at the SAME RATE no matter the initial lung volume or effort.
What is transairway pressure? the difference in pressure across the airway wall. **Pta=Pairwaywall-Pintrapleural. **always b/w the pressure gradient in the mouth & Alveoli
What determines whether or not an airway is open (patent) or compressed? Transairway Pressure.
Positive transairway pressure (Pta)? Pairwaywall > Ppleural and the airway is open.
Negative transairway pressure (Pta)? Pairwaywall < Ppleural and the airway is closed.
What is the transairway pressure duing inspiration? POSITIVE, Airway kept open: 1.Pre-inspiration: 0-(-5)= 5cm H2O. 2.Inspiration: -1-(-7)= 6cm H2O. 3.End Inspiration: 0-(-8)= 8 cm H2O.
Alveolar Pressure (Pa)? Pa= P(elastic recoil) + P(pleural). **therefore how expanded the Alveoli is (elastic recoil pressure) affects it's pressure.
What is the transairway pressure during FORCED expiration? NEGATIVE (airway compression). This is b/c during forced expiration, pleural pressure becomes positive, making alveolar pressure VERY positive, mouth pressure remains 0. Paw: 19. Ppl: 30. Pa: 38. Pmouth: 0.
Where does the compression (due to negative transairway pressure) occur during forced expiration? Peripheral airways b/c they are the main resitance limiting flow. **Also a reason why the trachea is supported by cartilage.
What patients are more susceptable to airway collapse due to negative transairway pressure? Those with Obstructive lungs diseases. The decreased radius and increased airway resistance cuases airway pressure to dec more quickly along the airway.
Can patients with obstructive pulmonary disease experience airway collapse during nonforced expirations? YES
Created by: WeeG



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