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Phys2 Airflow-Airway
| Question | Answer |
|---|---|
| 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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