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a 40 healthy woman inhaled total long capacity and exhaled forcefully. the rate of airflow decreaseed linear by exhalation continued. what is the reason of decrease in rate of exhalation?
a.airway compressin
b.decrease expiratory effort
c.decrease intraplural pressure
d.doming of diaphragm
e.increase elastic recoil
????
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I think A is the answer too....elasticity of lung cause increase in airway compressin which makes the intra alveolar pressure increase and then increase the air flow in the first seconds of expiration
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Excuse me , A would be right at the begging or exhalation, later it decreases gratually simple becauseof decrease respiratiry effect ( B )
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With expiration, as the Intra Pleural Pressure become more +ve , there is a dynamic compression of airways. I read this in Kaplan notes. A is the answer
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Let us imagine the flow volume loop ....Especally the Expiratory Flow Volume Curve
--On the Y axis----Expiratory Airflow
--On the X axis---Lung volumes
--The shape of this curve is---scooped- out appearance if we are moving along the curvein clockwise direction
--The first part fo this curve (from the TLC to the peak expiartory flow )dependent on effort and it is part of the curve where by the EXPIRATORY AIRFLOW IS STEADLY INCREASING ...
--The second part of the curve(from the peak expiratory flow to the RESIDUAL VOLUME)---IS EFFORT INDEPENDENT ---THIS IS the part of the curve in which the expiratory airflow rate is DECREASING LINEAERLY(the question is refering this part)....
---Why is the expiratory flow rate decreasing linearly after it reaches the PEAK EXPIARTORY FLOW RATE...partly explained by dynamic airway compression
--How is dynamic airway compression happens...
1-Airways arent rigid tubes
2-Lungs are deflated and inflated by changing the pressure around it
3-Hence the airways are prone to expansion (during inspiration) and compression (during ACTIVE expiration)
4-During Active Expiration INTRAPLEURAL PRESSURE is raised to above Atmospheric pressure---this pressure then compresses the AIRWAYS...becuase of this flow rates during forced expiration cant be increased by making a greater muscular effort
