threewalkers
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15. The graph shows an isovolumetric pressure-flow curve obtained at 25% of total lung capacity. An increase in which of the following is most likely to increase the plateau value of the expiratory flow rate?
curve showing experatory flow rate on Y-axis and pleural pressure on X-axis. curve shows increase in expiratiory folw rate which platues at 5 L/sec speed at around 20 cm H2O plural pressure and continues to be the same for further rise in pleural pressure.
A) Airway resistance
B) Amount of surfactant in the alveolar space
C) Ciliary beating frequency
D) Expiratory effort
E) Lung volume
F) Parasympathetic activity of fibers innervating the airways
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| littledoc
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E?
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| threewalkers
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please explain, thanks.
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| littledoc
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for A- by increasing airway resistance, expiratory flow decreases.
same for F- parasympathetics causes bronchoconstriction so decreases expiratory flow rate.
Cilia beating has no role in expiratory flow rate. same is for B.
FEV1/FEV is 80% so if we increase long volume, more volume will be expired per second.
If we increase lung volume, intrapleural pressure becomes more negative. The more negative the intrapleural pressure, the lower the resistance of airway, so expiratory flow rate increases
for D- if we increase expiratory effort, intrapleural pressure becomes positive & airways are compressed, causing flow rate to decrease!!
REmember, peak expiratory flow rates are "effort independent"
hope i am clear!
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| alirizvi
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and also if u breathe in more, u will breathe out more 
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