mdwannabe
Forum Guru
Topics: 37
Posts: 1,133
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May be I dont undestand the q.. but here we go ...
Vital Capacity (I assume) is the difference b/w TLC and RV, so At TLC the elastic recoil iz at MAX potential, all the force is directed inwards, pleural pressure is as negative as it gets, no expiratory air flow there, since we just took the largest breath IN ever. Pressure n alveolus 0.
As you exhale, pressure in alveouls becomes +, the flow starts and we measure the amount of air exitting with in 1 sec of start and then let the pt exhale to the fullest (to RV) At RV the elastic recoil potential is at MIN, pleral pressure is less negative than at TLC, but more negative than at FRC. I think this covers your question, if not, be more specific, I ll try again.
Size of alveolus at FRC... some (smaller ones) have collapsed, others are at the optimal size. I think whats important is that pressure at FRC in the alveolus is... 0, thats cuz the chest recoil equlas the elastic recoil of lung.
Hope this helps.
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| oddissy4u
Forum Guru
Topics: 107
Posts: 389
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thnx for ur efforts ----
:arrow: at FRC ,alveoli at the base r smaller thn at apex.
:idea: at VC,expiratory flow increases wth increasing pleural pressure,explain.
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