lung volumes

[cutedoc12]

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any mnemonic or easy way to remember lung volumes??????????

 

[Ibanez]

Lung Volumes

*Tidal Volume (TV): Volume inspired/expired with each normal breath.


*Inspiratory Reserve Volume (IRV): Volume that can be inspired OVER n ABOVE tidal volume.

Eg. You take 1 sec to normally inspire a single breath (TV), now if you forcefully inspire (the maximum that you can!) it will take more time than TV under normal circumstances... say, 2 secs. Now IRV here is the extra air inspired during the "2nd" sec of inspiration.

[Time is not a functional coordinate for Lung volumes, I just used it to explain. ]

*Expiratory Reserve Volume: Volume that is expired OVER tidal volume ie. volume expired after expiration of Tidal Volume.



*Residual Volume (RV): Volume that remains after a max. expiration. Like after a forceful expiration where TV aswell as ERV is lost. It is the air that is always present in the lungs.


*Dead Space:
Anatomical - Volume of conducting airways. (The air in the pipes!)
Physiological- which is almost equal to Anatomical dead space in normal lungs. (In lung diseases it may increase!) And is calculated from the formula;

V(D)= TV x [P(A CO2) - P(E CO2)/ P(A CO2)]

where P (A CO2)= P (CO2) of arterial blood
P (E CO2)= P (CO2) of expired air.


That means its the (fraction X TV). The fraction represents dilution of arterial P CO2 by dead space air, which is not used in gaseous exchange and is thus not expired.


To simplify its just the air in pipes (air-pipes, bronchi-bronhioles and so forth) This is the air that maintains the PATENT airway. It is this air which helps the airway pipes from collapsing. [Or if you think there's a Vacuum in there? 😛 ]


LUNG CAPACITIES


*Inspiratory Capacity: IRV+TV. It is how much you can INSPIRE (max inspiration)

*Funtional Residual Capacity (FRC): How much air is in the lungs after you've expired TV!
(ERV+RV)


Remember that RV is the remaining volume in the lungs after MAX. EXPIRATION (ERV). So RV + ERV= FRC...

Like if you're normally breathing, expiring TV per breath, you're not accomodating extra air (that you do when you expire forcefully; max. :ERV).
So this extra air space (/volume; ERV) plus residual volume (inherent, remains constant) is your forced residual capacity (the maximum volume of air that can stay in lungs at a moment!)


*Vital Capacity or Forced Vital Capacity

The volume of air that can be forcibly expired after a max. inspiration.

TV+ERV+IRV

Since Residual Volume cannot be measured by spirometry and is present at all times and is constant and has nothing to do with inspired air... CONSIDER IT NOT VITAL (read; UNIMPORTANT). So by default, the Vital capacity is IRV+TV+ERV. (These volumes can be determined and are thus VITAL for you to know 😛)


*Total Lung Capacity

TLC=IRV+TV+IRV+RV.

Volume in toto. Self Explainatory!

*FEV1: is just the volume that can be expired in the first second of a forceful expiration. Self Explainatory.



PS Get yourself BRS physiology for my sake. 😛 I'm so tired now

PPS Almost every physiology textbook has a diagramatical representation of lung volumes and capacities.

PPPS If you still have any doubts, Im mostly "ONLINE"@yahoo im.

[email protected]

 

[Ice2remember]

wow.....🙂🙂🙂

thanks.

 

[cutedoc12]

thanx a lot...........gr8888 job!!!!!

 

[Ibanez]

wow.....🙂🙂🙂

thanks.

No problemo. 🙂

 

[Ibanez]

thanx a lot...........gr8888 job!!!!!

No problemo. 🙂