Dead space - medico25

[ArchivalUser]

what happens to physiologic dead space during exercise ??

plz explain....with regard to anatomic and alveolar dead space also and why ?

[ArchivalUser]

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[ArchivalUser]

UW says ...exercise increases anatomic dead space but not physiologic dead space....

But physiologic dead space -- anatomic + alveolar dead space
anyone...??

[ArchivalUser]

According to BRS, cardiac output increases during exercise .As a result , more pulmonary capillaries are perfused and more gas exchange occurs.V/Q ratio through the lung is more even during exercise and there is decrease in physiologic dead space.
I think that means decrease alveolar dead space .
Fick law of diffusion shows (pg 268-kaplan LN 2008 edit) rate of difussion of gas increase with increase in surface area, and surface area for gas exchange increase in exercise.
Kaplan LN saids PACO2 to remain constant changes in ventilation must be made, exercise increases metabolic rate , but pACO2 remains constant due to increase in ventilation.

The formula is PACO2 ~ metabolic CO2 production/ alveolar ventilation (pg 266 kaplan LN-2008edit)

Although body produce more CO2 in exercise ,so increase venous CO2 but arterial CO2 remains the same due to increase ventilation blow off the CO2 .( BRS)

So another way to calculate is FA formula :
Physiological dead space=Tidal volume x (PaCO2_PeCO2)/ PaCO2
Pa CO2 remains constant but increase in Pe CO2 ( expired air CO2)
So physiology dead space decreased.

[ArchivalUser]

so you have to undersdtand what physiologic vs anatomic dead space is:

in short disscussion anatomic dead space is basically all the part of your airways that DONT participate in gas exchange so that would be you nose all the way to your terminal bronchioles right? so these structures dont have to do with gas exchange remember that


physiologic is basically happens in a pathology more because it means those alveloi in your lungs that are poorly perfused or ventilated due to COPD's etc any pathology that could do that baiscally.

So in excercise you are ventilating more correct because your body needs more o2 . So that gas coming in willl be more, so by proportion your anatomic dead space is also goign to increase.

But why woudl your physiolic dead space increase? your alveoli are fine right? there is no obstuction there so it wouldnt increase it would remain same.


if question was like a person has poor perfusion because of PE or something like that , you are not going to perfuse the alevoli well , so your physiolic space is increased then.

I hope this kinda helped, i am not the best at explaining this but i tried to help.