Chapter 3

A-a differnce: none
response to O2: good

A-a differnce: increased
response to O2: good

Vgas=(A/T) times D times (P1-P2)

area the length of the alveoli plus capilliary

thickness intestional space in between alveoli and capillaries
pretty much non-existant in healthy person

alveolar PO2

artieal PO2

pressure gradient

explosion of SA slows down movemtn of air to where only choice is diffusion

how good is your diffusion
if difference is small then you know that you are are reaching equilibrium at the blood gas phase
if big difference then something has gone wrong

CO is an example
size of the fence doesnt matter
gate size is what affects how much CO can come trhough

never contributes to P2 it gets picked up heme too fast so the amount isnt limited to the amount fo blood os it limited by diffusion

N2O is an example
the amount of blood flowing is what limits it
not the gate that matter but the size of the field
O2 is an exmaple of this too

it dissolves into the blood very quickly
takes a tenth of a second to reach equilibrium
only way to increase amount of N2) diffusion is to increase the amount of blood

takes a quarter of sec in cap to reach equilibrium but blood takes 3/4 sec to travel across alveoli space so plenty of time to reach equilibrium

diffuse and dissolve into the blood plasma to contribute to partial pressure

thickness of the blood gas barrier
exercise
breathing reduced PO2

scar tissue build-up in the lung
this changes the thickness
area stays the same
making it harder to diffuse oxygen
restctive diease har to get air in
have O2 that might never reach equilibrium

increase P1 by giving O2 therapy

when you do this cardiac output goes up which means that blood flow is going faster so less time to do equilibrium process
less time for diffusion
can show the affects of a pulmoary disease even more

this manipulating P1 aka Palveolar
Altitude
O2 is 21% of the air but if there is less air then that 21% becomes less and less
so less O2 means less PO2 so less to diffuse

have someone with severe fibrosis
on a mountain
andhave them exercise

made of 2 components
diffusion
rate of reaction with Hb

DL=VCO/PaCO
can see if something has thickened your barrier
use CO for this test because it is diffusion liited Pa in the blood basically 0

put a known amount of gases in a bag
dead space doesnt matter
alveolar sample-this will be different than bag because some CO is in the lung now
try to solve for VCO and PaCO from blood sample