00:02
In this lecture, we’re dealing
with the transport of O2 and CO2.
00:07
Our learning goals will be
to understand O2 transport
and be able to differentiate
between those modes of transport.
00:16
Also, you will be to identify the factors
that affect oxygen hemoglobin dissociation.
00:23
Furthermore, after this lecture, you’ll
be able to understand CO2 transport
and be able to differentiate
the modes of transport
as well as identify factors
that affect that transport.
00:35
So as we think about
O2 transport,
we really need to concentrate on what
the partial pressure of oxygen is.
00:44
And so there are three partial pressures
that we need to keep in mind.
00:48
PaO2, PaO2 and PVO2.
00:53
And the reason why I very much
distinguished between capital A
and small A O2, is it tells
you where to locate it.
01:01
So PaO2 is the partial pressure of
oxygen in the arterial circulation.
01:06
PAO2 is the partial
pressure of oxygen in the alveoli.
01:11
PVO2 is the partial pressure of
oxygen in the venous circulation.
01:16
And you need to remember what those
are as we walk through O2 transport.
01:22
So to give you an idea of those
numbers, the PaO2 is around 95.
01:27
The PAO2 is around 100,
and the PVO2 is around 40
millimeters of mercury.
01:34
And so those are numbers you
want to kind of keep in mind
as we walk through this
transport of oxygen.
01:43
Those numbers seem like they
are going to be very important
because these are the numbers that we
measure from an arterial blood gas.
01:52
So if were to take an arterial sample
and measure the amount of oxygen in it,
those are the numbers
that you get.
01:59
So this is a very important thing
to help us distinguish between if
someone has a hypoxemia, versus they
have a normal O2 concentration.
02:07
Those are the partial pressures.
02:11
However, partial pressure
only gives us one insight
into how much O2 is being
carried by the blood.
02:19
The other insight that we need to think
about is how much is diffused in a
gaseous form and that is really based
upon the amount of O2 solubility.
02:30
Unfortunately, O2 is
not very soluble.
02:33
So let’s go through a calculation to
edify this.
02:37
Dissolved O2 is the
partial pressure of O2
times the solubility of
O2 at body temperature.
02:44
If we go through this calculation,
it ends up that you have
less than 1 milliliter of O2
per 100 mL of blood or per
1 deciliter of blood.
02:56
So just a very small amount.
02:59
If we look on the venous side,
it’s even smaller 0.124.
03:04
So these are very, very,
very small concentrations
of oxygen in a dissolved form.
03:14
So having this amount of oxygen
only in the dissolved form is
unfortunately not compatible with life.
03:22
If you did not have someway
to carry the oxygen,
you would not be able to
transport enough blood to cells
to keep them alive via
aerobic metabolism.
The lecture Oxygen Transport – Gas Transport by Thad Wilson, PhD is from the course Respiratory Physiology.
Which are normal values for PAO2, PaO2, and PvO2 respectively?
Which of the following is the dissolved concentration of O2 in a normothermic patient, with a PaO2 of 90 mmHg?
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like it very much thanks Thad you are very good