00:02
So how do we actually
test pulmonary function?
We are able to test
our pulmonary function
using spirometry.
00:11
And usually this is able
to distinguish between
obstructive pulmonary diseases
and restrictive diseases.
00:18
And an obstructive
pulmonary disease,
you're going to have an
increased airway resistance
because of some
type of obstruction
such as with bronchitis.
00:29
In these diseases are
total lung capacity
our functional residual capacity
and our residual
volume may all increase
because of hyperinflation
of the lungs.
00:44
In restricted diseases,
we're actually going to have
a reduced total lung capacity
due to some type of disease
or exposure to an
environmental agent.
00:56
And this are vital capacity
our total lung capacity
are functional residual capacity
and our residual volume
are all going to decline
because long expansion
is compromised.
01:11
Usually in restricted
diseases we have a
restriction or a reduction
in our lung compliance.
01:20
So our pulmonary function
tests can measure the rate
of gas movement in our lungs.
01:27
First,
we have our forced
vital capacity or FVC.
01:32
And this is the amount of gas
that is forcibly expelled
after taking a deep breath.
01:41
We measure this using the
forced expiratory volume,
which is the amount
of gas expelled
during a specific time interval
of the forced vital capacity.
01:52
So for example,
an FEV1 is the amount of air
expelled in the first second
of a forced exhalation.
02:02
And a healthy individual
you're usually able
to expel about 80%
of your forced vital
capacity in the first second.
02:12
But when you have an
obstructive disease
you exhale less than the 80%
because there's some
type of blockage
and in a restrictive disease
you usually are going
to actually exhale more
even when you have a reduced
forced vital capacity.
02:30
And the why it's more is
because the overall lung
compliance is now low
so that forced vital
capacity or the denominator
and our percentage is decreased
while the force
expiratory volume
in that first second
remains the same.
02:48
So therefore it will still
be a higher percentage.
02:52
So we can also look at
alveolar ventilation
by looking at our
minute ventilation
or the total amount of gas
that flows into or out
of the respiratory tract
in one minute.
03:04
Normally at rest.
03:06
This is going to be
about 6 liters per minute
when we're exercising, however,
this can go up to as much
as 200 liters per minute.
03:18
But this is only
really a rough estimate
of our respiratory efficiency
and a better indicator
is our alveolar
ventilation rate our AVR
and which case we're
looking at the flow of gases
into and out of the alveoli
during a particular time.
03:36
So our alveolar ventilation rate
takes into account the amount
of dead space as well
as the title volume
and the rate of breathing
and it can be calculated.
03:47
By looking at AVR equals
the frequency of our breaths
our respiration rate
and our tidal volume.
03:56
Because the dead space
in an individual is
normally constant
the only two things we really
look at are the tidal volume
and the frequency or
the respiration rate.
04:07
Significant increases
and our AVR can be brought
about by increasing
the title volume more so than
increasing the frequency.
04:18
So for example,
rapid shallow breathing
can actually cause a decrease
not an increase in
alveolar ventilation rate.
04:28
So let's take a closer.
Look at that.
04:31
So let's say at a
normal rate and depth
you have a title volume
of about 500 milliliters
and a respiratory rate of
about 20 breaths per minute.
04:44
This would give you
a minute ventilation
or MVR of about ten thousand
milliliters per minute.
04:51
And then,
if we take all of these
and put them together
with an alveolar
ventilation rate
of 7,000 you would have an
effective ventilation of out 70%.
05:05
If I change in all of a
sudden started do doing slow
and deep breathing
where I'm going to decrease
my respiratory rate,
but I'm going to
increase my title volume
I'm actually going to end up
with an effective ventilation
that is higher than
at the normal rate.
05:26
Conversely, if I look at
my rapid shallow breathing
where instead my tidal
volume is really small
and my respiratory
rate is really fast.
05:37
I actually have a decrease
in my effective ventilation
to 40% compared to
the normal rate.