00:00
Continue. Okay, so goal of mechanical ventilation.
Mechanical ventilation. So this obviously
is invasive. Is that clear? So, if you talk
about non-invasive, the test that you will
be using for non-invasive. Remember, the one
that we used for obstructive and restrictive?
That was pulmonary function test. Was that
invasive or non-invasive? You put a mask on
the face. It might be invading your face,
but you're not invading your mouth. Is that
clear? So, you just put on a mask, that is
non-invasive. You must understand that.
00:34
And now pulmonary function test was made
up of what? FEV1 over FEC and that then puts
you into the family of obstructive or restrictive,
not to worry, we will go into those details
about the pathology soon enough.
00:46
Now, at this point, however, your patient
has and requires mechanical ventilation.
00:52
So this is definitely invasive. So these
ventilatory graphs, that we're looking at here,
become very important too. Minimize oxygen
to avoid possible oxygen toxicity. What does
that mean? Remember please, to drink a glass
of water is fantastic, in fact, it is highly
recommended. But, to drink out of a fire
hydrant, it will kill you. Same concept. And
oxygen, sure, vital, but if you give too much
oxygen, what is that called? Reactive oxygen
species or oxygen intermediates. You want
to be careful for your radical damage. What else
is the goal? Minimized PEEP. What does PEEP
mean? Once again, positive end expiratory
pressure. We had a full discussion of this
earlier. Meaning to say that if you have too
much PEEP, too much positive, why
do I keep saying that? Because here, you are
the lung, you are introducing positive pressure.
I want to keep reiterating that because I
want you to compare this to normal physiology
in which if you want to inhale then you want
that pleural pressure, or the individual, you
and I right now, we are creating a negative
pleural pressure. How many times have I mentioned
this? Continue. But, if you have too much
PEEP that means that you could then increase
the volume within the alveoli so much that
you might actually cause airway trauma and
quite a bit of discomfort. So therefore
mechanical ventilation is to then relieve
some of that.
02:15
What is your goal? Obviously here, you want
to increase your PO2. Your patient was already
in respiratory failure type 1 or type 2. By
definition, it means less than 60 and balanced
effect of high FiO2. I will walk you through
this. What is that FiO2 mean to you? Remember,
normally speaking, it’s approximately 20%,
isn’t it? And as long as you are at sea
level, then you are going to multiple that
0.2 times 760. This is a patient that requires
oxygen. What are you going to do in a hospital
setting? You are going to increase FiO2, may
be 0, 40%, maybe even 100%. But that is
a lot of oxygen. So you balance the effects
of high FiO2, understand every single physiologic
point here. With the high effect of high PEEP,
you want to balance these two ,because if you
do not, then please understand, that you are
going to be causing more harm than good. In
some cases, you need both. For example, acute
respiratory distress syndrome.
03:17
So, continue. These are goals of mechanical
ventilation. Next, remember the entire discussion
that we had between the frequency which means
your respiratory rate and you multiply that
by what? Your tidal volume. Which discussion,
Dr. Raj? You remember, I gave you two big
examples of increased respiratory rate and
tidal volume being either low, what is that
called, clinically? Good. Rapid shallow breathing.
Example may be such as PE (pulmonary emboli)
or number 2, rapid deep breathing. Give
me example for that, that I gave you. Kussmaul
breathing. What were the two parameters
that we looked at? It’s tidal volume, respiratory
rate. Of the two, which one was deep? Meaning,
which one determined the depth of breathing?
Good. The tidal volume. If you increase the
tidal volume and increase the respiratory
rate just a tad bit, you remember that alveolar
ventilation? Isn’t that what you truly are
trying to increase so that you have proper
gas exchange? Is that clear? So, with that
discussion, if you are unclear, make sure
you go back to that discussion that we had
when we specifically looked at alveolar ventilation,
total ventilation, the frequency and then
in terms of tidal volume. So tidal volume
and respiratory rate, there it is, that is
the frequency, to minimise barotrauma or volutrauma.
You must. Next, some hypercarbia, what does
that mean? Hypercapnia, same thing. And respiratory
acidosis is actually acceptable. Is that clear?
So, at some point in time, remember. At
some point, you can’t introduce too much oxygen and
you want to avoid barotrauma, so you call
this permissive hypercapnia, especially in
ARDS. In general, it’s okay to raise the
respiratory rate, but tidal volume should
be minimized. The formula for the recommended
tidal volume is about 6 milliliter per kilogram
of ideal body weight.