Let's continue taking a look at respiratory
failure and now however, you know how the
ECG or EKG was for the cardiovascular system.
Well, it’s just as important that you take
at look at the graphical presentation of what
is known as your ventilation or modes of in
We will begin by looking at the foundation
of setting up what you want to be very familiar
with when you are interpreting graphs of modes
of ventilation. What does that even mean?
Well, there are two modes, in general, that
you would be able to help your patient with
respiratory failure. You are extremely familiar
with one of them which is the management of
a patient that has obstructive sleep apnea.
Think about that patient who is obese and
maybe has a hard time breathing out and so
therefore might be, wow, apart from hypoxemia
might also be then retaining carbon dioxide.
So with this patient, you might want to think
about providing this patient with what is known
as a mode of non-invasive ventilation and
this is referred to as being CPAP and that
you already are familiar with. What CPAP stands
for is continued positive airway pressure.
Now on that note, what we will take a look
at is, well, non-invasive versus invasive.
What, really, what is the difference and how
does that then benefit you? Say at some point,
you do need to intubate your patient, right,
endotracheal. You need to intubate your patient,
then here, the graphical representation which
will be your ventilation graph through invasive
will be quite important for you to interpret.
So, just like we looked at pulmonary function
test as being non-invasive, let's begin
by dissecting our graphs. The graph
that you see in the bottom is pressure. And
how would you measure pressure in the respiratory
system? That will be centimetres of water
and then this corresponds to what happens
actually in the lung. And so therefore you
are looking at volume in the above graph.
Next, well you bring in your physiology.
What does that mean? Well, I want you to pay
attention to the bottom graph and take a look
at the black solid line. You see the black
solid line on the bottom graph of your pressure
and you should remember from physio that if
you were to breathe in or inhale, then you
have your pressure which is then going to
become more negative. Do you remember that?
You should. So all that physiology or lung
mechanics is going to come into play here
when dealing with clinics. So we have a negative
pressure which is the trigger for you to then,
guess what? Go back up to the top graph, you
will notice a spike. That spike in which
now, the volume, litres per minute, is increasing
from 0 towards positive. Now, understand the
concept first. At this point, it is not imperative
that you memorize the values, understand the
concept. Negative pleural pressure, therefore
brings about inspiration. Okay, great. Let's
say that your patient is having a hard time
with breathing. He is not able to properly
keep open the alveoli and probably has impairment
of gas exchange. So what does that mean to
you? Well, if this is impairment in gas exchange
and you feel the need to then give your patient
some type of ventilatory assisted control
and what might you want to do? Well, take
a look at the bottom graph. This time, I want
you to pay attention to red dashed lines.
The red dashed line, represents the fact that the
patient wishes to inspire, inhale. During
that process of inspiration this will be
a trigger in which now, guess what kind of
pressure? Do you remember that conversation
that you and I had with PEEP, positive end
expiratory pressure? It’s positive pressure,
isn’t it? And so, what you are doing and
how you are introducing air into the alveoli
is, remember. You are now the lung. You, the
clinician. So therefore you are going to
inject “positive pressure” into the respiratory
system so you can keep your alveoli open and
at this point, if you follow the red dashed
line in the bottom graph, you will notice
that there is a plateau. It’s nice and uniform
and so therefore, just like in EKG, you would
have your sinus rhythm and QRS complex. You
are going to have this pattern of breathing
taking place ever so often, intermittently.
This is the foundation in which you want to
keep in mind when dealing with expansion and
pressure of your lung with, What kind of pressure
that you are going to provide? Very good.
Positive pressure. Now, a host of side effects
or should we say, adverse effects that might
have occur when applying such positive pressure.
All these are discussions to be had as you
move forward. Important? Absolutely. This
is the evolution of a board exam.