as hospitals across the world are dealing with more patients in respiratory
distress from COVID-19 we wanted to offer this course as a refresher on
mechanical ventilation or a way to learn the key concepts for the first time
we've received a lot of comments from medical professionals physicians pas and
peas nurses students that don't have significant experience with mechanical
ventilation but who want to be ready if called upon to help the ventilator teams
in the critical care setting or maybe you have ventilator experience but want
a refresher course to help teach these skills to others this video series is a
collection of previously recorded videos and we've added some new kovat 19
specific ones as well part 1 of this course covers the core concepts of
mechanical ventilation we'll start with an introduction to the ventilator and
compliance pressure volume relationships and the different ventilator modes then
I'll illustrate plateau and peak pressure peep and other vent settings or
review the pathophysiology of acute respiratory distress syndrome and how
kovat 19 causes fatalities will then discuss vent changes and COPD we think
the discussion about Co P will be relevant because they'll be patients who
will come down with kovat 19 who have COPD
we'll finish part 1 with a checklist that you can use to see if a patient's
ready to be liberated from the ventilator in part 2 of this course will
progress to vent pearls tips clinical pitfalls more advanced strategies
involving heart lung interactions ventilation in metabolic acidosis more
on COPD and finally bi-level ventilation we're committed to keeping this course
free please share it with anyone you think may be interested be well and
thank you for joining us cram welcome to another make cram lecture we're going to
talk about mechanical ventilation and this is meant to be a introduction to
mechanical ventilation so if you've never done mechanical ventilation before
we're going to introduce you to the basics so you can go in and actually
feel competent about managing a patient on the ventilator
this is often a daunting task because typically these patients are critical
but actually the basics are fairly graspable and
series that's gonna actually go through a number of different lectures and we're
gonna start with the basic starting right now the first thing you've got to
know is you've got another definition of some of these things okay so you've got
the patient then you've got this thing coming out of their mouth
that's the endotracheal tube we're gonna show this a little bit more later
and then you have it hooked up to a big machine with a bunch of knobs on it and
dials and output this is what we know as the ET tube
that's the endotracheal tube and then finally you've got the actual ventilator
that's important to know because sometimes people are intubated that
means we've put a tube down into their mouth because they need airway
protection in other words because they can't protect their airway they can't
protect liquids and solids from going down their airway work that stuff
shouldn't go and because of this it's not too comfortable we've got to sedate
them and when we sedate them we've got to put them on a ventilator so that
might be one reason why we would have to do this the other reason is because they
can protect their airway okay but they just can't breathe on their own they're
struggling to breathe and so we help them out with the mechanical portion of
breathing and that's where the ventilator comes in and the way we
deliver that is through the endotracheal tube so it's kind of important to know
what a endotracheal tube looks like and the basic is pretty much the same all
the way around it's this long tube kind of looks like this and that's the part
that connects to the ventilator this is the part that goes inside the patient
and actually you'll see that there is a balloon on the end of that endotracheal
tube and the thing that allows you to blow it up it's a little thing that goes
up the pilot part comes out and it's like a little pilot balloon that you can
kind of feel what the pressure is and then there's a little port where you can
inject air into it so when this goes down and you intubate somebody goes into
their mouth past their vocal cords specifically and down into the trachea
so the vocal cords usually end up about right here and so this is going down
into somebody's trachea okay and then usually it branches off you've got the
left and the right mainstem bronchus okay so here you have the endotracheal
tube going down now this balloon gets inflated here so that stuff that might
make it down here doesn't go past and go into the lung this is called airway
protection and we blow up the balloon here after we intubate them to make sure
that that happens now in some versions of this they'll
have like a little device right here that also comes out the purpose of that
is to suck secretions that might come up and go out and at subglottic suctioning
that's kind of an option but this is the basic anatomy of an endotracheal tube
now of course we just talked about the ventilator that's got a bunch of buttons
and whistles and things we're gonna talk about in a little bit okay so going back
to our patient again we've got our endotracheal tube we've got our
ventilator so what's the purpose of this ventilator the purpose of the ventilator
is to maintain homeostasis between the dew gas concentrations that we're
talking about here which is carbon dioxide and oxygen okay so oxygen is
being put into the patient and carbon dioxide is coming out and for the most
part we want to keep those close to normal there's some exceptions to that
here's the point though there's many different ways to put air into somebody
okay we can say we're gonna put air into somebody based on volume so we're going
to put a certain X amount of volume into somebody and then let it come back out
that's one way of doing it another way of ventilating somebody is saying we're
going to inflate them to a certain pressure so we're gonna have this
ventilator put a certain amount of pressure into the patient and then when
that pressure is released then it's gonna come back out so we can do that
now we can do it at a certain rate we can do this fast and we can do it slow
okay so in other words how many breaths per minute we could also adjust the flow
rate so in other words yes we can port a certain volume in but we can give that
volume slowly or we can give that volume very quick
the other thing that we can do is we can decide how much pressure to leave in
there at the end of when we put the air in and then we can decide how much
pressure to leave in there after we're done putting the air in finally we can
decide how much oxygen we want to put in there we can put a lot or we can put a
little now just to further complicate this just to kind of see where we're
going with this we can have the ventilator be in charge of when the
patient gets a breath or we can have the patient be in charge of when they want
to get a breath so think about all of these different variabilities and now
you can quickly see how there are so many different ways that you can
ventilate somebody and each one of these ways is a different mode of ventilation
you may have heard of these before like AC or simv or pressure support or
CPAP these are all different modes and we're going to go through some of these
modes and show you how this is working okay so here's our system over here
we've got the ventilator here we've got the tubing that goes to the endotracheal
tube down into the lungs and we've got our balloon here filled with air to make
sure nothing else gets down there and we're ventilating our right lung and our
left lung so let's talk about the first mode of ventilation and this will become
important later the first mode that I want to talk about
is AC okay the other way we call it as assist control the other name for it
also is continuous mandatory ventilation or CMV now this is the most common mode
of ventilation that you'll see especially on a medicine floor or
medicine units the key here is that the patient triggers the vent how does that
happen well the patient takes a breath in and therefore there's a negative
pressure here which causes a negative pressure to be sensed here at the
ventilator the other way you could sense it is by flow if there is a flow that
actually goes through here by the negative pressure now as soon as the
ventilator picks on that negative pressure it's going to
deliver a specific volume and so there's an actual dial on here where you can
actually turn the knob to a specific volume or you can enter it in and that
volume can be anywhere from 500 CC's all the way up to 600 cc's usually the ideal
way of ventilating somebody would be around eight milliliters per kilogram
ideal body weight anyway whatever that volume is it's going to deliver that
specific volume in AC mode ventilation now the patient can trigger it you could
also set up a backup mode or a rate what does that mean if I set the rate to for
instance twelve because there are twelve five-second intervals in one minute that
means every five seconds the ventilator will give a breath to the patient of a
specific volume only if the patient does not take a breath if the patient is
breathing above 12 then the ventilator will only give breaths when the patient
triggers it by trying to take a breath in in other words if you set the mode to
AC set in a volume and set a rate of 12 the patient can never breathe less than
12 times per minute now there's something that you should understand
about this which is very important you may recall from chemistry an equation
that says P V equals n R T now in this system temperature is constant R of
course is always a constant n is a constant and so the thing that you must
realize is that pressure and volume are inversely proportional to themselves in
other words as the volume of a gas goes up the pressure goes down if you have
the same amount of gas however the other way of looking at this is compliance
which I'll abbreviate as a C compliance is equal to the change in volume over
the change in pressure which means to say
if the pressure changes a little bit and the volume changes a lot then you have a
very compliant lung if you don't have a very compliant lung it's gonna take a
lot of pressure to make just a small amount of change here's the point the
point is is that these set of lungs have a specific compliance and if you are
delivering a specific volume into these lungs you are going to get a specific
pressure after you deliver that volume that pressure can change depending on
the compliance the point of this is is that you need to have a readout that
tells you what the pressure is in that lung so you can know what the compliance
is so in other words in this mode of ventilation you set the tidal volume and
the ventilator will tell you what the pressure is so you're setting the tidal
volume you're setting how much volume of gas is going to go into the lung and
based on the compliance of the lung it will tell you what the pressure is if
the compliance of the lung goes down then typically you'll have higher
pressures if the compliance of the lung is very high in other words a very
compliant lung then your pressures are going to tend to be on the lower side
now let's make this converse to pressure control in pressure control what we're
doing is we're setting a pressure in other words we're going to decide how
much pressure we're going to ventilate this patient with and so as you can
imagine if we're setting a pressure there is a specific compliance to this
lung depending on what state it is in and if we set a certain pressure if the
compliance of this lung is very low then you can imagine we're gonna have lower
volumes however if the compliance of this lung is very high then we're gonna
have higher volumes because remember compliance is equal to the change in
volume over the change in pressure so in pressure control you can also have the
patient or time triggering a set change in pressure and depending on the
compliance the volume can change and so the key here is that you need to have
alarm setup and you need to know and understand what those alarms mean what
could happen here let's for instance say in a pressure control situation where
you're giving a specific pressure if the compliance of these lungs somehow drop
precipitously all of a sudden because of some pathology which we'll get into you
will notice that the volumes will drop you would want to know that and so you
could set a alarm on the lower side of the volume so that if the volumes did go
down an alarm would go off saying that you're not ventilating conversely if you
were back in our previous mode which was assist control and you're setting a
certain volume if the compliance of the lung dropped in that situation then as
you would realize the pressure would start to go up because you're trying to
put a set amount of volume into a low compliant lung and when that happens the
pressure goes up the pressure would then trigger an alarm so the point here is in
pressure control you're setting a pressure and your output to Reed is your
volume in AC it's the flip of this so when we come back we'll talk about the
pressure volume relationship and a few more modes of mechanical ventilation
you