welcome to our talk on ventilator associated pneumonia we're going to get
started with looking over some of the objectives that we're going to cover in
this lecture series so the first objective is that we're going to
identify or ID the epidemiology the pathophysiology detection and the risk
factors for vApp number two is we're going to identify the risk reduction
strategies and number three we're going to identify the pitfalls of
implementation and then finally for number four we're going to identify the
areas of controversy so there is controversy because this is a burgeoning
field in terms of research ok the first thing that we really want to attack is
the definition of vApp and really what is the definition of vApp or ventilator
associated pneumonia basically it's a pneumonia that arises more than 48 to 72
hours after endotracheal tube intubation ok so you really can't make this
diagnosis on admission unless the patients coming from another facility
where they were intubated more than 48 to 72 hours before so in terms of this
it's just simply looking up at the time when the patient was intubated so the
timeline is pretty easy the part that's difficult is figuring out the pneumonia
portion so what exactly is a pneumonia now typically when we think about
pneumonia we think of a fever we think of an increased WBC count and we think
of an infiltrate so you really should have an x-ray that's the cornerstone of
diagnosis of pneumonia the problem is is that some people may not get a fever and
other people may be on immunosuppressants
or they may have a low white blood cell count and then sometimes if they don't
have an immune system that is functional they may not even have an infiltrate or
what's even more common is other things may cause abnormalities on the chest
x-ray that have nothing to do with an in fact
or an ammonia and so really what the problem is in terms of definition is
that the timing but is what is exactly a pneumonia and as a result of that
there's been kind of two strategies that have looked at this definitional issue
one is known as the clinical strategy and the other is known as the bacterial
logic okay so here we have the non invasive and this would be more as the
invasive okay so what do these things mean and we're going to get back to
these two strategies the clinical and the bacterial logic be aware that there
is sufficient not being quite clear about how you define this pneumonia and
so there's been two strategies in the literature the clinical which will you
look at things clinically and make a determination based on some criteria or
the bacteriological which is the invasive typically involving tracheal
aspirates so where they put a tube down the tube and get a tracheal aspirate and
then culture it and see how many bacterial counts they have okay so we're
gonna get back to that but first of all let's go through our objectives and
let's talk about the epidemiology so in terms of epidemiology the the literature
is about ten to twenty percent of patients on mechanical ventilation so
that's about 6 to 21 times the risk of contracting pneumonia okay so that's the
prevalence now in terms of mortality
this can range anywhere from 13% to 55 percent depending on the literature that
you look at the attributed more tality which means you know how much can we say
that the vapp was actually the reason for the patient passing away is about 30
percent I don't think you need to know these numbers specifically but I would
say that this is a serious issue and that's why we're taking it very
seriously not only in terms of and life but in terms of financially the
length of stay in the hospital increases by about nine days so that's an increase
of about sixty two percent sixty two percent increase what does that
translate into in terms of dollars that's about forty thousand dollars per
patient so if we can prevent ventilator associated pneumonia you can see that we
can prevent a lot of bad things from happening let's talk about how it
actually happens okay so here is a drawing of a larynx and trachea and
bronchi with lungs and what I want to show you is the endotracheal tube so as
you know in intubation the endotracheal tube goes down about two to three
centimeters above the Carina up to about five and as you know there's a balloon
that gets inflated to prevent secretions from going down below into the lungs of
course it's not 100% but the pathophysiology is that there's
aspiration of these oral pharyngeal pathogens of gram negatives etc or
leakage of these secretions containing the bacteria which are up here in the
oral pharynx and what happens is they go down here and there's pooled secretions
which sit above this balloon and drip down into the lungs and this goes into
the lower respiratory tract now a lot of the pathophysiology and epidemiology has
come out of the latest guidelines from the infectious disease Society of
America and the American Thoracic Society which were published back in
2005 and sort of the definitive paper so if you want to do further reading please
go to the American Journal of respiratory and critical care medicine
2005 and look up the IDSA and 80s guidelines everything that they say they
give evidence for there's one evidence which is the highest level
two which is intermediate and then level three which is less and the evidence for
which they say this is the cause of the pathophysiology is level two evidence so
pretty good but not randomized placebo-controlled obviously the other
thing that they mentioned is that because this is a non living item here
inside the patient biofilm can form on top of this and it can be very difficult
to eradicate so this is not foolproof here the balloon is inflated but you
can't over inflate it and what you'll get is secretions which go down and that
causes the vApp and so you can see that a lot of the treatments that will talk
about later or prevention strategies are going to prevent this mode of
transmission and causation of vApp so now that we've talked about the
epidemiology the prevalence the pathophysiology let's go back to what we
were talking about before which was the actual diagnosis or the detection of
vApp and our dichotomy between the clinical non invasive and the
bacteriological or the invasive so let's talk about the
clinical the clinical strategy is quite simple what you really need is something
that has happened to the patient after 48 to 72 hours of intubation and those
things would be a new infiltrate but several things could cause a new
infiltrate and the way to make sure it's a pneumonia is by checking for a fever
and an elevated WBC count but a lot of things can cause that as well as we
mentioned so you also should look for purulent sputum if these things occur
there's a good chance that you're going to pick up a ventilator associated
pneumonia so an ammonia that the patient got while they were on the ventilator
remember has to happen 48 to 72 hours after intubation but there's a chance
that you could get a pneumonia and it may not cause an infiltrate it may not
cause a fever may not cause an elevated white count and the patient may not have
pure Yulin sputum so in other words which you may have here are some false
negatives okay so this is going to be very
specific but it may you may lose some more subtle types of vApp now in
contrast let's go over to the bacteriological here we use bronchoscopy
that goes actually down into the lungs and samples you could also use tracheal
aspirants but classically it's bronchoscopy we actually sample
secretions that are down in the lungs and typically those should be sterile or
certainly below a threshold now you know that if I were to culture your skin I
would get bacteria but your skin is not infected and you don't have cellulitis
but in people who do have cellulitis the bacterial counts are much higher on the
skin indicating that there is an infection and so what you could do is do
a bronchoscopy in culture and set a certain threshold like 10 to the 3 in
terms of colony forming units and that would determine whether or not there was
colonization or whether or not there is infection okay so the risk here is that
you may have enough bacteria causing colonization and you may call it a
positive when in fact it would be a false positive so here are the risk is
false positive rate and you can see how be very sensitive and there's pros and
cons on this in on both sides now the thing is is that there's some downsides
of the bacteriological if you've changed antibiotics within the last 24 hours
typically it's going to depress the colonization rate and you may actually
get a false negative in that sense there is some evidence on the upside using
this technique that if you don't see bacteria then you could stop antibiotics
and there's actually was a study that showed that after two weeks mortality
rates actually dropped also if you had a negative
colony forming unit threshold in other words if you did the threshold then it
was low is below your threshold then you could say that the infection might be
coming from another source maybe it's actually not from the lungs and that
would spur you on to look for sources elsewhere it actually could benefit the
patient I think in terms of what you should choose and certainly be IDSA
guidelines say you could use either one both are appropriate both are standard
of care one has more advantages than the other obviously if you don't have
somebody doing bronchoscopy then the bacteriological strategy is going to be
something that you can't do the clinical can be done fairly cheaply and it can be
done just about anywhere so there are advantages and disadvantages with either
the key that I would say is that if you're going to track ventilator
associated pneumonia rates in your hospital you ought to stick with one
definition and use it consistently because how you define vapp can change
your prevalence in your incidence of that I'll just say that there are a
number of algorithms out there of the diagnosis of ventilator associated
pneumonia some of them are related to vApp in immunocompromised patients and
some of them are related to vApp in immuno competent patients and so make
sure that you look it up make sure that you make a protocol and you stick with
it that's I think the key because you really want to make sure that you don't
have a moving target you want to make sure that you're consistent in terms of
your definition okay will join us for our next video when we get into the risk
factors for vApp
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