Asthma Exacerbation Case Study 1 – Treatment (Asthma Flare / Attack)


okay welcome to another MedCram
lecture we’re gonna talk about a case today so imagine that you go down to the
emergency room you get called and there’s a 25 year old Caucasian female
who is about four months postpartum and she’s having a hard time breathing so
she’s got shortness of breath it’s been going on for about a week and it’s
progressive and she has a history of asthma but she has been remiss in using
her inhaler and on physical examination you noticed that she’s got bilateral
expert ory wheezing and her respiratory rate is in the 20s and she certainly is
looking anxious and in fact she’s got a history of anxiety disorder as well her
vital signs she’s afebrile her blood pressure is 150 over 70 pulse is already
in the 120s and that’s because she’s already received an albuterol and
atrovent nebulizer she’s saturating in the low 90s about
92% and as we said her respiratory rate is in the 20s you do a blood gas and her
pH looks something like seven point three five pco2 is in the high 40s po2
is in the 80s and bicarb is 24 so you give her a nebulizer treatment again and
you start steroids so steroids nebulizers give her a little bit of
oxygen but she doesn’t get better she continues to have issues so you start
her on some BiPAP because she looks like she’s using some accessory muscle use
and you start her on regular setting of about ten over five when you increased
that to 12 over 6 and you draw another blood gas and instead of 7.35 after
about two or three hours of battling with her and everybody else in the
emergency room you now get a pH of seven point two zero sixty four seventy five
and 24 and that’s on BiPAP she is awake alert oriented but she’s a little bit
more lethargic than she was initially okay let’s stop there and talk a little
bit about what’s going on with her and the diagnosis so most likely this lady
has an asthma exacerbation and remember with asthma you’ve got a bronchus and
you’ve got smooth muscle that’s going all throughout this and because of
inflammation that is occurring in this area so inflammation causes contraction
of this down to a small hole and as a result of that the air has a hard time
getting out and that’s the key word there is out so air can come in but air
has a very hard time coming out and you have a problem therefore on exhalation
if you were to look at a flow volume loop you would see a normal flow volume
loop looks like this you have a lot of air coming out initially and then you
get to the small Airways and then you take a deep breath in so that’s what a
flow volume look will look like with flow here on the y-axis and volume on
the x-axis in small Airways disease either in COPD or when you have an
asthma flare you are going to look very similar on inhalation it’s not gonna
affect about of air that can go into the lung but what you will see on exhalation
is no issues with the large Airways but you’ll notice that the small Airways are
definitely decreased and so you can see her flow rates on exhalation are
incredibly reduced and again that’s primarily because these small muscles
here in the Airways in the small Airways particularly are contracted
now there’s two receptors that you’ve got to be aware of on here there is a
muscarinic receptor and there is a beta receptor the beta receptor actually
causes muscular relaxation and so you want to activate this receptor with a
beta agonist however the muscarinic receptors you
want to block with a muscarinic antagonist and so
those are just about all of the medications that end in I um so
tiotropium epitope reham you metla diem all of those anticholinergic medications
whereas these beta agonists are the ones that end in oh L that would be like
albuterol salmeterol for model so the I um s again are the muscarinic
antagonists there is one that does not end with I um and that is glyco pi
relate so that’s the one exception to this but the I UMS are the muscarinic
antagonist the OLS are the beta agonists and what that’s going to do is it’s
going to open up those Airways which is what you need to get air out and so
that’s the real problem here air cannot get out and of course it goes without
saying that the air must come out during the exhalation phase and so you want the
exhalation phase of breathing to be as long as possible well that’s hard to do
when the patient’s breathing fast because that gives a short amount of
time for both inhalation and exhalation so that is the issue with asthma and
that’s the issue with this patient that’s coming to the hospital okay so
let’s continue as it goes our patient continues to get worse and now she’s
becoming more confused and so the decision is made to intubate but before
the patient gets that intubation there’s another Blood gas that’s gotten on this
patient and it clearly shows a worsening acute respiratory acidosis this time
7.10 80 70 and 24 remember now that the
bicarb has not changed the po2 is a little bit less the pco2 has greatly
increased and that’s cause the pH to drop pretty precipitously and so the
patient’s intubated with an endotracheal tube and put on the ventilator and the
initial settings for the patient are AC of 20 a tidal volume of 500 a peep of 5
and an fio2 of 100% so this means that the patient’s got to get a breath at
least 20 times per minute more if the patient demands that the tidal volume of
each breath is good 500 MLS or half a liter the amount of
pressure left in the circuit is going to be 5 at the end of exhalation and the
patient’s going to be breathing in a hundred percent oxygen so after a while
of the patient being on the ventilator and x-ray is taken it shows that the
patient has clear lung fields there’s a heart but that the Hemi diaphragms are
very flattened and the rest of the lungs are consistent with hyper expansion the
patient’s blood pressure starts to drop slightly that could be because of the
fact that patient was sedated and had and intubated and sedated for that or it
could be because of hyperinflation and so what we are concerned about is the
patient is having something called dynamic hyperinflation and let me
explain to you what this is what happens here is that the air goes into the lungs
as the air goes into the lungs it inflates the lungs in this case we’re
giving 500 MLS of air but because the airways are so obstructed that it takes
such a long time for the air to come out that let’s say only 450 MLS of air come
out before the next breath which is either determined by a time constant or
when the patient takes another breath another 500 goes in when only 450 came
out and so what happens is with that next breath you’re gonna get a little
bit more hyper-inflated and with the next breath a little bit more
hyper-inflated and so that’s called dynamic because this happens over a
period of time hyperinflation so what happens there is that the intrapleural
pressure start to increase and that can prevent venous return that can also
increase your plateau pressures it can also cause issues with peak pressures
and so the compliance of the lung becomes less and less and less and with
less venous return you’re going to get less cardiac output and a decrease in
blood pressure and so really the crux here is that when patients have severe
asthma exacerbations and they’re put on the ventilator and they start to
dynamically hyper inflate the real key here is that there is not enough time
for exhalation exclamation point triple underline that
could be potentially a serious phase situation where the patient could die
because there’s not enough time for exhalation if you ever see a situation
like this where the patient is dynamically hyper inflated and they
can’t trigger the ventilator because there’s so much positive pressure inside
their lungs and their blood pressure is going down and their heart rates going
up you should detach them from the
ventilator and allow a appropriate amount of time for all of the air to
come out of their lungs so that blood can come back to their heart and they
can get a blood pressure short of that how would you prevent a patient from
getting in this situation well join us for our next video where we talk about
ventilator management issues and things that you can do to prevent specifically
patients with obstructive lung disease asthma or COPD to ventilate without
running into these situations but again the failsafe ways to disconnect the
patient immediately and let that lung deflate if you’re having any questions
about what we’re doing here in terms of PHP co2 oxygen bicarb
please visit us at Metron comm for a ventilator course that will answer
almost all of your questions that you will have thanks for joining us you

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