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  • welcome to another medcram lecture so I hear this question a lot how does the

  • corona virus actually kill people there's a recent article in The Lancet

  • that showed that of 41 people that were admitted to the hospital six of them

  • died and all of them were on ventilators and they died with something called a

  • RDS and a RDS is how the corona virus kills it's not just the corona virus but

  • many other viruses including the influenza virus that we have every year

  • how is it that this happens it's through acute respiratory distress syndrome and

  • I'm gonna explain to you how that happens so you first have to understand

  • lung Anatomy and to understand that I like to show you a tree so a tree has a

  • tree stump and then it branches and then those branches branch and then further

  • those branches branch until finally you get to the leaves and these leaves

  • capture the sun's rays and that's what gives you photosynthesis and that's how

  • the tree lives and so what happens is that this tree and the branches increase

  • the surface area of the leaves on the tree so that if you were to pluck off

  • all of the leaves and you were to put them on the ground next to each other

  • the surface area that is represented by those leaves would be larger than the

  • shadow that is produced by the Sun on that tree well it's the same exact thing

  • that happens with your lungs you've got an airway and then that airway divides

  • into a right mainstem bronchus and into a left mainstem bronchus and then you

  • have a right upper lobe you have a right middle lobe right lower lobe left upper

  • lobe and you have a left lower lobe so this is the left side this is the right

  • because you're looking at the patient and then these things of course divide

  • into much smaller branches and instead of leaves at the end of all of these

  • things what you have is something called an alveoli which is a tiny little small

  • grape like structure that the air gets into and the air of course has oxygen so

  • what does this look like on a large scale here's what an alveolus looks like

  • how many alveoli are there in the human body well there's

  • about 600 million of them these are very very small so what happens is

  • deoxygenated blood comes by and its job is to pick up the oxygen that comes in

  • to the alveoli and then when that oxygen comes in it oxygenates the blood and

  • then that blood goes back to the heart and then to the body and all your

  • muscles that's how you get oxygen and so you can imagine that this is very very

  • thin because the oxygen which comes down here has to diffuse into the bloodstream

  • so far so good but what happens well just like when you

  • hit your finger in the door your finger swells that's because there's

  • inflammation occurring where you hit your finger in the door and inflammation

  • causes a leakage of fluids into the tissue space so what happens here is

  • that you get a viral infection the virus affects your lungs and with a RDS the

  • entire lung becomes inflamed not just in one area like you would have with a

  • pneumonia

  • or one particular area for instance on your finger and it would just stay in

  • one particular finger in your whole hand wouldn't swell no with a RDS the entire

  • lung goes crazy with inflammation and so what happens air instead of having a

  • nice thin area inflammation goes everywhere and you get a large barrier a

  • fluid that goes into the interstitial space furthermore these capillaries

  • start to become leaky and fluid starts to leak into the alveolar space as well

  • and this starts to fill up with liquid proteinaceous liquid liquid that

  • prevents oxygen from getting into the bloodstream and so instead of having

  • nice oxygenated blood this blood becomes hypoxic and you become hypoxic if you

  • have a RDS and you have a hard time breathing and that's when you get placed

  • on the ventilator there's really nothing you can do to speed this up there's

  • nothing that you can do to slow it down you have to be supported on the

  • ventilator so that you're getting enough oxygen and that the Machine can breathe

  • for you until just like everything else after you hit your finger in the door

  • and the swelling goes away this fluid will eventually go away as well the key

  • though is keeping you supported during that period of time until the fluid goes

  • away and then once again the oxygen will be able to go back into the system and

  • you will get oxygen back to your tissues so here's another look at that we get

  • oxygen that's going down into these criminal structures called the alveoli

  • they go in to these alveoli and they cause deoxygenated blood to turn into

  • oxygenated blood and then go back to the heart so I'm going to show you three

  • things today that we have learned in the last 20 years that can improve survival

  • in these patients who are on ventilators to help them beat coronavirus or for

  • that matter any other virus whether it be influenza whether it be respiratory

  • syncytial virus any other kind of virus for beating and getting better if you

  • have a RDS and you're on the ventilator so the first thing that

  • look at is what they noticed back in 2000 and actually before is that when we

  • put people on the ventilator and the ventilator puts a breath into their

  • Airways what we were trying to do is we were trying to make sure that we were

  • ventilating patients well and that's important in some situations because the

  • blood that is poor in oxygen also has carbon dioxide which is given up from

  • the muscles well this carbon dioxide would need to

  • be ventilated to be taken out on exhalation so co2 would be coming out

  • well in order to do that we got to make sure that enough volume of air was going

  • back and forth back and forth the problem with that though is that we were

  • inflating these alveoli and then when we were releasing the pressure and letting

  • the air out these alveoli would collapse down and nothing was keeping them open

  • so they would be opening and closing opening and closing shutting and opening

  • and so that was causing a lot of shear stress and of course what's the whole

  • problem here that we've got inflammation is what's causing the whole problem here

  • in the first place and that's causing these membranes to become very thick and

  • the oxygen can't get in there and so by ventilating these patients with large

  • tidal volumes we were causing the inflammation to actually get worse than

  • it would have been if we hadn't done that and so the scientists started to

  • look at this and say wait a minute what happens if we just put a lot of

  • pressure down here to keep these alveoli open and only use a small amount of

  • tidal volume to ventilate these patients and yes we won't be able to get as much

  • carbon dioxide out of them but we don't really care so long as we're not adding

  • more inflammation to it and so that first thing that we looked at this is

  • back in the early 2000s that is came out is low tidal volume and that would

  • almost certainly cause the pco2 or the partial pressure of carbon dioxide in

  • the blood to go up so this was called a low tidal volume strategy and sure

  • enough paper was published in 2000 in the New England Journal of Medicine that

  • showed that we could affect change and we could decrease the mortality at

  • the time from 40 percent down to about 31 percent mortality so that was a huge

  • drop in mortality and all we did was we just ventilated people differently using

  • low tidal volume now when you're ventilating people with low tidal volume

  • it's not very comfortable they're trying to breathe more because they don't like

  • that increased carbon dioxide levels and so they would try to breathe over the

  • ventilator and it would try to breathe differently than what the ventilator was

  • telling them to do and in these cases we would usually sedate the patients but if

  • we sedated them too much bad things could happen to them they could get

  • blood clots their blood pressure would go down and so the second thing that

  • they came up with was actually paralyzing these patients using

  • medications so that they were in perfect sync with the ventilators and so that

  • was paralysis paralysis requires pretty intensive care in the intensive care

  • unit you need good ancillary services you need good respiratory therapists you

  • need good nursing something that you might not get if there's a huge outbreak

  • but you could get if attention was made to this so this paper also published in

  • the New England Journal of Medicine and by the way I'm gonna give links to all

  • of these papers in the description below they were able to drop the mortality

  • from 41 percent down to 32 percent and this paper was published in 2010 so far

  • so good what we also started to realize is that patients in the hospital for

  • whatever particular reason if you ever look at them in bed they're on their

  • back and what we decided to do was flip them over and there was a number of

  • reasons for this so that their belly was down and that their back was up we call

  • this prone positioning and if you do this for about 17 to 18 hours a day you

  • can actually decrease the mortality they found from 33 percent down to 16 percent

  • and this paper was published back in 2013 and so you can see here three

  • breakthroughs in treatment of a RDS the final common

  • pathway for morbidity and mortality in the coronavirus that we're talking about

  • but the other thing about this that's interesting is we can do a lot if we

  • catch it early and we get people into the hospital and we get them in the

  • intensive care unit and we get them on ventilators and we're able to

  • appropriately treat them with good quality medical care and three things

  • that really make a difference then we've got a good chance so that they're not

  • another statistic of mortality but they survive this and so really the purpose

  • of putting these updates on is to make sure that people understand the medical

  • background of what's going on sometimes these stories about how brakes can be

  • very scary and for good reason but we need to understand medically what

  • it is that's going on because knowledge is power if you have any other questions

  • about this please visit my site at make cram comm thanks for joining us

welcome to another medcram lecture so I hear this question a lot how does the

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B2 中上級 新型コロナウイルス 新型肺炎 COVID-19

コロナウイルスはどのように殺すのか。急性呼吸窮迫症候群(ARDS)と治療 (How Coronavirus Kills: Acute Respiratory Distress Syndrome (ARDS) & Treatment)

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    Mia Chang に公開 2021 年 01 月 14 日
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