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0:00
how is it that you can study so hard and yet not understand the questions being asked I've started with my current class preparing for their national exams and there's a general anxiety because they know no matter how hard they worked it won't necessarily translate into a good score on the exam and the answer to that is this it's a clinical exam which means you have to be able to take what you've Learned and say why do I need that in patient care and it gives you surprisingly different uses
0:35
than when you're memorizing it as facts before we dive into it though if you're a medical student and you want to learn how to think like a doctor be sure to subscribe every week I do a new video talking about how you can be better in learning how to think like a doctor and organize your data so that it's usable in clinical vignettes I'm Doctor Philip Tisdall I practice general pathology for decades over the past 12 years I've been teaching full time
1:03
and I must say all I dream and think about now is how do I teach you to be able to do what all of us practicing doctors can do because that's how you do really well on your exams you have to be able to take what you've Learned and say why do I need that in patient care and it gives you surprisingly different uses than when you're memorizing it as facts so the I'll give you an example from teaching this week we were talking about congestive heart failure
1:32
and that was fine I went to the standard discussion it's a good discussion but then I wrote multiple choice questions that were deliberately squishy meaning they didn't have really hard facts like what's the capital of Canada wasn't like that it was so here's the patient tell me why I see this and the the question that I really enjoyed was we talked about how the pressure backs up from left ventricle all the way to the lungs and when it's more than 20 millimeters of mercury
1:58
you get pulmonary edema everybody knows that but the question I asked was to walk me through the pathophysiological sequence you had to get the sequence right and it was surprisingly hard and I was surprised because this is what I hadn't realized everybody does their blood flow from right ventricle through lung to left ventricle but when you have heart failure and it's congestion you actually do it in reverse it goes left ventricle backs up into left atrium
2:27
backs up into pulmonary veins to capillaries and then the transudate into the alveoli which is easy for me I've done it a million times but I was trying to think you know it's exactly like doing the alphabet everyone can do the alphabet forwards you don't get any points for that but just right now try it try going backwards and you realize how awkward you are and so that's the difference between knowing the letters of the alphabet and being able to use them
2:53
and you know if you're a native English person I say what are the vowels well a e I o u and sometimes why everyone can do that but if it's your second language you might not recognize that's kind of a common thing and so to you it's the first time through and you have to hunt and peck and then the exam gets long and you miss the last four questions in your block which is easily the commonest way people lose score points so I've started thinking a lot about you have to be able to have a really
3:20
clear way of thinking of your pathophysiology yeah that's great no you gotta do that but then you've got to be able to read the question it's a clinical question and here's the mistake that's it's an innocent mistake I get it it's because you think it's the old question in which I somewhere hidden in there is what's the capital of Canada no no it's not it's a conversation I tell students all the time you should imagine I'm your senior colleague we're in the er and I'm telling you something
3:47
hey I got this 60 year old lady she's short of breath it's been getting worse for months go in and take the history and physical come back and tell me what you think that's a clinical question and that sure felt different than hunting and pecking for what country you're in are they asking the capital so what I thought of today is I want to introduce first of all this idea of exams and then I thought I'd just go through a really standard question I just wrote out a really common one
4:13
and we'll go through it and we'll talk about how do we think about clinical questions and here's here's just the truth I I I I talk to the school a lot about this you can't teach yourself pathophysiological reasoning you really do need tutoring and you know I felt really bad after the discussion because everyone floundered around and what I clearly thought were very straightforward questions and so they could tell I was like really surprised they couldn't do them so they felt bad
4:40
and then I felt bad that they felt bad so it was not a happy day and I was talking to a really excellent student that afternoon and I thought okay this will be really easy for Mr Marvelous well Mr Marvelous wasn't any better than anyone else and I said to myself you know learning your first aid perfectly doesn't give you clinical reasoning but here was the thing when I sat down with him one on one and I walked through how to order these facts for this very important path of his
5:07
he only needed to hear them once so I'm not saying this is really hard to do but I'm saying it's really hard to do for yourself
5:17
it's especially hard I'm sure none of my students are gonna do it they all love what I do they all appreciate how important it is oh it's all they all agree it's way better and I promise you none of them are gonna do it because they're writing their final exams in four weeks and they've got all of undergrad and two years to get to this point memorizing no one full of anxiety is going to do a major change in mental approach if they only have three or four weeks to go
5:44
so I hope you have more than three or four weeks to go because I'm gonna give you a sense of what it looks like to do pathophysiological reasoning which is all of medicine basically so here we go I've got a nice multiple choice question written out for you and we'll just sort of talk about what pathophys looks like so here we are with a standard multiple choice question and I want you to see how I treat this as a conversation all of which is based on basic medical sciences
6:15
so let's just dive in and take a look at it whenever we start our story we always start with see the patient and by that I mean we're talking about prevalence so predictive value positive is proportional to prevalence to sensitivity so sensitivity is of 100 people with the disease how many test positive got it all our testing is really good now it's all about 95% we're not gonna talk about that let's talk about prevalence that says if you have 100 people how many have the disease
6:49
and here's the deal the more you enrich that population the more likely you are that it will test for the disease right so let's just write this down if you haven't got this in your head predictive value positive is proportional to prevalence all diagnosis is based on that when you're reading the story get the prevalence right and we have to do prevalence in two different ways one is what I call the constitutional or fixed prevalence I'll show you that
7:16
and then you gotta have a quick peek of the chief complaint differential and then you say what are all the stories they give you within that that are gonna change the likelihood in the differential diagnosis so let's dive in we always start with age gender time frame I don't care where you are who you are what you're doing you always start with that let's talk about what that means hi there are three that are just really important over 65 middle aged women under 25 I'm just telling you
7:45
if you just get that in your head everything becomes easier over 65 you've increased the prevalence of degenerative and cancer middle aged women much more likely to have autoimmune disease and endocrine disorder when you get into practice you're gonna be convinced that every middle aged woman has thyroid disease and then when you're under 25 hereditary congenital does it have to be no it's how you enrich prevalence next you go to gender and that's pretty straightforward
8:19
right women female reproductive men male reproductive but atherosclerosis is so common in our western culture that your risk for that is actually baked into gender women have this 30 year lag when they're being protected by estrogen so they start that atherosclerotic curve 25 30 years behind male so women minus 1 atherosclerosis males plus 1 atherosclerosis you'll often see you include the site of service that actually isn't a big prevalence changer
8:51
it's a colorizer it gives you a sense of how severe how urgent is this if someone's gone to a miserable er to sit in those queues to get treated you know that they're really quite worried if they go to a doctor's office it must be much more casual and chronic because you had to make the appointment you don't get in for a week or two that's a different flavor of the urgency and severity of the symptoms and then you'll see oh look at that now we have a chief complaint
9:19
and you know Appendix a in the book has the 50 to 60 chief complaints you got to be able to do at the end of second year med school so you're always looking for them because they're really common shortness of breath chest pain abdominal pain they're very standard but what that means is anytime that you have a chief complaint it means that you can form a differential diagnosis and that goes to the absolute heart of diagnosis age gender then you've got to be able to do what is time frame
9:51
and remember when we talk about time frame it varies by organ so you got to have a quick little peek at the chief complaint and decide what organs you might be in because this is how it works right liver is six months kidney three months okay what about joints someone presents with a sore joint what makes it acute or chronic and the answer is six weeks well what about diarrhea kind of awkward here right less than two weeks is acute more than four weeks is chronic
10:18
so we got that little ugly gap yeah that's for practice not for you so that's not gonna come up at the medical student level and when we get to heart lung that's about a week so shortness of breath we know right off the top our differentials heart lung so 3 months makes it chronic so look at the power I've imposed on likelihood of disease just by saying old female chronic I've got my chief complaint this isn't a lesson on differential diagnosis so I'll just tell you what it is remember
10:48
differential diagnosis goes by organ family of disease as many subfamilies as you need till you have a diagnosis you notice what it is not you don't get your shotgun full of diagnoses and shoot at the wall and get a spray of a thousand possibilities it's very orderly organ family subfamily diagnosis so I'm not kidding when I say shortness of breath starts with heart lung so now I've got my chief complaint that's gonna be shortness of breath differential diagnosis that's by organ system right
11:24
heart and lung and now we can do our sub families yes you do really have to practice this when I say what heart disease is gonna give you shortness of breath the answer is left ventricular congestive heart failure are there subfamilies sure if you're in America and you say what are the commonest causes of heart failure 80% will be due to ischemia hypertension and an abnormal valve well you know is that still hasn't got to a diagnosis that valve could be aortic or mitral
11:57
still haven't got to a diagnosis it could be aortic regurg or aortic stenosis still haven't kind of got to a diagnosis cause aortic stenosis could be calcific or bicuspid so you can see how we work our way down the possibilities but you notice once we do that then we can start looking back at the risk factors okay lung lung is going to be obstructive or restrictive and now we can follow out their subfamilies so with that in mind we come and look at our diagnosis and say what else have they given
12:31
when you're in your first two years nothing in the stem is going to be irrelevant you don't have to go searching through the weeds to find the pearls everything there changes prevalence you just gotta say what's my differential does it rule it in or rule it out so let's talk about our risk factors here smoking
12:53
when I say smoking how do you organize the pathophysiology cause if you can't it doesn't help you very much well here's how I do smoking it affects the circulatory system we have to break that out it causes the No. 1 cause a risk factor for five cancers do you know what they are and it affects the lung both cancer and COPD so when you say smoking that's a very big deal but you notice it's not gonna help shortness of breath heart lung there's heart there's lung
13:25
so that's not gonna be very useful in the differential we come to hypertension can you do hypertension well hypertension is gonna be all circulatory yeah guess what how do you think about the circulatory system you can't just say circulatory because it has different diseases in different segments so when I say circulatory I mean ascending aorta abdominal aorta muscular arteries that's our dancing man don't have the dancing man it's a tough list to remember and then you've got to go to arterioles
13:57
totally different pathology right high line arteriolar sclerosis and that's the family of macrovascular disease you just gotta see it in your mind's eye and walk through it in your differential rule in rule out and then last is diabetes how do you think about diabetes cause everyone always forgets acute complications of diabetes acute and chronic and when I say acute that's d K a and H H s we could stop and talk about that couldn't we not applicable here cause this is 3 months
14:29
however we have to talk about chronic how in your mind do you organize the chronic complications of diabetes and the answer is yeah macro vascular micro vascular and you have to be able to talk about that because that's where you're gonna go looking in details of your history and physical exam so when I look at this story smoking hypertension diabetes I get heart on all three so that's pretty good I only get long for one so I'm betting heart not long doesn't mean it's not long
15:06
I'm just saying the weight of the evidence except you notice I left something out didn't I I left out this cause that's not a risk factor a risk factor says what is the relative risk of having this added to your population this is actually part of the pathophysiology
15:26
because what this says is when I lie down to sleep at night I wake a few hours later with this terrible sense of drowning people truly fear and hate it it is a terrible feeling and they quickly figure out they have to solve the problem and you know what they do they prop themselves up it's such a mandatory part of their life they don't think about it anymore so if you say are you sleeping well at night they'll often say yes I am yeah well you've got to understand
15:56
this is paroxysmal nocturnal dyspnea this is part of the path of physiology you've got to ask for it it's part of a directed history you say oh are you sleeping with pillows yep sleeping with three okay well that's not normal sleeping okay so it's not a risk factor it says this is one of the things that induces and is proof of congestive heart failure so when you say how does that work as a test if I just took P&D we sort of said how do you think about its value
16:26
you're always gonna break it into sensitivity and specificity well look at how powerful this is you only find it in about a third of your patients but it is greater than 90% specific so it's something you know to go looking for because if you have it nothing predicts that it's congestive heart failure better than that so let's take a look at our history now age gender time frame chief complaints of differential in the differential we now go into rule in rule out and we differentiate
16:59
findings that are part of the path of physiology really specific and findings that are risk factor make things more likely so based on this history I can with perfect confidence tell you this is left ventricular congestive heart failure
17:17
a lot of talking over just like two sentences isn't it a lot of thinking and so it gives you a lot of sympathy when you poor students having memorized your first aid faithfully are thrown into the pool and said well put that all together yeah it's not straightforward and I gotta tell you it's what I spend most of my days thinking about which is what have I taken for granted that I have to actually stepwise walk you through and obviously it starts with having a good pathology
17:45
OK that's all well and good now you've got to say OK that's the stem to my multiple choice question do you see how many questions I can make from this so we've talked about this before the universe of medicine is presentation path of physiology and natural history natural history means what happens if we do nothing cause all treatments have side effects so your treatment has to have a cost benefit analysis that's positive when I say presentation I mean symptoms signs
18:18
your physical exam and testing
18:21
when I say pathophysiology I mean the mechanism of disease but when I say natural history and this is very hard when you're just studying from a book you have to imagine you're talking to your mother's best friend you've got to be able to explain what's going on because when you say you have congestive heart failure she's gonna say right away to you what happens to me well that's prognosis when you say well what are we gonna have to watch for
18:46
and this is where all my students plowed out this week because I just sort of threw in there now she has a demo what happened and none of them thought through natural history that left ventricular failure leads to right ventricular failure that's how I Learned none of you can go backwards in your anatomy so the complications of congestive heart failure would be arrhythmia and now I'd stop and say what's the commonest well if you haven't studied it it's kind of hard to know
19:09
it's a fib and then we say thrombosis and now we're gonna stop and say oh really does it thrombose embolize well then we get into long discussions of where does it embolize to which is its own universal discussion and then so you do prognosis what happens to me complications things we have to look for and then of course what they really want to know is are there any treatments and now we get into this deep discussion of maladaptive remodeling cause that's the cornerstone
19:37
of treating congestive heart failure so you can see from this little stem I can ask any question I want and in all fairness I gotta tell you I miss lots of questions and the commonest way I miss questions is I answer the question I wish they'd ask not the question they did ask it's really easy to do because you feel so good about your answer and so what I do is when I read the stem I always stop I look away from the page I break intellectual contact and I consciously say to myself
20:08
are they asking about presentation patho phys or natural history and then I go back to my stem cause otherwise I'll just make up the answer I wish they'd ask you know they should have asked that well they didn't you got it wrong here's a stem and you can see it's driven by this idea of fixed prevalences age gender time frame differential diagnosis driven prevalence risk factors really different than if there's a piece of the pathophysiology and then you tear yourself away and you say okay
20:36
are they going to ask me about presentation pathophysiology natural history and you go read the question if you take anything out of this long winded discussion it's this age gender time frame I don't y'all the rest is great there's no question it really helps but don't miss that point age gender time frame then you won't pick some dumb answer for a five year old and your patient's 55 age gender time free so that's how I write my questions that's what a clinical question looks like
21:06
and I hope you find this helpful let me talk about why I've written some multiple choice question marks first of all I have to all of you are all tested that way do I like it nope that's a whole different video why I think they're a problem but here we are I know that you demand them because that's how you're tested the problem that we have with so many of the multiple choice questions is they're written so that students can be ranked meaning strong students weak students
21:32
that's really valuable for the system it's not valuable for you you want to know have I mastered this material so what you need are teaching questions and so you know with growing frustration dealing with everyone else who can sort all the students out I'm gonna start writing questions for the path of his book that are all saying do the question if you can do it right then you understood the point of that part of the book just to even get a sense of what those questions
21:59
look like we've made available 12 very standard clinical type questions go give them a try and see if you can appreciate the difference between a clinical question and a standard ranking question you can click the link in the description as well you can click the link to purchase the 2nd edition of the Clinical Pathophysiology book thanks for listening we'll see you next time
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