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Hi guys and welcome to the All you need to know respiratory talk. Thank you for coming today. Uh Just a reminder, we'll have four talks today, all based on respiratory and we'll get back in with the first talk. Just a reminder, guys that if you have any questions to put them in the chat, um uh function that we have. And on top of that, at the end of uh today, there will be a, a feedback form. If you, you guys can fill out the feedback form, that will be great. Once you fill out that feedback form, you'll get your certificate to say that you've attended as well as access to a note bank and the slide decks from today and the lecture recording. So, really worth doing the feedback from you guys. Um So I will pass over to our first um presenter today who is doctor and I'll let himself introduce um his tour. So, thank you so much. Cheers. Thanks. Thanks so much. Uh So my name is uh Doctor Babu. I'm one of the consultants here from hospital. Um Great to have everyone so early on Sunday morning, I hope I can keep you all awake for this riveting talk. Um So essentially, um we're gonna talk very brief, but it's gonna be the very basics of lung function tests because obviously, you know, um in terms of lung function tests, there's many different facets to it. And it's also very complicated to explain every single aspect of it. So I'm going to give you a very basic um and just getting an understanding of the key elements to a lung function test um including how different tests are performed. Um And a achieving and also a basic understanding of the lung function test, um which are the main aims. I've got a quiz for you at the end. So we can hopefully um do that. Um um and we can then we can see how much you've taken or, or um from our talk. So, in terms of uh introduction, I suppose it's very basic in terms of lung function test, you wanna understand the cause of someone's symptom, which is breathlessness. That is the predominant reason why we would do lung function test. Um Typically, obviously, we diagnose conditions like COPD and asthma. Um and also we help this, this lung function is help to con continue to um monitor the progression um of someone's lung disease. We also get to get an idea of the efficacy of a given treatment, lung function test. Um So, um it, it can help understanding, it didn't understand um how the disease is progressing on treatment as well and also sometimes preoperatively. And it just like to use lung function tests as a tool to assess um the almost like a lung function test to uh determine the fitness for surgery. So that some sometimes it is used uh to assess in terms of the next one. Ok. So I think basically we're gonna, I'm just gonna take a very brief, brief look at physiology. Um So you can see that um there's a, it splits into upper respiratory tract and the lower respiratory tract here, the upper respiratory tract involves the nasal cavity, the pharynx and the larynx and obviously, the air that's comes through the nasal cavity um is often um it's very important. Uh and the nasal cavity uses um obviously to remove the debris and also uh and the pathogens and also um humidifies and warms the incoming air as well, which is vitally important and obviously goes through the pharynx and into the larynx and the vocal cord is, well, it separates the upper and the lower respiratory tract. And following that, obviously, it goes into the trachea there and splits into the, to the right and left um bronchus. Um And in terms of um then obviously, it splits into lots of different um branches, there's many bronchial uh branches and then eventually it becomes a bronchial, which are essentially um which are essentially the smaller um um airways which uh doesn't remain differentiation between the bronchi uh, the bronchus, uh, the bronchial tree and, and the bronchioles is the fact that the bronchioles doesn't have any cartilage rings. It's just predominantly smooth muscle. So, um, it's kept open by the smooth muscle being, um, uh, being dilated. Um, and obviously when it, the end of the, the bronchioles or the terminal bronchioles you reach, um, essentially where the magic happens where the gas exchange uh between the, um, er, happens. So it's basically the end of the um terminal bronchio. So you've got these air sacs which are covered by capillaries and, and that's where um oxygen car obviously um goes from the alveoli into the um blood vessel. And these carbon dioxide passes from the blood vessel into the alveoli to be freaked out. It's simple. And then obviously, just obviously, before we do details of our lung function test, it's also important to understand what are the most important muscles involved in inspiration, expiration. So that's vitally important because obviously, um if you've got someone with a um reduction in their lung capacity, the reasons it could be due to obviously is it could be also due to the muscles. So it's important to know. So the key things to know are diaphragm is involved in inspiration. Uh And the external intercostal muscles are obviously also more in inspiration to a lesser extent extent. And the accessory muscles are often um uh vitally important when you are breathing quite hard. So, uh you've got the scaling muscles in the neck and the stent, the mastoid muscles in the, the neck and the trapezius, which helps to um essentially raise the thoracic gauge um to improve the inspiratory capacity even further when you've got a person who's actually really breathing hard to get as much air as possible when they're breathless. So that's, that's the key muscles of inspiration. So, expiration obviously is more of a, more of a passive thing because obviously, the elastic recoil of the lungs helps to um get rid of the um the air. Um So, but the obviously, if you're trying to breathe out as forcefully as you can, also, the abdominal muscles are involved um and the act to force the diaphragm uh upward to depress the lower ribs. Um And the internal costal muscles are also involved in the muscles as a muscle of exploration. Um It's important now. So, spirometry, just obviously, I'm sure you guys have heard the term. So it's very simple. It's like a forced respiratory maneuver um which um measures how much air a person can exhale. Um That's the key here. Um And if it's anything limiting the airflow, then obviously, um um we would um we would uh know, so in terms of um the key measurements, so that's the F EV one, which is the force expiratory volume in one second, forced one capacity, which is essentially the um the uh maximum um volume of air that can be forcibly exhaled. Um So it has to be force with exhalation. And you've got something called the VC Max, which is the maximum max capacity, which is uh under the deviation of FF VC, which is essentially the maximum volume of air that someone can exhale or inhale, slow or force. So that's, that's the big difference between F VC and the VC Max. So it, instead of VC max isn't that of a of, it doesn't have to be a forced exhalation. So it's supposed interpreting the results. It's just important to really understand how we kind of what's normal for patients. So I think we've gone away from, I think the key thing that I want to kind of impress upon you guys is I think we're going away from using percentage predictors. So it's commonly, that's the main thing we used to use obviously um in terms of assessing what's normal. So you can see here that on this diagram, you've got the mean, which is obviously, I'm sure many of you seen this diagram before uh mean middle. Um And you've got the standard deviation curve and you've got the sr or the standard residuals also known as the Z scores are the extremes uh at either end here. Um So the key things for you to know is that the lower limit of normal is less than minus 1.645. So anything that the value reaches well below that, then, you know, it's abnormal, uh upper limit of normal is less of a, I suppose, interesting stuff because it, because that's just means you're super normal um rather than anything else. So keeping is that value is 1.645. That's the main thing you need to look out for. So we've kind of gone away from percentage predicted. So I'm just purely looking at the lower limit of normal. So interpretations, the first thing you look at is the is the um the ratio. So the first thing we want to look at is the ratio and the ratio, if it's obviously the value is less than minus 1.645. Um Then obviously, we want to um um we want to um label it as low. So, so it's a low ratio, it's a low ratio of means and obstructive spirometry, which means there's a large airway obstruction and to grade the severity. Then we look at the F EV one. we go down this pathway and look at the F EV one to classify the sr and, and um anything over minus two essentially is classified um uh mi mild, there is different grades. But I think that uh basically, I don't want to go into that detail for you guys. I just want you to understand what is an obstructive spirometry. So, so basically anything a low fe and VC or F EC ratio, it means an obstructive spirometry. Um And obviously, then you grade it by looking at the fe we want. So if the ratio is normal, then there is no clear large airway obstruction. So it's not obstructor spirometry. But then what you want to look at is um the um VC max or the F VC. So I think, I don't, I don't mind what you look at. I think F VC is, is the standard measurement, um what you want to look at and if it's less than minus 1.6 or five, then you know, that's a, that's a restriction in the lung capacity because obviously, uh the ratio can be normal or high in a restricted um um lung and spirometry. Um So, um so that, that's a good um but it's not a great measurement for measuring restriction is so you look at the VCF VC or the VC max to see if a restriction in the lung capacity. Obviously, you can have mixed uh picture. Um So I'll speak to that, speak to you about that later on. So this is just an example. So you can see this is a typical spirometry you may see. Um So you can see here this is the predicted lower limit of the patient. So as well, there's a lower limit of the values that, that you expected for your age and your ethnicity and the upper limit here uh of the values that you've got here as well. So these patients should fit in um between those two values essentially to become kind of normal as you say. Um So the, the key things on the left here, fe one is like we talked about the force expiratory volume in one second and F EC here, vital capacity and the VC max um here as well. So FE VC, the we here in both hospitals now F and VC max is the ratio that people use. So that's the, the ratio that we're looking at and also the peak flow peak expiratory flow rate, which is essentially part of the spirometry. But II don't want you to kind of look at these figures for now just to focus on the first four things here um on the left. So first thing you look at, like I said before the ratio, so the ratio for this person is 32.45 and you can see it doesn't really fit in the all in, in the um a lower up limit and it's obviously very low and you can see the sr is minus 5.80. So it's well below the minus 1.645 that we that we have. So, so you can see it's an obstructive spirometry, then we look at the, if you want to grade the severity of it. And like I said, we're not gonna place too much emphasis on that, but you can see there's an uh obstructive spirometry with severe obstruction. Um If you want to classify it. And you can see here there's a flow volume loop um which you can and which you can gain from um spirometry. So that's different as opposed to it. It's because obviously you've got the flow uh on one grading and also you got the, the and the volume and the other axis as well. So I'll show you I'll speak to you in a more later on about that second example. So this is again, just getting through the, the, I suppose the algorithm or the pathway that we created to get the ratio first. So that's the ratio is a normal ratio of 7.75 0.66. Um But you can see um when we go to the, if it's normal, then we go to the VC max or, or the FBC, we can look at the FBC max and you can go minus 1.94. So it's less than minus 1.64. So you can know that is a quite a restrictive um spirometry. Um So that's a clear restriction, but it's all, it's very mild. Um So that's the key thing to get across there. So just to look at the flow volume, you've now, so that's important in spirometry because you can help us identify, um you can help us identify between a restriction obstruction. And also you can help us identify between a um if it's an upper airway obstruction or a or, or a um lower airway obstruction. So that can be quite useful in that sense and help us diagnose conditions which are not typically in the lungs as well. Um Because obviously there could be other reasons for the breathlessness. So just to look at the flow volume loop, um you got the, you got the uh volume and the X access. Um and you've got the um the flow on the Y axis here. So flow is measured by liters per second. Um So this is the typical kind of um a pattern or, or diagram you get with the flow volume loop which is a normal flow volume loop. Um And this just to just to make it clear, this is the inspiratory loop. OK. So that's when the patient is taking a deep breath in and then you go breathe out forcefully as you can. And obviously, the airflow goes down as you go on longer with your breath out. So just to kind of um not a few things here. So typically people talk about peak flow, which is a typical thing we use for asthmatics can be a very useful measurement. So peak flow is a is a is obviously a flow, you can either get liters per second or a liter per minute. And you can see that is the obviously the peak, the green represent the peak flow in this patient because that's the maximum grade, maximum expiratory flow rate of this patient when they're taking a breath out. And you can see the other one that you can actually get here is a vital capacity, which is right at the end, the maximum air you can inhale or exhale forcibly or slow or, or slowly as you can. So that's, that's the VC uh vital capacity, which is the volume. OK. So that's the big difference. Peak flow is the rate of flow and the vital capacity is the volume that we're looking at here. So this is just a very basic um pattern. And uh you, you might just recognize if you look at a flat volume, but you can help understand um whether there is an obstructive or restriction in the in the lung function um or even a mixed picture. So with the um you can see here, this is a um obstructive spirometry. You can see there's a normal inspiratory for water loop. You can see an expiratory and you don't get the same peak and you don't get the same curvature. You get a very kind of conc this curvature here, which is a typical thing you get in, in, in um obstructive spirometry restriction. You can see the vital capacities over here. It's predicted for the patient, you don't even reach that. And it's a very, just a very smaller flow volume loop with no curvature. That's a, that's a typical restriction and this is a bit more difficult. Obviously, it's mixed and it doesn't reach the full vital capacity that we expect for a patient. And obviously, it doesn't have the same height and it also has a bit of a curvature here, which will go with an obstructive spirometry. So essentially, it's a, it's a mixed um spirometry there. So, um the other thing I spoke to you about was the flow volume loop and how it can help us diagnose in our way, which is actually quite important. Um because obviously, you can get um local called paralysis, a goiter. Um um a large thyroid goiter that can also compress the airways and sometimes a cancer or a tumor can also help with um and can cause upper area obstruction, which it can be it completely, so it completely up to you because obviously, it can be a normal x-ray and it can sometimes be a normal spirometry. But unless you look at the flow volume loop, you don't really know um you don't get the diagnosis. So it's very important to look at the flow volume loop because the other thing, common thing that we see is tracheal maasia where you've got a collapsible trachea um um in expiration, it completely collapses um and it doesn't get the same flow. Um So that can be a huge issue in patients who are obese as well. So just to go through again, the left here, you got fixed um obstruction. Um It affects the inspiratory and expiratory loops. You can see that's a very not typical uh flow volume loop that we've been seeing lot loss of height just prolonged. So that's a, that's a very good example of a kind of fixed obstruction. It's a typical fixed obstruction, trachealis, strepto stenosis can happen. Usually. Um when you've got um uh previous history of intubation, uh prolonged intubation can, can result in stenosis and a foreign body or a neoplasm as well. So that's important to know And um then you've got the vial. So you can see here there's an extra extrathoracic obstruction. So that extrathoracic obstruction obviously um affects the inspiratory loop. So you can see the inspiratory loop is completely flattened here. It doesn't have the same kind of curvature that we've previously seen. Um completely flattened. And so it's more of a uh I suppose the way to remember is there's obviously, it's opposite. So, extrathoracic causes affects the interthoracic sorry, intra inspiratory loop six. So it's called variable because um it, it, it's um it's, it affects the expiration and when, when, when, when you, when you're expiring air, when you're on expiration, that's when the airway collapses and causes this obstruction. Um and that typically happens with um vocal cord paralysis um and goiter. So anything above the um the vocal chord. So essentially on the vocal cords. So above the vocal cord attacking course, is kind of typical picture. Um and intrathoracic construction obviously, as we say opposites affects the expiratory loop. So, expiratory loop is completely flat in here. Um It could ventricular Malaysia or in tumors of the um of the airways such grace. So the next bit that I'm going to cover uh is gas transfer like we talked about before the alveoli. Um um and the blood vessels that supply the alveoli is where the gas exchange happens. So we have the ability to measure the gas exchange, which is an important part of um um important way of diagnosing other common respiratory conditions as well. So sometimes the spirometry completely or flow volume loop completely, completely normal in patients. But a gas transfer can help us identify um if there's any other reason that the patient is breathless. So it's essentially very simply assess the ability of the lungs to transfer the oxygen to the bloodstream. Um So any sort of disturbance of the alveoli or the blood vessel can disturb that uh transfer of oxygen to the bloodstream. Um And what it, how we measure it is basically inhaling a known quantity of carbon monoxide and seeing how much um is remaining after the breath uh is held, held for a period. And so the carbon monoxide acts like a almost like a surrogate for oxygen because it has a higher affinity for hemoglobin and binds to it on the same active side. So essentially um press four, the carbon monoxide is measured um after they've inhaled it and also they exhaled it after uh holding a breath. So key, key, key time to know with, with gas transfer is you've got TLC O here, which is the total gas transfer for the whole lung. OK. And the case here is the, the transfer coefficient or the um, the gas or, or the trans transfer factor for each um unit of alveoli and the vital um the other va or the um um it's, it's basically measuring of the alveoli volume. So it's a very simple um measurement um that can help us um identify um the actual volume of the alveoli through the, using this particular method. OK. So, um so just, just to, just to go through um gas transfer very quickly here. So you can see here, um you call the Tu Martin Rat Kumm right here. So the t here here is um three, this is the actual numbers and obviously, this is the percentage predictive of like we, like I said before, we get away from percentage predicting we're listening, looking at more about the SR the TLC here is 3.87. You can see clearly here. It does not, it's well below the predicted lower limit of 5.96 and you can see it's minus 3.66 sr so that's obviously significantly reduced gas transfer. Um The case you is obviously what we said per unit long volume and that's also reduced a minus 2.83. Um So you can see there's a disturbance in the actual um the transfer of of oxygen and also trans and change of carbon. Um uh downside across these alveolar membrane. And that can be typically two main things you need to know about is emphysema. Um and also lung fibrosis, the main things we need to know. And so it can also be affecting pulmonary hypertension and chronic thromboembolic pulmonary hypertension. So, so anything that can disturb the alveola or the blood vessel across, so that obviously can be reduced. So it's releasing both the DLC O and the TLC and the KC O. And this one, you can see the different example here, the TLC O is obviously minus 3.55 which is again, significantly reduced. Um which is the total gas transfer across um the membranes. But you can see the KC O here actually falls within the normal limit. So 1.58 is 1.64 which is actually normal. So you can see the big difference there. So that indicates there is an extra thoracic, extra thoracic restriction essentially. So you've got someone with a um with a um TLC O which is um which is uh 59.3 which is restricted. And the case here, which um which is um uh normal. So the reason for that being is clearly because the alveolar volume is completely reduced. Ok. So you can see the alveolar volume is reduced and that is because of the restriction. Um from obesity, uh or muscle weakness is, you know, restriction caused by actual extra thoracic uh causes. So, typically, obesity and muscle weakness are no co key things just to make it completely clear. Um The, the other way of looking at it is essentially um the TLC O is worked out um by essentially um VA times KC O. That's very simply. So the VA times KC O equals TLC, that's why when the VA is reduced, you get a um significantly. Um And the case is normal, you can still get AAA reduced TL C. So you, if you understand that, let me see what we get next. So you, the thing and it's important to know here is obviously anemia can as um obviously affect the result of the um the gas transfer. So you can see here the TLC O results um you can see get, get SBA value and a corrected value. So the corrected values obviously um is is corrected for the hemoglobin count. So they all, when they do the gas transfer, they all often co common measure the hemoglobin count. And um typically, what you need to know is the polycythemia can overestimate the, the KC O and the anemia can underestimate the KC O as well. So you can see the corrected uh KC O is is normal. Um but the normal KC O is mildly reduced, I wouldn't say significant. But you can see that it's a underestimation of the normal KC O level because of the anemia. Um So that's important. I think. So if you could just um um get the QR code for the quiz if you can guys. Um But I don't think I can share the um the meantime thing here, but I'll, I'll let you guys know the results. Um um Just gonna start first question. So um first question is simple spirometry like we talked about just now F EV one is 2.0 L and the sr value is minus 1.2 and the F ec2 0.8 L and the sr value is minus 1.0 with an FE one BC ratio of 71% and the sr being minus 1.0. So quite simply put, if you could just vote for, if you think this is a normal spirometry, obstructive spirometry or restricted SP OK. Give me a few seconds for that. Hi, Aisha, I'm not sure how many responses I should be awaiting, but there's six responses so far. Uh Hi. Uh um there are about um 16 people. OK? So it should be, I don't know if people need the QR code just let me know. OK, I've got um yeah, it's got seven responses so far about OK. So um four out of seven I've got it right. Which is good. It's more than 50%. Um So four is it is a completely normal spirometry essentially. So you can see like I've said that we talked about the SR value is the key here. So if the SR is between minus 1.6645 and plus minus 1.645 and then you know, the value is essentially normal. So the fe one is normal here and the F EC is normal and the FE one BC ratio. So as we, as we spoke about before, the first thing you look at the ratio, the ratio is normal here and the ratio is well above minus 1.645. So that's, that's normal. So that the next thing you look at is the F VC and the F VC is also normal here. So essentially it's completely normal spirometry. Yeah. OK. So next one, so you can see here you've got a flow volume loop. Um So if you could just uh get, I'm gonna go to the next question. So you can get to um if you think it's a normal flow volume loop and it's a variable extrathoracic obstruction or a variable in thoracic obstruction or a fixed area obstruction. So you can see both the inspiratory and the expiratory loops are affected in this particular um log on in leep. So if you guys could vote and what you think haven't been bad so far, uh Let me just check. Um Has it changed now? Um I just on the, has it not changed? Slight? Um I don't think so. Ok, let me, has it changed now? Um It has now. Yes. Yeah. As you go on to the first question, what it says what it says on the um is there is a change for everyone? Yeah, great things and votes but two guys for so far. So I'm expecting five more guys again. Uh five say five it anymore. Sorry, I don't know why on my meter it says um fixed upper airway obstruction. It's meant to be just a fixed airway obstruction because it can affect anywhere in the upper or the lower tract. So, yeah, so I think we've got two votes for variable extrathoracic obstruction. Sorry. Three votes are very variable extra thoracic obstruction and one vote for intrathoracic obstruction and two votes for uh fixed airway obstruction. So the correct answer is fixed airway obstruction. The number four option, like we said before, um the fixed airway obstruction is where affects both the um the, the expiratory loop and the inspiratory loop. You can see both of them are flattened and both of them are prolonged. Um So that's a typical um, fixed um airway obstruction. Um Like I said before, if it's an extra thoracic obstruction, it will purely impact on the intrathoracic intra inspiratory loop here. So, and if it's an intrathoracic obstruction, it affects the expiratory loop purely and the, the other loop will be normal. So that's the reason why this is a, a fixed obstruction. Ok. And the next question here is um essentially looking at spirometry again. So very simply put F EV one is naught 0.89 L with an sr of minus 3.25 F EC is 3.28 L sr of minus naught 0.12 and an F EV and VC ratio of 27%. So just remember, look at the FE one F EC ratio first and then work yourself forward from that. Um And, and decide if it's a normal spirometry, obstructive spirometry or a restrictive spirometry. So if you could just have a look and that got one bit so far, someone's on it five so far, you know, OK, we'll leave it at that. So four out of five motive for obstructive and one person would for restrictive. So we're, it's right. It's obstructive spirometry. You can see the FU and BC ratio is low. So simply call, that's an obstructive spirometry. Uh So it's well below minus 1.64 value that we have previously. So, so that is a very low ratio. OK. So clearly obstructive, that's easy enough. So question four. So essentially we've got a, an F EV one of 1.52 L with an sr of minus 4.03 F EC of 2.02 to sr of minus 4.03. And we've got an F EV and F EC ratio of 75% which is normal sr as well. So if you just, whether there is a normal spirometry, obstruct spirometry or restrict his spirometry, yeah, so far one more be nice fibro anymore. Ok. So we've got six votes. Um, so four people voted for restrictive and two people voted for normal spirometry. Um So, so restrictive is the correct answer. Um So and so it's a well done everyone. Um So essentially what we're looking at the ratio, So the ratio first, that's normal. So you go, if that's normal, you go to the F we see you can see that it's um 2.02 L and it sr is minus 4.03. So it's well below minus 1.645 is the value that we've got. So that's a clearly a restrictive spirometry. I'm glad no one word for obstructive, which is good. So clearly people have been listening. So this is more trickier. Um So I've got a gas transfer here. Um So you've got ATLC O and AKC O here. Um You can see the TLC is 1.63 which is um four minus 4.78. So it's very low and the case is naught 0.44 which is minus 3.29. Again, very low. So do we have here um is, is basically we need to know whether it's gas transfer obviously is reduced but is it reduced due to interstitial lung disease, emphysema, obesity or is this, it could be 1 O2 or it could be 1203. So if you could just answer based on that, got three votes so far, your nose just to go back to the slide, it both TLC O and KC O is reduced. Uh Forget about the corrected value here. But you can see that both TLC and KC O both reduced any more rights. So we've got 44 votes so far and we've got three votes for 1 O2. So, so, um, so essentially either emphasis.