what's up Ninja nerds in this video today we're going to be talking about pfts pulmonary function test this is going to be part of our clinical medicine section if it helps you it makes sense to you please support us and you can do that in many ways one hitting the like button two commenting down the comment section three subscribing and if you really want to you can also support us and yourself by going down the description box below clicking the link to where it goes to our website where we have amazing notes it illustrations questions on top of that even developing exam prep courses and we have merchandise there all of those things are there please become a member and check out all those things that could be useful for your academic career all right let's start talking about pfts though pfts pulmonary function test it's not just one test it's a bunch of like small tests that come together to help you to discern does this patient have an obstructive versus restrictive lung disease and if they do have one of those which one is it is it asthma is it COPD is it a ex transic type of of lung disease for the restrictive categories is an intrinsic lung disease for the restrictive categories and it's really good at sifting that out we'll go through an algorithm I think that'll put all this together let's understand it first so the first thing that you usually do is you obtain lung volumes and this can be done via what's called pmog graphy now what this gives is this gives you a couple different volumes and I think it's actually kind of important to understand this in patients who have obstructive lung diseases their lungs are super big so that these big monstrous hyperinflated lungs their lungs are super compliant which means they want to stretch and unfortunately they're super stretchy and big and distended because they're hyperinflated they're obstructing their airways which causes the lungs to get Dynamic hyperinflation air trapping because of that they keep a lot of air in their lungs even at the end of expiration so because of that their residual volumes are relatively high and so can they also their expiratory Reserve volumes now there's actually a terminology here which is the combination of these two and that's called functional residual capacity here I'll put that as a little kind of note here that this plus this gives you this this is really the key thing in patients with obstructive lung disease their functional residual capacities are like really really high and that's because they can hold a lot of air in their lungs after a full expiratory you know phase now because they can have a lot of air in their lungs that remains in their lungs they don't have a lot of volume that they can take a deep breath in above that so imagine take a deep breath hold it don't expire and then try to take a deep breath on top of that what these patients are living with because of these three things here it makes it so that the actual amount of deep breath that they can take in above their normal title volume is Tiny so they can take potentially normal to lowest title volumes but here's the big thing their ability to take these deep breaths in are usually reduced and that's one of the classic things that you'll see in these patients that hyperinflation leads to reduct reductions in inspiratory volumes okay cool what about restrictive lung diseases and these patients their lungs are super fibrotic they're stiff they don't want to expand they don't have the ability to stretch they're not very compliant at all their elasticity is increased and they want to be the smallest size possible so because of that they don't keep a lot of air in their lungs even after expiration so their Reserve volumes are low their Erv is low which is the amount of air that you can forcefully exhale Beyond a normal tide of volume expiration so because of that if you take the combination of the these two and you look at the functional residual capacity it's also reduced right so you have a reduced functional residual capacity now you would probably think oh okay well if it makes sense of what Zach said if they have a low functional residual capacity they got tiny lungs so they can probably take in deep breaths no unfortunately they can't even take any deep breaths either because it's really hard to expand those lungs it takes a lot of effort and they unfortunately don't generate good title volumes and they don't generate good IVs now with all that being said one of the things that you'll notice is the combination of all of these components so the Irv plus the title volume plus the expiratory reserve Volume Plus the residual volume gives you what's called a total lung capacity the maximum amount of air that these patients can hold in their lungs in this scenario it's gargantuous because of their F FRC so they have a very large total on capacity and this scenario they have a tiny little total lung capacity so their total lung capacity be really really small now a lot of this stuff is all right Zach I see a lot of like abbreviations a lot of different things is there an easier way to remember this so in other words Zach if I get a graph that shows up on my exam or on my pfts and I'm having to read them as a clinician how do I determine if it's more obstructive versus restrictive well sometimes what they do is they use these things called flow volume loops and it kind of takes into consideration all of these things that we just talked about so here in black is going to be the normal patient right and the normal patient from this inspiration to expiration this whole component here is what we refer to as the forced vital capacity for the normal patient and then the amount of air that remains in their lungs right after a forceful expiration is called their residual volume and then from here to here is their total lung capacity this is all in a normal patient now you take an obstructed patient what's the characteristic here and these a s their curve or their flow volume Loop shifts to the left and when it shifts to the left look at now their Force vital capacity so here is the beginning part of inspiration and then expiration now their Force fital capacity in comparison to this one here if you compare these two so this one to this one it's reduced in compared to the normal scenario but look at this crap here from here to here is your residual volume it increases significantly and that again helps you to remember that and then finally if we were to take the combination of these two which is your total lung capacity it's going to be increased in compared to the normal patient look look how much wider that is so that's one of the big things that'll help you is total lung capacity goes up residual volume goes up as a responsibility of the residual Vol going up the Erv will also kind of go up a little bit and so will the functional residual capacity so they can't taking deep breaths now we go to the other patient with restrictive lungs so here's the normal from this point here of the inspiration to this point of expiration is your Force vital capacity this point here from the end of the force vital capacity the amount of air that remains in is your residual volume and then again the collection of these two is your total lung capacity if we look here at this what we notice from restrictive lung diseases is that they shift to the right of the curve and when they shift to the right of the curve what does that do their Force fital capacity in comparison here to this one will reduce significantly actually and then on top of that the residual volume will go down and then if you look at these patients total Lo capacities it's so tiny and that's one of the big things that you'll be able to obtain from these patients when you look at their flow volume Loops obstructed shifted to the left big residual volumes big total UNC capacities restrictive shifts to the right small total Lo capacities small residual volumes that is the big concept to take away all right so we perform this test and we get this it'll help us to say I'm supporting more obstructive versus more restrictive let's go to the next test this is really the hitter this is the mac daddy of most of the kind of PFT tests and that's called Force by ometry what you do is you take an apparatus you take a deep breath in and you breathe out as forcefully as you possibly can and it measures that expiration at 1 second and throughout the entire time that you expire and it gives you this graphical representation we see here now you get two values from this and then you can form a third one is you look at what was the amount of air or volume that expired on the y- axis at 1 second and both of these scenarios look at that was the amount of volume I expired at one second this is called the Fe V one F V1 so that would be the amount of air I can forcefully expire and this would be an obstructive patient afterwards and a restriced patient later right we're going to look at the comparison here what do I notice now holy stink and this patient if I go here and I come over here their fv1 drops significantly so they have difficulty getting air out more particularly within the beginning of expiration so their F1 is massively massively reduced okay here I don't notice as much there's a little bit of a drop off in the fv1 but not as much in comparison to this one but there is a little drop off in the fv1 so they do have a Teensy bit of a difficult time exhaling in the first one second then I look at the forced VTO capacities in the forc BTO capacities and want to form this to be a little bit worse just so you don't get confused here with the graphical representation okay in this scenario here what am I noticing well here this is the end point the maximum point the highest point of the curve is what we refer to and I'm going to say it's like right here as the force vital capacity same thing here kind of flattens out Force vital capacity of the normal patient all right the highest point of the graph here for the Blue Line will tell me what their Force vital capacity is and it's right right here and right here so look at the actual drop and force vital capacity between these two so you're getting the point which one has a worst Force vital capacity the restrictive patient so they usually have a very significantly low Force vital capacity whereas the patient who has obstructive is not as severe so with that being said if you're having a difficult time remember obstructive F1 is the problem restrictive fvc is the problem then from there take the ratio if this number is really really low and this one is just a little bit low the numerator is super super tiny what's going to happen to the F1 over FEC ratio it's going to be low and we say that low is less than 70% all right and that would be suggestive of obstructive lung diseases COPD asthma bronchia acusis one of those for this scenario the numerator is just a little bit tiny but the denominator is the problem here that's really tiny what happens to the overall number it's big you take a number like this okay number divided by a really really small number you're going to get a really big number so generally these are greater than or sometimes equal to 70% so they could be in normal or above normal ranges for restrictive lung diseases so so far if I take a combination of these two tests I will have a pretty good idea if I look at total L capacity residual volume I look at Force vital capacity F1 and F FC I should be able to get a good idea of whether it's obstructive versus restrictive lung diseases so if I had a patient who comes in I get this it shows shifting to the left High total lung capacity High functional residual capacity High residual volume and their fv1 over FC ratio is less than 70 it suggests obstructive whereas they have a tiny total L capacity tiny residual volume F1 over FEC suggests it's greater than or equal to 70% it suggests more restrictive type of diseases then what do I do let's come down to the next test the next test I'm going to do is I'm going to say I have a patient who has an obstructive lung disease and I want to know is it COPD or is it asthma in other words is it irreversible or reversible so what I do is I give the patient a Bronco dilator we call this a short acting beta 2 Agonist and what this will do is this will act on those bronchial smooth muscles and relax them so in this scenario look I can't get very much air out right the f1's probably really low on this one then I give them a Bronco dilator opens up the Airways I can get more air out in the first one second so I would expect my F1 to improve after we give them a beta 2 Agonist and if the F1 does increase that's great but what I need to know is does it increase greater than 12% if it does not it's more suggestive of what obstructive lung disease is secondary to COPD it's an irreversible process I take the asthmatic patient I do the same exact thing I give a short acting beta 2 Agonist goes and acts on these bronchial smooth muscles they super dilate all right now in this scenario Again difficult to get air out dilate them woo baby air be flowing the fe1 should do what it should go up I'm expiring more air now if the fe1 does increase by greater than 12% or at least equal to 12% then I'm more suggestive of a airway disease that is reactive and can be reversed all right cool well how do I even prove this even more more well I know that asthma is both a kind of Rea it's kind of a airway disease that is reversible but also inducible so in other words I can make it dilate but I can make it really really constrict so if I give him another drug called methine which is this short acting Bronco constrictor what would I expect to happen I'd expect the reverse thing to happen I expect them to go from having a dilated Airway to a super constricted Airway and I expect their F1 to drop if their F1 does drop I want to know how much does it drop if it drops by greater than equal to 20% that's suggestive of an inducible airway and if I have both inducibility right and on top of that reversibility it suggest asthma much more so than a COPD all right once we've done that that helps us with that scenario but then let's take it another step we do another test called dlco testing diffusion limitation of carbon carbon monoxide give the patient tiny bit of carbon monoxide sounds terrible right but it's not that bad it's not dangerous give a little bit and you look to see how much runs through the airway and how much diffuses across the actual alveoli into the blood and it'll be dependent upon how much carbon dioxide is detected when they exhale so an obstructive lung diseases what I want to know is what would actually affect the dlcl with an obstructive lung disease well osma is one of those that what it does is we're going to use this it actually decreases the surface area right so that's what obstructive lung diseases would do particularly empyema it causes alveolar sepal destruction it gives these big sucky huge Alvar Airways right or Big Al Airways because of that the surface area drops if surface area drops what does that do to the dlco directly proportional it should decrease the dlco so that would be one thing that I would be able to see in osma that I wouldn't really see in things like asthma I wouldn't really see this in a chronic bronchitis well that's interesting okay so I know that in this one I'm having difficulty with moving gases because of this decreased surface area available for gas exchange in interstitial lung disease or restrictive lung diseases for this matter what I know is if you have a problem where there's fibrosis of the Airways of the interstitial spaces I know that that's going to thicken the respiratory membrane and that's going to decrease diffusion capacity cuz if I increase the thickness I increase the denominator what will that do to the dlco it will also decrease the dlco so these both will decrease the dlco and I'm therefore I'm going to have a difficult time performing gas exchange or diffusion across this thick respiratory membrane or this decrease available surface area for exchange why this is helpful if I if I determine a patient has an obstructive lung disease off of the top two tests I do a Bronco dilator test and they showed that they more suggestive of COPD and then I want to determine is it osma or is it chronic bronchitis low dlco suggest osma rules out chronic bronchitis for the most part in a perfect world restrictive lung diseases I go through I determine they have based upon the top two test restrictive lung disease we don't really do Bronco dilator or Bronco constrictor test for them and then we do the dlco testing if it's low it tells me it's intrinsic lung diseases if it's normal it's suggestive of extrinsic lung diseases and that's super helpful so now what I want to do is I want to tell you guys step through step of how to diagnostically approach pfts let's do that now we check the F1 over the FEC that's the ratio if it is less than 70% that means that it's an obstructive lung disease all right from there check the total lung capacity the residual volume the functional residual capacity and all of those it should be increased and their flow volume Loop would support that that it would shift to the left all right again that's suggestive of obstructive the next thing is to administer a Bronco dilator test because I want to know is it a patient who has asthma or COPD if I do that and there is a greater than 12% increase in their fv1 it tells me that they have a really significant reversibility of their disease so it suggests asthma I could then take it another step further and say okay it's reversible is it inducible give them methine if their f drops to greater than 20% it definitely is suggestive of asthma in the other scenario if it's a less than 12% increase in the fv1 it suggests more of an irreversible process like COPD but which one is it is it osma or chronic bronchitis do the dlco if the dlco is going to be normal it's likely chronic bronchitis but if it's low in the scenarios of decreasing total surface area it's osma all right cool what if I said the F1 over the FC is greater than 7 % it's normal then okay but it could be suggestive of restrictive or normal how do I prove it check the TLC the residual volume and F FRC it would be normal in a normal patient but it would be low TLC RV and functional residual capacity and restrictive and the flow volume Loop would be shifted to the right that would be suggestive of restrictive okay how do I then go further and say restrictive lung diseases could be extrinsic or intrinsic check the dlco if I check the DLC o and there is a change in the lungs itself there's more thickening of the respiratory membrane it'll have a low dlco but if it has no change in that and it's normal DL so it's extrinsic if it's low it's intrinsic and it's an interstitial lung disease and that's how we would go about diagnosing obstructive versus restrictive lung disease based upon pfts all right my friends I hope that made sense I hope that you guys enjoyed it and as always until next time [Music] [Music]