Asthma Explained Clearly (Remastered) – Pathophysiology, Diagnosis, Triggers
22
August

By Adem Lewis / in , , , , , , , , , , , , , , , , , , , , , , , , , , /


welcome to another MedCram lecture we were talking about asthma and specifically the causes the pathophysiology diagnosis and treatment of this very common disease I want to kind of show you what’s going on at the bronchial level you remember if you look at our pulmonary function test discussion we looked at a flow volume loop and what happens when you blow out air very quickly your forced expiratory volume or flow rate goes up very quickly and then comes down and then you take a inhalation in and thus obstruction that occurs in asthma and in COPD occurs in this area here which is the small Airways and as that obstruction gets worse you see a decrement in the flow rates especially later on in blowing out and the point here I want to make is that these are the small Airways so this is where asthma is occurring it’s obstruction of these small Airways not the large ones but the small ones and as such I want a diagram what it is that’s going on so you’ve got the airway and this is a very simplified version of what it is that’s going on you’ve got this lumen of the airway that’s here and as you may know it is lined with smooth muscle when that smooth muscle contracts this lumen gets smaller okay so there’s two major things that are occurring in asthma or obstruction of these small Airways is you’ve got some sort of an inflammatory process for whatever reason that’s going on here this inflammation stimulates certain cascades that occur and it causes smooth muscle constriction and as a result the inflammation causes the lumen to get smaller and smaller and smaller until finally there’s wheezing there’s obstruction and the primary problem is that you can’t get air out of these small Airways and that is why in an asthma attack you will see that this flow volume loop comes down and the flow rates in these small Airways is almost non-existent that’s when you run into asthma attacks now the severity of this contraction is going to give you the severity of asthma attack and how we affect this and what the pathophysiology is of this is going to determine how this is treated so let’s talk about that a little bit once again I want to emphasize that in asthma what we have is reversible airway inflammation that is opposed to air reversible which we would see in COPD where this airway inflammation has occurred and this constriction has occurred in COPD it’s kind of irreversible in asthma we can actually reverse it back to almost completely normal this inflammation and constriction can sometimes be mediated by IgE so sometimes you will see elevated IgE levels and that fits into the pathophysiology and the treatment what is IgE it’s an immunoglobulin specifically it’s an immunoglobulin E and that’s important because immunoglobulin E affects a cascade that releases histamine which causes swelling which is going to make the area in that Bronco even smaller IgE uses the basophils and mast cells these release histamine there are ways of preventing these cells from releasing histamine and that is sodium chromo gleich 8 you’ll see for instance medications like Chrome illan sodium criminal glycated is used to stabilize these mast cells and basophils and prevent histamine so sometimes we actually use that in the treatment of asthma ok so again I want to review the bottom line here is is that we’ve got a situation where you have inflammation which causes constriction of the smooth muscles in the bronchioles so let’s talk a little bit about this smooth muscle then okay we’ve got nerves that affect this smooth muscle two types of nerves specifically and they have receptors the first one I want to talk about is the beta receptor so you have a nerve that come down and releases compound which hits this beta receptor and this causes relaxation and there’s another receptor which is the muscarinic receptor and that causes constriction and so in both asthma and COPD as it turns out we want this muscle to be relaxed that’s the goal we want relaxation and so what we’re going to actually end up doing is activating this receptor and blocking this receptor and so what you see is pharmacologically we’re going to be using anti muscarinic s’ and we’re going to be using beta agonists that’s how we get to the treatment now the other thing that we’re going to see pharmacologically and we’ll talk about this is inflammation inflammation is going to cause constriction because of inflammation so what we’re also going to use is anti-inflammatories so what I’ve just shown you here are the three cornerstones of asthma treatment some of them are going to be used first because they’re much more effective than others and you could probably guess which one is going to be most effective because inflammation is starting everything off the anti-inflammatories are gonna be number one the beta agonists are gonna be number two and the anti muscular necks are gonna be number three okay so we’ll get into the pharmacology of that let’s talk about the pathophysiology about perhaps clinically where this inflammation may be coming from things that can trigger problems in our Airways based on a number of things first of all because of the stuff that we breathe in so that’s a trigger the air that we breathe what else could trigger asthma what else could be causing it well there’s a tube that sits right next to the trachea which goes down to the stomach called the esophagus and sometimes stuff in the stomach can reflux up and irritate the airway that continues up so another thing that can cause this is gastroesophageal reflux disease that can sometimes cause symptoms of asthma now if we go up here we have the nasal passageway sometimes you can have allergies that drip down and cause irritation in there so then post nasal drip can cause asthmatic symptoms and so whenever you see a patient with asthma or you’re asked about on a test you should think about these things as causing asthma so what we call coffee variants asthma post nasal drip and gastro esophageal reflux disease some of the other things that can contribute to all of these think about down feather pillows pets in the bedroom these are places that you spend a good six seven eight hours a day and could affect some of the treatment symptoms so these are some of the things that by getting rid of we might improve asthma there’s also environmental things and things from work for instance from your occupation there’s something called isocyanates or cotton dust wood dust solvents all of these things can by breathing the men set off asthma exacerbations there’s one other thing that I should make you aware that they might ask you on a test they love to ask things that are uncommon in asthma that could be very unique or make you think of something and there’s something called samplers triad where you see number one aspirin sensitivity number two asthma and number three nasal polyps now when these people take aspirin or any type of NSAID what can happen is that these medications inhibit cyclooxygenase and as a result they’re going to have increasing compounds that are going to set off asthma exacerbations the key here is that within hours of taking aspirin they’re going to start to feel flushed and they’re going to go into an asthma exacerbation these patients who are typically sensitive to aspirin or NSAID products are also going to have nasal polyps the key here is that they need to stop using aspirin and NSAID products and find an alternative these patients by the way and we’ll talk about treatment also respond very well to leukotrienes antagonists and we’ll talk about those so just remember Sanders try it in your patients with asthma ask him if they’ve had a history of aspirin sensitivity or if you’ve noticed that their symptoms have gotten worse after taking aspirin or NSAIDs and then ask them about a history of sinus problems maybe even sinus surgery or nasal polyps okay we’ll join us for part two where we talk about the diagnosis and the treatment of asthma you


6 thoughts on “Asthma Explained Clearly (Remastered) – Pathophysiology, Diagnosis, Triggers

  1. Thank you for the videos. I am a practicing Paramedic and would like to see some videos in the prehospital setting. Every now and again I see some good medical calls. Any tips will be appreciated!

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