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Current time:0:00Total duration:5:37

Video transcript

so here's an example of a family that's been exposed to a highly contagious respiratory infection called pertussis this disease is also called whooping cough because the distinct noise an infected person typically makes when drawing in air after a lengthy coughing fit and this isn't just a regular coffee it's a powerful forceful cough that continues until all the air has been removed violently from the lungs and it's triggered by a reflex from the lungs responding to a buildup of mucus that occurs when the bacteria causes damage in the airways so let's look into how this cough is generated I've sketched out the muscles that play a role in the cough generation the chest muscles here the abdominal muscles here and the diaphragm muscle which rests just below the lungs and took off these muscles contract inward like this and this and the diaphragm relaxes pushing up on the lungs and the consequence of these muscles actions is to squeeze the lungs so let's look specifically at the lungs and I'm going to erase the muscles here so that I can bring up an image of the lungs all these forces from the muscles reduce the volume of the lungs so I'm showing that here at the dotted line think of this is like a water balloon if you have an untied water balloon filled with water and then you use your muscles to squeeze it the water comes spurting out the top but the Airways that the air needs to travel through are swollen from the infection which means that the air can't get out easily and this causes air pressure in the lungs to build so in the water balloon example think about if we had tied the water balloon off at the top and then squeezed it the water can't go anywhere so as we squeeze the balloon stronger and stronger the pressure builds until the balloon bursts and the same is true for lungs even though we're not tying off the air leaves we're constricting them enough that the air pressure builds and the lungs can actually tear and all the muscles squeezing can cause things like a rib fracture but remember that there's a lot of other organs in the chest that'll be feeling the pressure from the muscles squeezing the stomach for example will respond by emptying its content like the lungs and results in vomiting after coughing fits this is particularly a problem because it happens frequently dehydration and weight loss can occur the bladder also empties its content and leads to incontinence and even circulation is affected blood has trouble returning to the heart through this big vein that drains blood from the head and it backs up this means that the blood slicked air pushing against lungs that caused a tear builds up and pushes against blood vessels and causes delicate blood vessels to break leading to things like bloody nose red eyes and free blood in the head and while a coughing fit is happening a person could cough to the point where they faint from a sudden decrease in oxygen and even if fainting doesn't occur extremities like the fingers while cyanosis or turn blue from a lack of oxygen with all these complications you may be wondering why a violent reflex is so important and it's because the mucus that I'm drawing in the airways and pink builds in the airway because airway damage from pertussis infection makes normal removal of the mucus difficult and built up mucus is dangerous because it's a perfect place for other bacteria that we breathe in to get stuck and cause yet another lung infection in addition to pertussis battling multiple lung infections at the same time is a really difficult job for the body so the mucus needs to be removed with this violent coughing reflex then while all these complications that we just discussed didn't happen to anyone with pertussis there are some groups that have a higher risk of developing them so let's say that grandma has an underlying lung condition her lung functions already compromised and adding pertussis to her burden can lead rapidly to respiratory damage and failure maybe dad has a weak or suppressed immune system this means that his immune system may not be strong enough to fight a pertussis infection maybe grandpa had a vaccine but it was about 10 years ago and his immunity did the disease has decreased over time making him susceptible infants under 1 year old but particularly those under 6 months are a high risk group and this is for a couple of reasons they have an underdeveloped immune system gives small Airways that can accommodate too much swelling and for infants younger than 2 months they can't yet receive the protective pertussis vaccine so Ollis means that about 50% of infants you have pertussis will be hospitalized to stabilize complications from the infection to break this down further by complication in the 50% of infants who will be hospitalized from pertussis the vast majority will have apnea which is stopped breathing the reason probably happens so often in infants is because muscles in their airway tend to spasm in response to mucus building up and when a muscle spasm happens it means the muscles don't allow for breathing to occur in the hospital infants will be closely monitored for apnea and they may even need help breathing with machines but if apnea occurs and they stop breathing their bodies aren't receiving enough oxygen to function correctly so this means that they are prone to seizures from the brain being denied oxygen and about a quarter of the infant's hospitalized will have a secondary respiratory infection this goes back to what we were talking about earlier about how mucus in the airway is a great environment for the bacteria to thrive and unfortunately about two percent of the time these infants will have fatal respiratory failure and there might actually be a way to tell which infants are most at risk for this lymphocytes are cells of the immune system that help fight diseases and pertussis releases a toxin in the body that causes lymphocytes divide to high levels so average levels in infants during the infection can be about 20,000 lymphocytes or microliter of blood and generally the higher that counts the more severe the infection and the more severe the complications leading to respiratory failure