Sleep wake disorders breathing related sleep disorders

- [Instructor] When we think about breathing problems at night we can think about the problem coming from three key areas. The first one being a problem arising from the brain and the brain being a key central organ that controls the respiratory centers that help regulate the lungs. So, the brain is really important here. And the second one being a problem with upper airways. So if there is any obstruction to the airways from the mouth and the noise to the lungs that can cause a problem. And last but not least, we can also have a problem with the lungs themselves or the chest wall. Anything that stops the lungs from being able to expand out. So, let us take each one of these things as step by step. And let us start by looking at the airways. So, the main issue with the airways is that obstruction to the airways causes a significant problem in terms of breathing at night. And if we consider the air that goes in through our nose and in through our mouth reaches our lungs, we have points at which the soft tissues around our neck may potentially relax at night and they may potentially block this airflow intermittently. They may potentially cause an obstruction to this airflow. And when they cause an obstruction to this airflow you may notice some snoring or gasping. And this suggests that the airflow is being stopped. That term is, for a lack of airflow, it's called an apnea. And all that apnea really means is that there is an absence of airflow. So, if the airways are obstructed we can have something called Obstructive Sleep Apnea. And this condition, Obstructive Sleep Apnea, is actually very common. It gets worse as people get older. These soft tissues block this airflow that we have and this condition actually results in a variety of daytime and night-time symptoms. So, we actually mentioned some of the night-time symptoms, right? We mentioned this kind of snoring, gasping for air, and these kind of apneas, these kind of pauses, breaks in the breathing where there's a lack of airflow. This condition also poses problems during the daytime because during the daytime people can feel very tired and sleepy. And they may particularly comment that their sleep is never refreshing, so they wake up feeling unrefreshed. So, that's a little bit about this Obstructive Sleep Apnea. And the way that we diagnose it, we do a sleep study or a polysomnography. And what we're looking for is 15 or more of these apneas that not only have pauses in the breathing but you can also demonstrate evidence of the person's having obstruction in the airways per hour. And that's done on the sleep study, on the polysomnography. So, that's a little bit about Obstructive Sleep Apnea. That's a very important cause of Breathing Related Sleep Disorders. Alrighty. So, we've got obstructed sleep apnea but what happens if there's something that is wrong with the actual brain? Now, the brain is part of the central nervous system, right? So this is actually termed something different. This is termed Central Sleep Apnea. So, the way that we can thing about it, again, we have this apnea, which is this lack of... Complete stop in airflow. We have sleep cause it's going to happen at night, the breathing's going to be effected at night, and we have central because the brain is part of the central nervous system, and that's where there's a malfunction of the centers that help control breathing. And what we're looking for here is the presence of these apneas but there is no obstruction. Again, on the polysomnography we're only looking for five or more. These are kind of the arbitrary criteria that are used. We're looking for five or more of these apneas per hour to be happening during sleep. And really when we think about the apneas we believe that the Central Sleep Apnea, that there's a problem with the brain's control system for ventilation. So basically, the parts of the brain that help control the breathing, they are malfunctioning. Now, I'm just going to talk to you about a particular type of breathing malfunction that happens in the Central Sleep Apnea. And I'm just going to spend a second on that. If we consider our normal breathing to be in and out; inhale, exhale, inhale, exhale on this graph there's a particular type of breathing that we see sometimes in Central Sleep Apnea and it looks something like this. It's a crescendo-decrescendo apnea type displace. So, let me show you. So, we have the crescendo decrescendo then we have an apnea. No breathing. And then again it starts. Crescendo, decrescendo, apnea. And it carries on like that. And this is actually something that's called Cheyne-Stokes Breathing. And with this Cheyne-Stokes Breathing we believe that this is particularly related to Central Sleep Apnea that's as a result of heart failure, strokes, and renal disease. Renal failure, I should say. Okay. So, we talked a little bit about the brain being a site of malfunctioning and we talked a little bit about the airways being a site of obstruction. Now, finally the lungs. The lungs need to inflate and deflate when we breath in and out. So, any process that stops the lungs from inflating or deflating appropriately is going to cause us a problem. So, when we think about the lungs we can actually have something called Hypoventilation Disorders. Disorders of sleep associated hypoventilation. And when we say hypoventilation normally when we breath in and out we get rid of carbon dioxide but unfortunately when we don't breath in and out enough, when we don't ventilate our lungs enough, we can get a build up of carbon dioxide. And in some cases we can also not have enough oxygen. Now, these kind of hypoventilation problems with our breathing can occur because there's a problem with the lungs, the chest wall, if we're using some medications that depress our respiratory function. Like narcotic painkillers for example. If somebody is very obese and just the sheer amount of obesity reduces their ability to breath in and out and ventilate their lungs. And the problem here is that this chronically elevated carbon dioxide poses a problem because it can actually result in right sided heart failure. And never mind our low oxygen because one of the things that we know is that our brain, our heart, pretty much all the organs in our body need oxygen to function. So, if we have a low oxygen we're going to have problems with our brain over time, especially chronically, we could have a degree of cognitive impairment. We may have problems with our heart. Some people may develop arrhythmias, abnormal heart rhythms. Again, over time. And also our blood as well. So, we can develop polycythemia which is a very elevated amount of red blood cells in our blood. And this can also be a problem. That can cause it's own huge range of complications. So, as we can see here, Breathing Related Sleep Disorders, we can really break them down into these three big categories. Are they related to the airways? Obstructive Sleep Apnea. Are they related to the brain? Central Sleep Apnea. Or are they related to the chest wall, the lungs, this kind of sleep associated hypoventilation conditions or disorders?