Sleep Apnea and Stroke
In this episode of Kessler Foundation’s podcast, Brian Benoff, MD, FCCP, FAASM, of Holy Name Medical Center, presents “Sleep Apnea and Stroke.”
This is part eight, and the final podcast from the series.
Below is an excerpt from the lecture.
So good afternoon everyone. My name is Brain Benoff. Our practice is pulmonary critical care and sleep disorders. And so we wear different hats in addition to this one, depending on the site of practice. So I'm going to wear the sleep medicine hat for today. Today's topic is sleep apnea and stroke. So sleep, it's important that we all speak the same language.
Before we talk about sleep, I just want to give a general overview to the structure of this talk. We need to speak the same language. So first, we're going to define sleep as the medical community defines sleep. Thereafter, we will then-- once we know what normal sleep is, we can talk about pathological or pathology within obstructive sleep apnea. We can then talk about treatments for obstructive sleep apnea. And finally, we can finish off with how one deals with the post-stroke patient who has obstructive sleep apnea. So in terms of sleep, this is how we find out how the person's sleep is.
Generally, the patients don't look this happy when we do this to them [laughter]. The standard sleep test, the standard montage, it's called a polysomnogram. We've been doing them for decades at this point already. The polysomnogram consists of brainwave activity measurement, so we know objectively when the patient is awake and asleep. So you see the electrodes over the scalp. We measure eye movement. So you'll see one on the lateral aspects of each eye. Those are to help us gauge whether or not the patient is in rapid eye movement sleep. We measure muscle activity, muscle tone, and so there is a chin EMG, which is very easy to see. And finally, we measure chest and abdominal motion as well during sleep. This is important and vital for diagnosing obstructive sleep apnea.
This is how we define sleep. Sleep is not, well, I closed my eyes and I was unconscious and then, whatever happens, happens. So there are classic brainwave activity findings that help us define sleep. We call them stages. So there's stage wake. Stage wake, stage one and two are light or superficial sleep. They used to be-- stage three and four delta wave or slow-wave sleep used to be independent, now they've been grouped together. That's a very, very deep restorative sleep. And then finally, there is rapid eye movement sleep, which is classically when people have dream activity. And so we need all of these to define the stage of wakefulness or sleep. So the EOG, which is the eye movements, they'll be sort of rolling as the person falls asleep. They stop when the person's in deep sleep. And finally, when they're in REM, they're this rapid eye movements back and forth, very dramatic.
Sleep Occurs in Cycles
The EMG, which is muscle tone, which is also important to understand sleep apnea, is high. There's muscle tone while the person is awake. And then as the person falls progressively into a deeper stage of sleep, the muscle tone drops until finally, it's at its lowest during dream sleep. Sleep is not one homogeneous entity. Sleep occurs in cycles. The cycles are generally established in young childhood, and they persist throughout adulthood into old age. Sleep cycles are generally 90 minutes long, and they change as the night progresses.
Early in the evening, one will see a lot of slow-wave or a lot of delta, a lot of deep sleep, stages three and four. And then as the night progresses, one will get less and less, to the point where one may not see any at all. But one will see progressively increased amounts of REM sleep or our dream sleep, which is why when we wake up in the morning, we frequently will remember a dream that we're in the middle of because statistically speaking, you're having much more dream sleep at the end of the night than you're having at the beginning of the night or middle of the night. This is how we would like everyone to feel when they wake up in the morning. I have never met this person, but that's the goal.
So that's normal sleep, so now that we know what normal sleep is and how we define normal sleep and how we conceptualize it, now we can step back, and we can say, "Okay, so what is sleep apnea?" Apnea means not breathing. Hypopnea means breathing just a little. There are strict definitions to score an apnea event or a hypopnea event, and when we combine these together, we will generate something known as the apnea-hypopnea index. That's the amount of time, the average amount of time of partial or complete closures of the airway while the person sleeps.