Wrapping It Up

Hello all,

This is it. Tomorrow is my last day at Phoenix Neurological Institute. I can't believe how fast time has gone by. I still remember how scared I was to start interning back in February. I didn't want to drive all the way to Chandler three times a week.

Now, I can say I am very glad I got this opportunity. I learned a lot under the mentorship of Dr. Farrukh Qureshi and Dr. Yeeshu Arora. I would like to express my gratitude for allowing me to intern with them. Both of them let me get involved and ask questions and I learned things that I will never forget, such as life lessons.

I would also like to take a moment and thank BASIS Phoenix for giving me the chance to pursue a Senior Research Project and I would like to thank Ms. Brittany Holtzman for guiding me and helping me find the correct resources for my research.

This research project has been a success and has taught me a lot. I will be sharing my experiences with everyone at the presentations next Sunday, May 6. My presentation is scheduled at 10 am in the Gym and is open to all. I look forward to seeing all of you there and sharing my experiences with you.

I have attached my final presentation. Once again, thank you to everyone who has made this project a big success and great experience for me. I can happily say that I have learned many things that will stick with me for the rest of my life!

Warm regards,
Shubhangi Awasthi
BASIS Phoenix
Class of '17

Senior Project Presentation

Sleep Apnea and Cognition, pt 3

This is it! My second-to-last post! We are almost done!

In this post, I will be talking about the effect sleep apnea has on executive functions and memory. Executive functions are the processes that allow us to manage ourselves. They allow us, for example, to prioritize tasks, tell right from wrong, etc. Working memory and problem solving are one of the examples of executive functions.

Executive functions:

• Problem solving and planning: In a study done, subjects were timed to see how long it took them to complete the Tower of London Test (a video is attached below). Sleep apnea patients consistently had a longer response time. The Torrance Test of creative thinking was also performed, and deficits on this test were observed in sleep apnea patients.
• Working memory: Working memory is the memory that temporarily holds information for processing. Subjects in a study were given simple working memory tasks. An example is asking the subject to read multiple sentences and remember the last word of each. Decreased response times and reduced accuracy were observed in sleep deprived individuals and sleep apnea patients. This can also be explained by the fact simple working memory tasks require attention, but attention is impaired in sleep apnea patients.

Description of Torrance Test of Creative Thinking

Sleep deprivation also impacts memory in other ways. Sleep is important for the consolidation of memories. Different kinds of memories are consolidated in different stages of sleep. For example, REM sleep plays a crucial in the consolidation of procedural memory. Procedural memory is the memory responsible for knowing how to do things and motor skills. Thus, sleep apnea and sleep deprivation impacts the brain’s capacity to commit new things to memory.

Sleep Apnea and Cognition, pt 2

From reading articles, I have found out about many different experiments done to test for deficits in cognitive abilities in sleep apnea patients.

Response Time Experiment:

Sleep apnea patients showed a decrease in speed in simple response time tasks and choice response time tasks. Simple response time tasks are tasks in which one stimulus is given and one specific response is expected. An example would be a task in which a light is the stimulus and every time the subject sees the light go on, he has to press a certain button.

A choice response time task in one in which multiple stimuli are given and each stimulus requires a different response. An example would be a task in which the stimulus is seeing a letter on the screen and the response would be pressing the corresponding letter key on the keyboard. A study done showed that sleep apnea patients had a decreased reaction time for both kinds of tasks.

Short-Term Memory:

On auditory, spatial, or visual short-term memory tasks, the accuracy of the performance of OSA patients has been mixed. However, imaging of the brain has brought clearer results. Sleep deprivation in OSA patients has shown decreased activity in the intraparietal sulcus (IPS), the green line in the picture below. The IPS plays a key role in processing numbers and in visual working memory (I will talk about this in the next post). The reduction in this region of the brain was linked to a reduction in the memory capacity shown by the study.

Mental Arithmetic:

In mental arithmetic studies, sleep deprived patients have had slower performances and more errors. The study shows that small decreases in sleep and disturbed sleep can severely affect performance on tasks similar to the ones done.

Neuroimaging conducted during the serial subtraction task also showed decreases in the prefrontal cortex, the front part of the frontal lobe (shown below), which is responsible for tasks like problem solving and processing complex thoughts. It is also known to play a role in emotions. Imaging also shows abnormal activation of the parietal lobe (shown below), which integrates sensory information.

These are only a few of the many things that are affected by sleep loss and sleep apnea. I will go further into executive function in my next post.

Stay tuned!
Waters, Flavie, and Romola S. Bucks. "Neuropsychological Effects of Sleep Loss: Implication for Neuropsychologists." Journal of the International Neuropsychological Society 17.04 (2011): 571-86. Web. 16 Apr. 2017.

Preparations for the End of the Year!

Hello all,

Yesterday, I finished up a rough draft of my final presentation. Watching all of my work from the last three months culminate into a final product like this was very satisfying. Now, I am working with my BASIS Phoenix advisor to make edits to my powerpoint. I have also started writing my paper and planned out how I will be doing my poster. In my opinion, this is the best part of the project because this is where I get to realize how much I have learned throughout my time at my internship. I am very excited to finish writing my paper and I can't believe the end of the year is almost here! Thank you all for joining me through this journey and I hope you got to learn a lot!

~Shubhangi 

CPAP!

One of the treatment methods for sleep apnea is Continuous Positive Airway Pressure (CPAP) therapy. CPAP machines gently blow air at a constant pressure through the airway to keep it from collapsing.

The Machine:

The CPAP machine has three main parts, the motor, the hose, and the mask. The motor takes in room temperature air and pressurizes it. This way, air at the best pressure for the patient is delivered. Most newer machines have a built-in humidifier. These machines are great for patients who wake up with a dry mouth or throat.

The hose is the part of the machine that transports the pressurized air from the motor to the mask. The CPAP mask is the part of the machine that delivers the air to the patient’s airway. Masks come in different shapes and sizes since not all people will feel comfortable wearing each kind of mask.

There are three main categories of CPAP masks:

1. Nasal pillows: lightweight and smallest and are ideal for claustrophobic people
2. Nasal masks: triangular shaped mask that fits over the nose
3. Full face masks: covers the nose and the mouth
   

Getting Set Up With CPAP:

From the patient visits I have been in with Dr. Qureshi and Dr. Arora, I have seen that the first step in getting CPAP is having a sleep study (polysomnogram) done at a sleep clinic. The results from this study will tell the doctor how severe the sleep apnea is.

If the doctor determines CPAP is the best option, then he orders a follow-up sleep titration sleep in which the patient sleep at a sleep clinic overnight. There, he tries on different types of CPAP masks and uses different machines to see which one best fits his needs. The technician determines at which pressure the patient’s AHI is the lowest.

After getting a CPAP machine, the patient must make sure he uses it regularly (every night). If he stops using it, the symptoms of sleep apnea can return.

Results:
CPAP is really effective for treating sleep apnea. It decreases the amount of daytime sleepiness the patient experiences and improves the overall quality of sleep. It also prevents serious health conditions like cardiovascular diseases and lowers blood pressure during the day and night. As I mentioned in my last post, studies have also shown that CPAP therapy has also reversed tissue loss in different areas of the brain.

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

Sleep Apnea and Cognition

So far, I have talked about how sleep apnea and other sleep disorders cause physiological problems such as more weight gain and a weakened immune system. In this post, I will be talking about how they affect the structure of the brain itself.

Sleep apnea is known to affect cognition and mood. Patients suffer from mood instability and show a lot of cognitive deficits, especially impairment to attention and executive function. They are also emotionally reactive.

The cause behind this is still being researched. One possible reason this may happen is that repeated episodes of the airway collapsing and the patient not breathing during the night causes a reduction in the amount of oxygen the tissues of the brain receive. This causes gray matter loss in different areas of the brain.

One such area is the frontal cortex. This structure is responsible for executive function, or the self-regulation skills that allow us to plan things, manage time, and do other things. It is also associated with working memory.

Other areas in which gray matter loss due to sleep apnea occurs include the thalamus, the hippocampus (the structure that controls memory), and the amygdala (the structure that is associated with emotions). Therefore, this may be a reason why cognitive and emotional difficulties are seen in patients with sleep apnea.

OSA also causes tissue loss in the temporal and parietal lobes, which are responsible for attention and visual-spatial processing.

This tissue loss, however, is shown to be irreversible. Studies have been done which show that CPAP Therapy can reverse gray matter loss for OSA patients. CPAP Therapy is one of the treatment options for OSA patients and I will going further into it in my next post.

Source: Olaithe, Michelle, Shenooka Nanthakumar, Peter R. Eastwood, and Romola S. Bucks. “Cognitive and mood dysfunction in adult obstructive sleep apnoea (OSA): Implications for psychological research and practice.” Translational issues in Psychological Science 1.1 (2015): 67-78. 3 Feb. 2017.

Women Suffer More

Women are more likely to suffer from disturbances in sleep, and thus, sleep disorders. Biological conditions like pregnancy and hormonal changes can affect how well a woman sleeps. For this reason, many women suffer from sleep disorders like insomnia and sleep apnea.

Hormonal fluctuations during menopause and menstruation may cause women to not sleep well at night. They may also cause weight gain during menopause. Weight gain, as we know, increases the risk of getting sleep apnea.

Pregnant women are also susceptible to sleep apnea due to the weight they gain. Pregnant women who have sleep apnea are very prone to developing hypertension and diabetes. During pregnancy, hypertension can cause conditions like preeclampsia and eclampsia.

Preeclampsia symptoms include swelling of the hands and feet. When preeclampsia goes untreated, eclampsia occurs, which can eventually lead to coma and the death of the mother and the child.

Sleep disorders like OSA not only affect the mother but also the fetus. Sleep apnea restricts oxygen to the fetus, which can result in birth defects and developmental disabilities that can last for the child’s lifetime. The outcome of the mother’s oxygen level dropping and oxygen to the fetus being cut off is unpredictable and scary.

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

Sleep and Mental Health

Sleep problems used to be viewed only as symptoms of psychiatric disorders, but research has shown that they can actually contribute to mental illnesses. This research also indicates that treating the sleep problems have helped alleviate mental health problems.

Depression. Most patients with depression have insomnia, and some also suffer from obstructive sleep apnea. It can also work the other way in that people with sleep problems are more likely to develop depression. Additionally, depressed people who continue to experience problems with sleep are shown to be less likely to respond to treatment.

Anxiety disorder. Sleep problems are really common in those who suffer from anxiety disorders or post-traumatic stress disorder (PTSD). Anxiety may contribute to sleep loss in that many times people let their trouble interrupt their sleep at night. Additionally, insomniacs may also develop anxiety disorders. Insomnia may also make treatment for anxiety less effective.

ADHD. Children with ADHD experience many sleep problems, including difficulty falling asleep and restless sleep. Breathing problems like sleep apnea and restless leg syndrome can also affect children with ADHD. Children with ADHD are inattentive, hyperactive, and emotionally unstable and sleep disorders only worsen these symptoms.

Mania and Bipolar Disorder. Episodes of mania in bipolar patients can be triggered by lack of sleep. Research also shows that ongoing sleep problems can worsen episodes of mania or bipolar depression.

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

Sleep and the Immune System

In addition to obesity, lack of sleep can cause many physical ailments. People who get insufficient sleep suffer from weaker immune systems.

Ongoing research shows us that there is a complex relationship between sleep and our immune systems. Parts of our immune systems control sleep and how much sleep we get impacts how well our immune systems function.

The immune system provides defense against infectious organisms. Many different cells, tissues, and organs are involved in mounting an immune response. The most important are lymphocytes. We are most familiar with B cells and T cells. Each type has a different method of fighting off infection. B cells produce antibodies to infectious microorganisms.

Cytotoxic T cells, on the other hand, kill the cells that are infected. Helper T cells assist other blood cells in the immune response. Once they become activated, they divide rapidly and release cytokines and interleukins that aid the immune response.

During sleep, the immune system also releases cytokines. Thus, sleep deprivation, especially that of REM sleep or other stages of deep sleep, can result in a decrease in the amount of cytokines produced. Additionally, the production of antibodies is also reduced when we don’t get enough sleep, creating a weaker immune response to any foreign substance.

Long-term sleep loss can result in higher heart rates and blood pressures and lead to cardiovascular diseases and diabetes. This does not mean that we need to sleep more than normal to bolster our immune system. Consistency is the most important thing to having a healthy immune system and maintaining sleep hygiene.

Stay tuned for more!

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

Sleep Loss and Hunger

In this age of cellphones in every pocket and headphones in every ear, it’s no wonder most teens do not get enough sleep. Sleep-deprived teens suffer from various problems. Their health suffers, they experience mood problems, and their performance in school suffers.

These are only a few of the adverse effects of sleep loss. Another one includes weight gain. Poor sleep hygiene is one of the main causes of obesity. Teens who get inadequate sleep say they are too tired to exercise. Thus, they “burn less calories.”

Additionally, lack of sleep disrupts the key hormones involved in controlling hunger, leptin and ghrelin. Leptin inhibits hunger. It tells ours bodies to stop eating when we are full. Ghrelin, also called the “hunger hormone,” stimulates hunger.

Inadequate sleep results in more production of ghrelin and less production of leptin. The result? We keep on eating and gain weight.

The weird part is that obesity increases the risk of getting sleep apnea. Additionally, obesity and sleep apnea share common health risks like hypertension and diabetes. Sleep apnea also causes sleep deprivation, which in turn causes obesity. So, sleep loss causes obesity, which causes more sleep loss...where does this cycle end?

Source: Judd, Sandra J. Sleep disorders sourcebook. Detroit, MI: Omnigraphics, 2010. Print. 

Caffeine Kicks in, part 3

Hey everyone!

Last post of the week! I’ve been talking a lot about caffeine and its effects on adenosine and dopamine levels. I am going to end this week off by talking about another really important hormone, adrenaline.

Caffeine makes us more alert by prompting the release of more dopamine and speeding up the electrical activity in the brain. This in turn stimulates the adrenal gland to release adrenaline, or epinephrine, and the result is a response similar to the “fight-or-flight” one.

You may have wondered about the mechanisms behind this response. Why do our bodies react the way they do when put in a stressful situation? Why does our heart rate increase? Why does our blood pressure rise?

All of this is controlled by one specific branch of the nervous system, the sympathetic nervous system. When we are required to take action really fast, this branch of the nervous system signals to the adrenal gland to release adrenaline.

The result is an increase in heart rate and blood pressure. The pupils dilate and veins constrict to allow for more blood flow to the heart. The digestive system shuts down so more energy can be put to deal with the stress.  Smooth muscles relax so more oxygen can flow into the lungs.

Therefore, when we drink something that is caffeinated, the result is…MORE ADRENALINE! Adrenaline prepares the body for activity. Now, the body is primed for action, definitely not for sleep! 

P.S. I’ve attached a picture relating caffeine and all of the neurotransmitters I have talked about.

Source: Judd, Sandra J. Sleep disorders sourcebook. Detroit, MI: Omnigraphics, 2010. Print. 

Caffeine Kicks In, part 2

Hello everyone! I hope you had a restful spring break and are ready for some more good stuff about sleep disorders!

Before break, I talked about how caffeine affects the body by taking up adenosine receptors and preventing adenosine from binding. This week, I am going to talk about the effect caffeine has on neurotransmitters like dopamine and adrenaline.

Let’s leave adrenaline for later and talk about dopamine now. Dopamine is a neurotransmitter responsible for controlling emotions and motor abilities. It also controls cognition and feelings like pleasure.

Caffeine causes an increase in the production of dopamine. This elevates our moods, which results in an increase in brain activity and neuron firing. When our brains generate a lot of electrical activity, it is harder for us to fall asleep.

Researchers also consider dopamine the cause of caffeine addiction. This is because some of the withdrawal symptoms of caffeine include mild depression, irritability, and other emotional changes that dopamine is responsible for.

Sorry for such a short first post this week. In my next one, I’ll elaborate on the relationship between caffeine and the neurotransmitter adrenaline.  

Caffeine Kicks In, part 1

I am going to end this week off by starting to talk about caffeine. When many people drink tea or coffee, they tend to stay awake longer. This is because caffeine is a stimulant; it makes people alert and gives them more energy.

Caffeine affects many neurotransmitters and hormones in the body. In this post, I will talk about one of them, adenosine. Adenosine is the neurotransmitter that inhibits many processes associated with wakefulness.

Adenosine levels build up throughout the day and fall rapidly when we sleep. High levels lead to sleepiness and blocking adenosine’s actions results in an increased alertness. A stimulant like caffeine blocks adenosine’s actions.

Caffeine looks like adenosine to a neuron. It works as an antagonist and binds to the adenosine receptor, as shown below. Caffeine molecules take up all of the adenosine receptors and adenosine cannot bind. It does the opposite of what adenosine does and speeds up the neuron’s electrical activity.

The effect caffeine has on the neuron is it increases the number of times the neuron fires. This causes more sympathetic nervous system activity and the pituitary gland, or “master gland,” releases hormones that prompt the release of adrenaline (I will talk about it in the next post).

This release of adrenaline results in the pupils dilating, the heart beating faster, the blood pressure rising, blood flow to the stomach slows and blood flow to the muscles increases, and the liver releases more sugar.

The next few posts will cover the effect caffeine has on other chemicals, like dopamine and adrenaline. Next week is BASIS Phoenix’s spring break and I will also be taking the week off and going out of town. So, see you all after spring break!  

~Shubhangi 

Source: Judd, Sandra J. Sleep disorders sourcebook. Detroit, MI: Omnigraphics, 2010. Print. 

Periodic Limb Movement Disorder (PLMD)

My latest post was about Restless Leg Syndrome (RLS), a disorder in which patients experience uncomfortable twitches and prickly feelings in the legs.

About 80% of RLS patients also experience periodic limb movements. Patients with periodic limb movement disorder (PLMD) complain of insomnia and frequent awakenings during the night, sometimes due to excessive leg jerking. They also kick during their sleep.

I am going to go a little deeper into PLMD in this post. PLMD patients typically display periodic contractions of the tibialis anterior (shown in the picture below), a muscle in the leg that plays a role in the dorsiflexion of the toes and ankle. Dorsiflexion is the action of moving the foot in an upward direction. For this reason, PLMD patients also sometimes experience periodic dorsiflexion, which causes a leg jerk or a kick.

           

                             

PLMD also affects the quality of life in general. For instance, many patients cannot travel in airplanes or drive for long distances in cars. They also cannot sit and enjoy movies because they constantly need to be walking around to alleviate the tingling sensation in their legs.

Having this condition has caused many people to make drastic lifestyle changes. Some people have quit their jobs due to amount of discomfort they felt. Additionally, one patient suffered from this condition as a child. He was excluded and humiliated by the way he was treated, and he eventually entered a period of depression.

PLMD tortures patients during the day as well as during the night. During sleep, the patient is usually not aware of the leg jerks. He is, however, aware of waking up frequently. Thus, his sleep is fragmented. For this reason, PLMD can cause excessive daytime sleepiness. It is also a problem to bed partners in that they complain of the patient being very restless and kicking frequently.  

This speaks to the seriousness of this condition. PLMD is one of the causes of sleep disorders like insomnia and can force patients to reconsider their lifestyle altogether.

More to come soon!

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

What is Restless Leg Syndrome?

Hello everyone,

In the previous post, I mentioned that sleep disorders can be caused by chemical imbalances. In this post, I will talk about a physiological reason behind sleep disorders.

As well already know, physiological reasons are what cause sleep apnea. Abnormalities in other parts of the body may also cause sleeplessness. Research suggests that restless legs may be keeping people from getting proper sleep at night.

In the 1990s, there was not much known about restless leg syndrome (RLS). The doctors did not know what to do when their patients complained of staying up at night due to uncomfortable twitching and a prickly sensation in the legs. Now that we have become more familiar with RLS, it is easier to diagnose.

There are many things that can cause RLS:

1. It is believed to be hereditary, which means it runs in families and is passed on from generation to generation.
2.  It can be caused by peripheral neuropathy, or damage to the nerves in the legs.
3. Anemia, or a deficiency of red blood cells, can cause RLS.
4. Many pregnant women suffer from RLS, probably due to the pressure on nerves and blood vessels resulting in a restricted blood flow to the legs. RLS usually clears up after giving birth.
5. An iron deficiency can also cause RLS.

Many of the patients that have RLS also experience a condition called periodic limb movement disorder (PLMD). This can affect people during the day as well as the night, making this such a serious condition. In later posts, I will talk about PLMD in more detail. Stay tuned!

Melatonin

Before going deeper into how the different sleep disorders can affect the brain, I would like to touch upon a couple things that play a role in causing problems with sleep.

Anxiety, stress, and emotional problems all contribute to sleep disorders.  Additionally, according to research, many sleep disorders are caused by chemical imbalances in the brain and body. One of the hormones that appears to influence circadian rhythms is melatonin.

Melatonin enhances people’s ability to fall asleep. Its secretion is regulated by the pineal gland. The pineal gland is pea-sized pineal gland located in the center of the brain (pictured below).

The production of melatonin is controlled by the amount of light information relayed to the pineal gland from the suprachiasmatic nucleus (SCN). Secretion can be blocked by exposure to bright light at normally dark times (this is why they say that using our phones at night is eating away our sleep).

This is the reason night shift workers suffer from circadian rhythm disorders.  They sleep during the day when the sun is rising and their eyes are absorbing light when they are trying to sleep.

The cycle of regular melatonin release throughout the night is shown below. In most people, the pineal gland starts release melatonin a few hours before bedtime. It continues releasing it throughout the night. Production slows as we wake up and absorb the new day’s light.

It is also interesting to note that as we age, the amount of melatonin produced by our pineal glands decreases. This may be why many older adults have a more difficult time falling asleep.

Until next time!

Polysomnography (PSG)

The basics of PSG:

One of the diagnostic tools used in sleep medicine is polysomography (PSG), a type of sleep study. It is used to diagnose or rule out sleep disorders. It records several physiological variables, such as eye movements, brain functions, muscle activity, heart rate, respiratory effort, and oxygen saturation.

Typically, about 12 channels are recorded through PSG. Depending on the condition of the patient, more channels may be added. Patients with sleep-related breathing disorders may be studied using more measurements, such as esophageal pressure and expired air carbon dioxide, which provide clarification on the respiratory status. Patients with movement disorders may have electrodes put on multiple muscles and so on.

The procedure:

The examination normally takes place at night, but can happen during the day for day shift workers. The patient needs to report to the laboratory about 1.5 hours before his normal bedtime to ensure there is enough time to apply the electrodes. Then, the lights are turned off and the patient is allowed to sleep overnight. The recording times normally last about 7.5-8 hours.

Components of a PSG:

1. Electroencephalogram (EEG): measures electrical activity of the brain
2. Electrooculogram (EOG): measure activity of the eyes
3. Electromyogram (EMG): monitors leg movement during sleep
4. Electrocardiogram (ECG or EKG): measure electrical activity of the heart 

The results of a PSG:

The technician uses the information from the test to chart the patient’s sleep stages and cycles. This report is analyzed by the physician.

One of the components of the report includes the Apnea-Hypoapnea Index (AHI). This number is the number of apneas and hypoapneas in one hour during the sleep study. An apnea is the cessation of breathing for at least 10 seconds, while a hypoapnea is a decrease of airflow that lasts at least 10 seconds. Based on the AHI, we can tell how severe OSA is:

• ·         AHI<5: minimal OSA
• ·         5≤AHI<15: mild OSA
• ·         15≤AHI<30: moderate OSA
• ·         AHI≥30: severe OSA

Some patients have an abnormally high AHI, sometimes even above 100. This shows the seriousness of the obstructive sleep apnea and how necessary it is to seek treatment before it causes problems in other parts of the body. 

Until next time!

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.

Obstructive Sleep Apnea (OSA)

As a recap, in my previous post, I talked about various sleep disorders, including sleep apnea. There are two types: central and obstructive. In this post, I will be talking about obstructive sleep apnea. 

OSA is caused by the collapsing of the airway. When we inhale, the diaphragm moves downwards. This creates more room in the chest cavity for the lungs to expand. There are many things that can contribute to OSA. Some patients have a small oropharyngeal airway. The oropharynx is the part of the throat located at the back of the mouth. It includes the tonsils, the soft palate, and the base of the tongue. It also appears that in many OSA patients, muscle hypotonia, or a decreased muscle tone, combined with airway obstruction causes apnea.

The consequences of sleep apnea can be divided into two categories: medical effects and effects on sleep. This cessation of airflow results in a decrease in oxygen saturation of the blood. Oxygen desaturation is most severe when the apneic event is really long.

Additionally, during an apneic event, the pressure in the systemic artery, arteries that carry oxygenated blood away from the heart, and pulmonary artery, the artery that carries deoxygenated blood from the right ventricle of the heart to the lungs, increases (systemic and pulmonary circuits are shown in the picture below) Repetitive apneic events can cause a stepwise increase in both pressures. This means that OSA may cause problems like chronic systemic hypertension and cardiac dysrhythmias.  

Sleep apnea also affects sleep itself. When an OSA patient experiences an apneic episode, to terminate that event, he must be partially aroused. Thus, the sleep is fragmented and consists of short periods of light sleep and frequent arousals. Additionally, these arousals are accompanied by increased sympathetic nervous system activity and skeletal muscle activity. This causes more body movements, or “restless” sleep.

Together, sleep fragmentation and restless sleep most likely contribute to excessive daytime sleepiness the patient experiences.  

Source: Reite, Martin, Michael P. Weissberg, and John Ruddy. Clinical manual for the evaluation and treatment of sleep disorders. Washington, DC: American Psychiatric Pub., 2009. Print.