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.

An Overview of the Different Sleep Disorders

Hello everyone!

It has been another great week at my internship! I thought it would be best if I ended if off by talking about sleep disorders in detail since they are the focus of my project.

One of the sleep disorders I will be focusing my research on is sleep apnea. It is a very common but often undiagnosed disorder in which the patient experiences pauses in breathing while he is sleeping. Breathing pauses can be as short as a few seconds to as long as a few minutes. These pauses disrupt sleep and as a result, the patient is tired throughout the day.

There are two types of sleep apnea: obstructive sleep apnea (OSA) and central sleep apnea.

Obstructive sleep apnea (OSA) is the more common one. It occurs when the airway becomes blocked or collapses. The tissues in the throat can block the upper airway, as shown in the image below. This results in the breathing pauses. When this happens, the oxygen levels in the body decrease and the patient wakes up gasping. During this time, the patient transitions from deep sleep to light sleep. Additionally, breathing through a blocked airway can cause snoring.

The less common type of sleep apnea is central sleep apnea. This occurs when the part of the brain responsible for breathing does not send the correct signals to the breathing muscles. This is different from OSA because in central sleep apnea, the patient makes no effort to breathe for short periods of time.

Other sleep disorders include narcolepsy and insomnia. A person with narcolepsy tends to involuntarily fall asleep during normal activities. Additionally, characteristics of sleep can occur during wakefulness. During episodes, patients feel separated from reality. Between episodes, they are healthy.

Insomnia is another sleep disorder that is characterized by persistent difficulties falling asleep or staying asleep. This can cause problems with memory and concentration. It can be caused by psychological issues such as stress or depression.  

It’s been two exciting weeks and I can’t wait to learn more about the effects of sleep disorders on cognitive abilities during the rest of my time at PNPI!

~Shubhangi  

The "Clocks" of the Body

Hello everyone!

I would like to start the second week of my internship by talking about what I am researching about in detail. 

The body is complex and many things, such as temperature, blood pressure, oxygen levels, etc. must be regulated. To accomplish these things, our bodies have internal “clocks” that control biological rhythms. One of the rhythms is the circadian rhythm, which controls the sleeping-waking cycle every 24 hours. It also controls the ups and downs of biological patterns, like body temperature and blood pressure changes during sleep and wakefulness. 

For example, the body temperature falls right before we sleep and rises when we are about to wake up. Biologically, there is a cluster of cells in the hypothalamus of the brain, the suprachiasmatic nucleus, which controls the circadian clock. 

There are four (maybe five) distinct stages of the sleep cycle. Stage 1 is the stage of sleep where we are between wakefulness and sleep. The most predominant waves in the brain during this stage are theta waves. The body temperatures starts dropping and muscles start relaxing. The eyes also move from side to side. People in Stage 1 sleep are not aware of their surroundings, but can easily be woken up.  Additionally, not everyone experiences State 1 sleep in the same way.

Stage 2 is the first stage of “true sleep.” It lasts about 10-25 minutes. Heart rate and breathing is slower than when we are awake. Muscle activity decreases and consciousness fades away. The brain’s activity is irregular in that large, slow theta waves are present along with sleep spindles. These are shorts bursts of brain activity. Most time is spent in this stage than any other.

During Stage 3, or deep sleep, we are unresponsive to the outside environment. Stage 3 is longer during the first part of the night and decreases as we keep alternating between the different stages throughout the night. During this stage, our brain waves are predominantly large, slow delta waves. This stage used to be split into Stage 3 and Stage 4 sleep. Stage 4 was initially defined as when delta waves were most common. We are generally difficult to awaken and during this stage, many people start sleepwalking.

During REM (Rapid Eye Movement) Sleep, the motor cortex of the brain is active. Our eyes move rapidly from side to side and we dream. Also, during this stage, muscles are relaxed. Body temperature, blood pressure, heart rate, and breathing speed all increase. The sympathetic nervous system is very active during this stage. For this reason, REM sleep is sometimes referred to as paradoxical sleep.

The sleep cycle repeats itself approximately every 90 minutes. Further into the night, REM sleep gets longer, while Stage 3/4 sleep gets shorter and eventually ceases altogether, as shown by the image below:

Sleep patterns are affected by various things, including genetics and the environment. Any stage of the sleep cycle can be affected. In upcoming posts, I will talk about some common sleep disorders.

Until next time!

~Shubhangi

The Highlights of My First Week

Hello all,

I would like to finish off this week with some of the highlights of my experiences at PNPI. I met many different patients and since I am working with a general neurologist as well as a sleep specialist, I got to see many patients with problems not related to sleep.

Some of the most common problems patients came in with were migraines and sleep apnea. Another patient I also met had profound cerebral palsy, a disorder in which the patient experiences decreased muscle tone and cognitive impairment.

Many of the patients with severe migraines were given nerve blocks, injections that decrease or stop the passage of nerve impulses for pain signals going to the brain. These injections are used when medications are not helping with the headaches. 

Today, I watched an Electromyography (EMG), a procedure used to diagnose a problem with the motor neurons of muscles. An EMG (a picture of the machine is shown below) takes the electrical signals transmitted by motor neurons using needle electrodes or surface electrodes, and translates them into graphs. These electrical signals cause muscle contraction.

Through observing patients with sleep apnea, I realized how complicated neurology itself is. There are many different problems that can be attributed to a change in one's sleep cycle. For instance, a patient who had come in earlier because she felt really dizzy, came in for a follow-up visit saying she was experiencing memory loss. She was also diagnosed with sleep apnea.

Another patient came in due to a seizure he had recently. Dr. Qureshi asked him to get a CPI test done. During his follow-up visit, he was diagnosed with sleep apnea. Therefore, sleep disorders, like sleep apnea, not only lead to cognitive impairment, but can also cause a variety of other problems like seizures and memory loss.

Another thing I noticed was that the staff and the patients were very welcoming and encouraging. Dr. Qureshi and his medical student made me very comfortable.  We spent a half hour talking about how similar my language, Hindi, is to Dr. Qureshi’s language, Urdu! He also introduced me to each of the patients I visited and allowed me to ask questions during the sessions. 

This week was phenomenal and I am confident that the rest of my time at PNPI is going to be even better! 

Stay tuned for more!

~Shubhangi

Introduction

Hello everyone,

Welcome to my blog!

Now that the first two trimesters of senior year are over, the next 11 weeks of my life involve a journey through doing independent research. I will be shadowing a neurologist and from this experience, I hope to gain insight into various sleep disorders and how they alter the structure of the brain. 

My internship is taking place at Phoenix Neurological and Pain Institute in Chandler, an outpatient center that treats patients with neurological disorders and focuses on improving their quality of life. I am working with Dr. Farrukh Qureshi, a general neurologist who also specializes in sleep disorders, and a fourth-year medical student he has working with him. 

Apart from the hours I will spend there, I will be reading a lot about the various sleep disorders and their effects on cognitive abilities. I have a list of various articles and books I will be reading throughout my project. 

Through reading and doing research, I hope to learn more about the brain. It is one of the most complex organs and controls many different parts of the body. I am really happy to take you along through my journey and I hope that, by the end of it, both you and I have a thorough understanding of sleep disorders. 

Until next time,

Shubhangi Awasthi