Sleep Apnea Research Paper

Kristie Hodgens

Types of sleep apnea: Central (CSA), Obstructive (OSA) and mixed.

Obstructive sleep apnea is defined as a breathing pattern that has a 0- 10% airflow for at least 10 seconds with continued and increasing respiratory effort that repeats 5 or more times in one hour. This is the most common form of sleep apnea in the US, affecting about 25 million adults. It occurs more often in males over 40. (1) OSA occurs when the soft tissue in the back of the throat relaxes while sleeping causing a blockage to airflow. The effort and impulse to breathe remains but the air is blocked. The resulting hypoxia or hypercapnia induces an increase in ventilatory effort. The pharyngeal muscles open up the airways causing a gasp or snort whereby

normal breathing can then continue. This event may or may not cause the person to fully wake up. The continual interruption of sleep does not allow for complete restoration… as a good night’s sleep is intended to do. (1)
There are a number of factors that contribute to OSA. Physical characteristics that limit airflow include a thick neck, large tongue, micrognathia, large tonsils, deviated septum and a high mallampati score. Conditions such as obesity, GERD, goiters and tumors are also implicated in the obstruction of airflow. (2)

Central sleep apnea (CSA) is defined as a breathing pattern with 0- 10% airflow for at least 10 seconds along with a comparable decrease in respiratory effort. It differs from obstruction in that the impulse to breathe temporarily ceases. This is neurological in nature. It can have idiopathic origins or can stem from an injury to the brain stem such as stroke or trauma. It can also be caused by high attitude hypoxemia or from opiate use. It can occur secondary to an underlying disease such as amyotrophic lateral sclerosis (ALS), Parkinson’s and Alzheimer’s disease. (3) “Congestive heart failure (CHF) is the most commonly recognized cause of central sleep apnea.” (4) Central Apnea will be seen more in this population than in general. It is often associated with Cheyne- Stokes breathing which is characterized by increase in the rate and depth of breathing with a subsequent decrease followed by a period of apnea. (3)

Mixed sleep apnea (MSA) is when OSA and CSA overlap.

It starts out with a central feature but an obstruction feature follows. There may be a proponent of CSA in many people who have been diagnosed with OSA, but it may not become evident until the OSA has been addressed…after CPAP therapy, for instance. (5) CPAP therapy will be discussed in more detail later in this writing.

Signs and symptoms are similar in all forms of sleep apnea with a few distinctions. Typical signs are excessive fatigue and daytime sleepiness, snoring, hypertension, memory problems and weight gain. If the cause stems from a neurologic disorder, the patient may have difficulty with swallowing or may notice a change in his speech. (6)

Self-evaluation questionnaires such as the Epworth sleepiness scores assessment can give a patient a general idea if they are suffering from sleep apnea. Examples of questions asked are” “has anyone observed you not breathing at night…do you snore loudly….have you been treated for high blood pressure? (7) These are highly subjective, but can provide a person with enough information to seek further

diagnosis.
A polysomnogram (PSG) is considered the gold standard for diagnostic testing of sleep apneas. (8) PSG test are done in a sleep lab by a sleep technician designed to detect multiple apnea events in a night. Various electrodes are placed on the body. An electroencephalogram (EEG) measures brain waves. An electrocardiogram (ECG) measures heart rhythm and rate. An electrooculogram (EOG) measures eye movement. Electromyograms (EMG) are used to measure chin and leg muscle movement. Additional sensors are placed to measure airflow from the mouth and nose and a pulse oximeter is placed on the finger to measure O2 levels in the blood. A belt is secured around the stomach and chest to measure the strength and duration of a complete breath. (9)
The data collected from these sensors is monitored by a technician in another room. The data obtained from the EEG, the EOG and the chin EMG are used to determine if the patient is asleep or not and, if so, what stage of sleep he is in. (9)
Stages are as follows: Awake stage- eyes closed, normal to high chin tone, alpha activity of 8-13 hz, each epoch containing more than 50% alpha activity; stage N1- slow rolling eye movement, normal chin tone, theta activity of 4-7 hz; Stage N2- sleep spindles and negative and positive K complexes, high tone; N3 stage; slightly lower chin tone, 20-50% of an epoch contains delta; Stage R (REM)- rapid eye movement, lowest chin tone. (10)
The PSG test can also monitor and record the number of apneic events and can determine if obstructive, central or mixed in nature. The severity of the disorder can be determined by counting the number of apneic episodes within an hour. This is called the Apneic Hypopnea Index (AHI). Less than 5 on the AHI indicates no or minimal OSA. More than 5 but less than 15 is mild; more than 15 but less than 30 per hour is moderate and severe is an AHI of 30 or more. (10) The electrodes must be applied correctly and securely or all findings will be erroneous.
The data is then reviewed and a treatment plan is developed and explained by the sleep technician and your primary doctor. If it has been determined that the patient has OSA, a CPAP titration test may be performed to determine the proper settings. This can be done half way through the first PSG (known as a split-night sleep study) if the OSA diagnosis is severe and obvious. (11) The first half of the night is spent diagnosing the problem…the second half is spent sleeping with a CPAP device.

Treatment is determined by the type and severity of the disorder. Some home remedies and lifestyle changes can be fairly effective for OSA. Weight loss can make a significant difference in the presence of, and certainly, the severity of OSA. (12) The development of proper sleep hygiene is important, i.e. regular bedtimes, no eating within 2 hours before bedtime, etc. In some cases, with mild OSA, a simple change in sleeping position can help. A tennis ball sewn on the back of a shirt or pillows wedged behind the back can discourage sleeping on ones back. The use of various dental devices may be all that’s needed. Having said all that…more severe forms of sleep apnea require more serious treatment. (13)
Continuous Positive Air Pressure (CPAP) is the hallmark treatment for OSA. It stints the airways open by providing continuous airflow. The patient can choose the interface to his own comfort, i.e. nasal pillows, face mask or other options available at the time. OSA is defined by an obstruction to respiratory effort. If the obstruction is removed, then the apneas do not occur. The application of CPAP is very effective in eliminating the obstructive component. (12) Central Sleep Apnea is considerably more complicated.
In CSA, the breathing center in the brain is incapable of transmitting signals to the body to breathe. Treatment of this disorder requires working in tandem with other specialists to address the underlying condition. CSA doesn’t respond as quickly, if at all, to CPAP so options such as BiPAP should be considered. This is one reason for identifying CHF in a patient suffering from sleep apnea. As stated previously… the emergence of CSA is sometimes noted after a patient has been on CPAP to treat the obvious OSA. This is considered a “complex sleep apnea syndrome.” Once the continuous air pressure overrides the obstruction the central component becomes evident. (11)
The use of BiPAP is another option.

The higher IPAP level to the lower EPAP gives support to each breath. This also allows for a back- up rate to be applied for the longer apneic periods. Caution needs to be given to the application of IPAP to EPAP though. Too much of a difference can cause PaO2 levels to drop which would make the CSA worse. (5)

Adaptive servo ventilation provides a minimal EPAP support during normal breathing but also provides an IPAP that is servo controlled to coincide with the CSA. If it detects a lengthy pause time or reduction in breathing, enough pressure is delivered to keep the patient breathing at about 90% of his normal. (4) This is a particularly desirable option in patients with mixed or complex apnea syndrome.

A surgical procedure to remove the soft tissue and/or tonsils in the back of the throat is called uvulopalatopharyngoplasty. The laser option is called uvulopalatopasty. Permanent surgeries to move the jaw forward or to move the tongue away from the back of the mouth are also options. These all carry with them the risk of infection.

(6)
Sleep apnea affects the whole life of a person. It affects the health and well- being of not only the patient, but of those around them. Diagnosis and treatment are available.