Complications

The most obvious complication arising from OSA is diminished quality of life brought on by chronic sleep deprivation and the symptoms described above. Coronary artery disease, cerebral vascular accidents (strokes), and congestive heart failure are being evaluated to define the exact nature of their connection to OSA. Some linkage between OSA and coronary artery disease and stroke has been demonstrated, although it is still uncertain whether OSA leads to an increased risk of stroke and coronary artery disease or if both OSA and cardiovascular problems are caused by a common problem, such as obesity. Obstructive sleep apnea aggravates congestive heart failure by placing stress on the heart during sleep. There is a high prevalence of OSA in patients with congestive heart failure. Congestive heart failure patients also may have central sleep apnea, a condition in which the brain signals the patient to stop breathing for short periods of time.

Diagnosis

The primary method for diagnosing OSA at present is to have the patient undergo a sleep study, known as polysomnography.

A sleep technician administers and attends the study. To prepare the patient for sleep study, numerous physiological monitors are attached to the patient to record nighttime breathing, brain activity, and physical activity. Several electrodes are pasted to the patient's head to measure brain electrical activity with an electroencephalogram, or EEG. Electrical activity in the brain during the different stages of sleep is distinctly different from that while awake. The EEG allows the physician to see if the patient is reaching all the stages of sleep to the appropriate depth and if the patient is being aroused excessively from these stages.

Electrodes are also taped to the skin near the outer edges of the eyes to record data for an electrocculogram (EOG). This tells the examiner where the patient is in rapid eye movement sleep (REM). A device is placed near the patient's nose and mouth to measure airflow. Electrodes are connected to an electromyogram (EMG) and taped or pasted on the patient's chin to detect activity in the jaw muscles. The EMG detects the presence of REM sleep when the jaw muscles relax.

Special belts are placed around the patient's chest and abdomen to detect and record the rising and falling movements associated with the respiration. A pulse oximeter, a noninvasive device for measuring oxygen content in the blood, is attached to the finger, and electrodes to provide an electrocardiogram (ECG) are attached to the chest to measure heart rate. Various types of instruments, either straps around the feet or electrodes pasted to the lower legs, measure leg movements, which may indicate another sleep disorder called periodic limb movement disorder.

Obstructive sleep apnea is diagnosed if the patient has an apnea index greater than 5, that is, has more than five apneic episodes per hour, or a respiratory disturbance index (RDI), the combination of apneas and hypopneas, greater than 10 per hour. In the appropriate clinical setting, sleep apnea can be diagnosed by an RDI between 5 and 10. Experts disagree somewhat on precisely where the diagnostic threshold lies, so a reliable diagnosis needs to be made in the context of the individual. Furthermore, the criteria are even less precise in children, making an individual approach to diagnosis even more important.

Clinically speaking, an obstructive apnea is defined as a complete cessation of airflow for more than 10 seconds with persistent respiratory effort. An obstructive hypopnea is defined as a partial reduction in air flow of approximately 30 percent to 50 percent with persistent respiratory effort and a reduction in oxygen saturation by at least 3 percent to 4 percent and/or an arousal from sleep.

The many physiological measurements taken usually enable the physician to diagnose or reasonably exclude OSA. Sometimes, however, a patient does not sleep long enough to obtain all the data needed. Polysomnography can not provide data from patients who have mild OSA only at home or only after using certain medications or alcohol but who do not experience any episodes during the sleep study. Therefore, a polysomnogram must be interpreted with the entire clinical picture in mind.

Another condition, called upper airway resistance syndrome, cannot be seen on polysomnography. This syndrome is characterized by repetitive arousals from sleep that probably result from increasing respiratory effort during narrowing of the upper airway. These patients suffer the same sleep disruption and deprivation as other sleep apnea patients. In such cases, the only abnormality that appears on the polysomnogram is recurrent arousal. It is possible to measure an increase in the negative pressure exerted by the patient in an effort to breathe against increasing resistance as the airway narrows. This measurement of inspiratory pressure is not usually done during a standard polysomnogram. Patients with upper airway resistance syndrome, therefore, constitute a group whose OSA could be easily missed by the polysomnogram.

Because polysomnography is expensive and labor intensive, efforts are underway to find a better method of diagnosing or screening for OSA. The only alternative at present is a procedure called overnight oximetry, which measures a patient's oxygen saturations throughout the night. Overnight oximetry is not considered completely adequate as a screening test, however, as the oxygen levels in the blood of many patients with OSA do not provide the information needed to understand their condition.

Treatment

Several treatment options exist for dealing with OSA. These include weight reduction, positional therapy, positive pressure therapy, surgical options, and oral appliances.

Weight gain is a significant risk factor for the development of OSA. While sleep apnea usually can be corrected by weight loss, other factors involved in the pathophysiology of OSA, such as anatomic abnormalities, may cause the condition to persist. However, the vast majority of OSA cases can be improved, if not eliminated, with significant weight loss. The amount of weight a patient needs to lose to achieve these benefits varies. Some may need only a modest reduction in weight to gain improvement, while others require significant weight loss. It is not necessary to slim down to "ideal body weight" to achieve these benefits.

Positional therapy can be used to treat patients whose OSA is related to body positioning during sleep. Most people with sleep apnea have worse symptoms if they lie flat on their back during sleep. Indeed, most bed partners know this from experience and often try to make their partner move onto their side during the night to stop their snoring. There are several strategies which can help patients who have mild apnea only when lying on their back. One is to sew or attach a sock filled with tennis balls, length-wise down the back of their pajama top or nightshirt. This makes it uncomfortable for the sleeper to lie on their back, and they usually will move onto their side. Another technique is to use positional pillows to assist in sleeping on the side. Positional therapy has its limits, but it has been tried with success in some patients.

Positive Pressure Therapy
Positive airway pressure is a very effective therapy for obstructive sleep apnea. It has three forms: continuous positive airway pressure (CPAP), autotitration and bi-level positive airway pressure.

Regardless of the mechanism used it is desirable to use the lowest possible pressure to eradicate the sleep apnea. In most cases, positive airway pressure is easier to tolerate at lower pressures. Every patient requires a different pressure. To determine precisely the individual patient's optimum airway pressure, it is necessary to titrate the pressure to each individual patient during a polysomnogram. A polysomnogram will show not only when the respiratory events have ceased, but also when the arousals from the respiratory events occur.

CPAP, the more common of the three therapy modes, usually is administered at bedtime through a nasal or facial mask held in place by Velcro straps around the patient's head. The mask is connected by a tube to a small air compressor about the size of a shoe box. The CPAP machine sends air under pressure through the tube into the mask, where it imparts positive pressure to the upper airways. This essentially "splints" the upper airway open and keeps it from collapsing.

Approximately 55 percent of patients who use CPAP do so on a nightly basis for more than four hours. It is the most commonly prescribed treatment for OSA. The advantages of CPAP are that it is very safe and completely reversible. Generally, it is quite well tolerated. The main disadvantage is that it requires active participation every night; that is, the patient must put it on for it to work.

Mask fitting is an essential element of a patient's success with positive airway pressure therapy since it affects compliance and effectiveness of treatment. Higher pressures can result in air leak and patient discomfort. Demands on mask stability increase as pressure increases. Higher pressures may also require tighter head gear to maintain an adequate seal contributing to the discomfort. When selecting a CPAP mask the following factors should be considered.

  • Comfort
  • Quality of air seal
  • Conveninence
  • Quietness
  • Airventing

Side effects of CPAP include contact dermatitis, skin breakdown, mouth leaks, nasal congestion, runny nose (rhinorrhea), dry eyes, nose bleeds (rare), tympanic membrane rupture (very rare), chest pain, difficulty exhaling, pneumothorax (very rare), smothering sensation, and excessive swallowing of air (aerophagia).

Nasal congestion often can be reduced or eliminated with nasal steroid sprays and humidification placed into the machine. Rhinorrhea can be eliminated with nasal steroid sprays or ipratroprium bromide nasal sprays. Epistaxis is usually due to dry mucosa and can be combatted with humidification. Dry eyes are usually caused by mask leaks and can be eliminated by changing to a better fitting mask.

Autotitration devices are designed to provide the minimum necessary pressure at any given time and change that pressure as the needs of the patient change. Autotitration devices respond to different parameters and rely on different algorithm so they do not all operate the same.

The AutoSet® by ResMed acts by monitoring the patient's inspiratory flow-time curve. A flattening of the inspiratory flow-time curve typically precedes an upper airway obstruction, which causes apnea, hypopnea, or snoring. Monitoring and responding to the flow-time curve, reduces the number of respiratory events and arousals improving sleep quality.

Bi-level positive airway pressure is a variation of CPAP. Most of the problems patients experience with CPAP are caused by having to exhale against a high airway pressure. Because the air pressure required to prevent respiratory obstruction is typically less on expiration than on inspiration, bi-level positive airway pressure machines are designed to sense when the patient is inhaling and exhaling and to reduce the pressure to a preset level on exhalation. Bi-level positive airway pressure machines usually are used when the patient does not tolerate CPAP or when the patient has more than one respiratory disorder.

Oral Appliances
Oral appliances used for the treatment of OSA generally come in two categories: mandibular advance devices and tongue-retaining devices. A variety of both types exists.

Mandibular advance devices essentially consist of a plastic (or other material) mold of the teeth. They resemble the athletic mouth guards commonly used in boxing, football, and other contact sports. The mold for the lower teeth is advanced further forward than the mold for the upper teeth. Advancement of the lower teeth moves the jawbone forward and opens the airway, preventing its collapse during sleep. It is effective in mild cases of OSA, particularly if the patient's OSA is positional.

Tongue-retaining devices also resemble an athletic mouth guard. The device is like a suction cup and is placed between the upper and lower teeth. The tongue sits in the suction device and is pulled forward during the night. Positioning the tongue forward may eliminate any obstruction caused by the base of the tongue.

There is limited overall experience with either of these devices, compared with the other treatments for OSA. They appear to be useful in treating mild cases of OSA. They are best fitted by a dentist experienced in their use. Complications associated with them include temporal mandibular joint pain and excessive salivation.

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