Part 2 - Surgery
Obstructive sleep apnea (OSA) is a disorder characterized by obstruction of the upper airway during sleep. This page is one of three describing treatment for OSA. In this page we will concentrate on various types of breathing support used for OSA. Other pages describe (1) lifestyle and dental appliances and (2) surgical treatment.
As described in the introduction section, obstructive sleep apnea is essentially caused by a partial or complete collapse of the upper airway during sleep. Up until the early 1980s, the most common treatment for severe OSA was a tracheotomy. Although this certainly help relieve the obstruction, tracheotomy tubes can require a lot of care and cause some of their own problems.
Beginning in the 1980s, various pieces of equipment for assisting breathing at nighttime were developed for OSA. These machines all act to increase the airway pressure in the throat, thereby "stenting" open the airway and prevent collapse. Since OSA is so common there has been a lot of interest in improving the effectiveness and the acceptability of these machines. This page will briefly discuss the various types of airway pressure support used for OSA.
Continuous Positive Airway Pressure (CPAP)
Continuous positive airway pressure is a highly effective treatment for OSA that helps to eliminate the collapse of the upper airway. CPAP consists of applying a constant pressure to the airway through a special facemask that holds open the airway during sleep. The mechanism of action appears to be strictly the physical effect of increased pressure, similar to the way in which air pressure inflates a balloon. Some people have postulated that there may be some changes in the various reflexes in the upper airway that also helps increase the muscle tone of the throat but, even if present, this effect is probably small.
Typical pressure applied through the face mask are 5-15 cm H2O. Pressure is measured in terms of the pressure generated by a column of water. An easy way to get a feel for this pressure is that it takes a negative pressure of 5 cm H2O to suck water 5 cm, about 2 inches, up a straw. Or if you had a straw filled with water to a height of 5 cm and you put it against your finger, it would exert a pressure of 5 cm H2O.
There are various types of face mask used for CPAP. The most common consists of a mask that goes over the nose and is held in place with an elastic strap. There also are nasal "pillows" which are soft plastic nosepieces that are placed at the nostril.
Diagnosis of sleep apnea is also made with a sleep study, which is described at an earlier page. Many sleep centers do what is called a split night study meaning that if OSA is obvious in the early part of the night, they will apply CPAP during the later part of the study. In this way they can adjust the pressure applied through the mask to optimize treatment of the apnea.
CPAP is highly effective and people with severe OSA often notice dramatic changes after just the first night. With obstructive sleep apnea, very little time is spent in the deep stage of sleep called REM (Rapid Eye Movement). Individuals with OSA who use CPAP will often experience a "REM rebound" the first night, with a much longer period of REM than usual. After a few days of CPAP, the stages of sleep begin to resemble normal structure.
A second type of CPAP is called BiPAP. This type of pressure delivery uses two different pressure, one during inspiration and one during exhalation. It is felt that if lower pressure is used during exhalation, BiPAP may be better tolerated.
A variety of different companies make CPAP machines designed for home use. The machines are usually fairly portable and can be taken along when traveling.
The major shortcoming with CPAP is that some people simply cannot tolerate the mask or the equipment. If high pressures are needed to prevent OSA, the mask can be uncomfortable for some individuals. Other people cannot wear the mask, even if the pressures are low. Sometimes this can be alleviated by different types of masks or with gradual acclimation to the facemask over time. Although the equipment is relatively compact, frequent travelers also may be reluctant to take it along with them everywhere they go. |
