CPAP is an acronym (pronounced
see-pap) for
Constant
Positive
Airway
Pressure. This is a medical technique/device designed to combat the effects and risks of
sleep apnea. In cases of apnea, the patient's
airway becomes blocked intermittently during sleep, usually (in
chronic sufferers) due to
swollen mucus membranes or
tonsils, or to an overweight condition. In the latter, the weight of the
neck may be enough to
compress the airway closed when the patient is lying on their back. In any case, the effects of
apnea can range from
snoring, through
exhaustion due to not dropping deeply enough into sleep before being (nearly) awoken by
acidosis, up to
death in extreme cases.
A CPAP machine is a small box (the largest ones are usually shoebox sized), electrically powered, with a compressor in it. It is connected via hose to a mask which fits snugly over the patient's nose, and is retained in place (usually) by an elastic strap. The CPAP machine maintains a set overpressure in the tube and thence in the patient's nasal passages. This overpressure (humidified by the CPAP machine to avoid parched throat or nose) travels into the nose, and barring effort by the patient, usually has two functions. First, it makes breathing in less onerous, as some of the 'work' is done by the machine. Second, it maintains a slight overpressure in the nasal passages and the throat; this keeps the airway open.
While annoying, a CPAP system can make the difference (in most adult sleep apnea cases) between semipermanent exhaustion and restful sleep. It can also greatly ease the strains on the cardiopulmonary system that are placed upon it by the sudden frequent interruption of airflow.
Although CPAP can prove helpful, it should be remembered that it is not a cure - it is a palliative measure. That is, the use of CPAP will not actually reverse the condition which the user suffers from, just ameliorate the effects of it while it is used. In addition, the use of CPAP can produce extreme muscle tension and other symptoms of 'restricted' sleep - if the user 'trains' his or herself to avoid motion in order to avoid disrupting the mask's position, it can interfere with adjusting position for comfortable sleep. Although this is better than getting no sleep, or frequently interrupted sleep, users of CPAP should be alert to the possibility that although they are sleeping what appear to be normal intervals with fewer or no symptoms of hypoxic arousals, they may still not be getting proper REM sleep. This can cause complications over mid to long term; it has been associated with depression and metabolic disruption (yes, I speak from experience, but ask your doctor about it, not a website).
Finally, remember that the use of CPAP will in essence bind you to a power outlet whenever you need sleep. It is a sobering realization to understand that, in essence, you have become dependent on life support for your survival. Even falling asleep safely on airplanes becomes impossible if your condition is severe enough, and only recently have CPAP systems become available which will operate from battery - and they are quite bulky.