The Basics of CPAP

by Michael Rack, M.D. Health Professional

Continuous Positive Airway Pressure (CPAP) is the most common treatment for obstructive sleep apnea (OSA). Except for tracheotomy, it is also the most effective treatment for OSA. CPAP is basically a computerized air pump that delivers pressurized air through a hose and then through a nasal interface into the patient's throat. The pressurized air splints open the upper airways, preventing the airflow pauses (apneas) and airflow reductions (hypopneas) seen in OSA. CPAP also prevents the subtle upper airway collapsing that results in snoring.

Although the CPAP machine can deliver the pressurized air through an oronasal mask that covers both the mouth and nose, this type of mask is less effective at delivering the air pressure to the upper airways than a nasal interface. In addition, there is a risk of aspiration should a patient vomit or reflux into the mask.

Two types of nasal interfaces are commonly used with CPAP: a nasal mask or nasal pillows. A nasal mask fits over the nose while nasal pillows are prongs that fit inside the nostril. Both are equally effective, though most patients find the nasal mask more comfortable. Clinical lore has it that nasal pillows are especially hard to tolerate at higher pressures.

Most CPAP machines today have a heated humidifier that moistens and warms the air before its delivered through the hose and interface. The heated humidifier helps prevent 2 common side effects of CPAP: nasal congestion and nasal dryness. However, in my experience, it
is often necessary to add a nasal steroid spray to treat residual nasal congestion.

It is necessary to keep the mouth closed while using CPAP in order to have the air pressure reach the throat where it is needed, rather than to have the air pressure flow out of the mouth. Sometimes a chin-strap is necessary to help patients keep their mouths closed while using CPAP. However, the fact that a person is opening their mouth while using CPAP is a sign of possible nasal obstruction. Nasal interventions such as steroid nasal sprays or nasal surgery may allow more effective airflow through the nose and may prevent the need for a chin-strap.

It can take up to a week to get used to using the CPAP machine. After about a week the patient should be able to use CPAP and wear the CPAP interface throughout the night. Problems can often be solved with a call to your sleep physician. CPAP should get rid of all snoring and breathing pauses. Sleepiness should resolve gradually over a period of 1 to 2 weeks.

You should let your sleep physician know if sleepiness, snoring, or apneas persist. Also let your physician know if mouth-breathing or nasal problems develop. Problems with the nasal pillows/mask can often be solved by calling the medical equipment company that provided the CPAP machine and supplies.

There are many brands of nasal pillows and masks, and usually a prescription is not required to make a change in your nasal interface. Do not change to an oronasal mask without discussing this with your doctor. Often the CPAP machine will have to be set at a higher pressure if an oronasal mask is used.

Michael Rack, M.D.
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Michael Rack, M.D.

Michael Rack a board certified internist in Southaven, Mississippi. He wrote for HealthCentral as a health professional for Sleep Disorders.