Southeast Houston Sleep Medicine

CPAP and BiPAP

Continuous positive airway pressure machines (CPAP) blow air
into the back of the throat. This stream of air opens the upper
airway during sleep and prevents apnea (cessation of breathing).
The basic CPAP machine consists of a 3 to 10 pound box connected
to plastic tubing and a mask. The patient places the mask over the nose
or the face. The machine pushes air through the plastic tubing connected to the mask, allowing
the stream of air to flow into the back of the throat and prevent upper airway collapse, snoring and apnea. SleepApnea.org

Over the past 15-20 years, medicine has made significant progress in the treatment of sleep apnea. Nocturnal CPAP machines now include heated humidifiers, which moisten the nose and the back of the throat, preventing dryness and nasal irritation. Some machines alternate the pressure depending on the resistance in the upper airway or the phase of ventilation (BiPAP, auto titrating machines, and servo-ventilation).

A wide variety of masks are now available. The basic nasal mask now comes in a large variety of sizes and shapes. Technicians at durable medical equipment companies or sleep laboratories can fit each patient individually for the correct sized mask. The various nasal masks use padding in different areas of the face and nose to prevent abrasions or irritation of the skin. For those patients who are unable to tolerate a nasal mask, full face masks and nasal pillows, which fit directly into the nostrils without covering the face, are available.

TYPES OF MACHINES

Continuous Positive Airway Pressure (CPAP)

The basic CPAP machine blows air at a constant pressure during both inhalation and exhalation. The exact pressure required for each patient is titrated in a sleep laboratory. During this titration the technician (registered polysomnographer) applies different pressures to find the minimum pressure necessary to eliminate upper airway closure and abnormal breathing. The CPAP is subsequently set at this minimum titration pressure, and the patient’s nose and face are fit with the correct sized mask. Continuous positive airway pressure (CPAP) machines now include a heating humidifier to prevent irritation of the nose and drying of mucous membranes. In addition, modern machines monitor the number of hours and minutes the patient keeps the mask on his or her face and stores the data on a removable card.

Bi-Level Airway Pressure (BiPAP)

The BiPAP machines use a higher pressure when the patient breathes in and a lower pressure when the patient exhales. This variation in pressure helps patients with severe sleep apnea, who are resistant to standard CPAP, eliminate their upper airway closure, snoring, and nocturnal apnea. In addition, BiPAP assists patients with weak respiratory muscles (i.e. patients with muscular dystrophy or spinal cord injuries) breathe at night by decreasing the resistance against which the patient must exhale.

Adaptive Servo-Ventilation

Adaptive servo-ventilation (VPAP) is used by sleep specialists in unique circumstances. In rare cases, CPAP causes patients to breathe too vigorously. This hyperventilation lowers the level of carbon dioxide in the blood stream, which tells the brain to stop breathing until the carbon dioxide level returns to normal. These brief periods in which the brain tells the patient not to breathe are called "central sleep apneas."

The adaptive servo-ventilation monitors the amount of resistance in the airway and the amount of air exhaled during each breath. By monitoring these parameters, the adaptive servo-ventilation machine varies the pressure with each breath, using the minimum necessary pressure with each breath. By continuously adjusting the pressure, adaptive servo-ventilation prevents the hyperventilation that causes central sleep apneas in some patients.

Expiratory Positive Pressure Ventilation (EPAP)

Expiratory positive pressure ventilation blows air through the nose into the back of the throat as the patient finishes exhaling with each breath. This flow of air prevents the airway from collapsing at the very end of expiration and at the beginning of the next inhalation. By preventing airway collapse, EPAP prevents the snoring and abnormal breathing that occurs with sleep apnea.

MASKS

Modern technology offers a large variety of masks including pure nasal masks, full face masks, and nasal pillows.

Nasal Masks

The nasal CPAP mask was the original mask used for treating sleep apnea. It is a triangle-shaped mask with a soft gel surface that is applied directly over the nose. Different accoutrements allow polsomnographers to fit the mask snugly. In addition to measuring the patient's face and nose and to find the correct sized mask, technicians further adjust nasal masks with cloth straps fastened to the top of the head. Small pieces of foam can be used on the bridge of the nose to prevent skin irritation. If patients open their mouths frequently, a chinstrap can be applied to keep the mouth closed.

Full Face Masks

Full face masks consist of a large shield with a rim of soft plastic that covers the entire face. Sleep specialists recommend these when patients persistently breathe through the mouth and can’t tolerate chin straps. The full face mask also helps prevent air from leaking around the nose and irritating the eyes as well.

Nasal Pillows and Variations

The original nasal pillows were two soft foam plugs that fit directly into the nostrils. Cloth headgear held the foam plugs in place. Sleep specialists use nasal pillows when patients experience claustrophobia and are unable to tolerate anything covering the nose or face. The Nasal Breeze is a variation of the nasal pillows. The nasal breeze mask uses a thin piece of plastic over the top of the head to hold the foam plugs in place instead of cloth headgear.

Another variation is the Nasal-Aire apparatus. Soft plastic tubing placed behind the ears holds plastic plugs in the nostrils. Although the NasalAire apparatus superficially resembles nasal cannulas used for oxygen delivery in hospitals, the nasal prongs of the NasalAire mask are wider than the prongs of an oxygen cannula. The wide prongs occlude the nostril on both sides, allowing the CPAP machine to push air through the nostrils into the back of the throat and open the airway.