CPAP

Continuous Positive Airway Pressure

 


In patients with sleep apnea, the airway collapses due to the negative pressure produced by inspiration, as muscle tone is reduced during sleep.  CPAP acts as an airway splint, with the machine-generated air pressure counteracting the negative inspiratory pressure and maintaining airway patency.

Initial settings are usually determined by a technician during a lab titration session, or during a split-night polysomnographic study. An initial follow-up is recommended during the first few weeks to insure proper usage and effectiveness. Objective monitoring (a record of CPAP wear patterns) and regular follow-up are also recommended for long term management as well as insurance reimbursement. Many initial difficulties in adapting to CPAP use can be resolved with proper education and a variety of adjunctive approaches (see below). 




Variations of CPAP include:

·         Bi-level CPAP (in which the CPAP pressure on expiration is reduced) may be useful in treating some types of restrictive  lung disease or hypoventilation syndromes

·          Auto-CPAP (auto-titrating, or smart CPAP) machines automatically and continuously adjust the pressure based on the patient's need, which may vary significantly in patients with position-dependent or sleep stage-dependent apnea. Auto-PAP machines are also used for in-home titration (instead of overnight lab titration) and in patients where time is limited, such as pre-operative cases

·          Adaptive Servo-Ventilation is used for patients with central and/or mixed apnea and periodic breathing

 

Although compliance with CPAP wear is reported between 60-85%, a number of approaches have been shown to result in better acceptance rates. These include:

·         trying a variety of different mask interfaces, including custom masks, to reduce pressure spots and air leakage.

·         patients with beards, or those who cannot tolerate the feeling of a mask on their face,  can consider Nasal Pillows, which fit into the nostrils with a soft seal to prevent air leakage.

·         another emerging therapy that shows significant promise for patients having difficulty with facial masks or excessive CPAP pressure is a combination of Auto-PAP with a mandibular repositioning appliance, which mechanically opens the airway, allowing the pressure on the PAP machine settings to be reduced to more tolerable levels  

·          using a chin strap to prevent spontaneous mouth opening during sleep, which cause mouth dryness, air leakage and greater airway resistance due to the retro-positioning of the tongue

·         adding a heated humidifier so the nasal airway does not become dry or irritated

·         using nasal decongestants or steroids to reduce nasal congestion during a cold

·         ENT surgery to remove nasal obstructions and improve the patency and function of the nasal airway

·         using a lower expiratory pressure (Bi-PAP) for patients who find it difficult to exhale against the machine air pressure

·         ramping up the pressure gradually, so the full pressure level is not reached until after the patient is asleep

·         Adaptive Servo-Ventilation provides ventilatory support during episodes of central sleep apnea. The ASV algorithm adapts to patients' ventilatory needs on a breath-by-breath basis, compensating for variations seen in central and complex sleep apnea syndrome, normalizing breathing, improving sleep architecture and increasing patient comfort 

·         Auto-PAP, which self-adjusts the pressure settings depending on changes in airflow or ventilatory effort