In a sleep lab when a patient is being “adjusted” for Continuous Positive Airway Pressure therapy (CPAP), a mask is placed over the patient’s face to allow air to be forced into the patient’s nose during sleep.  This positive air pressure forces open the collapsed part of the upper airway allowing patients to breathe uninterruptedly during sleep.

 

 

The patient goes to sleep with the CPAP mask in place and the sleep lab technician watches the patients sleep data on her instrument panel.  When the patient has a respiratory event caused by upper airway collapse, the technician turns up the air pressure going to the face mask.  Without the CPAP mask in place the patient may have anywhere from 5 respiratory events an hour if they have mild sleep apnea up to over 100 events an hour for the most severe!  

 

The sleep lab technician tries to keep the CPAP air pressure as low as possible while still keeping the number of respiratory events under 5 per hour.  It is important to keep the air pressure as low as possible because higher air pressures are extremely annoying for most patients.  The higher the air pressure, the more difficulty patients have tolerating CPAP therapy.  Patients with higher air pressure often complain of air leaking out from under the CPAP mask and blowing in their eyes during sleep and waking them up.  High air pressure also may cause air to be forced into the stomach rather than the lungs.

 

Many times it is impossible for the technician to turn the air pressure high enough to completely stop the upper airway collapse without disrupting the sleep of the patient or causing the patient to have what is called a central sleep apnea event.  As opposed to a typical apnea event where the patient is trying to inhale a breath of air but can’t because of a collapsed upper airway, a central sleep apnea event is one in which the patient stops breathing and does not try to start breathing again.  The best way to understand a central sleep apnea event is to hyperventilate for a period of time and then abruptly stop.  Notice that immediately after stopping the hyperventilation, there is no urge to breathe for awhile.  A similar phenomenon happens when air pressure is blown into someone’s lungs at too high a pressure.  The urge to breathe disappears.

 

Many patients who have a difficult time tolerating high air pressures and who must use CPAP due to the severity of their disorder do great with combination therapy. Combination therapy is oral appliance therapy and CPAP combined. Using these therapies together allow much lower CPAP pressure. This is due to the fact that the oral appliance slightly moves the lower jaw (along with the tongue) forward. With the tongue out of the way, lower pressures are required with CPAP.