CPAP therapy is the standard treatment for obstructive sleep apnea, delivering pressurized air to prevent the collapse of the upper airway during sleep. While effective, the introduced air pressure can sometimes lead to uncomfortable gastrointestinal side effects like gas, bloating, and abdominal distention. This common side effect is known as aerophagia, the medical term for the excessive swallowing of air. This discomfort is a direct consequence of the pressurized air entering the digestive tract instead of the lungs.
The Mechanism: Aerophagia and Pressurized Air
Aerophagia is the process that translates CPAP air pressure into digestive discomfort. The air is intended for the respiratory system, but during sleep, the muscles surrounding the esophagus often relax. This relaxation allows the pressurized air stream to be inadvertently diverted down the esophagus. Once swallowed, this air accumulates in the stomach and the rest of the gastrointestinal tract. This influx of gas results in symptoms like bloating and a feeling of fullness. If the trapped air cannot be expelled through belching, it continues through the intestines, causing abdominal discomfort and flatulence. Aerophagia is estimated to occur in approximately 16% of CPAP users.
Technical and Behavioral Contributors
The primary cause of air swallowing is often related to the machine’s pressure setting. If the pressure required to keep the airway open is too high, the force of the air can overcome the esophageal sphincter’s resistance, pushing air into the stomach. Conversely, if the pressure is too low, the patient may subconsciously gulp or swallow air in an effort to breathe, forcing air down the esophagus. Finding the correct therapeutic pressure is therefore a delicate balance.
User habits and equipment issues also contribute significantly to air swallowing. Many users with nasal masks or nasal pillows begin breathing through their mouth, especially if they have nasal congestion or allergies. When the mouth is open, the pressurized air escapes or is gulped down the throat, leading to aerophagia and dry mouth upon waking.
The fit and style of the mask also play a role in the problem. A poor seal allows air leaks, which disrupt consistent pressure and prompt the user to compensate by gasping or swallowing. The patient’s sleeping position can also influence the severity of air swallowing. Sleeping flat on the back increases the risk, as gravity and body position make it easier for air to enter the digestive tract.
Practical Strategies for Relief
Addressing CPAP-related gas and bloating involves a combination of equipment adjustments and behavioral changes. The most effective starting point is consulting a sleep physician to evaluate the machine’s pressure settings. The physician can determine if the pressure can be safely lowered without compromising sleep apnea treatment.
If the necessary pressure remains high, switching to an Auto-CPAP (APAP) or a BiPAP machine may offer relief. APAP automatically adjusts pressure throughout the night based on need. BiPAP uses two distinct pressure levels—one for inhalation and a lower one for exhalation—making it easier to breathe out against the flow. Utilizing comfort features like Expiratory Pressure Relief (EPR) can also help by reducing pressure during the exhale phase.
Improving mask fit is another practical step, involving checking for leaks and ensuring the seal is snug but not overly tight. For those who mouth-breathe with a nasal mask, adding a chin strap can help keep the mouth closed and prevent air from being swallowed or escaping. If these measures are unsuccessful, switching to a full-face mask might be warranted to contain the airflow.
Adjusting sleeping posture can also reduce the likelihood of air swallowing. Side sleeping is recommended, as it naturally reduces pressure on the abdomen and may require a lower therapeutic pressure. Elevating the head of the bed by about 30 degrees, often with a wedge pillow, helps prevent air from flowing easily into the esophagus. For temporary symptom management, over-the-counter anti-gas remedies containing simethicone can help break down gas bubbles.