A Continuous Positive Airway Pressure (CPAP) machine is the most common treatment for obstructive sleep apnea (OSA), a disorder where breathing repeatedly stops and starts during sleep. The device delivers a steady stream of pressurized air through a mask to keep the upper airway open, preventing soft tissues from collapsing. CPAP therapy frequently leads to uncomfortable gastrointestinal symptoms, including gas, abdominal bloating, and belching. If left unaddressed, this common side effect can unfortunately cause people to stop their beneficial therapy.
The Reason CPAP Use Causes Gas
The physiological mechanism behind CPAP-related gas and bloating is the unintentional swallowing of air, a condition known medically as aerophagia. When the CPAP machine delivers air pressure, the goal is for that air to enter the lungs to stabilize breathing. However, some pressurized air can inadvertently be directed into the esophagus, the tube leading to the stomach.
During sleep, the muscles surrounding the upper esophageal sphincter (UES), which normally seals off the esophagus entrance, relax. The positive pressure from the CPAP can overcome this relaxed barrier, forcing air into the digestive tract. Once in the stomach and intestines, this air results in abdominal distension, a feeling of fullness, and excess gas.
The distension caused by swallowed air can also trigger transient relaxations of the lower esophageal sphincter (LES). The LES is the barrier between the esophagus and the stomach, and its relaxation is the main cause of gastroesophageal reflux (GER). This creates a cycle where swallowed air increases pressure in the digestive system, leading to the physical symptoms of bloating and gas experienced upon waking.
Factors That Increase Aerophagia Risk
The likelihood of air swallowing increases due to factors related to the CPAP setup and user physiology. A primary factor is having a prescribed CPAP pressure that is higher than necessary to treat sleep apnea. Excessive pressure puts greater force on the relaxed upper esophageal sphincter, making it easier for air to be forced into the digestive system.
The type and fit of the mask also play a significant role in aerophagia risk. Full face masks, which cover both the nose and mouth, sometimes require higher pressures. If a mask does not fit properly and allows air to leak, the machine may automatically increase the pressure to compensate, further raising the risk of air being swallowed.
Nasal congestion from allergies or a cold also contributes to the issue. When breathing through the nose is difficult, the user may unconsciously gulp air or breathe through their mouth, directing pressurized air into the esophagus. Finally, sleeping on one’s back (the supine position) promotes the entry of air into the digestive system, especially for users with underlying conditions like gastroesophageal reflux disease (GERD).
Strategies for Reducing CPAP-Related Bloating
Managing CPAP-related bloating often begins with reviewing device settings with a sleep specialist. The most effective strategy is optimizing air pressure, as reducing an unnecessarily high pressure setting directly decreases the force available to push air into the esophagus. Switching from a standard fixed-pressure CPAP to an Auto-CPAP (APAP) machine can be beneficial. APAP devices automatically adjust the pressure throughout the night, often resulting in a lower average pressure, which reduces symptoms of air swallowing.
Changing the sleeping position can provide immediate relief for some users. Sleeping on the side or elevating the head of the bed by about 30 degrees helps reduce the gravitational effects that promote air entry into the stomach. A wedge pillow or blocks placed under the head of the bed can achieve this elevation.
Addressing mouth breathing is another important step, as an open mouth allows air to escape and subsequently causes the machine to compensate with higher pressure. Using a chin strap with a nasal mask or switching to a mask style that covers both the nose and mouth can help maintain a closed mouth. If symptoms are persistent, severe, or accompanied by other gastrointestinal distress, consulting a healthcare provider is prudent to ensure that other medical conditions are not contributing to the discomfort.