Continuous Positive Airway Pressure (CPAP) therapy treats obstructive sleep apnea by delivering pressurized air to prevent airway collapse during sleep. Many users report experiencing gas, bloating, and abdominal discomfort, which can undermine the benefits of the therapy. This common side effect, often leading to burping and flatulence, is well-understood and can usually be managed effectively without interrupting necessary treatment.
How CPAP Pressure Causes Swallowed Air
The technical term for swallowing excessive amounts of air is aerophagia, which directly causes CPAP-related gassiness. CPAP machines deliver pressurized air to keep the upper airway open. When muscles relax during sleep, the separation between the windpipe and the esophagus weakens, allowing air to be misdirected.
If the air pressure exceeds the closing pressure of the upper esophageal sphincter, air can be forced into the esophagus instead of the lungs. This pressurized air travels into the stomach and intestines, leading to a buildup of gas. The resulting gastric distension causes bloating and belching as the body attempts to release the trapped air.
Air entering the esophagus can also cause the lower esophageal sphincter—the barrier between the esophagus and the stomach—to relax, further facilitating air entry into the digestive tract. This mechanism explains why many users wake up with abdominal discomfort or feel bloated shortly after using their machine.
Identifying Contributing Factors
The primary factor contributing to aerophagia is often the pressure setting. If the pressure is set higher than necessary, the excess force is more likely to overcome the resistance of the esophageal sphincter. Conversely, a pressure setting that is too low can cause the user to gulp air unconsciously while struggling to breathe against insufficient pressure, forcing air into the stomach.
The type and fit of the mask also play a substantial role. A poor-fitting mask can cause air leaks, which may prompt the user to mouth breathe or swallow air to compensate for the pressure imbalance. Full-face masks, which cover both the nose and mouth, sometimes require higher pressures to maintain an effective seal, potentially increasing the risk of air being pushed into the stomach.
Sleeping position influences how easily air is swallowed. Lying flat on the back increases the pressure required to keep the airway open, which increases the risk of aerophagia. Underlying conditions such as nasal congestion or gastroesophageal reflux disease (GERD) can also weaken the esophageal sphincters, contributing to air swallowing during CPAP therapy.
Practical Steps to Reduce Aerophagia
Working with a sleep specialist to adjust pressure settings is one of the most effective steps to mitigate aerophagia. Switching from a standard CPAP machine to an automatic positive airway pressure (APAP) device can help, as APAP machines adjust pressure throughout the night to use only the minimum effective pressure needed. A bilevel positive airway pressure (BiPAP) machine is another option, delivering different pressures for inhalation and exhalation, making it easier to breathe out against the flow.
Many modern CPAP devices include comfort features that reduce air swallowing. The ramp feature starts therapy at a lower pressure and gradually increases it as the user falls asleep. Expiratory pressure relief (EPR) temporarily lowers the pressure when the user exhales, improving comfort and reducing the urge to swallow air against the pressure.
Addressing mask issues involves trying a different style or size to ensure a perfect seal. If mouth breathing is the issue, a chin strap can be used with a nasal mask, or the user may switch to a full-face mask. Positional therapy, such as training to sleep on the side or elevating the head of the bed by about 30 degrees using a wedge pillow, also helps reduce air ingestion. Over-the-counter anti-gas medications containing simethicone may provide temporary relief from bloating and discomfort while underlying issues are being addressed.
When to Consult a Healthcare Provider
While gas and bloating are common side effects of CPAP therapy, certain symptoms warrant a medical consultation. If the abdominal pain is severe, persistent, or sharp, it may indicate a more serious condition. If discomfort continues despite adjustments to the CPAP machine and mask, a medical review is necessary to rule out other causes.
A healthcare provider should also be consulted if the user experiences other concerning gastrointestinal symptoms:
- Nausea or vomiting.
- Significant changes in bowel habits, including diarrhea or constipation.
- Unexplained weight loss.
- Blood in the stool.
These symptoms are not typically related to CPAP use and require evaluation for unrelated digestive tract issues. A doctor may recommend further evaluation, such as abdominal imaging, to confirm excessive air or to rule out conditions like irritable bowel syndrome or peptic ulcers.