CPAP therapy is the standard method for treating obstructive sleep apnea, a condition where breathing is repeatedly interrupted during sleep. The machine delivers a constant stream of pressurized air through a mask, acting as a pneumatic splint to keep the upper airway open. While highly effective, a common side effect of CPAP use is increased abdominal gas, leading to burping, bloating, and flatulence. This gassiness is a recognized consequence of the therapy, though the severity varies among users.
How CPAP Use Leads to Swallowed Air
The root cause of increased gas is the unintentional swallowing of air from the machine. Although the pressurized air is meant for the lungs, a portion can be diverted into the digestive tract because the upper airway sits close to the entrance of the esophagus.
During sleep, the muscles controlling the upper esophageal sphincter—a ring of muscle at the top of the food pipe—naturally relax. The CPAP air can easily bypass this barrier and be pushed into the esophagus and stomach. This air intake is more likely if the pressure setting is higher than necessary.
This continuous flow of air into the digestive system is called aerophagia. The stomach becomes distended with air, leading to discomfort. Sleeping on the back further increases the risk of air swallowing, as this position makes the throat and esophagus more conducive to air entry.
The Digestive Path of Ingested Air
Once air is forced into the stomach, it must exit the body. The simplest path is to reverse course, causing belching as the stomach releases excess gas back up the esophagus. This upward expulsion is common, especially upon waking.
Not all swallowed air is released through belching; some continues through the digestive system. The air travels from the stomach through the small and large intestines, combining with gases produced by gut bacteria breaking down undigested food. This mixture accumulates in the lower gastrointestinal tract.
The eventual release of this gas through the rectum is known as flatulence. Excess swallowed air directly increases the volume and frequency of gas passed. While the swallowed air is primarily nitrogen and oxygen, the odor comes from trace sulfur compounds created by the gut bacteria.
Adjustments and Changes to Minimize Gas
Practical adjustments to CPAP equipment and user habits can significantly reduce the amount of air swallowed during the night.
- Confirm the mask fit: A poor seal causes air leaks, triggering the machine to compensate with higher pressure, which increases the risk of air swallowing. Ensuring a snug mask minimizes these pressure fluctuations.
- Utilize the “ramp” function: This feature allows the pressure to start at a lower, more comfortable level and gradually increase over time. Starting low gives the body time to fall asleep before the full therapeutic pressure is reached, reducing the chance of air being forced into the esophagus.
- Change sleeping position: Sleeping on the side instead of the back reduces the gravitational pressure that encourages air to enter the stomach. Elevating the head of the bed slightly can also help make the upper esophageal sphincter less susceptible to pressurized airflow.
- Consult a physician: If initial steps fail, a doctor can adjust the machine’s pressure settings or consider switching to an automatic positive airway pressure (APAP) machine. APAP automatically adjusts pressure throughout the night to only the minimum required level.
In some cases, over-the-counter anti-gas medications can provide temporary relief, but addressing the mechanical issue of excessive air intake remains the most effective long-term solution.