Continuous Positive Airway Pressure, or CPAP, therapy is the leading treatment for obstructive sleep apnea, a condition where the airway repeatedly collapses during sleep. The machine works by providing a consistent stream of pressurized air through a mask to act as a pneumatic splint, holding the upper airway open and preventing breathing interruptions. While highly effective at improving sleep quality and reducing the risk of serious health issues like heart problems, some users experience an uncomfortable side effect: stomach bloating. This buildup of gas in the digestive system is a recognized complication of CPAP therapy, and understanding its cause is the first step toward finding relief.
The Mechanism of Air Swallowing
The technical term for the excessive swallowing of air is aerophagia, and it is the direct cause of the bloating experienced by CPAP users. A CPAP machine delivers air at a pressure greater than the surrounding atmosphere, which is necessary to keep the pharynx from collapsing. This constant flow of pressurized air is primarily meant to travel down the trachea and into the lungs.
However, the esophagus, the tube leading to the stomach, lies close to the airway and can sometimes remain open or relax during sleep. When the pressure of the air being delivered is too high, or if the airway is partially obstructed, the air can be inadvertently forced past the upper airway and into the esophagus. The air then travels down into the stomach and intestines, accumulating there and causing the uncomfortable symptoms of abdominal distension, belching, and flatulence.
Contributing Factors and Equipment Issues
The primary contributor to aerophagia is an incorrect pressure setting on the CPAP machine. If the prescribed pressure is higher than the minimum required to keep the airway open, the excess force can more easily bypass the throat and enter the digestive tract. Conversely, a pressure setting that is too low can also cause problems, as the user may reflexively gulp air when the airway partially closes, forcing air into the esophagus.
Equipment issues, particularly mask fit, also play a significant role in causing air swallowing. A mask that fits poorly or has leaks can cause a rush of air that disrupts the normal breathing pattern, leading to mouth breathing or air turbulence. Mouth breathing, which is common with nasal masks, creates an open pathway that allows the pressurized air to be swallowed more easily. Users with chronic nasal congestion or those who tend to breathe through their mouths are therefore more susceptible to CPAP-induced aerophagia.
Actionable Strategies for Prevention and Relief
The most effective strategy for managing CPAP bloating is working with a sleep clinician to optimize the machine’s pressure settings. If a fixed pressure is causing aerophagia, switching to an Auto-Adjusting PAP (APAP) machine may help, as it automatically delivers the lowest pressure necessary, reducing the average pressure throughout the night. For individuals requiring high pressure, a Bi-Level PAP (BiPAP) machine delivers a higher pressure upon inhalation and a lower pressure upon exhalation, making breathing out easier and lessening the likelihood of air being forced into the stomach.
Equipment Adjustments
Many modern CPAP devices include comfort features to help with exhalation, such as Expiratory Pressure Relief (EPR) or C-Flex, which temporarily drop the air pressure when the user breathes out. The Ramp feature is also useful; it starts therapy at a very low pressure and gradually increases it, allowing the user to fall asleep before the full therapeutic pressure is reached. Addressing mask fit is also important; using a chin strap can prevent the mouth from opening during sleep, which significantly reduces the opportunity for air to be swallowed.
Positional and Medical Relief
Changing the sleeping position can offer relief, as sleeping flat on the back can increase the pressure required and make air swallowing easier. Elevating the head of the bed by about 30 degrees, perhaps with a wedge pillow, can help reduce the amount of air entering the esophagus. Additionally, sleeping on the left side has been shown to reduce gastroesophageal reflux, which can compound the discomfort of aerophagia. For immediate relief of trapped gas, over-the-counter anti-gas medications containing simethicone can help break up gas bubbles in the digestive tract.
Recognizing When to Seek Medical Guidance
While CPAP-related bloating is common, certain symptoms warrant immediate consultation with a healthcare provider. If the abdominal bloating is accompanied by severe or sharp pain, a high fever, or blood in the stool, it could indicate a more serious non-CPAP related gastrointestinal issue. Persistent nausea, vomiting, or a sudden change in bowel habits, such as unexplained diarrhea or constipation, also require prompt medical evaluation.
A doctor or gastroenterologist may need to rule out other digestive disorders, such as Irritable Bowel Syndrome (IBS) or Small Intestinal Bacterial Overgrowth (SIBO), which present with similar bloating symptoms. If the symptoms of aerophagia persist despite working with your sleep specialist to adjust pressure and equipment, a medical professional can conduct a thorough assessment to ensure the discomfort is not masking another health concern.