CPAP Belly: Causes, Symptoms, and Relief Methods

Continuous positive airway pressure (CPAP) therapy is a widely used treatment for sleep apnea, helping individuals maintain open airways during sleep. However, some users experience gastrointestinal discomfort, often referred to as “CPAP belly,” which includes bloating and abdominal distension. This occurs when pressurized air from the CPAP machine enters the digestive system instead of remaining in the respiratory tract.

Understanding the causes, symptoms, and relief methods can help those affected manage discomfort while continuing necessary CPAP therapy.

Mechanisms of Pressurized Air in the GI Tract

CPAP machines deliver continuous air pressure to keep the upper airway open and prevent apnea episodes. While effective for breathing, this pressure can force air into the esophagus and stomach, leading to discomfort. The lower esophageal sphincter (LES), which separates the esophagus from the stomach, typically prevents this from happening. However, sustained positive airway pressure can overwhelm the LES, allowing air to enter the digestive tract.

Higher CPAP pressure settings, particularly above 10 cm H₂O, increase the likelihood of air swallowing, or aerophagia. Excessive pressure can force the upper esophageal sphincter to open momentarily, directing air into the stomach. Individual factors such as a weakened LES or gastroesophageal reflux disease (GERD) can make some users more susceptible to this issue.

Sleep position also plays a role. Lying on the back increases the risk of air entering the stomach due to gravitational effects on the esophagus and diaphragm. In contrast, side sleeping, particularly on the left side, promotes better esophageal clearance and reduces pressure on the stomach. Adjusting sleep posture may help minimize CPAP-related bloating.

How Aerophagia Relates to CPAP Belly

Aerophagia, or excessive air swallowing, is a primary cause of CPAP belly. The continuous flow of pressurized air can enter the digestive tract if airway muscles allow air to bypass the intended respiratory pathway. This swallowed air accumulates in the stomach and intestines, causing bloating, discomfort, and distension. The severity varies, with some users experiencing mild symptoms and others reporting significant gastrointestinal distress.

The upper esophageal sphincter (UES) normally prevents excessive air intake. However, when CPAP pressure is too high, the UES may relax, allowing air to pass into the digestive system. This effect is more pronounced in individuals with esophageal motility disorders or a weakened LES.

A study published in Chest found that patients using CPAP pressures above 12 cm H₂O were more likely to experience aerophagia. Adjusting pressure settings based on individual tolerance may help reduce discomfort. Auto-adjusting CPAP machines, which modify pressure in real time, can prevent excessive air delivery and lessen aerophagia.

Mask fit and breathing patterns also influence aerophagia. A poorly fitting mask can lead to air leaks, causing users to gulp air to compensate. Nasal congestion can also lead to mouth breathing, increasing air swallowing. Using nasal decongestants, chin straps, or alternative mask designs may help address these issues.

Characteristics of CPAP-Induced Bloating

CPAP-induced bloating typically presents as abdominal distension, with users often waking up with a swollen stomach that persists for hours. This sensation is accompanied by a feeling of fullness, even without food intake. Unlike bloating caused by gas-producing foods, CPAP-related bloating develops rapidly overnight and gradually subsides as the body expels excess air through belching or flatulence.

Pain and cramping may also occur, varying in intensity depending on the volume of air swallowed. The buildup of air stretches the gastrointestinal tract, leading to discomfort similar to irritable bowel syndrome (IBS) or small intestinal bacterial overgrowth (SIBO). Some users experience increased burping or excessive gas as the body attempts to relieve pressure.

The severity of bloating depends on CPAP pressure settings, sleep position, and individual physiological factors. Higher pressure levels or fixed-pressure devices may worsen symptoms, while users with preexisting gastrointestinal sensitivities, such as acid reflux, may experience prolonged discomfort. Some individuals also report tightness in the lower abdomen, indicating that swallowed air can travel further into the intestines before being expelled.

Differentiating CPAP Belly From Other GI Conditions

CPAP belly symptoms can resemble those of other gastrointestinal disorders, making it important to determine whether bloating stems from air ingestion during therapy or an underlying condition. Bloating that occurs exclusively after CPAP use and improves as the day progresses is more likely CPAP-related. Persistent bloating unrelated to CPAP therapy may indicate conditions such as IBS, SIBO, or functional dyspepsia.

GERD can also present with bloating, particularly when acid reflux leads to stomach distension. However, GERD typically includes heartburn, regurgitation, and a sour taste in the mouth, which are not primary features of CPAP belly. GERD symptoms often worsen when lying down, whereas CPAP-induced bloating peaks overnight and improves throughout the day.

A trial of acid-reducing medications, such as proton pump inhibitors (PPIs), can help differentiate GERD from CPAP-related aerophagia. GERD-related bloating may improve with acid suppression, while CPAP belly will persist unless therapy adjustments are made.