Puffing out air during sleep is most often caused by one of three things: a condition called catathrenia (sleep groaning), obstructive sleep apnea, or simple mouth breathing due to nasal congestion. The pattern is distinctive enough that a bed partner usually notices it before you do. What’s happening depends on the timing of the sound, whether it occurs on the inhale or exhale, and whether other symptoms like daytime fatigue are present.
Catathrenia: The Most Common Explanation
Catathrenia is a sleep disorder where you take a deep breath in, briefly hold it, then slowly release it through a partially closed voice box. The result is a puffing, groaning, or moaning sound on the exhale that can last several seconds. It affects roughly 4% of adults, though it’s rarely diagnosed because most people don’t know it’s happening unless someone else tells them. Bed partners typically describe hearing a deep inhale followed by a long, slow exhale with a high-pitched squeak or groan at the end.
The sound is produced in the larynx (voice box), where the vocal cords actively press together and vibrate during exhalation. This is fundamentally different from snoring, which happens during inhalation and originates higher up in the throat from soft tissue vibration. That exhale-versus-inhale distinction is the simplest way to tell the two apart.
About 81% of catathrenia episodes occur during REM sleep, the stage associated with dreaming. Research from the largest study of catathrenia patients found that over 80% of episodes were linked to brief micro-arousals, moments where the brain partially wakes during sleep. This has led researchers to classify catathrenia as a disorder of arousal rather than a breathing problem, even though it sounds like one. The episodes tend to cluster in the second half of the night when REM sleep is most concentrated.
Catathrenia is generally harmless to the person doing it. It doesn’t reduce oxygen levels or fragment sleep the way apnea does. The main consequence is social: the groaning can be loud enough to disturb a bed partner’s sleep. Some people with catathrenia report mild embarrassment or avoid sharing a room, but the condition itself doesn’t typically cause daytime symptoms.
Sleep Apnea and Forceful Exhalation
If the puffing is more forceful or explosive, sleep apnea may be the cause. In obstructive sleep apnea, the airway collapses during sleep, temporarily blocking airflow. When the brain detects dropping oxygen levels, it triggers a brief arousal that reopens the airway. The rush of air that follows can come out as a puff, snort, or gasp. These events can happen hundreds of times per night in severe cases.
One study that video-recorded sleeping patients found that mouth puffing was significantly associated with higher apnea severity, lower blood oxygen levels, and more time spent with oxygen saturation below 90%. The puffing was essentially the body’s recovery breath after each blocked-airway episode.
The key differences between apnea-related puffing and catathrenia: apnea puffing tends to be sudden and forceful rather than slow and drawn out, it’s often preceded by silence (the pause in breathing), and it comes with other signs. Those signs include feeling unrested despite a full night of sleep, excessive daytime sleepiness, nodding off while reading or watching TV, increased irritability, and reduced productivity. A bed partner might notice pauses in your breathing punctuated by loud snorts or gasps. Frequent colds and a weakened immune response can also result from the chronic poor sleep quality that apnea causes.
Mouth Breathing From Nasal Obstruction
Sometimes the explanation is simpler. If your nasal passages are partially blocked from allergies, a deviated septum, or chronic congestion, air gets rerouted through your mouth during sleep. When your lips are loosely closed, exhaled air pushes through them and creates a puffing or fluttering sound. This is especially common during deeper sleep stages when your jaw muscles relax and your mouth falls open slightly.
This type of puffing tends to be quieter and more rhythmic than catathrenia or apnea-related sounds. It often worsens during allergy season or when you have a cold. Keeping your sinuses clear before bed with saline rinses or treating underlying allergies can reduce or eliminate it.
CPAP Users and Air Puffing
If you already use a CPAP machine for sleep apnea and notice air puffing from your mouth, that’s likely a mask leak. During deeper sleep, your jaw relaxes and falls open, allowing pressurized air to escape through your mouth instead of reaching your airway. This reduces the effectiveness of your treatment and can dry out your mouth and throat.
A few adjustments can fix this. A chin strap keeps your jaw closed and prevents the air from escaping. Switching from a nasal mask to an oronasal mask, which covers both your nose and mouth, delivers air through both pathways so an open mouth doesn’t cause a leak. If dry air is irritating your nasal passages and driving you to breathe through your mouth, adding or adjusting a heated humidifier on your CPAP can help. Treating any underlying nasal congestion is also important, since a blocked nose forces mouth breathing regardless of mask type.
How to Tell Which Type You Have
The best starting point is asking a bed partner (or recording yourself with a phone or sleep app) and paying attention to the pattern. A slow, drawn-out exhale with a groan or hum points toward catathrenia. Sudden puffing or gasping after a silent pause suggests apnea. Gentle, rhythmic lip-fluttering throughout the night is more likely simple mouth breathing.
Context matters too. If you wake up feeling rested and have no daytime symptoms, catathrenia or mild mouth breathing is the most likely explanation, and neither is medically dangerous. If you’re tired during the day despite enough hours in bed, if you’re more irritable than usual, or if a partner has noticed actual pauses in your breathing, those are signs that something is disrupting your sleep quality and worth investigating with a sleep study. A sleep study records your brain waves, breathing, oxygen levels, and body movements overnight, and it’s the only way to definitively distinguish between these causes.