PEP therapy, short for positive expiratory pressure therapy, is a breathing technique that uses a small device to create resistance when you exhale. That back-pressure forces air behind mucus trapped in your lungs and airways, loosening it so you can cough it out. It’s one of the most widely used airway clearance methods for people with conditions like cystic fibrosis and bronchiectasis, and a typical session takes about 20 minutes.
How PEP Therapy Works
You breathe through either a face mask or a handheld mouthpiece attached to a resistance valve. Air flows in freely when you inhale, but when you exhale, the device restricts airflow so you have to push harder to breathe out. It takes roughly four times as long to exhale against this resistance as it does to inhale normally.
That extra effort does two important things inside your lungs. First, the pressure temporarily increases the volume of air sitting in your lungs (called functional residual capacity), which forces air through small side channels and gets behind mucus stuck to airway walls. Second, the outward pressure acts like a splint, holding smaller airways open so they don’t collapse during exhalation. Over 12 to 15 breaths, this air gradually builds up behind secretions and pushes them toward your larger, central airways where you can cough them out.
A study in Physical Therapy measured how well this actually works in people with cystic fibrosis. By 45 minutes after a session, gas mixing in the lungs (a marker of how well air reaches all parts of the lung) improved by 15% with low-pressure PEP and 23% with high-pressure PEP, compared to just 5% with no PEP. Those improvements corresponded with better lung function, more sputum cleared, and higher blood oxygen levels.
Static PEP vs. Oscillatory PEP
PEP devices fall into two main categories. Static PEP devices create steady, constant resistance. You exhale against a fixed pressure, typically between 10 and 25 cmH₂O (a measure of resistance), though high-PEP versions can go as high as 40 to 120 cmH₂O. These are the simpler devices, often just a mask or mouthpiece with an adjustable resistor.
Oscillatory PEP devices combine that same back-pressure with rapid vibrations during exhalation. These pulses shake the airway walls, helping dislodge mucus from the lining and into the open airway, while repeated bursts of faster airflow push secretions upward toward the mouth. Common oscillatory devices include the Flutter valve, Acapella, RC-Cornet, and Aerobika. They’re handheld, portable, and don’t require a partner to operate.
What a Typical Session Looks Like
Your respiratory therapist will tailor the specifics to your situation, but a standard PEP session follows a consistent pattern. You sit upright, seal your lips around the mouthpiece (or fit the mask snugly over your nose and mouth), and breathe in a slightly larger breath than normal. Then you exhale steadily against the device’s resistance, not forcefully, just enough to maintain pressure through the full breath out.
After about 10 breaths, you remove the device and perform two or three “huff coughs,” a technique where you exhale sharply with an open throat (like fogging a mirror) to move loosened mucus up and out. You repeat this cycle of 10 breaths plus huff coughing until the session is done, which usually takes around 20 minutes. With oscillatory devices, the process is similar: blow through the device several times, then huff cough to clear what’s been loosened.
Who Uses PEP Therapy
PEP therapy is most closely associated with cystic fibrosis, where daily airway clearance is essential to prevent the thick, sticky mucus characteristic of the disease from building up and causing infections. It’s also used in bronchiectasis (a condition where damaged airways accumulate mucus), COPD during stable periods, and sometimes during recovery after chest surgery to prevent mucus from pooling in the lungs while you’re less active.
Children can start PEP therapy remarkably young. At some specialized centers, babies newly diagnosed with cystic fibrosis begin PEP right away using a small fitted mask while sitting on a parent’s knee. The initial resistor is set to its smallest size (3.5 mm for term babies), and therapists adjust it as the child grows. Sessions for infants alternate two-minute cycles of PEP with assisted breathing techniques, repeated about four times. By around age 3, many children can transition to a handheld oscillatory device they use more actively on their own.
PEP Therapy Compared to Chest Physiotherapy
Traditional chest physiotherapy, sometimes called “chest clapping” or postural drainage, involves someone physically percussing your chest and back while you lie in specific positions to drain mucus by gravity. It works, but it requires another person and can be time-consuming and uncomfortable.
A large Cochrane review comparing the two approaches in people with cystic fibrosis found no measurable difference in lung function between PEP and traditional chest physiotherapy across six studies involving 169 participants. Neither approach showed a clear advantage in preventing flare-ups either. What the review did find, repeatedly across narrative reports, was that people prefer PEP because they can do it independently. That independence matters: an airway clearance routine you’ll actually stick with every day is more valuable than a theoretically better one you skip.
Keeping Your Device Clean
Because PEP devices sit in direct contact with your mouth and the warm, moist air from your lungs, they can become breeding grounds for bacteria if not cleaned properly. The general process involves four steps: cleaning, disinfecting, rinsing, and air-drying between uses.
For daily cleaning, most manufacturers recommend soaking the device in warm water with liquid dish soap, gently agitating it, and rinsing thoroughly. Disinfection can be done with heat (boiling for 5 to 10 minutes, running through a dishwasher, or microwaving if the device allows it) or with cold methods like soaking in 70% isopropyl alcohol or 3% hydrogen peroxide. One important detail: after cold disinfection, rinse with sterile water rather than tap water, since tap and even distilled water can harbor organisms you’re trying to eliminate.
Each device has slightly different instructions. The Acapella, for example, can be boiled for five minutes or run through a dishwasher. The Aerobika should be soaked for 15 minutes in soapy water and air-dried. Check your specific device’s guidelines, and if you’re unsure, your respiratory therapist can walk you through a routine that fits your equipment.
Situations Where PEP Should Be Avoided
There are no absolute contraindications to PEP therapy noted in the medical literature, but several situations call for caution or avoidance. An untreated collapsed lung (pneumothorax) is the most serious concern, since added pressure could worsen the air leak. Other relative contraindications include elevated pressure inside the skull, active coughing up of blood, recent surgery or trauma to the face, mouth, or esophagus, a ruptured eardrum or inner ear problems, and acute sinusitis or nosebleeds. During an acute asthma attack or a severe COPD flare-up, the extra work of breathing against resistance can be too much to tolerate safely.