What Is an Acapella Device and How Does It Work?

The Acapella device is a handheld airway clearance tool that combines positive expiratory pressure with airflow oscillations to help loosen and move mucus out of the lungs. When you exhale through it, a counterweighted plug or magnet inside opens and closes rapidly, creating vibrations in the air column that travel back into your airways. These vibrations, combined with the back-pressure of breathing against resistance, work together to shake mucus free from airway walls and push air behind plugged sections of the lung to help mobilize secretions. The device is widely prescribed for people with chronic lung conditions that cause excess mucus production, but how well it works, who benefits most, and how it stacks up against alternatives are more nuanced questions than the prescription alone suggests.

How the Device Moves Mucus

The Acapella works on two principles simultaneously. The first is positive expiratory pressure, or PEP. When you blow against resistance, the back-pressure splints your airways open and pushes air through collateral ventilation channels, getting behind mucus plugs that are blocking normal airflow. This temporarily inflates regions of the lung that might otherwise stay collapsed, which helps mobilize secretions from those areas.

The second principle is oscillation. The vibrations the device produces travel back through the air column and into your airways, physically jostling mucus loose from the bronchial walls. The device is engineered to produce oscillation frequencies in the range of about 12 to 15 Hz, which lab testing has shown aligns with both the natural resonance frequency of the respiratory system and the beat frequency of the tiny cilia that line your airways and sweep mucus upward.¹ Matching those frequencies is thought to maximize how effectively the vibrations reduce mucus viscosity and encourage the cilia to do their job. Lab evaluations of three Acapella models found that at an intermediate dial setting, all produced vibration frequencies in that 12–15 Hz sweet spot, with resistance pressures between roughly 5 and 11 cm of water.²

A Cochrane review of PEP therapy in cystic fibrosis described the underlying idea: back-pressure during exhalation builds up gas behind mucus via collateral ventilation and temporarily increases the volume of air sitting in the lungs at rest, both of which help push secretions toward the larger airways where they can be coughed out.³ The oscillatory component adds a shaking effect on top of that baseline pressure, which is why devices like the Acapella are categorized as oscillatory PEP (sometimes abbreviated OPEP) rather than plain PEP.

Which Model Do You Need

The Acapella comes in two main color-coded versions designed for different levels of lung function. The green model is intended for people who can sustain an expiratory flow of at least 15 liters per minute, while the blue model is made for those who cannot reach that threshold.⁴ In practice, 15 liters per minute is a fairly low bar; most adults with moderate lung disease can clear it. The blue model is typically reserved for people who are very debilitated, post-surgical, or pediatric patients with limited respiratory effort.

There is also a third variant, the Acapella Choice, which is a transparent, disposable version designed for single-patient or short-term use. All three models share the same basic mechanism and have a numbered dial (settings 1 through 5) that adjusts resistance and oscillation frequency. Turning the dial higher increases the resistance you blow against and changes the vibration characteristics. Lab bench testing found that at an amplitude of 20 cm of water, the blue Acapella’s resistance rose from about 26 to 47 cm H₂O/L/sec as the dial went from 1 to 5, while the green Acapella’s resistance went from roughly 13 to 38 over the same range.⁵ The green model produces lower resistance at matching dial settings, which makes sense given it is built for people with stronger airflow.

Most respiratory therapists start patients at a moderate setting (around 3 or 4) and adjust based on comfort and how productive the sessions feel. The lab data supports setting 4 as a reasonable starting point for most patients, since it landed in the optimal frequency range across all three device variants.⁶

Evidence in COPD

COPD is one of the most common reasons people are prescribed an Acapella. A randomized controlled trial published in Thorax studied people with COPD who produced sputum daily or most days and found that regular Acapella use improved cough-related quality of life, reduced cough frequency by about 60 coughs over 24 hours, and improved general quality-of-life scores compared with a control group.⁷ The improvement in cough-specific quality of life crossed the threshold considered clinically meaningful, which matters because COPD trials often show statistically significant results that patients themselves cannot actually feel. This trial, however, did not find a significant effect on sleep disturbance.

A systematic review looking at both the Acapella and the Aerobika (another OPEP device) in COPD concluded that both devices can reduce rehospitalization and improve lung function, though the authors noted the evidence base remains small.⁸ The practical takeaway for people with COPD is that the Acapella is most likely to help if you produce sputum regularly and have trouble clearing it. If your COPD is mainly about airflow limitation without much mucus, the benefit is less clear.

One small trial explored whether adding biofeedback (visual cues showing whether the patient is exhaling correctly) to Acapella therapy in moderate COPD would improve outcomes beyond standard Acapella use. By five days, the biofeedback group was clearing more sputum per session and showed modestly better improvements in lung volumes compared to the group using the Acapella without feedback.⁹ This is a single study with a short follow-up, but it raises an interesting point: technique matters, and knowing whether you are using the device correctly can make a real difference in how much mucus you actually move.

Evidence in Cystic Fibrosis

Cystic fibrosis was one of the earliest clinical targets for OPEP devices, since daily airway clearance is a cornerstone of CF management. A randomized trial comparing the Acapella with a standard PEP mask in children hospitalized for a CF exacerbation found no statistically significant differences between the two devices across any outcome measured after ten days of treatment. Both groups improved, and patients reported high satisfaction with both devices.¹⁰ That is a common finding across the airway clearance literature: different devices tend to produce similar results, and individual preference ends up being a major factor in which one gets chosen.

A Cochrane review of conventional chest physiotherapy versus alternative airway clearance techniques in CF reinforced this pattern. Across 15 data sets involving 475 participants, there was not enough evidence to confirm or rule out meaningful differences between traditional manual techniques and device-based approaches. Participants generally preferred techniques they could do themselves, which is a significant practical advantage for handheld devices like the Acapella.¹¹

Bronchiectasis and Post-Surgical Use

Bronchiectasis (outside of CF) is another condition where mucus retention drives repeated infections and lung damage. A review of mucociliary clearance techniques in non-CF bronchiectasis concluded that airway clearance therapies appear safe and may improve sputum expectoration, some measures of lung function, and quality of life, but highlighted a shortage of randomized trials, especially in children.¹² The evidence here is thinner than in CF or COPD, which does not mean the devices are ineffective but rather that fewer researchers have studied the question rigorously.

A separate application is preventing lung complications after chest or upper abdominal surgery. When someone has an incision in the chest wall or upper abdomen, deep breathing and coughing become painful, which can lead to mucus buildup, collapsed lung segments, and pneumonia. A systematic review and meta-analysis found that OPEP therapy in this context can help clear airways and improve mucus drainage, reducing the risk of postoperative pulmonary infections and atelectasis.¹³ This is one of the more intuitive applications: if a patient cannot cough well and needs help moving secretions, a device that does some of the work for them fills an obvious gap.

How the Acapella Compares to Other Devices

The Acapella is not the only OPEP device on the market. The Flutter (a pipe-shaped device with a steel ball that rolls against gravity to create oscillations), the Aerobika, the Shaker, and the VibraPEP are all alternatives. Head-to-head lab comparisons reveal real mechanical differences between them, even if clinical trials often struggle to show that those differences translate into meaningfully different patient outcomes.

The Acapella and the Flutter have similar overall performance characteristics, but one practical advantage of the Acapella is that it works in any orientation. The Flutter depends on gravity acting on its steel ball, so it must be held at a specific angle to function correctly. The Acapella uses a magnetic counterweight mechanism instead, meaning you can use it sitting up, reclined, or even lying on your side.¹⁴ For patients who need to do airway clearance in different positions (such as those practicing postural drainage), that flexibility matters.

A lab comparison of six OPEP devices during active exhalation found that the Acapella, Aerobika, and Shaker devices were not mechanically interchangeable, with different pressure, oscillation, and flow profiles.¹⁵ A separate study simulating CF conditions found that the Aerobika delivered more consistent pressure amplitude across resistance settings and produced higher mean pressure amplitude at medium and high resistance levels than the Acapella.¹⁶ Whether that mechanical consistency translates to better clinical outcomes is still an open question; the trials comparing patient-level results tend not to show dramatic differences between devices.

One area where devices do differ meaningfully is how much airflow they demand. A study measuring the flow rates needed to sustain target pressures found that valved devices like the VibraPEP required significantly less flow than mechanical devices like the Acapella and Aerobika.¹⁷ For patients with very limited lung function who cannot generate much airflow, a lower-flow-requirement device may be easier to use effectively.

Using the Acapella With a Nebulizer

Many people who need airway clearance also use nebulized medications, so there is a natural appeal to combining the two. Some Acapella models (particularly the Acapella Duet) are designed with a port for attaching a nebulizer, allowing you to inhale medication and then exhale through the OPEP device in one circuit. In theory, this saves time and might improve drug delivery by opening airways first and then depositing the medication.

In practice, the combination introduces tradeoffs. A scintigraphy study (which tracks where inhaled particles land in the lungs using a radioactive tracer) found that when a nebulizer was attached directly to the Acapella, lung deposition was lower than when the nebulizer sat between the mouthpiece and the Acapella, or when the nebulizer was used without any Acapella at all.¹⁸ In other words, where you place the nebulizer in the breathing circuit matters a great deal.

A bench study reinforced the concern by measuring how much of a medication dose actually makes it to the patient when the nebulizer is connected to the Acapella. Connecting a standard nebulizer to either the Acapella Choice or Acapella Duet dramatically reduced the particle size and the total amount of drug available, with the patient dose dropping by roughly 76% and 84%, respectively. Between 17% and 25% of the medication was retained inside the PEP device itself.¹⁹ If you are prescribed a combined setup, it is worth discussing these findings with your respiratory therapist to make sure you are still getting an adequate medication dose.

Cleaning and Infection Risk

Any device you breathe through repeatedly becomes a potential reservoir for bacteria, and the Acapella is no exception. A study of airway clearance devices used by children with cystic fibrosis found that over a third of the devices tested positive for pathogenic bacteria.²⁰ Interestingly, the bacteria found on the devices did not always match the organisms identified from the patients’ own airway swabs, suggesting that environmental contamination (from sinks, countertops, or hands) is a factor alongside respiratory secretions.

The same study found that non-sterilization cleaning methods were ineffective at removing pathogens. Most manufacturers recommend disassembling the device, washing parts with warm soapy water, and either boiling, steam-sterilizing, or soaking in a vinegar solution. In practice, many patients do not follow these steps consistently. If you are using an Acapella daily, the cleaning routine is not optional, particularly if you have a condition like CF or bronchiectasis where colonization with harmful bacteria can accelerate lung damage.

Adherence Challenges in Younger Users

Airway clearance is only helpful if people actually do it, and adherence is a persistent challenge, especially among teenagers. A study tracking real-time breath-by-breath data from 145 children and young people with CF over two months found that only 60% completed at least half of their prescribed treatments. Among teenagers, the numbers were worse: 56% did the right number of daily sessions compared with 77% of pre-teens.²¹

The study also revealed something about quality, not just quantity. When using OPEP devices like the Acapella, children tended to take shorter breaths at higher pressures, and very few breaths (just 1–3%) fell within the recommended ranges for both pressure and breath length simultaneously. PEP devices fared better, with 30–31% of breaths meeting both targets. This does not necessarily mean PEP devices are superior clinically, but it suggests that many children are not getting the intended therapeutic effect from their OPEP sessions even when they sit down and do them.

Usability research has explored why teenagers struggle with the Acapella specifically. One study identified that adolescents do not use the device as regularly or correctly as prescribed and pointed to design factors that contribute to the problem.²² Five factors emerged that could improve adherence: better engagement, clearer information, increased user confidence, improved aesthetics, and compatibility with the patient’s lifestyle. A companion study found that older teens were better at weighing long-term health benefits against short-term inconvenience and that all adolescents wanted devices that respected their growing independence and fit into their social lives.²³ The Acapella, in its current form, looks like a medical device. For a teenager trying to navigate school, social identity, and chronic illness all at once, that alone can be a barrier to pulling it out and using it.

Practical Tips for Getting the Most Out of It

The standard protocol most therapists teach involves sitting upright, taking a breath slightly larger than normal (but not a maximal gasp), and exhaling actively through the device for about three to four seconds. You are not trying to blow as hard as possible; the goal is a steady, moderately forceful exhalation that lets the device oscillate properly. A typical session involves sets of 10 to 20 breaths through the device, followed by two or three “huff” coughs (forced exhalations with an open throat, like fogging a mirror) to move loosened mucus up and out. Most prescriptions call for two to four sessions per day, though this varies by condition and severity.

Timing the session matters. Many people find the device most productive in the morning, when mucus has pooled overnight, or about 30 minutes after inhaling a bronchodilator or hypertonic saline, when airways are more open and mucus is more hydrated. If you are combining the Acapella with nebulized medications, the evidence on physical setup suggests keeping the nebulizer between your mouth and the device rather than attaching it downstream of the oscillation mechanism, to avoid losing a large portion of your medication dose inside the device.

The dial setting is not a “higher is better” situation. If the resistance is too high, you may not be able to sustain the exhalation long enough for the oscillations to do their work, or you might fatigue quickly and cut sessions short. If it is too low, the device may not generate enough back-pressure to be therapeutic. A respiratory therapist can help find the setting where you feel the vibrations in your chest without straining, and you can fine-tune from there as your comfort level changes. The research on optimal settings suggests the middle of the dial range is a reasonable starting point for most adults, adjusting upward only if you can maintain consistent, comfortable exhalations at the higher resistance.

When the Acapella May Not Be Right

The Acapella is generally considered safe, but there are situations where breathing against resistance is not advisable. People with untreated pneumothorax (a collapsed lung from an air leak) should not use any PEP or OPEP device, since the added pressure could worsen the leak. Active hemoptysis (coughing up significant amounts of blood) is another contraindication, because the increased airway pressure and vigorous coughing the device promotes could aggravate bleeding. Patients with severely elevated intracranial pressure, recent facial or oral surgery, or an acute sinus infection may also need to avoid it. These contraindications are common across all PEP and OPEP devices, not unique to the Acapella.

Beyond outright contraindications, some people simply do not produce enough mucus to benefit from the device. If your primary symptom is breathlessness without significant sputum production, the Acapella is unlikely to address that, and your therapy time would be better spent on other interventions like pursed-lip breathing exercises or pulmonary rehabilitation. The strongest evidence of benefit is consistently in people who produce sputum daily or nearly daily, whether from COPD, CF, bronchiectasis, or post-surgical mucus retention.