Suction? PEP? Percussion? Oscillation? Cough assist? With an array of airway clearance therapies available for respiratory therapists, how do RTs choose the right method for the job?


Suction? Positive expiratory pressure? Percussion? Oscillation? Cough assist? With an array of airway clearance therapy options available for respiratory therapists, what device is the right tool for the specific job? Retained secretions create increased risk for infection, increases airway resistance and work of breathing, and can lead to consolidation, mucus plugging, atelectasis, V/Q mismatching and poor oxygenation. Diseases such as cystic fibrosis, bronchiectasis, COPD, asthma, and pneumonia are linked to increased mucus production. Neuromuscular diseases such as Duchenne muscular dystrophy, amyotrophic lateral sclerosis, or spinal cord injury contribute to weak, ineffective, or absent cough and lead to retained secretions.1 

A recent 2021 publication about ACT points out a continuing problem concerning research on this topic: “Up to now, for all ACTs there is insufficient evidence to prove their efficacy and effectiveness in different clinical scenarios or to affirm the superiority of one technique over another. This absence of evidence, however, does not necessarily mean an absence of efficacy. Obviously, there is a need for more studies to increase the body of scientific evidence on this topic.”2 

ACT can be divided into breathing techniques (ie active cycle of breathing, autogenic drainage), manual techniques (postural drainage and manual percussion), and mechanical devices (ie PEP, OPEP/VPEP, HFCWO, IPV). This article will discuss the range of airway clearance therapy (ACT) options with a focus on devices, and discuss their applications and effectiveness for treatment of these respiratory diseases and the problem of secretions that cannot be cleared spontaneously.

Airway Clearance Therapies: Suctioning 

Suctioning the airway involves an invasive procedure using a suction catheter inserted past the larynx to suction out secretions. Patients who have weak or ineffective cough and exhibit signs of retained secretions (increased heart rate and/or respiratory rate, higher ventilator peak pressures, decreased SpO2, coarse breath sounds, etc) may need to be suctioned. (Note: see Reference 3 for more clinical indications.) The suctioning procedure can cause patient discomfort, changes increased or decreased heart rate, arrhythmias, increased respiratory rate, increased blood pressure, loss of PEEP, atelectasis, and decreased oxygenation.4

Suctioning can be used to remove secretions from both the upper and lower airway. However, nasotracheal (NT) suctioning often causes upper airway mucosal damage, bleeding, (which increases as repeated procedures occur) and major patient discomfort. A nasopharyngeal airway (“nasal trumpet”) can be inserted to reduce upper airway trauma and aid in passing the catheter successfully. With an artificial airway in place, the upper airway is protected from trauma and inserting the catheter is much easier but in either case (NT suctioning or suctioning through an airway), the catheter can cause damage to the trachea or carina if deep suctioning is used. Shallow suctioning involves inserting the catheter to a predetermined depth that ensures to tip of the catheter does not extend beyond the end of the airway while deep suctioning has the catheter inserted to the point that resistance is felt when it touches the carina. 

Suctioning guidelines have recommended using shallow suctioning to avoid damaging the carina, but a recent study comparing deep versus shallow suctioning in a total of 144 patients found that: “Deep sputum suction has a great influence on the vital signs of patients, but there was no ill effect on the vital signs. Shallow sputum suction cannot effectively clean the airway of patients without a cough response; therefore, patients with weak cough response need deep sputum suction.”4 Careful, gentle insertion of the catheter to perform deep suctioning can avoid damage to the trachea. 

Due to increased risk of infection during suctioning, use of a closed suction system is recommended for all patients receiving mechanical ventilation. This has become a standard of care for COVID-19 patients due to infection control precautions. The closed suction system also preserves PEEP, FiO2, and continuation of ventilation. Closed suction systems currently available include the Smiths Medical Portex SuctionPro 72 Closed Ventilation Suction System and the Avanos Medical Ballard Standard Closed Suction System. 

(A final note on suctioning: instillation of sterile normal saline has often been used through the years during suctioning but guidelines recommend not using this approach due to causing “severe coughing episodes, hypoxemia, hypertension, bronchospasm, and dislodgement of bacterial biofilm colonized in the ETT into the lower airway.”)5

Positive Expiratory Pressure and Oscillatory or Vibratory PEP devices

PEP devices are noninvasive and create a positive pressure during exhalation that is thought to increase airway diameter, decrease the tendency for airways to collapse during exhalation, and increase expiratory flow distal to the mucus that encourages mucus to loosen and move more easily.6 Expiratory pressure in PEP devices is achieved by one of three methods; flow resistor, threshold resistor, or imposing an external flow opposite to the natural expiratory flow (some devices use a combination of these methods). Several PEP devices are available including: Aptalis Pharma Flutter, Philips Respironics TheraPEP and Threshold PEP, Mercury Medical Resistex, Sarnova AccuPEP, Smiths Medical EzPAP, Monaghan Medical Versa PAP, Acoustic Innovations Lung flute, and DR Burton Healthcare Oxyjet.

Adding a brief occlusion to the expiratory flow generates an oscillation or vibration in the airway pressures and flow waveforms (this describes the OPEP/VPEP devices). The oscillation/vibration in the flow waveform (described as a “mini-cough”) has been shown to decrease the viscosity of mucus and provides shear forces that increase secretion clearance. PEP and OPEP devices are useful in treating non-ventilated patients providing the patient is cooperative and able to perform the therapy correctly. Some of the OPEP devices can be applied to patients receiving mechanical ventilation. Several OPEP devices are available including the Smiths Medical Acapella DH, Acapella DM, and Acapella Choice, the Sarnova VibraPEP, Monaghan Medical Aerobika, DR Burton Healthcare vPEP and PocketPEP, and Mercury Medical ShurClear. 

Clinical application of PEP and OPEP based on published guidelines for airway clearance has been described in an article from Respiratory Care 2013. This article includes an algorithm to assist in deciding which ACT approach to use on which patients and when to consider moving to a different approach.7 (See Figure 1 on page 1675 here.)

However, an article from 2021 reviewing ACT approaches states that, regarding OPEP: “Studies investigating this strategy are very contradictory.” The article goes on to describe studies and Cochrane reviews regarding patients with diseases including cystic fibrosis and bronchiectasis where some of the outcomes were positive/significant for a particular approach while others showed no advantage of one approach versus another.2 

A technical evaluation of eight PEP devices and eight OPEP devices was published in Respiratory Care in 2021.6 Most of the devices had the capacity to provide adjustments in expiratory resistance by change settings on the device. The authors conclude, “the devices with the highest oscillation index have the highest flow amplitude and frequency, which may indicate better clinical performance.”4 There was a wide variation in technical performance in the devices. On the high setting top performance was found in the Acapella DH, the ShurClear, and, the Aerobika. However, on the low setting the Acapella DH and the Aerobika had no flow amplitude. On the low setting, the top performance was found in the ShurClear. The VibraPEP had next highest performance rating for both the high and low setting.6 

Airway Clearance Therapies: Percussion Devices

Percussion devices are noninvasive and can be divided into external and internal percussion. External percussion devices use a handheld percussion device, driven by compressed gas or electricity, to percuss the chest surface with the impulses transferring into the tissues and reaching the airways. This is similar to the use of manual percussion or clapping. Internal percussion utilizes a mouthpiece or mask to provide a percussion effect through the upper and lower airways by delivering a positive pressure breath (pressure support) along with short bursts of air during both inspiration and expiration (or only during exhalation) at a high frequency to utilize the column or air within the airways to provide internal percussion. IPV devices also deliver an aerosol to the airways and are used with 0.9% saline or used to deliver various medicated aerosols. This added humidity (and possible bronchodilation with medication) is likely to enhance movement of mucus by changing the rheology of the mucus and by improving airflow. The Bird Intrapulmonary Percussive Ventilator (IPV), Hillrom Metaneb, and Hillrom Volara are examples of the internal percussion devices. 

Once again, the review article from 2021 of ACT approaches states that “There are conflicting opinions, however, about IPV in the literature” but goes on to say that IPV “may offer some benefit during COPD exacerbations by improving gas exchange and possibly reducing hospitalization days.”2 In a survey of acutely ill cystic fibrosis (CF) patients, results showed that IPV therapy was as good as chest physical therapy (CPT) in terms of ease of use and overall preference.8

High-Frequency Chest Wall Oscillation

HFCWO uses an inflatable garment (jacket, vest or bladder) that is worn by the patient over the chest. In ealier versions of the devices the garment is connected to a pulse generator by hoses that inflate the garment to gently compress and support the chest wall, then transmit short bursts of air at high frequencies (5-25 Hz) into the garment causing it to rapidly inflate and deflate. The resulting brief squeeze and release of the chest wall causes an oscillation in the air within the airways that dislodges mucus from the airway wall.9-10 Some evidence suggests that the oscillations also change the rheology of the mucus, making it less viscose and easier to mobilize.11 Later changes in the design have made the devices portable. These devices incorporate rechargeable battery-powered discs or pods that vibrate to set up the airway oscillations.10 

HFCWO has been researched in a number of studies to examine its usefulness in clearing secretions in conditions including thoracic trauma, neuromuscular diseases, COPD, bronchial asthma and CF.9 In the US, HFCWO has become a standard of care in patients with CF. In the UK and Europe, HFCWO has been used in other lung diseases such as COPD, acute exacerbations of COPD or exacerbations of bronchial asthma.9 

Even though this ACT has become more utilized, as one author states: “The effects of HFCWO on sputum production as well as lung function is in dispute.”9 Despite the lack of high level research, HFCWO therapy has been widely used and has a growing number of applications for patients with chronic lung problems and issues with sputum clearance. Some of the HFCWO devices currently available include the Philips Respirtech InCourage, the Electromed Smartvest, Hillrom Vest and Monarch Vest systems, and Tactile Medical’s AffloVest.

Cough Assist Devices

Cough assist devices provide a slow deep positive pressure breath followed by a rapid switch over to negative pressure to mimic a deep breath followed by a cough. The process is described as mechanical insufflation-exsufflation (MI-E) and the inspiratory–expiratory pressures use cmH2O as the units of measure. The goal of the settings for MI-E pressures and timing of the switch is to achieve a peak cough flow of 270 LPM or greater, which is considered by some to be the lowest point for effective secretion clearance (according to the Canadian Thoracic Society Position Statement on MI-E devices).12 Other sources recommend using a cough assist device in individuals with a CPF ≤160 LPM.13

In general, the positive pressure is set around +30 to +40 cmH2O and the negative pressure is set to approximately -35 to -45 cmH2O. The therapy may be self-administered or performed by a trained assistant. Often the treatments will be given as needed (based on clinical signs of retained secretions) with 3 or 4 sets of 10 inspiratory-expiratory cycles followed by suctioning. The patient interface can be a mouthpiece, facemask, or the device can be attached to an endotracheal or tracheostomy tube. The Philips CoughAssist T70 device offers the option of adding high-frequency oscillations generated by air pulses to just the inspiratory cycle, expiratory cycle, or both.14 This option is being evaluated for effectiveness, etc. 

Patients who can be treated with cough assist devices include those with a very weak or absent spontaneous cough. Diseases that have been treated include amyotrophic lateral sclerosis, Duchenne muscular dystrophy, spinal cord injury (especially those with quadriplegia) and those with general neuromuscular disease including such diseases as a variety of muscular dystrophy forms, poliomyelitis, post-polio syndrome, spinal muscular atrophy, multiple sclerosis, cerebral palsy and Ulrich syndrome.12 Cough assist devices include the Hillrom Synclara Cough System and Philips CoughAssist T70.


An editorial concerning ACT approaches published in Respiratory Care 2017 sums up the problem that continues to plague those dealing with patients who have retained secretions. In this editorial the author states: “Although airway clearance techniques are often prescribed, there is no evidence of benefit in asthma, pneumonia, atelectasis, bronchiolitis, COPD, chronic bronchitis, or non-cystic fibrosis bronchiectasis, and data regarding long-term benefit even in cystic fibrosis is limited.”15 Guidelines provide recommendations based on high level research the desired strength of the research is lacking. This problem is due to many factors such as bias, low numbers of patients, heterogeneity in the population, low numbers of administered treatments, short time frame for follow-up, missing data, etc.

Many agree that ACT is useful but that the particular approach for a patient needs to be carefully selected based on effectiveness, cost/benefit, patient preference, patient adherence to therapy, adverse effects, and achievement of goals of the therapy. The advice given in the Clinical Practice Guideline from the AARC published in 2013 still holds true: “Although lack of evidence does not mean lack of benefit, it is desirable to have better evidence to support the practice. Appropriately powered and methodologically sound research is needed.”1


Bill Pruitt, MBA, RRT, CPFT, AE-C, FAARC, is a writer, lecturer, and consultant and recently retired from over 20 years teaching at the University of South Alabama in Cardiorespiratory Care. He also volunteers at the Pulmonary Clinic at Victory Health Partners in Mobile, AL. For more information, contact [email protected].


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Airway Clearance Therapies