Airway Clearance: The Earlier, The Better?

This post was written by Michael W. Hess, MPH, RRT, RPFT, COPD Foundation.

Inhaled medications tend to get the lion’s share of attention when it comes to COPD therapies, and for good reason. They’re familiar, they’re accessible, and they have long been some of the most effective tools we have for reducing symptom burden and managing other aspects of COPD, especially as we’ve focused on overall symptom control and reducing exacerbations. As COPD management evolves in the 21st century, the idea of “treatable traits” that can be directly addressed in order to manage symptoms and reduce exacerbation risk has risen to the fore, allowing for a more individualized approach to someone’s care.¹

One of those traits is mucus hypersecretion, common in those people whose COPD leans more toward the chronic bronchitis side of things. Frequent, productive coughing is a way of life for this population, as their airways struggle to stay clear. For these folks, aerosol medications may not be enough to keep their COPD in check. That’s where basic airway clearance techniques come in. From breathing exercises like huff coughing to oscillatory positive expiratory pressure (OPEP) devices, these therapies assist the body’s own mechanisms clear out excess mucus, reducing cough and improving comfort. They come in several form factors, but the general idea of providing expiratory resistance coupled with airway vibration to both recruit alveoli and loosen secretions is consistent across all these devices. They are generally easy to use and have a track record of improving outcomes, at least in the short term.² There are certain subsets of people living with COPD who need a still more aggressive option. Historically, this role has been filled by mechanical insufflation-exsufflation equipment. These devices use positive inspiratory pressure with a shift to negative expiratory pressure, simulating a forceful natural cough and assisting mucus clearance.3 However, there is limited clinical information to actually support the use of these devices in any disease state, and rates of adherence to therapy.⁴ Fortunately, there is another potentially valuable option for people who need higher-level airway clearance but who may not tolerate insufflation-exsufflation: high-frequency chest wall oscillation (HFCWO). HFCWO has long been used in other lung conditions, notably cystic fibrosis and bronchiectasis. Research into its application for COPD is still relatively young, but there are some promising signs.

As a quick review, HFCWO is delivered through the use of a percussive vest that uses either rapid air pressure cycling or small electric motors to induce percussion and vibration all around the thoracic cage. These impacts work to loosen mucus and move it from peripheral airways to more central ones with larger caliber, facilitating a more effective cough.⁵ Clearing the mucus out not only reduces cough frequency, but also reduces the risk that stagnant, pooled mucus will become infected, leading to what is often described as a vicious cycle of infection, inflammation, dysfunction, and structural damage in the airways.⁶

This cycle has been clearly identified in processes like the aforementioned bronchiectasis, but not necessarily confirmed in COPD. However, it’s important to recognize the growing body of evidence of a link between COPD and bronchiectasis. Studies regarding the prevalence of bronchiectasis in people with COPD have been somewhat inconsistent, but there’s evidence to support that somewhere around half of everyone with at least moderate COPD symptoms also has bronchiectasis.⁷ It’s currently unclear which is the chicken and which is the egg (or whether the conditions develop concurrently), but there’s an emerging school of thought that the chronic bronchitis aspects of COPD often end up leading to bronchiectasis (likely due to the vicious cycle mentioned earlier). A recent study found that in 201 people with COPD, 42% went on to develop bronchiectasis within 7 years.⁸ One of the leading risk factors? The chronic presence of purulent sputum, just the sort of thing seen with many cases of chronic bronchitis.

Arresting someone’s journey along this path is of paramount importance. In general, people with chronic bronchitis are at higher risk for more frequent exacerbations, as well as early mortality.⁹ That risk rises substantially after the onset of bronchiectasis; those with the overlap tend to be hospitalized more frequently and for longer stays,¹⁰ and their already-higher mortality rate can double.¹¹ Thus, considering the often-progressive nature of both conditions and the known utility of early diagnosis specifically in COPD, it seems to be in everyone’s best interest to aggressively treat those with signs of chronic bronchitis as early as possible in their course.

That’s where therapies like HFCWO come in. By aggressively supplementing the body’s own airway clearance capabilities with the judicious application of physics, people with mucus hypersecretion are far better able to manage their sputum production. In turn, that appears to have beneficial effects on healthcare utilization and, of course, quality of life. A study presented at the 2017 American Thoracic Society looked at claims data for 135 people with COPD without bronchiectasis and found statistically significant reductions in emergency department visits, hospitalizations, and office visits.¹² A 2018 meta-analysis also found the use of HFCWO appeared to improve exercise capacity in terms of distance and duration.¹³

While the body of evidence to support airway clearance techniques like HFCWO may not be as robust as that of more common therapies like bronchodilators, the evidence we do have is increasingly compelling. These devices should be near the front of your mind when caring for anyone with heavy sputum production. The sooner we can clear the air(ways), the better!

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