A single round of airway clearance therapy (ACT) led to immediate improvements in some lung function tests for cystic fibrosis (CF) patients, a study found.

However, mucus that plugs up the airways wasn’t cleared by a single treatment.

Overall findings from the study highlight “the potential remaining importance of ACT,” even as new, highly effective CF therapies emerge, according to study researchers.

The study, “Short-term structural and functional changes after airway clearance therapy in cystic fibrosis,” was published in the Journal of Cystic Fibrosis

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ACT is an umbrella term for devices that help clear mucus from the airways, enabling better breathing for CF patients. High-frequency chest wall oscillation (HFCWO) is a type of ACT comprised of an inflatable vest connected to an air compressor. The vest is rapidly inflated and deflated to put pressure on the chest wall, working to loosen mucus that can then be coughed up.

While the approach has well-established benefits, it’s time consuming, with one report finding that CF patients spend an average of 108 minutes (1 hour, 48 minutes) every day performing ACT. This can create a burden that affects life quality and adherence.

As the CF treatment landscape changes to include new highly-effective CFTR modulator therapies, it is important to re-evaluate the use of ACT vests as part of CF daily regimens, according to researchers.

In the study, the researchers examined the immediate effects of a single round of HFCWO on lung structure and function among 20 CF patients seen at the Cincinnati Children’s Hospital in Ohio.

The participants’ mean age was 20.7 (range 10.8–36.1 years). These 11 males and nine females all had at least one copy of F508del, the most common CF-causing mutation.

During the single-day, in-hospital study, patients underwent a range of clinical evaluations before and after a single round of ACT. The procedure was performed with their own equipment brought from home, and in combination with any usual inhaled therapies.

Several lung function tests

A few different tests were used to evaluate lung function. Standard measures included the forced expiratory volume in one second (FEV1) and multiple breath washout (MBW) tests.

FEV1 measures how much air can be forcibly exhaled from the lungs in a single breath, with a higher value reflecting better lung function. MBW measures how long it takes a person to clear an inhaled tracer gas from their lungs, with longer times to clearance typically indicating worse lung function.

Results showed small, yet significant improvements in FEV1 performance after ACT. Most participants — 15 of 20 — saw increases in the percent predicted FEV1 performance.

Still, no significant improvements were seen in the MBW, with faster clearance times observed in only five patients.

Xe MRI imaging

The researchers also employed a newer imaging technique, called Xe MRI, which quantifies ventilation non-invasively through the use of an inhaled gas that can be visualized with an MRI scan. With this approach, a ventilation defect percentage (VDP) is generated, with a higher percentage reflecting worse ventilation.

As with FEV1, small but significant improvements were observed on Xe MRI scans after ACT. Specifically, 16 of 20 patients experienced reductions in VDP after the therapy.

At the same time as the Xe MRI, structural lung changes were assessed with another type of MRI analysis called UTE.

In terms of structural lung disease, patients were generally mildly affected, with large mucus plugs being the only type of structural change commonly identified.

Mucus plugs were not significantly affected by ACT, suggesting that “larger plugs are difficult to mobilize after a single instance of ACT,” the researchers wrote.

In general, areas of ventilation deficits on Xe MRI were not associated with any structural changes on UTE MRI. However, areas of ventilation deficits that didn’t improve with ACT often corresponded to the presence of a mucus plug, consistent with the notion that “plugs act as barriers to ventilation,” the researchers wrote.

Overall, findings were generally similar among the subgroup of 13 patients using highly-effective CFTR modulator Trikafta (elexacaftor/tezacaftor/ivacaftor).

It hasn’t been well-explored whether the use of Trikafta or other effective therapies might allow for a reduction of ACT in the future.

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“At present, all patients with CF on modulator therapy are advised to continue their regular ACTs,” the researchers wrote.

The team noted that a strength of their study was the use of multiple different techniques, including functional and structural imaging tests.

“A combination of functional and structural evaluations of CF lung disease are likely needed in the future to better understand changes in treatment,” the team concluded.

The study was funded partially by Vertex Pharmaceuticals, which markets Trikafta.

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