Airway Clearance Vests Don’t Operate by Increasing Airflow Bias in the Lungs, Study Shows

Airway Clearance Vests Don’t Operate by Increasing Airflow Bias in the Lungs, Study Shows

Vests used to thin and loosen mucus in patients with respiratory and neuromuscular diseases — called high-frequency chest wall oscillation (HFCWO) vests — do not increase airflow bias in the lungs, trial data shows.

In the first study using spirometry measurements in such vests — including forced vital capacity, forced expiratory volume, and forced expiratory flow — researchers actually observed declines in lung function in the short term.

AffloVest, by International Biophysics — the trial’s sponsor — showed the smallest drop in key measurements.

The study, “Effect of High Frequency Chest Wall Oscillation Vests on Spirometry Measurements,” was published in Respiratory Therapy‘s online issue and will be featured in the October print issue.

High-frequency chest wall oscillation is an airway clearance therapy that uses inflatable vests that produce vibrations to help separate mucus from airway walls so that it can be expelled more easily.

These vests have become one of the standard therapies to manage respiratory conditions such as cystic fibrosis, bronchiectasis, and chronic obstructive pulmonary disease.

Although it has been hypothesized that these vests work by increasing airflow bias in the lungs, their effects on cephalad airflow bias has never been evaluated in a clinical setting.

Cephalad airflow bias is the term used to describe the opening of the airways when we breathe in and the narrowing when we breathe out. It is responsible for mucus movement in normal breathing.

“It has been claimed that one of the operating principles of HFCWO vests is creating ‘airflow bias’ in the lungs, but valid clinical evidence supporting that claim is lacking. We aimed to prospectively evaluate lung function scores before, during and after use using different types of HFCWO vests to evaluate the claims of increased vest-induced airflow bias in the lungs,” Thomas W. O’Brien, MD, pulmonologist at Pulmonary Disease Specialists in Kissimmee, Florida, and the study’s principal investigator, said in a press release.

The prospective, single-center, three-arm study (NCT03103880) enrolled 32 healthy people in February and March 2018. The subjects were evaluated for baseline lung function parameters, including forced vital capacity (FVC), forced expiratory volume (FEV1), peak expiratory flow (PEF), tidal volume (TV), and forced expiratory flow (FEF25%-75%), according to the guidelines of the American Thoracic Society (ATS).

Each participant was fitted with two types of HFCWO vests: the motor-based AffloVest and  compressor-based devices The Vest, SmartVest, and inCourage, manufactured by Hill-Rom, Electromed, and Respirtech, respectively.

Lung function tests were then performed at baseline and while wearing each vest to compare function before and after using the different types of vests.

While there were no significant differences in TV and PEF at baseline and when wearing any of the vests, this study showed for the first time that the use of compressor-based devices leads to a significant decrease of FVC, FEV1, and FEF25-75%, in comparison to baseline values.

Although both types of vests led to a significant decline in FEF25-75% compared to baseline, the group wearing the compressor-based devices had a reduction three times higher compared to the AffloVest group. The measures, however, went back to normal once patients stopped wearing the vests.

In addition, none of the HFCWO vest groups showed statistically significant increased airflow in the lungs, which goes against the idea that HFCWO devices work by increasing cephalad airflow bias.

These findings demonstrated for the first time that the use of compressor-based HFCWO vests significantly reduced several lung function parameters, while AffloVest only decreased FEF25-75%. Moreover, the study challenged the idea that these vests operate by increasing cephalad airflow bias in the lungs.

“This clinical study challenges the long-held belief that HFCWO vest-induced cephalad airflow bias correlates to effective airway clearance therapy,” said David Shockley, International Biophysics’ president and CEO.

“Manual Chest Physical Therapy (CPT) has always been considered the gold standard in mobilizing and clearing lung secretions. We engineered and developed the AffloVest to mimic hand CPT using our patented Direct Dynamic Oscillation technology that also provides the benefit of mobility and portability during use for the user,” Shockley added.


  1. miriam cohen says:

    It is not clear what the significance of the study reported above is to me (a lay person). Air flow is not affected the way someone thought it is, but is that good or bad for those of us who want to brethe easier.

    • Joana Carvalho says:

      The study is merely testing how different types of vests affect lung function. Although both types seem to have some negative impacts, AffloVest performs a little bit better in comparison with the other compressor-based vests. But of course this will also have to be tested in patients.
      And yes, throughout the study researchers came to the conclusion these vests do not operate exactly as they expected.
      Hope this makes it clearer!

  2. Cecile Maurice says:

    I would like to see a comparison study of the effects of using the most promising vest vs. using inhaled saline solution via nebulizer. If the goal is to loosen, thin and expel airway clogging mucus secretions, which process is the most effective in the most people? I know how I would vote!

  3. Sandra Hart says:

    Does anyone else find it curious that Afflo sponsored the study and their vest turned out to perform the best? I can’t help but be suspicious of this type of company sponsored testing. I feel that there is a good possibility of the tester being biased toward the company that is paying for the study? I have been using the Incourage compressor inflated vest for about 10 months and my breathing has improved. I have bronchiectasis, walk for exercise and previously had to take a break half-way through a 3 mile walk to “catch my breath.” Now, I walk the full 3 miles without any problem. That’s proof enough for me!

  4. Bernhard Rindlisbacher MD says:

    In my view the basic assumption of this study is _wrong_. I cite: “Based on the concept of increased cephalad airflow bias in the lungs during use of HFCWO devices, one might expect that the expiratory peak flow should be increased.”
    Why should the expiratory peak flow in _healthy volunteers_ be increased if the wear a (quite) heavy vest and their thorax is compressed by oscillations ??
    To prove anything one should measure the peak flow within the bronchi and not in a normal device testing the lung function. The flow depends on the volume of air blown out but also on the diameter of the bronchi the air flows through. If the volume of air blown out is the same (exspiratory peak flow measured in the device) and on the other hand the diameter of the bronchi is reduced this means that the _flow in the bronchi is augmented_.
    So “no increases in PEF” does by no means prove that “the concept of HFCWO vest-induced cephalad airflow bias” is wrong.

  5. Bernhard Rindlisbacher MD says:

    … It is simply not possible to deduce from the lung function measurements anything on the situation in the bronchi because you do not have any information on the narrowing of the bronchi or the diameter of the bronchi. It can well be that the compressor-based HFCWO vests that showed a reduction of FEV1 perform better than Afflovest as they possibly achieve a more intense compression of the bronchi and so a higher flow in the bronchi.

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