High-frequency chest wall oscillation (HFCWO) is an airway clearance technique in which external chest wall oscillations are applied to the chest using an inflatable vest that wraps around the chest. These machine produces vibrations at variable frequencies and intensities, helping to loosen and to thin mucus, and separate it from airway walls.1
How does HFCWO work?
HFCWO devices use positive and negative pressure changes to increase peripheral and tracheal mucus movement toward the airway opening. High-frequency air pulses to the vest make oscillatory chest wall compressions, increasing the pressure during inflation and leading to a short burst of expiratory flow of up to 1.6L/second. Typically, a user pauses during the 20- to 30-minute HFCWO treatment every 5 minutes to cough out loosened mucus that has moved into the large airways.
Different lines of thought exist as to why airway clearance vests are effective at mobilizing secretions to clear the airways. The first is that the HFCWO device increases the air-liquid sheer forces during expiration (outbreath) to improve mucus removal. The second is the very oscillation of the airway walls loosen secretions to improve air-liquid flow. Finally, the device is believed to boost ciliary beating to change the nature of bronchial secretions, making them less thick and sticky and, hence, easier to expel.2
Studies of HFCWO in bronchiectasis and other diseases
A number of studies have tested the various HFCWO devices available, often used as a treatment for cystic fibrosis. A study in bronchiectasis patients, published in BMC Pulmonary Medicine in 2013, found that high frequency oscillation of the chest wall (HFCWO) improved both “pulmonary function and quality of life” in patients needing daily airway clearance.
Most of these devices use air bladder technology, requiring connection to an external generator that delivers the air pulses that squeeze and release the chest. A newer device, called the AffloVest, uses individual oscillators built into the vest, and is battery powered so a generator is not required, making it a more portable device.
HFCWO devices are doctor prescribed to improve bronchial drainage (clear mucus) in a number of diseases or conditions, from bronchiectasis to cystic fibrosis, acute asthma and immotile cilia syndrome.
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