High-Frequency Chest Wall Oscillation, or HFCWO, is a therapy for cystic fibrosis and other pulmonary diseases. It is typically performed using an inflatable vest and an air pulse generator. The generator sends rapid pulses of air to the vest, causing it to inflate and deflate, putting pressure on the chest walls. This has an effect similar to the physical therapy technique known as clapping.

How HFCWO works

Cystic fibrosis patients produce an abnormally thick mucus. It can build up in the lungs and airways, leading to frequent and serious chest infections. Treatments to reduce and remove mucus build-up are a major part of managing the disease.

HFCWO is one of the treatments used to remove mucus build-up. The percussive pressure produced by the vest helps separate mucus from the airway walls in the lungs, helping it move up and out. Patients typically use the vest in 20- to 30-minute sessions, stopping every five minutes to cough up sputum.

Some studies have found HFCWO to be no more effective than manual chest physical therapy or the positive expiratory pressure technique (PEP). In PEP, a patient breathes through a device that causes resistance, and sometimes vibrations, as they exhale. This helps get air behind the mucus and loosen it, allowing it to be coughed up.

Most PEP studies have been short term, however. They often examine the results of a single session of HFCWO.

In addition, patient preference must be considered. Some patients prefer HFCWO, while others prefer other airway clearance techniques.

In addition, refinements of the HFCWO technique have made it more effective. Using higher pressure and variable frequency settings led to patients coughing up more mucus from the lungs. Some manufacturers are adding “targeted kinetic energy” devices to their vests to help mobilize mucus.

HFCWO in clinical trials

A clinical trial (NCT03091062) to evaluate a new HFCWO vest called the Monarch Airway Clearance System is recruiting patients with cystic fibrosis in Belgium. Participants must be 15 years or older. The Monarch Airway Clearance system is a battery-powered vest that allows patients to be mobile while they are using it rather than being tethered to a generator. In addition, the vest contains what the company calls pulmonary oscillating discs that generate targeted kinetic energy.

Trial participants will try two types of HFCWO vests, the Monarch Airway Clearance System and the Vest Airway Clearance System, both made by Hill-Rom. Researchers will use several measures to assess the vests’ effectiveness, including the wet weight of the sputum produced, respiratory imaging using CT scans, and a lung function test called spirometry.

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