What is High Frequency Chest Wall Oscillation (HFCWO)?
Assistance to Ventilation in Spontaneously Breathing Subjects
Our lungs are constantly producing mucus. It is our natural way to keep the lungs clear of infection. In healthy lungs, patients swallow the mucus naturally. When a person is no longer able to effectively clear mucus from their lungs on their own, airway clearance therapy becomes increasingly important to help prevent infection and inflammation.
How Does HFCWO Vest Work?
High-frequency chest wall oscillation (HFCWO) is an airway clearance technique where external chest wall oscillations are applied to the torso using a fitted vest. These vest produces vibrations at variable frequencies and intensities in order to help loosen and to thin mucus, and separate it from airway walls, so it can be coughed up.
HFCWO uses positive and negative pressure changes to augment peripheral and tracheal mucus movement towards the airway opening (Gross & King, 1984). Air pulses are transmitted to the vest at a high frequency increasing oscillatory chest wall compression. During inflation, the pressure increases to between 5 and 20 cm H2O causing a short burst of expiratory flow of up to 1.6L/second. The device usually operates between 2 and 25Hz.
It is thought that secretion mobilization is enhanced by the use of HFCWO via increasing the air-liquid sheer forces during expiration. Another theory is that displacement of the airway walls may disengage secretions and enhance the effect of air-liquid flow. HFCWO is also thought to enhance ciliary beating and change the tenacity of bronchial secretions, making them less thick and therefore easier to expectorate (Hansen & Warwick, 1990).
Many of these devices use air bladder technology with hoses connected to an external, programmable air pulse generator. HFCWO vests, however, feature built-in oscillating modules and is battery-powered, allowing for greater mobility during therapy. Treatment can also be given regardless of whether a person is sitting, standing, or laying down.
The percussion and vibration during HFCWO vest therapy do three things:
- Break up mucus, making it thinner
- Create “mini-coughs” in the lungs, which help push the mucus out
- Make the cilia move faster, helping them carry the loosened mucus to the upper airways
Which Patients Can Benefit from HFCWO?
There are a wide range of diseases and health conditions that cause increased mucus production and ineffective airway clearance. The diseases listed below are among those for which HFCWO has been prescribed:
- Amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease)
- Cerebral palsy
- Chronic bronchitis
- Cystic fibrosis
- Multiple sclerosis
- Muscular dystrophy
- Disorders of the diaphragm
- Post-operative lung transplant
- Post-polio syndrome
- Primary ciliary dyskinesia
- Spinal cord injury
- Spinal muscular atrophy
- Tracheal stenosis
Who Can Use HFCWO Vests?
There is no minimum age requirement for HFCWO therapy. Generally, once a child’s chest measurement is big enough for the Vest to fit properly, he or she can begin using it with a prescription from their physician.