Airway clearance devices in cystic fibrosis
John H. Marks
Management of the pulmonary complications of cystic fibrosis (CF) patients involves airway
clearance therapies (ACTs) to remove obstructing secretions from the airways.
Conventional Chest physiotherapy (CCPT) is considered the ‘gold standard’ method of airway
clearance for CF patients but time and need of assistance often leads to lack of adherence.
Aerosolized bronchodilators and mucolytics have been used to aid airway clearance by dilation of
respiratory passages and breakdown secretions.
Several airway clearance devices have been shown to be effective in aiding airway clearance in CF
patients.
Positive Expiratory Pressure (PEP) – is the simplest and least expensive device. Upon exhalation, PEP
creates a resistor to generate positive pressure in the airways. Different resistance orifices allow for
different pressures of 10-20cm h2o with an inspiration to expiration ratio of 1:3 or 1:4. PEP
exhalation (approx 10) should be followed by a series of huffs and should be repeated several times
until clear or over a 20 min interval.
Flutter – provides PEP therapy with oral airway oscillations. During exhalation, pressure from the
airways is transmitted to the flutter causing the steel ball to bounce creating several opening and
closing cycles with each breath. PEP develops in the range of 10-25 cm h2o at an oscillatory
frequency of about 15 Hz, lifting the device adjusts the frequency to achieve the greatest amount of
airway vibration. Several series of 5-10 exhalations followed by 1 or 2 forceful exhalations and huff
coughs over 10-20mins.
Acapella – same principle as flutter, but not gravity dependant. Three models: low flow(less than
15L/min), high flow (greater than 15L/min) and the acapella choice – can be used in line with a
nebulizer.
RC cornet – consists of a semi circular tube containing a flexible latex free hose. Expiration through
the hose causes it to flex, buckle and unbuckle causing oscillatory positive pressure in the airways
which fluctuates many times per second.
Intrapulmonary Percussive Ventilation (IPV) – delivers small bursts of air through a mouthpiece at a
rate 200-300 cycles per min (2-5 Hz) using a sliding venture to cause rapid flow interruptions. It
entrains an aerosol of up to 20ml of saline with or without a bronchodilator over about 20 mins.
Optimal effect achieved by pressure and frequency is determined by direct observation of chest
movement and patient comfort. Oscillations occur mainly during inhalation. The presumed
mechanism of action of the IPV include bronchodilationfrom increased airway pressure and delivery
of nebulized bronchodilator, prevention of airway collapse, improved distribution of ventilation and
stimulation of cough.
Percussive Nebulizer – is an oral intrapulmonary percussive treatment device that incorporates a
large volume nebulizer (20ml) for delivery of aerosolized medication with oscillating positive
pressure. Oscillatory frequency ranges from 6 to 30 with airway pressures of 6–15 cm H2O. The PNeb oscillates during both inhalation and exhalation, enhancing aerosol delivery and maintaining
airway patency. Presumed mechanisms of action are similar to the IPV and include bronchodilation,
prevention of airway collapse and shearing of mucus from airway walls, and possible
thinning of secretions by high expiratory percussive flow.
High frequency chest wall oscillation - There are two devices utilizing an inflatable vest connected
to an air-pulse generating compressor to deliver high-frequency chest wall oscillation (HFCWO), The
Vest and the SmartVest.The airpulse generator rapidly inflates and deflates the vest,
gently compressing and releasing the chest wall several times per second. Oscillation frequency can
be adjusted from 5 to 25 Hz with pressure to the vest ranging from 3 to 25 cm H2O. The chest wall
oscillations are transmitted to the airways creating mini-coughs. Treatment sessions
generally last 20 to 30 min and consist of short segments at different frequencies separated by huff
coughs. The proposed mechanism of action of HFCWO is enhancement of mucus transport in three
essential ways: by altering the rheologic properties of mucus, by creating a cough-like expiratory
airflow bias that shears mucus from the airwaywalls, and by enhancing ciliary beat frequency, all
of which help move mucus toward central airways. HFCWO has also been shown to improve
distribution of ventilation.One study found that patients with moderate
or severe airway obstruction may benefit fromlower vest pressures at frequencies of 10–15 Hz to
minimize decrease in end-expiratory lung volume and maximize oscillatory flow.