Airway Clearance Therapy in Cystic Fibrosis Patients Insights from a Clinician Providing Cystic Fibrosis Care

Figures & data

Table 1 Physiology of Mucus, Cough, and Airway Clearance

Mucus Secretion and Regulation	Function
Less than 10 mL per day	First line defense for lower respiratory tract
Mucus hypersecretion, submucosal gland hypertrophy, goblet cell hyperplasia, increased mucin synthesis, plasma exudation, decrease mucociliary transport, mucus stasis, mucous plug	Pathologic mucus. Loss of protection
Cough and airway constriction	Improved airway clearance provided airways do not collapse

Table 2 Role of Pharmacologic Categories in Airway Clearance

Pharmacological Class	Function
Sympathomimetics	Bronchodilation, Improved mucociliary clearance
Anticholinergics	Bronchodilation
Expectorants	Increase volume and hydration of secretions and induce cough
Mucolytic agents	Reduced mucus viscosity
Mucokinetic agents	Increased mucus clearance by cough
Mucoregulators	Reduction of mucus hypersecretion

Table 3 Role of Optimal Position and Ventilation in CF ACT

Clinical Problem	Technique	Effect
Prolonged supine position	Assume upright posture	Improved: Lung compliance Oxygenation Diaphragmatic excursion Secretion mobilization.
Atelectasis due to less mobility	Mobility and exercise	Improved: Alveolar ventilation Tidal volume Respiratory rate V/Q matching Recruitment lung units Secretion mobilization Lymphatic drainage Enhanced surfactant
Critical CF with renal failure	Prone position	Improved: Arterial oxygen tension Tidal volume Dynamic lung compliance Cardiac stroke volume Sympathetic activity Urine flow
Lung secretions	Decubitus position	↑dependent lung gas exchange
Maximal FRC needed	Standing > sitting > supine	Reduced airway closure
Postop. pain	Frequencer	Frequencer requires no patient cooperation and can be placed at targeted areas in the lungs, avoiding chest tubes and other painful areas
Bronchospasm	Bronchodilators, Breath hold to ERV and use PEP to help increase FRC	Helps collateral ventilation for air to go behind mucus

Note: ↑Improve ventilation due to increase dependent lung gas exchange and thus improved mucus clearance.

Abbreviations: PEP, positive expiratory pressure; FRC, functional residual capacity; ERV, expiratory reserve volume.

Table 4 Various ACT Without Devices

Technique	Physiology	Advantage	Disadvantage
Conventional chest physiotherapy (CPT)	Chest clapping Chest wall vibration End expiratory chest compressions	Assists cough Supports exp maneuvers Reduces air trapping	Reduced autonomy Labor intensive
Postural drainage (modified) with percussion/vibration	Recumbent or semi-recumbent position that enables gravity to clear mucus	Peripheral airways and selected lung segments to more central airways for expectoration	Gastroesophageal reflux Headaches Sinus pressure
Active cycle of breathing technique (ACBT)	Breathing control at tidal volume Thoracic expansion exercises Three-second breath holds Forced expiration/huff open glottis	Gets airflow behind mucus Moves sputum cephalad by dynamic compression and collapse of the airways creating pinch point	Learning required to perform correctly Breathing treatments prior to ACBT
Autogenic drainage	Achieves high expiratory flow from different lung volumes from peripheral to central airway	Maximal expiration produces shearing forces Moves secretions Sequential lung volume change more distally with the aim of improving flow in small airways	Must learn lung volume control
Exercise	Increased ventilatory demand Increased PEFR > 30–60 L/min PEF/PIF >1.1	Autonomy Increased mucus water content Physical mobility Cardiac and pulmonary benefits	Must be combined with PEP maneuvers

Abbreviations: PEFR, peak expiratory flow rate; PEF, peak expiratory flow; PIF, peak inspiratory flow; PEP, positive expiratory pressure.

Figure 1 ACT positioning recommended in clinical scenarios.

Table 5 Airway Clearance Therapy with Devices

Device	Physiology	Advantage	Disadvantage
Positive expiratory pressure (PEP)	Exhale through fixed resistance, stents airways open	Allows air to enter peripheral airways via collateral ventilation	Risk of pneumothorax Epistaxis Sinusitis Ear infection
Oscillating PEP	Combines PEP with oscillations (11–18 Hz) on exhalation	Oscillations reduce viscosity Moves secretions towards large airways	Not be well tolerated during exacerbation Moderate expense
High-frequency chest wall oscillation (HFCWO) vest	Creating an oscillatory airflow bias: Greater airflow out is equivalent to 300–1500 staccato coughs	HFCWO can achieve 300–1500 staccato coughs to move secretions	Caution with chest tubes, indwelling catheters Contraindicated with head and neck injury Expensive
MetaNeb	Vibrates, enlarges airways Delivers gas to distal lung units beyond retained secretions Mobilizes secretions	Hydrates Utilizes mucoactive agents at different time points	Cost Expertise required for set up by dedicated therapist for monitoring
Lung Flute	Uses vibrating reeds to generate frequency of 16–25 Hz on exhalation	Frequency of oscillations reduce mucus viscoelasticity	Contraindicated in pneumothorax
Frequencer	Acoustic waveforms generated at a lower frequency over a large area Delivered outside the chest	Patient cooperation not needed. Can target lung areas Avoids chest tubes and other painful areas	Operator dependent for knowledge and expertise required
Vibralung	Generates sound energy to a column of gas with exhalation and inhalation	Add aerosol treatments Equine use White noise helps with bronchodilation	Caution with hemoptysis and pneumothorax
Noninvasive ventilation (NIV)	Positive inspiratory pressure	Useful adjunct to ACT in with difficulty expectorating sputum Improves gas exchange	Risk of pneumothorax
Intrapulmonary percussive ventilation (IPV)	Combines positive and negative pressure throughout respiration with or without airway oscillations Creates air-liquid shear forces mini coughs	Helpful with secretions and atelectasis	Risk of pneumothorax