Airway Clearance Therapy (ACT): ACT utilizes physical or mechanical methods to influence airflow, aiding in the expulsion of secretions from the trachea and bronchi, or triggering coughs to expel mucus. In previous lessons, we learned methods such as positional drainage, chest percussion, and active cycle breathing techniques. Today, we will learn about Autogenic Drainage and Positive Expiratory Pressure Therapy.
Autogenic Drainage (AD) is a technique for airway clearance that involves breathing at different lung volumes to facilitate the expulsion of secretions, aiming to increase expiratory flow rates. At low lung volumes, peripheral secretions are loosened; at tidal volume, secretions are gathered in the central airways; and at high lung volumes, the expiratory flow reaches its maximum, helping to expel secretions from the central airways or through coughing.
The Process of Autogenic Drainage
Phase 1: Begins with a normal inhalation followed by a breath hold to ensure equal filling of the lung segments through collateral ventilation; then a deep exhalation to the range of the supplemental exhalation volume. The functional residual capacity is achieved below the supporting level with moderate tidal volume, clearing peripheral secretions by compressing them with peripheral alveoli. This phase is also known as the “Loosening” phase.
Phase 2: Involves tidal volume breathing gradually transitioning from the supplemental exhalation volume to the supplemental inhalation volume range, clearing secretions from the lung apex. The airflow speed must be adjusted at each inhalation level to achieve a maximum expiratory flow that does not cause airway collapse. This phase is also known as the “Collecting” phase.
Phase 3: Involves deeper inhalation within the supplemental inhalation volume, with huffing often used to aid in the expulsion of secretions. This phase is also known as the “Expelling” phase.
*Lung volume chart for normal individuals during Autogenic Drainage phases. Phase 1: Loosening; Phase 2: Collecting; Phase 3: Expelling. VT: Tidal Volume; ERV: Supplemental Exhalation Volume; RV: Residual Volume; IRV: Supplemental Inhalation Volume.
Steps for Autogenic Drainage
(1) Preparation Before Operation
● The patient should be seated upright in a chair with back support. The surrounding environment should be free of distractions, allowing the patient to focus on the breathing technique.
● The upper respiratory tract (nose and throat) should be cleared of secretions through huffing or nasal blowing.
● The caregiver should sit beside the patient, close enough to hear the patient’s breathing. One hand should be placed on the patient’s abdomen to feel the contraction of the abdominal muscles, and the other hand should be placed above the patient’s chest.
(2) Basic Breathing Techniques
● In each phase, inhalation should be performed slowly through the nose, utilizing diaphragmatic breathing.
● Hold the breath for 2-3 seconds at the end of inhalation to loosen and detach thick secretions through collateral ventilation.
● Keep the mouth and glottis actively open, exhaling with appropriate force (huffing). The hand placed on the chest can feel the vibrations of the mucus. The frequency of vibrations indicates the location of the mucus. High-frequency vibrations indicate that secretions are located in the small airways, while low-frequency vibrations indicate that secretions have moved to the large airways.
● Utilize diaphragmatic breathing for tidal volume inhalation, holding the breath for 2-3 seconds at the end of inhalation.
● Contract the abdomen and exhale as deeply as possible until all air is expelled.
● Repeat 3-4 times before entering Phase 2.
● Slowly inhale to a moderate level of inhalation volume, but do not forcefully inhale deeply.
● Repeat inhalation-holding for 3 seconds-forceful exhalation.
● Repeat 3-4 times to promote the movement of mucus to the large airways.
● Utilize diaphragmatic breathing to slowly inhale until lung capacity approaches total lung capacity.
● In this position, repeat inhalation-holding for 3 seconds-forceful exhalation at least three times.
● Increase the expiratory speed appropriately to promote the expulsion of secretions. For patients with severe airway obstruction or dynamic airway collapse, the expiratory flow rate can be reduced to prevent airway collapse. Beginners may use pursed-lip breathing to avoid compressing the airways.
(6) The duration of each phase of Autogenic Drainage depends on the location of the secretions. The duration of each cycle depends on the quantity and viscosity of the secretions. The average treatment duration is about 30-45 minutes.
Positive Expiratory Pressure
● Positive Expiratory Pressure (PEP) devices include a one-way breathing valve and an adjustable expiratory resistance, which generates a force to keep the airways open during exhalation. Theoretically, PEP promotes the movement of secretions to larger airways through gas flow via collateral ventilation, allowing collapsed alveoli to reinflate.
● Oscillatory PEP (OPEP) builds on PEP by generating airflow vibrations through a vibrating device, causing resonance in the airways, thereby loosening and removing secretions.
● PEP maintains airway stability, improving ventilation, gas exchange, and airway clearance. PEP breathing has been shown to benefit patients at risk of postoperative atelectasis and has gained widespread practice in the field of airway clearance, particularly for patients with cystic fibrosis.
● Currently commonly used devices include Acapella, Flutter, etc.
● Acapella consists of a mouthpiece connected to the body, using a weighted balance plug and magnets to create oscillatory airflow, with a scale on the other end displaying expiratory resistance. Acapella has the following models: acapella® DH: suitable for treatment of patients with essentially normal respiratory function who can sustain exhalation for 3-4 seconds during the acute phase. acapella® DM is suitable for treatment of patients with reduced respiratory function who cannot sustain exhalation for 3 seconds during the acute phase. acapella® choice and acapella® Duet: can be used in medical or home settings, and can be disassembled for cleaning and disinfection, the latter having a dedicated interface for connecting small-volume nebulizers.
● Acapella has no specific postural requirements; patients can choose a comfortable position.
● Wash hands and set the vibration and resistance scales according to medical advice.
● Hold the mouthpiece, inhale normal tidal volume, and hold the breath for 2-3 seconds.
● Ensure tight closure of lips around the mouthpiece, exhale continuously for 3-4 seconds.
● Continue to inhale through the mouthpiece, preparing for the next exhalation, ensuring an inhalation-to-exhalation ratio of 1:3 or 1:4.
● Each set consists of 10-20 breaths, followed by 2-3 forceful huffs or coughs, recommended 2-3 times/day, 1-2 sets/session.
Advantages and Disadvantages of PEP
● PEP treatment does not have the limitations of traditional airway clearance techniques such as postural drainage and percussion, making it suitable for a broader patient population.
● PEP is suitable for hospitalized patients experiencing acute episodes and for long-term use by patients with chronic lung diseases.
● PEP devices can be used in any position and are easy to learn and master.
● Patients with acute sinusitis, ear infections, nasal bleeding, and recent oral or facial surgeries or trauma should be carefully evaluated before using PEP.
(1) Frownfelter D, Dean E, Guo Qi et al. (2017). Cardiovascular and Respiratory System Physical Therapy – Evidence to Practice [M]. Beijing Science and Technology Publishing House. 2017 p292-296.
(2) Wang Chen et al. Respiratory Therapy Tutorial [M]. People’s Health Publishing House. 2010 p61-64.
Thus, the introduction to airway clearance techniques has been completed. If readers have valuable suggestions, please leave a message below, or if you have any needs regarding respiratory rehabilitation knowledge, feel free to contact us. Thank you for your support.
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