Airway clearance therapy

Airway clearance therapy is treatment that uses a number of airway clearance techniques to clear the

Clearance techniques

Airway clearance therapy uses different airway clearance techniques (ACTs) in a number of respiratory disorders including,

Breathing techniques include the active cycle of breathing which includes huffing; and autogenic drainage, a technique that requires concentrated effort.[1]

Huffing

Huffing or a huff cough, is also called forced expiration technique, and helps to move mucus away from the lung wall so that it can finally be

The active cycle of breathing technique is carried out in three phases. Phase one is used to relax the airways; phase two involves moving the inhaled air to behind the mucus in order to clear it; phase three helps to clear the mucus out from the lungs.[6]

Phase one

Gentle effortless breathing, in through the nose, and out through the mouth is used in phase one to relax the airways. The shoulders and upper chest are kept relaxed. On breathing out, the pursed lips method is advised. Keeping the lips pursed (as in kissing somebody) when exhaling creates a back pressure that keeps the airways open for longer. One recommendation is for six breaths of control to take place before phase two of the cycle.^[6]

Phase two

Phase two involves using exercises to expand the chest. Breathing is deep and may use a breath-hold of three seconds to move the air into the smaller airways, and reach behind the mucus. The out breath is unforced and may include some percussive clapping, or vibration.^[6]

Phase three

Using huffing coughing, mucus is moved from the smaller airways to the larger airways, and huffing needs to be continued until all the mucus is expelled.^[6]

Autogenic drainage

Autogenic drainage is a controlled airway clearance technique using different depths of inhalation, and different speeds of exhalation that enables mucus to be moved up the airway producing a voluntary cough. This method does not require any equipment, however, it is challenging to perform and appropriate training is required.^[2] Evidence supporting different techniques is limited. A review of the studies that have been conducted concluded that there is no strong evidence that autogenic drainage is better than other airway clearance techniques.^[2]

Manual

Mechanical devices used include positive expiratory pressure (PEP), intrapulmonary percussive ventilators, mechanical insufflation-exsufflation known as a mechanically assisted cough,^[1][9] and airway oscillatory devices.^[10] Several mechanical techniques are used to dislodge mucus and encourage its expectoration. Chest percussion can be administered as a manual technique but can also be performed using specific devices that use chest wall oscillation or intrapulmonary percussive ventilation. Intrapulmonary percussive ventilators (IPVs) are machines which deliver short bursts of air through a mouthpiece to help to clear mucus. The air is delivered at a rate of approximately 150 pulses per minute and may be used with nebulized medication. Chest wall oscillation is a passive system that is not dependent on effort from the user. It involves the use of a special vest that employs the use of a compressor to inflate and deflate the vest rhythmically at timed intervals, and thus imposes high frequency chest wall oscillations that are transferred to the lungs. These oscillations thin airway mucus, and facilitate its removal by coughing. Delivery of air to the vest can be controlled manually.

Other methods such as

Positive expiratory pressure physiotherapy consists of providing a back pressure to the airways during expiration. This effect is provided by devices that consist of a mask or a mouthpiece in which a resistance is applied only on the expiration phase.[12] Operating principles of this technique seems to be the increase of gas pressure behind mucus through collateral ventilation along with a temporary increase in functional residual capacity preventing the early collapse of small airways during exhalation.^[13][14]

See also

• Airway management

References