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Introduction

Percussion is a manual technique used by respiratory physiotherapists to help aid the clearance of secretions. Chest Percussion is one of the intervention for airway clearance which augments the mobilization of secretions in one or more lung segments to the central airways by placing the patient in various positions so gravity assists in the drainage process. Gravity-assisted positioning will facilitate the clearance of secretions in patients with abnormalities of the cilia. Chest percussion is usually used in combination with active cycle breathing techniques, or coupled with positioning in those who are unable to actively participate in active controlled breathing exercises.

Percussion can be performed in two ways-

1. Manual Percussion
2. Mechanical Percussion^[1]

Percussion is often a beneficial manual technique to help in the removal of secretions in a number of respiratory conditions, these include:

Physics of Chest Percussion^[2]

The physics of respiratory system is dominated by transmission properties of respiratory system which is considered as a coupled system, composed of chest wall and lung in series. Under the influence of external shock, chest wall tends to vibrate and ring as a resonant cavity partially damped by thoracic contents.

In healthy conditions, the vibration of percussions are underdamped, because of a large acoustic mismatch between chest wall (semi-rigid) and underlying lung parenchyma (homogeneous mixture of gas and tissue). Therefore, a large proportion of the vibratory energy of percussion is reflected at the gas-tissue interface, yielding a clear, long-lasting sound described as resonant. Whereas, in conditions like pneumothorax, where lung parenchyma is replaced by air, the acoustic mismatch is maximal so the underdamping is even more pronounced resulting in sound of greater amplitude and duration (described as tympanic sound). Furthermore, in conditions where alveolar air is filled with exudate and/or solid tissue, the mismatch is minimal so that the percussion vibrations are overdamped (propagate away from the surface very rapidly and vanish quickly) resulting sound of low amplitude and duration (described as dull sound).

Technique

• Patient should be in a comfortable or painless position.
• Chest percussion is performed with cupped hands which strike’s the patient chest wall in an alternating rhythmic manner over the lung segments being drained.
• The technique is applied over a towel to ensure it does not feel uncomfortable. 
• Therapist should try to keep shoulders, elbows and wrist loose and mobile during the manoeuvre.
• Duration: Several minutes or until the patient needs to alter the position to cough^[1]

Positions for Chest Percussion:

LOBE OF LUNG	SEGMENTS OF LUNG	PATIENT’S POSITION	AREA OF PERCUSSION
UPPER LOBE (Right & Left)	Anterior apical segments	Sitting with back supported	Percussion is applied directly under the clavicle.
	Posterior apical segments	Sitting with head down on a table	Percussion is applied above the scapulae. Fingers should curve over the top of the shoulders.
	Anterior segments	Supine	Percussion is applied bilaterally, directly over the nipple o just above the breast.
	Posterior segment (left)	Patient lies one-quarter turn from prone and rests on the right side. Head and shoulders are elevated 45 degrees or approximately 18 inches, if pillows are used.	Percussion is applied directly over the left scapula.
	Posterior segment (right)	Patient lies flat and one-quarter turn from prone on the left side.	Percussion is applied directly over the right scapula.
LINGULA (Left)		Patient lies one-quarter turn from supine on the right side, supported with pillows and in a 30 degrees head-down position.	Percussion is applied just under the left breast.
MIDDLE LOBE (Right)		Patient lies one-quarter turn from supine on the left side, supported with pillows behind the back and in a 30 degrees head-down position.	Percussion is applied under the right breast.
LOWER LOBE (Right & Left)	Anterior segments	Patient lies supine, pillows under the knees, in a 45 degrees head-down position.	Percussion is applied bilaterally over the lower portion of ribs.
	Posterior segments	Patient lies prone with a pillow under the abdomen in a 450 head-down position	Percussion is applied bilaterally over the lower portion of ribs.
	Lateral segments (left)	Patient lies on the right side in a 45 degrees head-down position.	Percussion is applied over the lower lateral aspect of the left rib cage.
	Lateral segments (right)	Patient lies on the left side in a 45 degrees head-down position.	Percussion is applied over the lower lateral aspect of the left rib cage.
	Superior segments	Patient lies prone with a pillow under the abdomen to flatten the back.	Percussion is applied bilaterally, directly below the scapulae.

Guidelines

Manual respiratory techniques guidelines for practice 2015^[3]

ACTION	RATIONALE
Prepare the patient by giving a clear explanation of the treatment	Minimises distress and informs the patient of the procedure
Obtain consent from the patient	Confirms the patient is willing to take the treatment
Auscultate the patient’s chest	To ensure no bronchospasm is present prior to the treatment and to assess which area(s) of the lung(s) is/are to be treated
Check the patient’s skin integrity over the area of the rib cage to be treated and take care to avoid performing manual techniques over a portacath and lines and drains	To ensure skin is intact and no areas of skin are damaged
Check the patient’s SpO2 level	To ensure desaturation is detected if it occurs during the treatment
Position the patient to optimise secretion clearance. This may include modified postural drainage positions.	Tilting or side lying the patient may use gravity to assist the mobilization of secretions
When performing chest percussion a towel may be placed over the area to be treated. However, avoid to much padding	The technique should not be performed on bare skin as this may be uncomfortable for the patient,but to much padding may reduce the effectivness of the technique
Perform chest percussion rhythmically with a loose wrist and a cupped hand over the lung area that is to be treated	This creates an energy wave that is transmitted to the lung parenchyma to loosen secreations
A slow single handed technique or a rapid double handed technique can be used	Depending on patients preference. A slow single handed technique may be more suitable if the patient is at risk of bronchospasm
Observe the patient to ensure they are not holding their breathe	Breathe holding may cause oxygen desaturation
Encourage the patient to perform three to four thoracic expansion during chest percussion	This can prevent desaturation
If the patient is prone to desaturation, monitor the patients’ oxygen saturations and respiratory rate throughout the procedure. Supplementary oxygen may be required during treatment	To ensure the patient remains stable during the treatment.
To perform shaking and vibrations the hands are placed over the area where secretions are to be mobilized from and oscillations directed inwards against the chest in the direction of bucket handle rib movement	Chest compression assists the mobilisation of secretions from peripheral to more central airways
The height of the bed should be adjusted to allow the therapist to use their body weight to assist with the vibratory/compression action	To augment expiratory flow and mobilise secretions. The therapist must be aware of their own posture to protect heir back.
Encourage the patient to take a deep inhalation and perform the technique on their exhalation	To encourage movement of secretions during expiratory flow
Encourage the patient to relax their breathing in between the technique	To prevent airway closure, desaturation or bronchospasm
Use forced expiratory technique or coughing to assist the patient to expectorate	Allows secretions that have mobilized to central airways to be expelled
Document the physiotherapy treatment and its outcome in the patients medical notes	To provide a legal record of the treatment and to communicate it;s outcome with other health care professionals.

Indications

• Patients with pulmonary disease that are associated with increased production or viscosity of mucus, such as chronic bronchitis and cystic fibrosis.
• Patients who are on prolonged bed rest.
• Patients who have received general anesthesia and who have painful incisions that restrict deep breathing and coughing postoperatively.
• Any patient who is on ventilator if he or she is stable enough to tolerate the treatment.
• Patients with acute or chronic lung disease, e.g. COPD.
• Patients who are generally weak or elderly.
• Patients with artificial airways.^[1]

Contraindications

• Over fractures, spinal fusion, or osteoporotic bone.
• Over tumor area.
• If a patient has a pulmonary embolus.
• If a patient has a condition in which hemorrhage could easily occur.
• If the patient has an unstable angina.
• If the patient has a chest wall pain.
• In recent neurosurgery, head down position is contraindicated.^[1]
• If patients has a hyper-reactive airways and severe bronchospasm; though, not an absolute contraindication.

Key Evidence

1. Chest percussions has been shown to cause an increase in hypoxemia, but when short periods of percussions ([4].
2. Some patients with severe lung disease demonstrate oxygen desaturation with self chest percussion. This may be due to the work of the additional upper limb activity.
3. In patients with neuro-muscular weakness or paralysis and in those who are intellectually impaired, in addition infants and in small children, percussion technique (manual and mechanical) may be a useful airway clearance technique which stimulates cough possibly by mobilization of secretions.^[4]

References

1. ↑ ^1.01.11.21.3 Colby LA, Kisner C. Therapeutic Exercises. 5th Edition. U.S.A.: F.A. Davis Company, 2007. p870-873
2. ↑ Yernault JC, Bohadana AB. Chest Percussion. ERS Journals Ltd. 1995; 8: 1756-1760.
3. ↑ Nottingham University Hospital, NHS Trust.Manual Technique Guidelines. 2015. Available from : https://www.nuh.nhs.uk/download.cfm?doc=docm93jijm4n677 [Accessed 12 June 2019]
4. ↑ ^4.04.1 Pryor JA. Physiotherapy for airway clearance in adults. European Respiratory Journal.1999;14: 1418-1424