Con traindica tionscautions

• Aggressive hyperinflation in already hyperinflated lungs, e.g. asthma, emphysema — though can be very useful in removing mucus plugs.

• Undrained pneumothorax.

• Raised intracranial pressure.

Techniques Hyperinflation

Hyperinflating to 50% above ventilator-delivered VT, aiming to expand collapsed alveoli and mobilise secretions. VT is rarely measured, so either excessive or inadequate hyperinflations may be given depending on lung compliance and operator technique. Pressure-limiting devices ('blow-off valves') or manometers can avoid excessive airway pressures. A recommended technique is slow inspiration, a 1-2s plateau phase and then rapid release of the bag to simulate a 'huff' and mobilise secretions. Pre-oxygenation may be needed as PEEP may be lost and the delivered VT may be inadequate. Cardiac output often falls with variable blood pressure and heart rate responses. Sedation may blunt the haemodynamic response. Full deflation avoids air trapping.


Removing secretions from trachea and main bronchi (usually right). A cough reflex may be stimulated to mobilise secretions further. Tenacious secretions may be loosened by instillation of 2-5 ml 0.9% saline. Falls in SaO2 and cardiovascular disturbance may be avoided by pre-oxygenation.

Percussion and vibration

Drumming and shaking actions over chest wall to mobilise secretions.

Inspiratory pressure support (Bird ventilator)

The aim is to increase FRC and expand collapsed alveoli.

Postural drainage

Patient positioning to assist drainage — depends on affected lung area(s).

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