Practical Guide: The active cycle of breathing technique (ACBT)

The active cycle of breathing technique (ACBT) is an airway clearance technique that consists of a five-step cycle with three essential components: breathing control, thoracic expansion exercises and forced expiration technique (a three-step sub-cycle of breathing control – huffing – breathing control).1 Breathing control aims to partially assist the patient to regain the control of breathing through relaxation and, during the process, gives the patient an opportunity to achieve the correct breathing pattern. This is followed by thoracic expansion exercises, which aim to entrain air into the basal airways behind the secretions. This is followed by a ‘huff’ or forced expiratory breath, which shifts the basal secretions to more proximal airways. The force of the huff induces dynamic compression of the airway in the direction of the lung bases, as far as the equal pressure point (EPP), a point where the pressure inside and outside the airway is equal. The EPP shifts further towards the more distal and smaller airways in proportion to the increase in intrapleural pressure and the duration of the huff. Put simply, secretion mobilisation is effected by a dynamic shift in the EPP.