Active cycle of breathing technique

Original Editor ­- Faye Underwood

Top Contributors - Faye Underwood, Aarti Sareen, Magdalena Hytros, Scott Buxton and Alex Curran


The Active Cycle of Breathing Techniques (ACBT) is an active breathing technique performed by the patient to help clear their sputum the lungs. The ACBT is a group of techniques which use breathing exercises to improve the effectiveness of a cough, loosen and clear secretions and improve ventilation.[1]

ACBT consists of three main phases:[2]

  1. Breathing Control
  2. Deep Breathing Exercises or thoracic expansion exercises
  3. Huffing OR Forced Expiratory Technique (F.E.T)

Additionally, a manual technique (MT) or positive pressure can be added if and when indicated, to create a more complex cycle to help improve removal of secretions on the lungs.

Breathing Control

Breathing control is used to relax the airways and relieve the symptoms of wheezing and tightness which normally occur after coughing or breathlesness[3]. Breathing should be performed gently through the nose using as little effort as possible. If this is not possible then breathing should be done by mouth. If it is necessary to breathe out through the mouth this should be done with ‘pursed lips breathing’. While performing this technique it is important to encourage the patient use it as an opportunity to reduce any tension they may have, Encouraging the patient to close their eyes while performing Breath Control can also be beneficial in helping to promote relaxation. It is very important to use Breathing Control in between the more active exercises of ACBT as it allows for relaxation of the airways[4]. Breathing Control can also help you when you are short of breath or feeling fearful, anxious or in a panic. The length of time spent performing Breathing Control will vary depending on how breathless patient feels.

When using this technique with a patient as part of the ACBT the patient should be instructed to usually 6 breaths. Instructions to patient: Rest one hand on your stomach and keep your shoulders relaxed to drop down. Feel your stomach rise as you breathe in and fall when you breathe out.

Deep Breathing Exercises

Deep breathing is used to get air behind the sputum stuck in small airways:[4]

  1. Relax your upper chest.
  2. Breathe in slowly and deeply.
  3. Breathe out gently until your lungs are empty – don’t force the air out.
  4. Repeat 3 – 4 times, if the patient feels light headed then it is important that they revert back to the Breathing Control portion of the cycle.
  5. At the end of the breath in, hold the air in your lungs for 3 seconds (this is known as an inspiratory hold).[3]

Deep breathing/thoracic expansion exercises recruit the collateral ventilatory system assisting, the movement of air distal to mucus plugs in the peripheral airways.[5]

Deep breaths to utilise collateral channels and get air behind sputum to mobilise it towards larger airways and towards the mouth. Instructions to patient:

  1. Relax your shoulders.
  2. Place both hands on either side of ribs.
  3. Breathe in deeply feeling as your ribs expand.
  4. Breathe out gently as far as you can until your lungs feel empty.

Deep breathing/thoracic expansion is usually repeated 4 times.

Huffing or FET

The FET is an integral part of the ACBT described by Pryor and Webber [6].

A huff is exhaling through an open mouth and throat instead of coughing.Huffing moves sputum from the small airways to the larger airways, from where they are removed by coughing[3]. Coughing alone does not remove sputum from small airways.[4]

  1. Take a small-medium sized breath in
  2. Squeeze the breath out by contracting your tummy muscles and keep your mouth and throat open to perform a huff. This small-medium sized huff helps with the removal of sputum in the lower reaches of the lungs.
  3. To remove sputum in the higher portions of the lungs take a large breath in.
  4. Squeeze the air out as before to perform a huff.
  5. Cough and expectorate any sputum. If no sputum is produced with 1 or 2 coughs, try to stop coughing by encouraging the patient to use Breathing Control, the main technique used in between the more active stages of the as ACBT.
  6. Allow your breathing to settle with breathing control and then repeat the cycle until your chest feels clear.

Small long huffs move sputum from low down into chest whereas big short huffs moves sputum from higher up into chest, so use this huff when it feels ready to come out, but not before; huffs work via dynamic compression.[4]

Instructions to patient:

  1. Take a medium sized breath in.
  2. Squeeze the breath out fairly hard and fast keeping mouth and throat open. Imagine trying to steam up a mirror or blow a tissue held out in front of you.
  3. Attempt to clear sputum 2-3 times then return to breathing control (Phase one) to relax airways.
  4. Repeat as above except for a larger breath in to remove secretions/sputum in other areas of the lungs. 


  • Post surgical /pain (rib fracture/ICC).
  • Chronic increased sputum production e.g in Chronic bronchitis, cystic fibrosis[7].
  • Acute increase sputum production.
  • Poor expansion.
  • Sputum Retention.
  • Cystic Fibrosis.
  • Bronchiectasis.
  • Atelectasis.
  • Respiratory muscle weakness.
  • Mechanical ventilation.
  • Asthma.

Clinical Presentation

It is important to constantly assess for dizziness or increased shortness of breath throughout ACBT. If patient feels dizzy during deep breathing decrease the number of deep breaths taken during each cycle and return to normal breathing to reduce dizziness.[8]


ACBT can be performed in sitting, lying or side-lying positions. Initially you should start in a sitting position until you are comfortable and confident to try different ones.Extensive evidence supports its effectiveness in sitting or gravity assisted positions. A minimum of ten minutes in each productive position is recommended. The ACBT may be performed with or without an assistant providing vibration, percussion and shaking. Self percussion/compression may be included by the patient.


  • Maintain a good breathing pattern with relaxed shoulders and neck.
  • Breathe in through nose and out through mouth. Breathing should be slow, like “sighing out”. This can help minimise any wheezing.
  • Remember the principles of Diaphragmatic breathing.



  1. Thomson A, Skinner A, Piercy J. Tidy's Physiotherapy. 12th edition.Butterworth Heinemann publication.
  2. Larner E, Galey P. Active cycle of breathing technique. Available from: (accessed 20 Oct 2013).
  3. 3.0 3.1 3.2 Emma Larner & Penny Galey.THE ACTIVE CYCLE OF BREATHING TECHNIQUE (ACBT).Sept 2002 – review date Sept 2004.
  4. 4.0 4.1 4.2 4.3 The Active Cycle of Breathing Techniques.Association of Chartered Physiotherapists in Respiratory Care.Leaflet no.GL-05.Available at
  6. J.A. Pryor.Physiotherapy for airway clearance in adults. Eur Respir J 1999; 14: 1418±1424
  7. McKoy NA, Saldanha IJ, Odelola OA, Robinson KA.Active cycle of breathing technique for cystic fibrosis. Cochrane Database Syst Rev. 2012 Dec 12;12:CD007862.
  8. Harden B, Cross J, Broad MA, Quint M, Ritson P, Thomas S. Respiratory Physiotherapy: An On-Call Survival Guide, 2e. London: Churchill Livingstone, 2008.
  9. 10 ACBT for Respiratory illness. Available from: (accessed 20 Oct 2013).