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Forced Expiration Technique

Published on Mar 08, 2023   -  4 min read


The forced expiration technique is a maneuver that transfers secretions, mobilized by thoracic expansion exercises, downwards and towards the mouth.


Huffing is a maneuver that transfers secretions, mobilized by thoracic expansion exercises, downwards and towards the mouth. It is also known as the forced expiration technique (FET) when performed with breathing control. Although it is a stand-alone treatment, it must be a part of any practice of clearing the airways. The FET is the most effective airway-clearing technique if taught properly. A medical specialist with training in instructing this procedure should teach it.

What Is the Physiology of the Forced Expiration Technique?

What Is the Technique of Forced Expiration?

  1. The method is often taught while seated. The patient takes as much time as necessary to breathe calmly and at their speed before puffing.

  2. The patient is taught to take a medium-sized breath in and exhale with a mild to moderate effort and a lengthy expiratory flow while keeping their glottis open.

  3. To optimize the clearance of secretions by maximizing airflow, the duration of the huff and the power of contraction of the muscles of expiration should be changed.

  4. Three degrees of puffing can be taught to patients who have cognitive competence.

  5. To help move secretions from the peripheral airways down the medium airways and into the mouth, the patient must first huff with tiny, medium, and high-volume inspiratory breaths.

  6. The expiratory power and expiration duration are comparable for each inspiratory volume.

  7. The patient can be taught to huff with a piece of cardboard spirometry tubing (or any tube of a comparable diameter) and put at least four centimeters inside their open mouth to help the glottis open.

  8. When the capacity of the lungs diminishes, and the pressure outside the airway rises, the EPP goes upstream toward the alveoli. When the volume inside the lungs expands, and the pressure outside the airway drops, the EPP travels downstream toward the mouth.

  9. Therefore, starting huffing at low lung volumes and working up to medium and big lung volumes is more beneficial to clear secretions from peripheral airways.

  10. A tissue can be placed before the mouth for feedback if glottis closure continues. The tissue will float away when the glottis is opened. When the glottis is closed, it will not move.

What Are the Types of Forced Expiration Techniques?

  1. Low - Volume huffing is inhaling very little air and then gently but forcefully exhaling through the mouth until they run out of room to breathe.

  2. Mid - Volume huff entails inhaling to a moderate volume and expelling through an open mouth at a slightly higher rate than a low-volume huff.

  3. High - Volume huffing takes in much air and quickly exhales it from an open mouth. It should only be used when the mucus has risen and is about to spit out since it is much shorter and harsher.

How Was the Forced Expiration Technique Demonstrated?

  • Huffing includes breathing in, forcing the throat (glottis) open, and then actively exhaling (breathing out). To assist in transporting mucus up the airway, this movement causes a controlled squeezing of the airways and quicker airflow.

  • One must breathe in and out quickly while maintaining an open "0"-shaped mouth such that one is fogging up a mirror to perform a huff.

  • The huff will sound open if the mouth and throat are open when standing up straight. The airways may narrow or shut down because they are too vigorous if every huff sounds wheezy and tight.

  • If this is the case, one must modify the pace and power they exhale and the head and mouth posture. To help with the huffing method, the physiotherapist may occasionally provide a circular tube.

  • After inserting it there, one should huff while the tube is in the mouth. Then, to check if they generate a beneficial flow of air, place a tissue about 20 cm from the mouth. The tissue should ascend into the air during the huff and remain there.

  • The easier for anyone to transport secretions up towards the mouth for easy clearing, the better the airflow out with the huff.

  • If the secretions have now been transferred to big enough airways to be readily coughed up, a clearing cough can be conducted following a series of huffs.

  • One might need to puff many times to drive secretions up and toward the mouth. One may use various huffs to target particular areas of the lungs, which might be useful for locating the mucus.

  • Try to do the huff from lower down if they cannot feel or hear any secretions. To do this, exhale completely, inhale normally, and huff from this smaller air. The pitch of the huff will be lower than a usual huff.

  • A normal-sized huff is the best bet if one feels like some secretions are not ready to come out since they are "too far away" from the upper airways and mouth.

  • On the other hand, one should do a larger volume huff, a forceful huff following a huge breath in if the secretions are high, and one can hear mucus collecting as one breathes out.


Huffing is one method to help improve airflow out of the lungs (forced expiration techniques). For mucus to migrate up towards the mouth and off the walls of the airways, there must be sufficient airflow (movement of air over the mucus). It is important to exercise caution while exhaling because doing so can cause the airway to constrict and occasionally shut. Additionally, it may lead to early or uncontrollable coughing, which hinders the removal of mucus from the smaller airways. With much effort and the help of the physiotherapist, one might feel where the secretions are before they huff and huff from where the secretions are resting in the lungs.

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Last reviewed at:
08 Mar 2023  -  4 min read




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