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The lung has no muscles (other than the muscles surrounding the larger bronchial airways) to cause it to expand and contract, to pump air in and out. The lung in fact is a totally passive elastic structure that for inspiration depends on the chest wall and diaphragm to literally suck it outwards, and therefore expand the lung, to pull air into the alveoli. This is essentially what we have been discussing under diaphragmatic breathing.
The act of expiration under normal conditions is passive, and simply involves the chest wall and diaphragm relaxing, and the elastic forces within the the lung and chest wall that have been stretched out by inspiration, now retract to their resting state. The lung therefore collapses and pushes the stale air out.
There are muscles in the rib cage and that can actively cause the rib cage to contract, and push air out. And if the muscles of the abdominal wall contract, they cause the diaphragm to be pushed up into the chest cavity, and press on the lungs, and thereby further assist active expiration. Normally however these expiratory muscles are not used, except during conditions of exercise, where they are used to literally pump air in and out of the lungs.
So, if Dynamic Hyperinflation correction needs to get air out of the chest, why not use these expiratory muscles to actively push that stale air out? The answer is, yes, you can do this to assist in expiration, but there is a special problem here for the COPD and Emphysema patient. And this problem is called Dynamic Bronchial Compression.
This diagram simplifies the lung down to one alveolus and one bronchial tube within the chest wall, and the bronchial tube leading to the outside air.
When the lung exhales, the chest wall retracts and moves in and therefore applies pressure and everything within the chest gets smaller. The pressure applied to the alveoli is desirable, because that is what pushes the stale air out.
However, this same pressure is also applied to the bronchi, and also makes them smaller, and that is not desirable, because the bronchial tubes also become narrower, and therefore impose a greater degree of airway obstruction for the stale air trying to get out. In the normal lung this is not a problem, but in COPD, and particularly with Emphysema, the bronchial walls are diseased and narrowed, and they are less well outward supported by diseased and deficient elastic structures. These COPD bronchial tubes therefore are much more susceptible to collapse, and they collapse prematurely at particularly weak areas, when the so-called Critical Closing Pressure of these airways is exceeded. The expiration collapse of a regional area of the smaller bronchial tubes is depicted in the diagram.
If you now apply active muscular pressure on expiration, the internal chest pressure will be higher than normal, and the problem of Dynamic Bronchial Compression will be exacerbated. Therefore the airways will collapse prematurely, and to a greater extent, and the problem of getting stale air out of your chest will be made worse. And furthermore, forced exhalation increases the expiratory Work of Breathing, and can be very exhausting.
Here again you have an example of the problem of conflicting actions within the physiology of breathing, and the need to balance these conflicting forces, namely, desirable passive expiration versus active expiration muscular contraction to help get overinflation stale air out of your lungs.
Forced active expiration, and particularly chronic forced expiration, is seldom used as a routine technique, because it is usually exhausting.
However, as a "Rescue Technique," to help correct Dynamic Hyperinflation, gentle forced expiration, applied in a controlled manner, can be very helpful. And the occasional patient with particular problems of emptying their lungs properly, can use a modification of this technique in a chronic manner.
This technique should not be done throughout all of expiration. As with all expiration, the initial act of breathing out should be done in a totally relaxed manner, and this relaxation should be continued as long as possible. However, when it is apparent the lung is not going to empty within a reasonable time, the Rescue Technique of forced expiration should be applied. This is usually at approximately two thirds to three quarters of the way through expiration. The exhalation muscular force must be very deliberately and gently applied.
Think of this force as though you are wringing water out of a wet bath towel. If you apply a strong,sudden force, you will get out a certain amount of water. If however you apply a gentle firm squeezing force, over a longer period of time, you will get out more water, and with less overall effort. Learn to apply this expiration squeezing force within your chest as gently as possible, and with just enough force to get the air out within an appropriate amount of time, that is, the end of expiration. Doing so will minimize the problem of aggravating the Dynamic Bronchial Compression problem, and will make overall expiration easier.
With the Breathing Trainer it is easy to see not only how long you should be breathing out, but also where you should apply this controlled expiration force.
So there you have it, the desired major component parts of the therapeutic COPD breathing pattern, and all of them conflicting with one another to a greater or lesser degree:
All of these component parts must be balanced carefully, to get an optimal breathing pattern for your individual needs.
So far you have spent a lot of time learning about the underlying complexities of breathing training. If you understand why these various breathing recommendations are made, you will be better able to utilize, and to work with these recommendations, and to fine tune them to your individual needs for increased comfort.
The more you know, the better you will do in chest physiotherapy and breathing training.
We will now show you some COPD breathing patterns, and what to do about them.