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Lung Overinflation or Hyperinflation is a critically important component part of both COPD and Emphysema, and particularly so with Emphysema. In fact, recent evidence suggests that correction of Hyperinflation appears to be more important in the relief of dyspnea, than is the correction of airway obstruction with broncodilator therapy. Said another way, if you use so-called Rescue Drugs such as Metered Dose Inhalers to relieve dyspnea caused by airway bronchospasm, the majority of your dyspnea relief comes not from the bronchospasm relief, but rather as a result of relieved bronchospasm now permitting correction of hyperinflation.

This section will tell you how to obtain further dyspnea relief, after you have used your bronchodilator medications. Bronchodilator medications are very important, but they are only the first step to obtain maximal dyspnea relief.

There are two general types of overinflation. The first is so-called "Anatomic Hyperinflation" seen in Emphysema, where there is actual destruction of alveolar lung tissue, to create enlarged cystic overdistended air spaces.

The second general type of overinflation is so-called "Physiologic Hyperinflation" seen in both COPD and Emphysema. The underlying problem here is the airway obstruction common to both conditions. With increased airway obstruction causing increased resistance to air flow, the lung may not have enough time to empty before the next inhaled breath.

Remember, on breathing in, all the structures in the lung, including the airways, get larger, and therefore air moves into the lung relatively easier on inspiration. Conversely, on breathing out, everything in the lungs, including the airways, gets smaller. Therefore, it is always relatively more difficult to to get air out of the lung on expiration. As a result, some air is trapped in the lung, causing it to overinflate.
This diagram is from 1955 first edition of The  Lung, by Dr. Julius Comroe et al.
The lung is depicted as a single air sack, and the arrow indicates air moving in and out of the lung. The dark wavy line below is the subject breathing in and out.

Figure A shows the normal condition, with air moving out freely, and no lung overinflation.

Figure B shows some airway obstruction, and therefore "Air Trapping" on expiration, and with overinflation developing. Note the breathing tracing moving upward.

Figure C shows even more airway obstruction, and the resulting increased overinflation.

The problem here is not enough time for the lung to empty on expiration. The so-called Time Constant required for lung emptying has been exceeded. Note carefully, the faster you breathe, the worse this problem will become.

The older term "Physiologic Hyperinflation" is now evolving into the name "Dynamic Hyperinflation," and more recently has generally been used as a phenomenon related to patient exertion. However, this is not entirely correct, as it is now clear that this type of hyperinflation is commonly present to some degree, even with mild to moderate airway obstructive disease, even while patients are at rest. Dynamic Hyperinflation therefore is of two general types, "Resting Dynamic Hyperinflation" and "Active Dynamic Hyperinflation."

The importance of this surprising recent observation that Dynamic Hyperinflation is frequently present at rest in mild to moderate airway obstructive disease is not that it is causing significant dyspnea at rest. In fact, it generally is not of significance. However, it is clear that these generally asymptomatic patients are indeed vulnerable to further exacerbation of their Dynamic Hyperinflation should they increase their breathing rate for exertion or whatever reason, and therefore have an exagerated dyspnea response. Clearly, this problem can no longer be considered as a significant factor only in severe COPD.

Active Dynamic Hyperinflation in COPD occurs most commonly:

• With general increased effort and Exertion
• After an uncontrolled Coughing spell
• With the Rescue Breathing Pattern

The Rescue Breathing Pattern ("RBP") may be briefly characterized as "....trying to pump air in and out of your lungs as fast and as hard as you can...."

It is a basic psychological cognitive reflex (i.e. controlled by a persons thoughts), generated by a persons conscious will to try and breathe in a manner to relieve acute dyspnea distress. It is not a part of the complex traditional mechanical feedback reflexes from the lung, or the blood chemical (Oxygen and Carbon Dioxide) feedback mechanisms, that automatically control breathing via the Respiratory Center in the brain. This cognitive reaction to dyspnea distress is seen commonly, in both people with normal lungs, and those with COPD diseased lungs. It is perfectly normal and natural for patients with COPD to get upset and anxious if they are experiencing increased shortness of breath, and to react with the Rescue Breathing Pattern. Unfortunately this reaction will only make their dyspnea worse.

If you have COPD and have an acute breathing attack, the more you struggle to catch your breath by breathing rapidly, the worse your problem will become. This is because of a so-called "Vicious Circle" phenomenon, because the faster you breathe, the less time you have to get air out of your lungs. This is physiologic disaster, because it makes Dynamic Hyperinflation progressively worse. It is also a sad and paradoxical reality, that your natural instincts to help yourself, should in fact be turned against you, to make your breathing attack worse.

Rapid breathing, for whatever reason, will trigger this vicious circle response, and produce Dynamic Hyperinflation to make your breathing worse. Literally, and in fact, the basic mechanics of COPD breathing have been tricked into what can only be considered as a self destructive abnormal breathing response. And this is why learning recognize and control the emotional aspects of the Rescue Breathing Pattern, and why breathing control in this situation is so important, because your natural breathing defense mechanisms have been turned against you.

It is very important you clearly understand, if you have a mild episode of increased dyspnea, and then become anxious and upset, you may trigger the Rescue Breathing Pattern and rapidly make your dyspnea attack much worse. This is because the increased breathing rate of the RBP produces Dynamic Hyperinflation. Remaining calm and not allowing yourself to become upset by your dyspnea is a critically important component of COPD breathing control to prevent or minimize acute dyspnea events.

Typically in this situation, patients use their so-called Rescue Medications, usually a Metered Dose Inhaler, to relieve acute dyspnea exacerbations. This is desirable treatment, but rescue drugs are only the beginning of the process to obtain full dyspnea relief. This is because, even after complete, 100% maximal bronchospasm correction achieved by medications, the patient is still left with their original underlying problem of severe airway obstructive disease. It should therefore be obvious that it is imperative that you learn breathing control to prevent and/or fully correct this problem of Dynamic Hyperinflation.

In other modules we will show you how to control Dynamic Hyperinflation with exertion, and after uncontrolled coughing spells. These future lessons will all be based on what you have learned here with the Rescue Breathing Pattern response.

A recent large bronchodilator study involving some 957 patients revealed that 48% of these patients had Resting Dynamic Hyperinflation. Clearly, Resting Dynamic Hyperinflation is a major problem in the COPD population.

What is not clear is, how many patients among those 48% had their Resting Dynamic Hyperinflation fully resolved by their bronchodilator therapy. Until this question is answered, it would seem prudent that all patients with symptomatic COPD have breathing control skills to determine whether or not these skills can enhance their overall resting breathing comfort.

This study makes it very clear, that almost half of the COPD population, even while stable and at rest, are critically vulnerable to any increase in their breathing rate, and that any increase in their breathing rate may precipitate them into acute Active Dynamic Hyperinflation.

Well, since the emptying of the lung on expiration is generally by passive elastic recoil of the chest wall and lung, why not solve the problem of hyperinflation by simply exerting voluntary muscular force to expiration and force the air out? Sadly, the answer to that question varies somewhere between "Yes" and "No." To understand this problem we will explain the subtle and important problem of "Dynamic Bronchial Compression" in the next module.

As to all Dynamic Hyperinflation therapy, always remember, it is mainly an expiration TIME problem. You must learn to manipulate your breathing pattern to generate enough time to allow appropriate emptying of your lung on exhalation. We will show you later how to adjust your breathing time constraints with the Breathing Trainer, to balance the conflicting constraints within a breathing pattern, and give you enough time to breathe out in an optimal manner.

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