Emphysema has three major effects on breathing that cannot be ignored!

Author: Wang Guangfa, Chief Physician, Peking University First Hospital

Reviewer: Wu Xueyan, Chief Physician, Peking Union Medical College Hospital

Emphysema is a pathological concept. It refers to the enlargement of air spaces and destruction and reduction of alveolar septa in the distal lung tissue, including alveolar ducts and alveoli. It is a chronic lung disease.

In fact, many diseases can cause emphysema. The most common ones are chronic bronchitis or COPD (chronic obstructive pulmonary disease). There are nearly 100 million COPD patients in my country, and almost all of them will eventually develop emphysema.

How does emphysema affect breathing?

1. Difficulty in breathing

Emphysema will have a very significant impact on respiratory mechanics. The mechanism is the enlargement of air cavities and destruction of alveolar septa. The enlargement of air cavities will cause the entire lung volume to expand. The lung volume expands, but lung function does not improve. Why?

For example, car tires and bicycle tires, once fully inflated, it is difficult to pump more air in. The human lungs are actually like this. People breathe in through the movement of respiratory muscles. When the lungs are over-expanded, it becomes difficult to breathe in because it takes more effort to expand the lungs.

In addition, after the lung volume increases, the diaphragm moves downward. The normal diaphragm is like a dome. When you inhale, the diaphragm contracts and moves downward, pulling the lungs to expand, so the air goes in. After the diaphragm moves downward and becomes flat, the space for moving downward becomes very small, so this is also one of the reasons why patients with emphysema have difficulty inhaling.

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Especially when exercising, as we all know, when walking, it is enough to breathe calmly. When running, as the running speed increases, the breathing will be more forceful and the breathing amplitude will increase. Because the maximum effective capacity of emphysema patients is reduced, when the body needs more air, it cannot provide it, and the symptoms of dyspnea will be more obvious. It is not enough to increase the breathing rate, and the respiratory movement is restricted.

Therefore, a very important characteristic of patients with emphysema is that they gasp when they move. They look fine when they are not moving, but as soon as they walk, go to the toilet, or brush their teeth, they will have very obvious difficulty breathing. This is one of the effects of emphysema on the human body.

Type II respiratory failure

In addition to the expansion of the air cavity, patients with emphysema also have damage to the alveolar septum. What is the alveolar septum? There are capillaries between the two alveoli. The oxygen in the alveoli passes through the alveolar epithelium to the alveolar interstitium, and then enters the capillaries and combines with the hemoglobin in the red blood cells. After combining, the oxygen is brought from the alveoli to the required organs, such as the brain, heart, liver, and all other places that need oxygen. When it reaches that place, the oxygen is released, and the oxygen turns into carbon dioxide, which is brought back to this location. Carbon dioxide diffuses from the capillaries into the alveoli, and through the opening and closing of the alveoli, the expansion and contraction, the carbon dioxide is squeezed out and can be discharged from the body.

When the alveolar septa decrease, the first thing affected is the diffusion of oxygen. Because the oxygen diffusion area is reduced, the patient will suffer from hypoxemia. When hypoxemia develops to a certain extent, the disease progresses, the airway resistance increases, and the ventilation function is further reduced, which will make it difficult to discharge carbon dioxide and produce type II respiratory failure, that is, hypercapnic respiratory failure, which is also a very important impact on patients.

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3. Difficulty in breathing

What else can alveolar septum destruction cause? The airways of COPD patients are already narrow, with local edema, exudation, some fibrous tissue hyperplasia, and some secretions. This can cause airway obstruction and make it difficult to breathe in and out.

When emphysema is more severe, airflow limitation becomes more serious, especially when exhaling. The airflow can pass through, relying on the alveolar septa to pull it. The lungs are elastic. After the lungs expand, they stretch in all directions. Correspondingly, the alveoli attached around the airways pull the lungs, just like the spokes of a bicycle. When the forces in all directions of the spokes are balanced, the axle is fixed in the center. In fact, the alveolar septa also play this role.

However, when the alveolar septum is damaged more, just like the spokes of a bicycle are broken, it will be found that it will deviate to one side. The alveoli do not deviate to one side, because a little deviation is not a big problem, but it will cause this place to be pulled, but it will be weak. In this way, the expansion of the airway is weakened, and the cross-sectional area of ​​the airway will be reduced, especially when exhaling, the pulling force is weaker, so when exhaling, it is very narrow or even completely closed. These patients will experience expiratory dyspnea.

Figure 3 Original copyright image, no permission to reprint

The patient seems to be able to inhale fine, but finds it very difficult to exhale, and the exhalation time is relatively long. This is an abnormality in human respiratory mechanics caused by emphysema, or respiratory physiology.