Obstructive and restrictive pulmonary diseases: Nursing pathophysiology

Obstructive and restrictive lung diseases are groups of conditions affecting ventilation, which is the mechanical movement of inhalation and exhalation that moves air in and out of the lungs so gas exchange can occur. Obstructive lung diseases are characterized by obstruction of exhalation, causing air to be trapped within the lungs; whereas restrictive lung diseases restrict inhalation, preventing the lungs from filling with adequate amounts of oxygen-rich air.

So, the primary role of the lungs is facilitating gas exchange between the external environment and the circulatory system, and a key step in this process is ventilation.

During the inhalation phase of ventilation, the respiratory muscles, primarily the diaphragm and the external intercostal muscles, contract. The diaphragm moves downward and flattens, while external intercostal muscles cause the rib cage to expand, increasing the volume of the chest cavity. This creates pressure in the lungs that’s lower than atmospheric pressure, allowing oxygen-rich air to move in and fill the lungs.

Then, during exhalation, the respiratory muscles relax, and the lungs return to their resting state. This creates pressure in the lungs that’s higher than the atmospheric pressure, allowing air to move out of the lungs.

Now, there are some crucial factors that support the process of ventilation. First, there’s the ability of the lungs to expand and fill during inhalation, which is called compliance. Lung compliance is determined by other factors like the presence of elastin fibers within the lung tissue and the ability of the chest wall to expand and contract during ventilation.

Compliance is also dependent on the surface tension within the alveoli, which are the tiny sacks where gas exchange happens. The alveoli are lined with a thin film of water which creates a force, called surface tension, that tends to collapse the alveoli.

To counteract this, certain cells within the alveolar walls, called type II pneumocytes, produce surfactant, which is a lipoprotein that lines the alveolar walls, reduces surface tension, prevents the alveoli from collapsing, and allows them to easily expand and contract during ventilation.

Then, after the lungs have expanded, elastic recoil, which is the tendency of the lungs and the chest wall to passively return to their resting state, facilitates exhalation.

Another factor that’s important in ventilation is airway resistance, which is the resistance in the respiratory tract to the flow of air.

Normally, resistance in the airways, such as the trachea, bronchi, and bronchioles, is low; and they easily expand along with the lungs during inhalation and then return to their resting state during exhalation.

Factors affecting airway resistance include the bronchial smooth muscle, which controls the diameter of the airways, and mucociliary clearance, the process where mucus produced by goblet cells trap bacteria and inhaled particles while the ciliated epithelium moves the mucus upward and out of the respiratory tract.

When there are alterations in the muscles of respiration, lung compliance, elastic recoil, or airway resistance can obstruct or restrict ventilation, and increase the work of breathing needed for oxygen to reach the alveoli so gas exchange can occur.

Now, after ventilation, the next step needed for gas exchange is perfusion, which is the flow of blood through the pulmonary system, so gases can move between the alveoli and the circulatory system.