Question

In an asthmatic patient, there is an inflammation of bronchioles and alveoli. Which of the following processes will be affected the most in the patient?

• A. Normal inspiration
• B. Forced inspiration
• C. Normal expiration
• D. Forced expiration

Answer 1

The correct option is D Forced expiration

Under normal conditions, diaphragm contraction produces a negative pressure inside the intrathoracic cavity. The negative pressure gradient pulls air into the lungs. This leads to expansion of the lungs, and thus increases the radius of respiratory bronchioles during inspiration.

The elastic force of the lungs and chest wall induces a positive pressure in the lungs, which forces air out during expiration.
The airways inside the thoracic cavity (such as bronchioles) are also affected by this positive pressure. This force causes its radius to decrease.

If the airways are inflamed and smaller than usual, they would be more prone to collapsing entirely. This is what occurs during expiration in an asthmatic patient. The inflamed airways in the thoracic cavity collapse, interfering with the expiration and trapping the air inside the lungs.

Now, a forced expiration generates an additional force on the air in the lungs; this pressure is of greater magnitude than normal expiration, and it also occurs rapidly. Therefore, an inflamed airway will collapse much sooner in this case, and more air will get trapped.

In asthma, where the respiratory bronchioles become inflamed and narrowed, forced respiration would be greatly impaired.