What is the primary effect of cystic fibrosis on the respiratory system?

Cystic fibrosis primarily affects the respiratory system by causing thick mucus accumulation that leads to airway obstruction. This results from a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which disrupts the normal transport of chloride and bicarbonate ions across epithelial cells. As a consequence, the mucus produced is not only thicker and stickier but also less able to trap and clear pathogens effectively.

When thick mucus accumulates in the airways, it creates a favorable environment for bacterial infections, chronic inflammation, and lung damage. The obstruction can lead to difficulty in breathing and reduced airflow, ultimately impairing gas exchange. This accumulation makes it challenging for individuals with cystic fibrosis to clear the mucus from their lungs, resulting in recurrent lung infections and progressive lung disease over time.

In contrast, while increased mucus secretion and decreased lung capacity are associated with the disorder, they are not the primary effect. The statement regarding the reduction of respiratory rate is also less relevant as patients with cystic fibrosis often maintain a normal respiratory rate unless they are experiencing an acute exacerbation. Thus, the essence of cystic fibrosis's impact on the respiratory system is best captured by the concept of thick mucus leading to airway obstruction.