Topic Overview

Normal lung and respiratory function

The breathing tubes, or bronchi, leading to the air sacs (alveoli)
are lined with cells that produce
mucus. Normally, the cells produce a thin, runny mucus
that coats the surface of the airways.

Foreign particles, such as dust and germs, constantly enter the
airways and become trapped in the mucus. Tiny hairs called cilia on the surface
of the breathing tubes sweep the mucus and foreign particles upward into the
larger air passages and then up to the throat where they can be swallowed or
coughed up.

Effects of cystic fibrosis on lung and respiratory function

Cystic fibrosis causes the mucus that coats the
breathing tubes to become so thick and sticky that the cilia are unable to
sweep the germs and other particles up and out of the lungs. The trapped
bacteria lead to frequent, serious infections and permanent lung damage.

In response to infections, the body’s
immune system sends white blood cells to the lungs to
attempt to destroy the infection. White blood cells release chemicals that kill
both bacteria and surrounding normal cells. After attacking the bacteria, the
white blood cells die, adding to the thickness of the mucus and destruction of
the airways.

In the upper respiratory tract, thick, sticky mucus may also clog
the nasal passages and sinuses. Small growths, or polyps, on the inner lining
of the nose may develop from repeated infection and inflammation.


Complications of cystic fibrosis usually involve some aspect of
long-term impaired respiratory function. These complications may include:

  • Coughing up blood. Coughing up small amounts of
    blood is often a symptom of chest infection. Coughing up very large amounts of
    blood can be life-threatening. If you are coughing up blood, call your
  • Pneumothorax, a buildup of air between
    the lungs and chest wall that causes the lung to collapse. This affects adults
    with cystic fibrosis more often than children.
  • Enlargement of the right side of the heart. Over time,
    this can cause
    heart failure and death.
  • Increased
    pressure in the lungs (pulmonary hypertension). The arteries in the lungs
    narrow (constrict) in response to impaired oxygen flow between the lungs and
    blood cells. The heart must pump harder to move blood through the blood
    vessels, which increases pressure in the lungs.
  • Enlarged, damaged airways (bronchiectasis) which can lead to infection.

Related Information


ByHealthwise Staff
Primary Medical Reviewer John Pope, MD – Pediatrics
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP – Pulmonology, Critical Care Medicine, Medical Toxicology

Current as ofMay 4, 2017