Breathing problems (also called respiratory or pulmonary problems) affect the lungs and the airways and are the most serious problems associated with CF. The severity of respiratory problems differs for each person. For most people with CF, lung disease affects how well they do and how long they live. Many treatments are available to keep the lungs as healthy as possible.

The Lungs

The right lung has three lobes — upper, middle, and lower. The left lung has two lobes — upper and lower. The lobes branch off into smaller segments. Airway clearance techniques (ACTs) help clear the mucus from these segments. Each segment has airways (bronchi), air sacs (alveoli), and blood vessels (arteries, veins, and capillaries). Oxygen and carbon dioxide are exchanged between the blood and air in the air sacs.

The Respiratory System

The respiratory system has two main parts:

• Upper respiratory tract: the nose and sinuses 
  The upper respiratory tract filters out particles such as dust and germs in the air we breathe. It also warms and moistens that air.
• Lower respiratory tract: the airways and lungs 
  The lower respiratory tract starts at the trachea (the main windpipe), just below the vocal cords, and keeps branching until it gets to the air sacs.

The air sacs are where oxygen (O2) enters into the blood (“in with the good air”) and the carbon dioxide (CO2) comes out (“out with the bad air”). The tubes that go from the windpipe to the air sacs are called the “airways.”

The airways have cells with “house cleaning” tools called cilia (small hair-like structures). They move together to push the dust, germs, and mucus out of the lungs where it can be coughed out. The cilia are normally bathed in a thin layer of fluid that is kept at just the right volume and has a mixture of chemicals (like sodium and chloride) and special chemicals that help fight infections.

CF and the CFTR Protein 

Cystic fibrosis is caused by abnormalities in a protein called CFTR (cystic fibrosis transmembrane conductance regulator). When working properly, the CFTR protein moves to the surface of cells in the lungs — and in the pancreas and other organs — where it helps move chloride, water, and other small molecules out of the cells and onto the surface.

But in people with CF, this protein doesn't get to the cell surface, or it doesn't function properly if it does reach the cell surface. The right amounts of chloride, water, and other molecules do not move into the airways. This results in the buildup of thick, sticky mucus. The mucus becomes so thick that the cilia cannot easily move the mucus to the throat. So, instead of the cilia cleaning the airways, the mucus clogs the airways. When mucus blocks an airway, it is called a mucus plug.

The following video shows what it looks like when the CFTR protein functions normally in the lungs — hair-like cilia can move mucus and germs out of the airways — and what happens when the protein doesn't work.

Mucus plugs keep air from getting into or out of some alveoli (air sacs). Oxygen cannot get into the blood and carbon dioxide cannot get out. The thick, sticky mucus in the small airways:

• Gets in the way of air getting into and out of alveoli
• Makes it hard to remove particles and germs from the airways

If not cleared from the lungs, mucus plugs can lead to lung infections and lung damage. Lung infections cause serious problems for people with CF because:

• Infections cause inflammation, which can damage the cilia and airways, making them even less able to clear mucus, particles and germs from the lungs.
• Infections often cause more mucus to be made. This can lead to more mucus plugs and worse infections.
• This infection-inflammation cycle causes lung damage. Mucus plugs airways, allowing germs to grow and cause infection. When the body's defense system — white blood cells — attack the germs, the lungs become inflamed. This inflammation spurs the creation of more mucus, which then blocks the airways and allows more germs to grow. As you can see, it's a vicious cycle.

See how the lungs work normally and how cystic fibrosis can affect the lungs over time.

How Your CF Care Team Can Help You Protect Your Lungs 

Monitoring and minimizing the buildup of germs, like bacteria in your lungs, is one of the main ways your CF care team can help you protect your lungs.

Starting at age 5 or older, your CF care team will ask you to take a type of breathing test, known as a pulmonary function test (PFT), during one of your quarterly visits. You will also be asked about your breathing, coughing, and the amount of sputum (mucus or phlegm from the lungs) you are producing.

Your care team will ask for a sample of your sputum which is tested to see what kinds of bacteria are growing in your lungs and determine which antibiotics might fight the bacteria. This is called a “sputum culture.”

Your PFT results will probably look like a sea of numbers and maybe a line graph. Your care center team will review your PFT results with you to help you understand what they mean. One component of your PFT report is the forced expiratory volume (FEV₁), which is the amount of air you can blow out in the first second of a forceful exhalation. Your care team will work with you on ways to keep your FEV₁ as high as possible.

Clearing the airways to reduce lung infections and improve lung function with airway clearance techniques is a big part of keeping your FEV₁ numbers high.