Pulmonary function testing (PFT) is used to test for several different breathing changes which can be indicative of lung problems. One result is a reduced diffusing capacity, which requires a differential diagnosis to determine if there is a true lung problem.

Problems With Gas Exchange

Your lungs function to oxygenate blood while also removing carbon dioxide from the blood. There are small blood vessels within the lung (capillaries) where this gas exchange occurs. When you cannot diffuse at a normal rate, either oxygen from your lungs cannot enter the blood at a normal rate or your lungs are not removing carbon dioxide from the blood in an acceptable manner. Depending on the extent of the problem, you may be asymptomatic, or you may notice you have labored breathing, especially when doing seemingly normal activities.

Underlying Problems

When diffusing capacity is not significantly reduced, there may be reasons for the problem that are easy to fix. For example, iron deficiency will make it difficult to oxygenate your blood. Your doctor will want to test your hemoglobin to see if anemia might be the culprit. If you have low iron, you will need another PFT after your anemia is resolved to see if your diffusing capacity has returned to normal. If your doctor already knows anemia is not the problem, the reduced diffusing capacity is likely caused by early-stage lung problems. The different symptoms you experience will help point in the direction of a specific diagnosis. Symptoms with an abrupt onset are more likely to be issues with a blood clot in the lungs rather than lung disease, which typically causes problems over a longer span of time.

Treatments

Treatment will be based on the underlying problem. If changes in diffusing capacity are determined to be early stages of emphysema, medications and lifestyle changes are helpful. Medications may include daily use of inhaled bronchodilators, which are used to help keep the airway open and reduce inflammation. Lifestyle changes include quitting smoking and engaging in pulmonary rehabilitation programs to assist with breathing. Sometimes part of treatment will be controlling other underlying diseases. Interstitial lung disease is another cause of decreased diffusing capacity, and in some instances, an underlying autoimmune disease is part of the problem. Better control over the autoimmune disease may prevent or slow further damage to the lungs.

Every instance of reducing diffusing capacity is not an indication of a severe, progressive lung disease. Your doctor will need to look at all symptoms to make the determination of whether additional medical intervention is necessary.